International Geology Review Vol 46 2004 p 1022ndash1041Copyright copy 2004 by V H Winston amp Son Inc All rights reserved

0020-6814047691022-20 $2500 1022

Geochemical and Pb-Sr-Nd Isotopic Constraints Indicating an Enriched-Mantle Source for Late Cretaceous to Early Tertiary

Volcanism Central Anatolia TurkeyMUSA ALPASLAN1

Department of Geology Mersin University 33343 Ciftlikkoy-Mersin Turkey

ROBERT FREI Geological Institute University of Copenhagen ster Voldgade 10 DK-1350 Copenhagen Denmark

DURMUordm BOZTUG Department of Geology Cumhuriyet University Sivas 58140 Turkey

MEHMET ALI KURT Department of Geology Mersin University 33343 Ciftlikkoy-Mersin Turkey

AND ABIDIN TEMEL

Department of Geology Hacettepe University 06532 Beytepe Ankara Turkey

Abstract

Bulk-rock major trace and REE geochemistry and Pb-Sr-Nd isotopic compositions identifymantle sources involved in the genesis of volcanic rocks of the Upper CretaceousndashLower TertiaryUlukiordmla Formation Ccedilamard-Ulukiordmla Basin Nigde Province central Anatolia Incompatible trace-element patterns exhibit a large Nb-Ta trough and strong enrichment of LILE such as Ba Th and Uand LREE which indicate a subduction-zone signature Trace-element ratios are compatible with asubcontinental lithospheric source Isotopic data demonstrate the presence of an EMII-like protolith(87Sr86Sr = 0707242ndash0707582 143Nd144Nd = 0512336ndash0512390 206Pb204Pb = 1870ndash18917207Pb204Pb = 15716ndash15796 208Pb204Pb = 39157ndash3945) These geochemical and isotopicdata indicate the derivation of the studied volcanic rocks from an enriched subcontinental mantlesource modified by earlier subduction events This petrogenetic conclusion is compatible with ageodynamic setting of post-collisional extension for the Ccedilamard-Ulukiordmla Basin

Introduction

ANATOLIA IS WIDELY considered to constitute anamalgamation of microcontinents separated by oce-anic realms (ordfengoumlr and Yilmaz 1981 ordfengoumlr andNatlrsquoin 1996 and references therein) Within thesegeotectonic segments the intervening Neo-Tethysocean was separated into northern and southernNeotethys oceanic realms The northern realm wasfurther subdivided into a Northern branch (ordfengoumlrand Yilmaz 1981 Yilmaz et al 1997 Okay andordfahintuumlrk 1997) and an Inner Tauride oceanictrough (Goumlruumlr et al 1984 Goumlruumlr and Tuumlysuumlz 2001)The evolution of these oceanic domains is docu-mented by igneous and sedimentary records such asarc magmatism in the eastern Pontides (Okay and

ordfahintuumlrk 1997 Yilmaz et al 1997 Boztug et al2003 2004) syn- to post-collisional magmatism incentral Anatolia (Boztug 2000 Duumlzgoumlren-Aydin etal 2001 Koumlksal et al 2001 Boztug et al 2003lbeyli et al 2004) Fore-arc and post-collisionalbasins in central Anatolia resulted from the Neo-tethyan convergence system in Turkey (Goumlruumlr et al1984 Goumlncuumloglu et al 1992 1993 1995 Erdoganet al 1996 Poisson et al 1996 Boztug et al2003 2004) The latter group includes the Ccedilamard-Ulukiordmla Basin described herein

The basin consists of volcanic and sedimentaryrocks of Late Cretaceous + Paleocene + MiddleEocene age reaching thicknesses of 5 km (Oktay1982 Nazik 1989 Goumlruumlr et al 1998) Mafic pillowlavas in this basin are suggested to have beenemplaced during an extensional regime in the LateCrateceous (Blumenthal 1956 Oktay 1973)

1Corresponding author email malpaslanmersinedutr

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1023

Formation of this basin has been variably interpretedin terms of geodynamics as an inter-arc basin (Goumlruumlret al 1998) a back-arc basin (Demirtaordmli et al1984) or an island-arcndashrelated basin (Oktay 1982Baordm et al 1986 Iordmler 1988) Boztug et al (2001)pointed out that the Ccedilamard-Ulukiordmla volcano-sedi-mentary sequence comprises rift-related basin fillthat was intruded by mantle-derived plutons some-time around latest Cretaceous to Early Tertiary timeClark and Robertson (2002) documented thewithin-plate character and subduction geochemicalsignature of these volcanic rocks However there isnot agreement on the genesis and evolution of thevolcano-sedimentary rocks in the Ccedilamard-UlukiordmlaBasin This paper presents new geochemical andPb-Sr-Nd isotopic data all of which yield newinsights into the genesis of this basin

Tectonic Setting

There are two different interpretations of tectonicsetting of the Ccedilamard-Ulukiordmla Basin The firstinterpretation assumes that an Inner Tauride oceanexisted between the Bolkar Carbonate platform tothe south and Nigde-Kirordmehir microcontinent to thenorth (Goumlruumlr et al 1984) In this model the InnerTauride ocean was subducted northward in LateCretaceousndashEarly Tertiary time during which theUlukiordmla Basin was formed in a fore-arc geotectonicsetting along the margin of Nigde-Kirordmehir micro-continent (Goumlruumlr et al 1984) Geological and struc-tural data all indicate an extensional setting Theseinclude (1) unconformity between the rocks of theCcedilamard-Ulukiordmla basin and the Bolkar Carbonateplatform (2) lack of a contemporaneous accretion-ary prism related to arc volcanism (3) a within-platecharacter of the volcanic rocks in this basin and (4)correlative stratigraphic and sedimentological rela-tionships (Clark and Robertson 2001 2002)

The second interpretation assumes that only asingle Northern Neotethys ocean existed (Goumlncuumlo-glu 1986 Dirik et al 1999) In this interpretationthe Central Anatolian Crystalline Complex existedas a promotory of the Mesozoic Bolkar (Tauride)continent to the south rather than as a microconti-nent and no suture formed beneath the Ulukiordmlabasin (Oumlzguumll 1976 Goumlncuumloglu 1986) The LateCretaceousndashEarly Tertiary basins bordering thesouthern margin of the Central Anatolian CrystallineComplex are considered to have formed as a resultof post-collisional extension following closure of theNorthern Neotethys along the Ankara-Erzincan

suture zone (Ccedilemen et al 1999 Dirik et al 1999)Clark and Robertson (2002) demonstrated that thelatest Cretaceous (Maastrichtian)ndashLate EoceneUlukiordmla Basin is extensional (or transtensional) andformed after that initial closure of the local strand ofthe Northern Neotethys ocean (Inner Tauride ocean)

Geological Setting

The study area lies in southern part of CentralAnatolia bounded by the Central Anatolian Crystal-line Complex (Goumlncuumloglu et al 1991) to the northby the Bolkar Carbonate platform to the south bythe left-lateral Ecemiordm fault zone and associatedOligo-Miocene deposits (Yetiordm 1984 Koccedilyigit andBeyhan 1998 Jaffey and Robertson 2001 Clarkand Robertson 2002) to the east (Fig 1) The west-ern boundary of the basin is not clear because basi-nal sediments are overlain by continental Neogeneto Recent sediments (Clark and Robertson 2002)however the Ccedilamard-Ulukiordmla Basin is consideredto be genetically linked with the Tuzgoumlluuml BasinComplex to the northwest (Goumlruumlr et al 1984)

The volcano-sedimentary rocks of the basin lieuncomformably on top of the Upper CretaceousAlihoca ophiolite (Fig 2) which was emplaced ontothe Bolkar Carbonate platform (Demirtaordmli et al1984 Lytwyn and Casey 1995 Dilek et al 1999Clark and Robertson 2002) The rock types in theCcedilamard-Ulukiordmla Basin consist of interlayeredconglomerate sandstone marl pelagic limestonereefal limestone claystone and volcanic rocks thelatter consist of pillow lava lava flows and pyro-clastics of the Ulukiordmla Formation (Fig 2 Alpaslanet al 2003) The Ulukiordmla Formation is intruded bysome crustal thinningndashrelated mantle-derived intru-sive rocks the Uccedilurum monzogabbro the Elmalitrachyte and the Yaglitaordm diorite (Fig 2) asdescribed by Boztug et al (2001) and Alpaslan et al(2003) In the lower portion of the basin pillowlavas occur at several stratigraphic horizons Towardthe middle of the sequence they gradually decreasein abundance and are replaced by massive lavaflows at the top of the sequence (Alpaslan et al2003) There are no published radioisotopic agedeterminations for any of these units but fossilrecords indicate that the volcanism occuredbetween the Late Cretaceous and Paleocene (Fig 2Demirtaordmli et al 1975 Oktay 1982 Demirtaordmli etal 1984 Dellaoglu and Aksu 1986 Goumlncuumloglu etal 1991) However Clark and Robertson (2002)

1024 ALPASLAN ET AL

FIG 1 A Location of the study area and Neotethyan sutures of Turkey (after Clark and Robertson 2002) B Majorsedimentary basins of central Anatolia Abbreviations BP = Bolkar Carbonate platform NKM = Nigde-Kirordmehir MassifUB = Ulukiordmla Basin TB = Tuzgoumlluuml Basin HB = Haymana Basin KKB = Kirikkale Basin CB = Ccedilankiri Basin YSB =Yozgat-Sorgun Basin KB = Kizilirmak Basin YB Yildizeli Basin RB = Refahiye Basin SB = Sivas Basin SKB =ordfarkiordmla Basin EFZ = Ecemiordm fault zone (after Clark and Robertson 2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1025

FIG

2 S

impl

ified

geo

logi

cal m

ap o

f the

stu

dy a

rea

afte

r A

lpas

lan

et a

l (2

003)

1026 ALPASLAN ET AL

suggested that the volcanism continued until Earlyto Middle Eocene time

Major structural elements of the mapped area arecomposed of nearly E-Wndashtrending thrust faultsNE-SWndashand NNE-SSWndashtrending left-lateralstrike-slip faults and some ENE-WSW folds (Fig2) A major and presumably early thrust is presentbetween the Alihoca ophiolite and Bolkarda carbon-ate platform The ophiolitic unit was thrust onto thecarbonate rocks from north to south (Fig 2) mostprobably before the opening of the Ccedilamard-Ulukiordmla Basinmdashie it belongs to the imbricatedbasement Another later thrust developed justwithin the Ulukiordmla formation again from north tosouth due mainly to a later N-S compressionalevent Such N-S compression would also have beenresponsible for the ENE-WSW folds and NE-SWfaults both of which affect only the Ulukiordmla Forma-tion as well as the later thrust (Fig 2) Therefore allthese structural elements such as E-W thrustsENE-WSW folds and NE-SW faults affecting onlythe Ulukiordmla Formation are considered to have beenderived from a N-S compressional event that tookplace after Eocene time The NNE-SSWndashtrendingfault in the southeast parts of the mapped area ispart of the well-known Ecemiordm fault that is one of themajor neotectonic faults of the Anatolian provinceinduced by ongoing convergence between theEurasian and Arabian plates (Bozkurt 2001)

Analytical Techniques

Twenty-eight rock samples were selected forgeochemical analyses (major and trace elementsREE) and six of them for isotopic (Pb Sr and Nd)analyses (Table 1) For major element analysesfused disks were prepared using six parts of lithiumtetraborate and one part rock powder The mixturewas fused in crucibles of 95 Pt and 5 Au at1050degC for 60 minutes to form a homogenous meltThe melt then was poured into a preheated moldand chilled as a thick glass disk Whole-rock analy-ses were performed at Hacettepe University using aPHILIPS PW 1480 X-ray spectrometer using USGSrock standards Trace and rare earth element con-centrations were analyzed at ACME laboratories(Vancouver Canada) by ICP-MS using the fusionmethod reported accuracy is better than plusmn3

Sm-Nd Pb and Sr isotopic data and concentra-tions were obtained from 300 mg aliquots of thesame powders For isotope dilution data of Sm andNd a mixed 147Sm-150Nd spike was added Dissolu-

tion of the samples was achieved in two successivebut identical steps which consisted of a strong 8NHBr attack followed by HF-HNO3 and then bystrong HCl Lead leaching experiments involveda 1N HCl attack for 5 minutes after which theleachate was pipetted off and processed as a sepa-rate sample

Chemical separation of Sr and REEs fromwhole-rock samples was carried out on conventionalcation exchange columns followed by separationusing HDEHP-coated beads (BIO-RAD) charged in6 ml quartz glass columns Purification of the Srfraction was achieved by a pass over micro-columnscontaining SrSpec resin REEs were further sepa-rated over HDEHP-coated bio beads (BioRad)loaded in 6 ml glass stem columns Pb was sepa-rated conventionally in 05 ml glass columnscharged with anion exchange resin followed by aclean-up on 200 microl Teflonreg columns A standardHBr-HCl-HNO3 elution recipe was applied for bothcolumn steps

Total Pb procedural blanks were lt125 pg forwhole-rock chemistry and are negligible relative tothe amount of Pb recovered from each sample Pro-cedural blanks for Nd (lt30 pg) and Sr (lt100 pg) areinsignificant and do not influence the measuredisotope ratios beyond their respective precisionsMass spectrometric analyses were carried out on aVG Sector 54-IT instrument at the Geological Insti-tute University of Copenhagen

The mean value for our internal JM Nd standard(referenced against La Jolla) during the period ofmeasurement was 0511115 for 143Nd144Nd with a2σ external reproducibility of plusmn 0000013 (five mea-surements) Fractionation for Pb was controlled byrepetitive analysis of the NBS 981 standard (valuesof Todt et al 1993) and amounted to 0103 plusmn 0007amu (2σ n = 5) Sr was normalized to 86Sr88Sr =01194 and repetitive analyses of the NBS 987 Srstandard yielded 87Sr88Sr = 0710248 plusmn 0000004(2s n = 6)

Rock Descriptions

When plotted on the total alkali vs silica diagramof Le Maitre et al (1989) the volcanic rocks of theUlukiordmla Formation range from trachybasalt throughbasaltic trachyandesite to trachyandesite in composi-tion (Fig 3) All these rock types show a moderate tostrong porphyritic texture with a hypocystallinegroundmass except for some trachybasalts thatalso may have intersertal texture The major mafic

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1023

Formation of this basin has been variably interpretedin terms of geodynamics as an inter-arc basin (Goumlruumlret al 1998) a back-arc basin (Demirtaordmli et al1984) or an island-arcndashrelated basin (Oktay 1982Baordm et al 1986 Iordmler 1988) Boztug et al (2001)pointed out that the Ccedilamard-Ulukiordmla volcano-sedi-mentary sequence comprises rift-related basin fillthat was intruded by mantle-derived plutons some-time around latest Cretaceous to Early Tertiary timeClark and Robertson (2002) documented thewithin-plate character and subduction geochemicalsignature of these volcanic rocks However there isnot agreement on the genesis and evolution of thevolcano-sedimentary rocks in the Ccedilamard-UlukiordmlaBasin This paper presents new geochemical andPb-Sr-Nd isotopic data all of which yield newinsights into the genesis of this basin

Tectonic Setting

There are two different interpretations of tectonicsetting of the Ccedilamard-Ulukiordmla Basin The firstinterpretation assumes that an Inner Tauride oceanexisted between the Bolkar Carbonate platform tothe south and Nigde-Kirordmehir microcontinent to thenorth (Goumlruumlr et al 1984) In this model the InnerTauride ocean was subducted northward in LateCretaceousndashEarly Tertiary time during which theUlukiordmla Basin was formed in a fore-arc geotectonicsetting along the margin of Nigde-Kirordmehir micro-continent (Goumlruumlr et al 1984) Geological and struc-tural data all indicate an extensional setting Theseinclude (1) unconformity between the rocks of theCcedilamard-Ulukiordmla basin and the Bolkar Carbonateplatform (2) lack of a contemporaneous accretion-ary prism related to arc volcanism (3) a within-platecharacter of the volcanic rocks in this basin and (4)correlative stratigraphic and sedimentological rela-tionships (Clark and Robertson 2001 2002)

The second interpretation assumes that only asingle Northern Neotethys ocean existed (Goumlncuumlo-glu 1986 Dirik et al 1999) In this interpretationthe Central Anatolian Crystalline Complex existedas a promotory of the Mesozoic Bolkar (Tauride)continent to the south rather than as a microconti-nent and no suture formed beneath the Ulukiordmlabasin (Oumlzguumll 1976 Goumlncuumloglu 1986) The LateCretaceousndashEarly Tertiary basins bordering thesouthern margin of the Central Anatolian CrystallineComplex are considered to have formed as a resultof post-collisional extension following closure of theNorthern Neotethys along the Ankara-Erzincan

suture zone (Ccedilemen et al 1999 Dirik et al 1999)Clark and Robertson (2002) demonstrated that thelatest Cretaceous (Maastrichtian)ndashLate EoceneUlukiordmla Basin is extensional (or transtensional) andformed after that initial closure of the local strand ofthe Northern Neotethys ocean (Inner Tauride ocean)

Geological Setting

The study area lies in southern part of CentralAnatolia bounded by the Central Anatolian Crystal-line Complex (Goumlncuumloglu et al 1991) to the northby the Bolkar Carbonate platform to the south bythe left-lateral Ecemiordm fault zone and associatedOligo-Miocene deposits (Yetiordm 1984 Koccedilyigit andBeyhan 1998 Jaffey and Robertson 2001 Clarkand Robertson 2002) to the east (Fig 1) The west-ern boundary of the basin is not clear because basi-nal sediments are overlain by continental Neogeneto Recent sediments (Clark and Robertson 2002)however the Ccedilamard-Ulukiordmla Basin is consideredto be genetically linked with the Tuzgoumlluuml BasinComplex to the northwest (Goumlruumlr et al 1984)

The volcano-sedimentary rocks of the basin lieuncomformably on top of the Upper CretaceousAlihoca ophiolite (Fig 2) which was emplaced ontothe Bolkar Carbonate platform (Demirtaordmli et al1984 Lytwyn and Casey 1995 Dilek et al 1999Clark and Robertson 2002) The rock types in theCcedilamard-Ulukiordmla Basin consist of interlayeredconglomerate sandstone marl pelagic limestonereefal limestone claystone and volcanic rocks thelatter consist of pillow lava lava flows and pyro-clastics of the Ulukiordmla Formation (Fig 2 Alpaslanet al 2003) The Ulukiordmla Formation is intruded bysome crustal thinningndashrelated mantle-derived intru-sive rocks the Uccedilurum monzogabbro the Elmalitrachyte and the Yaglitaordm diorite (Fig 2) asdescribed by Boztug et al (2001) and Alpaslan et al(2003) In the lower portion of the basin pillowlavas occur at several stratigraphic horizons Towardthe middle of the sequence they gradually decreasein abundance and are replaced by massive lavaflows at the top of the sequence (Alpaslan et al2003) There are no published radioisotopic agedeterminations for any of these units but fossilrecords indicate that the volcanism occuredbetween the Late Cretaceous and Paleocene (Fig 2Demirtaordmli et al 1975 Oktay 1982 Demirtaordmli etal 1984 Dellaoglu and Aksu 1986 Goumlncuumloglu etal 1991) However Clark and Robertson (2002)

1024 ALPASLAN ET AL

FIG 1 A Location of the study area and Neotethyan sutures of Turkey (after Clark and Robertson 2002) B Majorsedimentary basins of central Anatolia Abbreviations BP = Bolkar Carbonate platform NKM = Nigde-Kirordmehir MassifUB = Ulukiordmla Basin TB = Tuzgoumlluuml Basin HB = Haymana Basin KKB = Kirikkale Basin CB = Ccedilankiri Basin YSB =Yozgat-Sorgun Basin KB = Kizilirmak Basin YB Yildizeli Basin RB = Refahiye Basin SB = Sivas Basin SKB =ordfarkiordmla Basin EFZ = Ecemiordm fault zone (after Clark and Robertson 2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1025

FIG

2 S

impl

ified

geo

logi

cal m

ap o

f the

stu

dy a

rea

afte

r A

lpas

lan

et a

l (2

003)

1026 ALPASLAN ET AL

suggested that the volcanism continued until Earlyto Middle Eocene time

Major structural elements of the mapped area arecomposed of nearly E-Wndashtrending thrust faultsNE-SWndashand NNE-SSWndashtrending left-lateralstrike-slip faults and some ENE-WSW folds (Fig2) A major and presumably early thrust is presentbetween the Alihoca ophiolite and Bolkarda carbon-ate platform The ophiolitic unit was thrust onto thecarbonate rocks from north to south (Fig 2) mostprobably before the opening of the Ccedilamard-Ulukiordmla Basinmdashie it belongs to the imbricatedbasement Another later thrust developed justwithin the Ulukiordmla formation again from north tosouth due mainly to a later N-S compressionalevent Such N-S compression would also have beenresponsible for the ENE-WSW folds and NE-SWfaults both of which affect only the Ulukiordmla Forma-tion as well as the later thrust (Fig 2) Therefore allthese structural elements such as E-W thrustsENE-WSW folds and NE-SW faults affecting onlythe Ulukiordmla Formation are considered to have beenderived from a N-S compressional event that tookplace after Eocene time The NNE-SSWndashtrendingfault in the southeast parts of the mapped area ispart of the well-known Ecemiordm fault that is one of themajor neotectonic faults of the Anatolian provinceinduced by ongoing convergence between theEurasian and Arabian plates (Bozkurt 2001)

Analytical Techniques

Twenty-eight rock samples were selected forgeochemical analyses (major and trace elementsREE) and six of them for isotopic (Pb Sr and Nd)analyses (Table 1) For major element analysesfused disks were prepared using six parts of lithiumtetraborate and one part rock powder The mixturewas fused in crucibles of 95 Pt and 5 Au at1050degC for 60 minutes to form a homogenous meltThe melt then was poured into a preheated moldand chilled as a thick glass disk Whole-rock analy-ses were performed at Hacettepe University using aPHILIPS PW 1480 X-ray spectrometer using USGSrock standards Trace and rare earth element con-centrations were analyzed at ACME laboratories(Vancouver Canada) by ICP-MS using the fusionmethod reported accuracy is better than plusmn3

Sm-Nd Pb and Sr isotopic data and concentra-tions were obtained from 300 mg aliquots of thesame powders For isotope dilution data of Sm andNd a mixed 147Sm-150Nd spike was added Dissolu-

tion of the samples was achieved in two successivebut identical steps which consisted of a strong 8NHBr attack followed by HF-HNO3 and then bystrong HCl Lead leaching experiments involveda 1N HCl attack for 5 minutes after which theleachate was pipetted off and processed as a sepa-rate sample

Chemical separation of Sr and REEs fromwhole-rock samples was carried out on conventionalcation exchange columns followed by separationusing HDEHP-coated beads (BIO-RAD) charged in6 ml quartz glass columns Purification of the Srfraction was achieved by a pass over micro-columnscontaining SrSpec resin REEs were further sepa-rated over HDEHP-coated bio beads (BioRad)loaded in 6 ml glass stem columns Pb was sepa-rated conventionally in 05 ml glass columnscharged with anion exchange resin followed by aclean-up on 200 microl Teflonreg columns A standardHBr-HCl-HNO3 elution recipe was applied for bothcolumn steps

Total Pb procedural blanks were lt125 pg forwhole-rock chemistry and are negligible relative tothe amount of Pb recovered from each sample Pro-cedural blanks for Nd (lt30 pg) and Sr (lt100 pg) areinsignificant and do not influence the measuredisotope ratios beyond their respective precisionsMass spectrometric analyses were carried out on aVG Sector 54-IT instrument at the Geological Insti-tute University of Copenhagen

The mean value for our internal JM Nd standard(referenced against La Jolla) during the period ofmeasurement was 0511115 for 143Nd144Nd with a2σ external reproducibility of plusmn 0000013 (five mea-surements) Fractionation for Pb was controlled byrepetitive analysis of the NBS 981 standard (valuesof Todt et al 1993) and amounted to 0103 plusmn 0007amu (2σ n = 5) Sr was normalized to 86Sr88Sr =01194 and repetitive analyses of the NBS 987 Srstandard yielded 87Sr88Sr = 0710248 plusmn 0000004(2s n = 6)

Rock Descriptions

When plotted on the total alkali vs silica diagramof Le Maitre et al (1989) the volcanic rocks of theUlukiordmla Formation range from trachybasalt throughbasaltic trachyandesite to trachyandesite in composi-tion (Fig 3) All these rock types show a moderate tostrong porphyritic texture with a hypocystallinegroundmass except for some trachybasalts thatalso may have intersertal texture The major mafic

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1024 ALPASLAN ET AL

FIG 1 A Location of the study area and Neotethyan sutures of Turkey (after Clark and Robertson 2002) B Majorsedimentary basins of central Anatolia Abbreviations BP = Bolkar Carbonate platform NKM = Nigde-Kirordmehir MassifUB = Ulukiordmla Basin TB = Tuzgoumlluuml Basin HB = Haymana Basin KKB = Kirikkale Basin CB = Ccedilankiri Basin YSB =Yozgat-Sorgun Basin KB = Kizilirmak Basin YB Yildizeli Basin RB = Refahiye Basin SB = Sivas Basin SKB =ordfarkiordmla Basin EFZ = Ecemiordm fault zone (after Clark and Robertson 2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1025

FIG

2 S

impl

ified

geo

logi

cal m

ap o

f the

stu

dy a

rea

afte

r A

lpas

lan

et a

l (2

003)

1026 ALPASLAN ET AL

suggested that the volcanism continued until Earlyto Middle Eocene time

Major structural elements of the mapped area arecomposed of nearly E-Wndashtrending thrust faultsNE-SWndashand NNE-SSWndashtrending left-lateralstrike-slip faults and some ENE-WSW folds (Fig2) A major and presumably early thrust is presentbetween the Alihoca ophiolite and Bolkarda carbon-ate platform The ophiolitic unit was thrust onto thecarbonate rocks from north to south (Fig 2) mostprobably before the opening of the Ccedilamard-Ulukiordmla Basinmdashie it belongs to the imbricatedbasement Another later thrust developed justwithin the Ulukiordmla formation again from north tosouth due mainly to a later N-S compressionalevent Such N-S compression would also have beenresponsible for the ENE-WSW folds and NE-SWfaults both of which affect only the Ulukiordmla Forma-tion as well as the later thrust (Fig 2) Therefore allthese structural elements such as E-W thrustsENE-WSW folds and NE-SW faults affecting onlythe Ulukiordmla Formation are considered to have beenderived from a N-S compressional event that tookplace after Eocene time The NNE-SSWndashtrendingfault in the southeast parts of the mapped area ispart of the well-known Ecemiordm fault that is one of themajor neotectonic faults of the Anatolian provinceinduced by ongoing convergence between theEurasian and Arabian plates (Bozkurt 2001)

Analytical Techniques

Twenty-eight rock samples were selected forgeochemical analyses (major and trace elementsREE) and six of them for isotopic (Pb Sr and Nd)analyses (Table 1) For major element analysesfused disks were prepared using six parts of lithiumtetraborate and one part rock powder The mixturewas fused in crucibles of 95 Pt and 5 Au at1050degC for 60 minutes to form a homogenous meltThe melt then was poured into a preheated moldand chilled as a thick glass disk Whole-rock analy-ses were performed at Hacettepe University using aPHILIPS PW 1480 X-ray spectrometer using USGSrock standards Trace and rare earth element con-centrations were analyzed at ACME laboratories(Vancouver Canada) by ICP-MS using the fusionmethod reported accuracy is better than plusmn3

Sm-Nd Pb and Sr isotopic data and concentra-tions were obtained from 300 mg aliquots of thesame powders For isotope dilution data of Sm andNd a mixed 147Sm-150Nd spike was added Dissolu-

tion of the samples was achieved in two successivebut identical steps which consisted of a strong 8NHBr attack followed by HF-HNO3 and then bystrong HCl Lead leaching experiments involveda 1N HCl attack for 5 minutes after which theleachate was pipetted off and processed as a sepa-rate sample

Chemical separation of Sr and REEs fromwhole-rock samples was carried out on conventionalcation exchange columns followed by separationusing HDEHP-coated beads (BIO-RAD) charged in6 ml quartz glass columns Purification of the Srfraction was achieved by a pass over micro-columnscontaining SrSpec resin REEs were further sepa-rated over HDEHP-coated bio beads (BioRad)loaded in 6 ml glass stem columns Pb was sepa-rated conventionally in 05 ml glass columnscharged with anion exchange resin followed by aclean-up on 200 microl Teflonreg columns A standardHBr-HCl-HNO3 elution recipe was applied for bothcolumn steps

Total Pb procedural blanks were lt125 pg forwhole-rock chemistry and are negligible relative tothe amount of Pb recovered from each sample Pro-cedural blanks for Nd (lt30 pg) and Sr (lt100 pg) areinsignificant and do not influence the measuredisotope ratios beyond their respective precisionsMass spectrometric analyses were carried out on aVG Sector 54-IT instrument at the Geological Insti-tute University of Copenhagen

The mean value for our internal JM Nd standard(referenced against La Jolla) during the period ofmeasurement was 0511115 for 143Nd144Nd with a2σ external reproducibility of plusmn 0000013 (five mea-surements) Fractionation for Pb was controlled byrepetitive analysis of the NBS 981 standard (valuesof Todt et al 1993) and amounted to 0103 plusmn 0007amu (2σ n = 5) Sr was normalized to 86Sr88Sr =01194 and repetitive analyses of the NBS 987 Srstandard yielded 87Sr88Sr = 0710248 plusmn 0000004(2s n = 6)

Rock Descriptions

When plotted on the total alkali vs silica diagramof Le Maitre et al (1989) the volcanic rocks of theUlukiordmla Formation range from trachybasalt throughbasaltic trachyandesite to trachyandesite in composi-tion (Fig 3) All these rock types show a moderate tostrong porphyritic texture with a hypocystallinegroundmass except for some trachybasalts thatalso may have intersertal texture The major mafic

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1025

FIG

2 S

impl

ified

geo

logi

cal m

ap o

f the

stu

dy a

rea

afte

r A

lpas

lan

et a

l (2

003)

1026 ALPASLAN ET AL

suggested that the volcanism continued until Earlyto Middle Eocene time

Major structural elements of the mapped area arecomposed of nearly E-Wndashtrending thrust faultsNE-SWndashand NNE-SSWndashtrending left-lateralstrike-slip faults and some ENE-WSW folds (Fig2) A major and presumably early thrust is presentbetween the Alihoca ophiolite and Bolkarda carbon-ate platform The ophiolitic unit was thrust onto thecarbonate rocks from north to south (Fig 2) mostprobably before the opening of the Ccedilamard-Ulukiordmla Basinmdashie it belongs to the imbricatedbasement Another later thrust developed justwithin the Ulukiordmla formation again from north tosouth due mainly to a later N-S compressionalevent Such N-S compression would also have beenresponsible for the ENE-WSW folds and NE-SWfaults both of which affect only the Ulukiordmla Forma-tion as well as the later thrust (Fig 2) Therefore allthese structural elements such as E-W thrustsENE-WSW folds and NE-SW faults affecting onlythe Ulukiordmla Formation are considered to have beenderived from a N-S compressional event that tookplace after Eocene time The NNE-SSWndashtrendingfault in the southeast parts of the mapped area ispart of the well-known Ecemiordm fault that is one of themajor neotectonic faults of the Anatolian provinceinduced by ongoing convergence between theEurasian and Arabian plates (Bozkurt 2001)

Analytical Techniques

Twenty-eight rock samples were selected forgeochemical analyses (major and trace elementsREE) and six of them for isotopic (Pb Sr and Nd)analyses (Table 1) For major element analysesfused disks were prepared using six parts of lithiumtetraborate and one part rock powder The mixturewas fused in crucibles of 95 Pt and 5 Au at1050degC for 60 minutes to form a homogenous meltThe melt then was poured into a preheated moldand chilled as a thick glass disk Whole-rock analy-ses were performed at Hacettepe University using aPHILIPS PW 1480 X-ray spectrometer using USGSrock standards Trace and rare earth element con-centrations were analyzed at ACME laboratories(Vancouver Canada) by ICP-MS using the fusionmethod reported accuracy is better than plusmn3

Sm-Nd Pb and Sr isotopic data and concentra-tions were obtained from 300 mg aliquots of thesame powders For isotope dilution data of Sm andNd a mixed 147Sm-150Nd spike was added Dissolu-

tion of the samples was achieved in two successivebut identical steps which consisted of a strong 8NHBr attack followed by HF-HNO3 and then bystrong HCl Lead leaching experiments involveda 1N HCl attack for 5 minutes after which theleachate was pipetted off and processed as a sepa-rate sample

Chemical separation of Sr and REEs fromwhole-rock samples was carried out on conventionalcation exchange columns followed by separationusing HDEHP-coated beads (BIO-RAD) charged in6 ml quartz glass columns Purification of the Srfraction was achieved by a pass over micro-columnscontaining SrSpec resin REEs were further sepa-rated over HDEHP-coated bio beads (BioRad)loaded in 6 ml glass stem columns Pb was sepa-rated conventionally in 05 ml glass columnscharged with anion exchange resin followed by aclean-up on 200 microl Teflonreg columns A standardHBr-HCl-HNO3 elution recipe was applied for bothcolumn steps

Total Pb procedural blanks were lt125 pg forwhole-rock chemistry and are negligible relative tothe amount of Pb recovered from each sample Pro-cedural blanks for Nd (lt30 pg) and Sr (lt100 pg) areinsignificant and do not influence the measuredisotope ratios beyond their respective precisionsMass spectrometric analyses were carried out on aVG Sector 54-IT instrument at the Geological Insti-tute University of Copenhagen

The mean value for our internal JM Nd standard(referenced against La Jolla) during the period ofmeasurement was 0511115 for 143Nd144Nd with a2σ external reproducibility of plusmn 0000013 (five mea-surements) Fractionation for Pb was controlled byrepetitive analysis of the NBS 981 standard (valuesof Todt et al 1993) and amounted to 0103 plusmn 0007amu (2σ n = 5) Sr was normalized to 86Sr88Sr =01194 and repetitive analyses of the NBS 987 Srstandard yielded 87Sr88Sr = 0710248 plusmn 0000004(2s n = 6)

Rock Descriptions

When plotted on the total alkali vs silica diagramof Le Maitre et al (1989) the volcanic rocks of theUlukiordmla Formation range from trachybasalt throughbasaltic trachyandesite to trachyandesite in composi-tion (Fig 3) All these rock types show a moderate tostrong porphyritic texture with a hypocystallinegroundmass except for some trachybasalts thatalso may have intersertal texture The major mafic

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1026 ALPASLAN ET AL

suggested that the volcanism continued until Earlyto Middle Eocene time

Major structural elements of the mapped area arecomposed of nearly E-Wndashtrending thrust faultsNE-SWndashand NNE-SSWndashtrending left-lateralstrike-slip faults and some ENE-WSW folds (Fig2) A major and presumably early thrust is presentbetween the Alihoca ophiolite and Bolkarda carbon-ate platform The ophiolitic unit was thrust onto thecarbonate rocks from north to south (Fig 2) mostprobably before the opening of the Ccedilamard-Ulukiordmla Basinmdashie it belongs to the imbricatedbasement Another later thrust developed justwithin the Ulukiordmla formation again from north tosouth due mainly to a later N-S compressionalevent Such N-S compression would also have beenresponsible for the ENE-WSW folds and NE-SWfaults both of which affect only the Ulukiordmla Forma-tion as well as the later thrust (Fig 2) Therefore allthese structural elements such as E-W thrustsENE-WSW folds and NE-SW faults affecting onlythe Ulukiordmla Formation are considered to have beenderived from a N-S compressional event that tookplace after Eocene time The NNE-SSWndashtrendingfault in the southeast parts of the mapped area ispart of the well-known Ecemiordm fault that is one of themajor neotectonic faults of the Anatolian provinceinduced by ongoing convergence between theEurasian and Arabian plates (Bozkurt 2001)

Analytical Techniques

Twenty-eight rock samples were selected forgeochemical analyses (major and trace elementsREE) and six of them for isotopic (Pb Sr and Nd)analyses (Table 1) For major element analysesfused disks were prepared using six parts of lithiumtetraborate and one part rock powder The mixturewas fused in crucibles of 95 Pt and 5 Au at1050degC for 60 minutes to form a homogenous meltThe melt then was poured into a preheated moldand chilled as a thick glass disk Whole-rock analy-ses were performed at Hacettepe University using aPHILIPS PW 1480 X-ray spectrometer using USGSrock standards Trace and rare earth element con-centrations were analyzed at ACME laboratories(Vancouver Canada) by ICP-MS using the fusionmethod reported accuracy is better than plusmn3

Sm-Nd Pb and Sr isotopic data and concentra-tions were obtained from 300 mg aliquots of thesame powders For isotope dilution data of Sm andNd a mixed 147Sm-150Nd spike was added Dissolu-

tion of the samples was achieved in two successivebut identical steps which consisted of a strong 8NHBr attack followed by HF-HNO3 and then bystrong HCl Lead leaching experiments involveda 1N HCl attack for 5 minutes after which theleachate was pipetted off and processed as a sepa-rate sample

Chemical separation of Sr and REEs fromwhole-rock samples was carried out on conventionalcation exchange columns followed by separationusing HDEHP-coated beads (BIO-RAD) charged in6 ml quartz glass columns Purification of the Srfraction was achieved by a pass over micro-columnscontaining SrSpec resin REEs were further sepa-rated over HDEHP-coated bio beads (BioRad)loaded in 6 ml glass stem columns Pb was sepa-rated conventionally in 05 ml glass columnscharged with anion exchange resin followed by aclean-up on 200 microl Teflonreg columns A standardHBr-HCl-HNO3 elution recipe was applied for bothcolumn steps

Total Pb procedural blanks were lt125 pg forwhole-rock chemistry and are negligible relative tothe amount of Pb recovered from each sample Pro-cedural blanks for Nd (lt30 pg) and Sr (lt100 pg) areinsignificant and do not influence the measuredisotope ratios beyond their respective precisionsMass spectrometric analyses were carried out on aVG Sector 54-IT instrument at the Geological Insti-tute University of Copenhagen

The mean value for our internal JM Nd standard(referenced against La Jolla) during the period ofmeasurement was 0511115 for 143Nd144Nd with a2σ external reproducibility of plusmn 0000013 (five mea-surements) Fractionation for Pb was controlled byrepetitive analysis of the NBS 981 standard (valuesof Todt et al 1993) and amounted to 0103 plusmn 0007amu (2σ n = 5) Sr was normalized to 86Sr88Sr =01194 and repetitive analyses of the NBS 987 Srstandard yielded 87Sr88Sr = 0710248 plusmn 0000004(2s n = 6)

Rock Descriptions

When plotted on the total alkali vs silica diagramof Le Maitre et al (1989) the volcanic rocks of theUlukiordmla Formation range from trachybasalt throughbasaltic trachyandesite to trachyandesite in composi-tion (Fig 3) All these rock types show a moderate tostrong porphyritic texture with a hypocystallinegroundmass except for some trachybasalts thatalso may have intersertal texture The major mafic

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1027

TABLE 1 Whole-Rock Major Trace and Pb-Sr-Nd Isotopic Compositions of the Volcanic Rocksof the Ulukiordmla Volcanics from the Ccedilamardi-Ulukiordmla Basin1

Sample CU26 CU34 CU42 CU49 CU51 CU56 CU68 CU94Longitude 37deg3436 37deg3528 37deg3638 37deg3622 37deg3620 37deg3720 37deg3837 37deg4042Latitude 34deg3355 34deg3215 34deg3955 34deg4010 34deg4017 34deg4019 34deg4550 34deg4505

SiO2 519 5072 5287 5147 4921 4857 5348 4769TiO2 113 101 089 099 092 092 141 097Al2O3 1733 1608 1746 1796 1485 1649 1702 1737tFe2O3 872 745 656 683 8 741 806 693MnO 013 012 01 02 013 01 013 011MgO 388 823 351 452 963 762 353 624CaO 491 527 63 838 97 895 556 908Na2O 415 407 432 462 25 276 383 301K2O 401 246 399 282 267 232 458 37P2O5 053 051 041 032 043 039 082 056LOI 276 4 282 225 242 406 168 441

Total 9945 9992 9923 10036 10046 9959 1001 10007

Pb 28 27 30 21 16 15 19 32Rb 143 71 109 96 71 44 159 85Cs 09 11 119 25 812 69 16 03Ba 2230 1831 2098 1185 1662 1503 2008 1022Sr 1404 1268 1340 943 1198 1028 1311 788Ta 05 08 09 06 07 06 13 09Nb 93 13 116 97 109 91 231 133Hf 41 41 48 44 37 36 73 52Zr 172 157 187 157 163 162 303 215Y 26 23 23 22 22 21 29 24Th 234 178 221 206 226 147 257 257U 37 4 49 43 45 42 54 45La 999 866 789 65 837 59 796 893Ce 1779 1582 1391 1175 1505 1091 1503 1671Pr 1876 1731 1485 1277 1614 119 167 1799Nd 659 629 533 472 593 462 611 651Sm 99 93 82 79 96 74 95 103Eu 22 211 189 187 213 181 218 243Gd 694 593 536 568 676 534 718 658Tb 088 084 074 079 086 074 094 093Dy 469 443 414 44 453 393 494 471Ho 084 075 074 075 078 074 102 073Er 22 204 208 214 196 183 268 216Tm 034 03 032 029 03 026 04 028Yb 213 191 199 179 194 157 238 184Lu 034 031 033 033 028 029 035 02687Sr86Sr ndash ndash ndash 0707242plusmn6 ndash ndash ndash ndash143Nd144Nd ndash ndash ndash 0512390plusmn7 ndash ndash ndash ndash206Pb204Pb ndash ndash ndash 18920plusmn0009 ndash ndash ndash ndash207Pb204Pb ndash ndash ndash 15767plusmn001 ndash ndash ndash ndash208Pb204Pb ndash ndash ndash 39415plusmn003 ndash ndash ndash ndash

Table continues

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1028 ALPASLAN ET AL

TABLE 1 (continued)

Sample CU95 CU98A CU98B CU111 CU117 CU159 CU164 CU274Longitude 37deg4046 37deg4051 37deg4051 37deg3150 37deg3301 37deg3442 37deg3500 37deg3534Latitude 34deg4511 34deg4536 34deg4536 34deg4326 34deg4410 34deg4358 34deg4339 34deg4724

SiO2 1 5262 5329 5787 5421 4812 495 5333TiO2 093 1 102 06 069 107 091 096Al2O3 1659 1831 1838 1825 1737 1829 1764 1779Fe2O3 729 667 68 686 612 784 734 702MnO 009 01 01 013 009 019 016 019MgO 711 367 379 265 183 59 627 616CaO 715 624 633 273 65 987 953 505Na2O 295 391 384 606 642 235 247 568K2O 341 396 399 122 21 29 275 123P2O5 043 051 051 018 026 042 036 03LOI 269 201 239 364 462 293 31 297

Total 9964 99 10044 10019 10021 10018 10003 10068

Pb 20 30 32 3 6 10 13 337Rb 113 122 125 30 35 93 87 72Cs 18 12 11 06 06 31 26 37Ba 1697 2144 2075 227 408 2312 1598 517Sr 1276 1269 1271 352 864 1237 1010 966Ta 07 1 08 05 04 07 06 06Nb 103 135 134 59 51 103 92 91Hf 45 49 54 37 33 37 35 31Zr 177 209 213 127 131 152 146 152Y 22 24 24 23 19 26 23 27Th 198 301 304 77 79 159 2006 198U 46 73 66 18 22 28 34 46La 672 1034 1045 165 371 813 828 637Ce 1218 1814 1855 317 732 1502 1523 1219Pr 1324 1901 1894 351 849 161 1617 1325Nd 496 683 688 144 334 601 583 503Sm 79 105 102 29 62 92 89 84Eu 184 223 216 074 166 228 219 229Gd 581 651 67 329 477 674 655 612Tb 077 081 091 053 065 087 085 079Dy 415 474 464 339 348 463 457 449Ho 076 076 084 071 06 081 077 084Er 197 207 221 199 173 216 2 24Tm 033 032 034 039 027 035 031 035Yb 184 198 187 207 179 223 206 227Lu 03 032 031 037 03 036 031 03687Sr86Sr 0707472plusmn6 ndash ndash ndash ndash 0707271plusmn6 0707522plusmn6 ndash143Nd144Nd 0512362plusmn5 ndash ndash ndash ndash 0512348plusmn8 0512336plusmn6 ndash206Pb204Pb 18896plusmn0013 ndash ndash ndash ndash 18870plusmn0017 18918plusmn0025 ndash207Pb204Pb 15729plusmn0013 ndash ndash ndash ndash 15787plusmn0015 15796plusmn0023 ndash208Pb204Pb 39238plusmn004 ndash ndash ndash ndash 39381plusmn0042 39454plusmn0042 ndash

Table continues

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1029

TABLE 1 (continued)

Sample CU288 CU310 CU315 CU332 CU345 CU351 CU370 CU372Longitude 37deg3420 37deg3350 37deg3354 37deg3415 37deg3559 37deg3554 37deg3340 37deg3341Latitude 34deg4715 34deg4637 34deg4643 34deg4520 34deg5345 34deg5320 34deg4945 34deg4947

SiO2 4835 4794 5492 51 5408 546 5046 5187TiO2 112 095 106 091 137 131 094 101Al2O3 1754 1543 1823 1642 1656 1705 1707 1793Fe2O3 702 714 602 682 678 655 755 59MnO 018 01 01 014 01 008 012 008MgO 636 75 223 706 205 462 786 574CaO 894 793 339 532 533 26 561 551Na2O 318 227 609 322 642 41 288 479K2O 204 356 32 472 156 411 326 163P2O5 033 08 051 037 057 048 029 032LOI 515 679 459 38 541 456 385 576

Total 10021 10041 10034 9978 10023 10006 9989 10054

Pb 30 15 14 22 7 12 25 12Rb 53 112 95 118 51 106 94 45Cs 1 43 12 21 12 22 22 33Ba 1161 2500 1672 1963 673 1019 2199 1228Sr 422 1584 426 1482 216 139 871 1047Ta 04 08 12 16 1 11 04 05Nb 91 138 211 252 165 17 7 79Hf 35 46 69 64 58 61 33 35Zr 160 192 290 249 258 245 125 140Y 20 24 30 28 30 36 20 22Th 153 244 336 247 334 248 16 197U 27 48 7 59 54 6 32 34La 62 1303 1254 798 1062 928 49 581Ce 1074 2376 2188 1436 1933 1671 884 1055Pr 113 247 2126 1404 1913 1685 916 1069Nd 457 979 774 544 759 695 375 425Sm 75 141 118 88 118 103 66 69Eu 196 359 265 198 241 266 167 194Gd 498 88 816 62 815 845 483 533Tb 072 098 102 085 095 109 066 076Dy 394 475 525 473 549 665 38 397Ho 071 075 094 09 099 115 071 076Er 182 201 276 269 316 318 195 219Tm 026 031 046 04 043 049 027 034Yb 166 192 299 272 252 279 19 194Lu 028 031 045 042 041 046 028 03387Sr86Sr 0707712plusmn6 ndash ndash ndash ndash ndash ndash ndash143Nd144Nd 0512318plusmn6 ndash ndash ndash ndash ndash ndash ndash206Pb204Pb 18803plusmn001 ndash ndash ndash ndash ndash ndash ndash207Pb204Pb 15745plusmn001 ndash ndash ndash ndash ndash ndash ndash208Pb204Pb 39167plusmn003 ndash ndash ndash ndash ndash ndash ndash

Table continues

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1030 ALPASLAN ET AL

constituents of trachybasalts and basaltictrachyandesites consist of olivine and clino-pyroxene occurring as euhedral and subhe-dral phenocrysts and microphenocrysts set ina hypocrystalline groundmass The only min-eralogical difference in trachyandesites isthat the major mafic phase comprises solelyclinopyroxene phenocrysts and micrphenoc-rysts In all the rock types of the UlukiordmlaFormation plagioclase is the main felsicconstituent which is found as phenocrystsmicrophenocrysts and microliths Most ofplagioclase and some of clinopyroxenephenocrysts also display zoning in some rocksamples Opaque minerals (magnetite)occur as microphenocrysts and microliths Avariable degree of hydrothermal alterationas evidenced by chloritization in the ground-mass and iddingsitization and serpentiniza-tion of some olivine phenocrysts in somesamples is evidenced by a relatively highLOI (loss on ignition gt2 wt)

Whole-Rock Geochemistry

Major-element trace-element andPb-Sr-Nd isotopic results are presented inTable 1 All the rock samples of the UlukiordmlaFormation from the Ccedilamard- Ulukiordmla Basinhave an apparent alkaline composition inthe total alkali vs silica diagram (Fig 3) ofIrvine and Baragar (1971) They show acoherent major-element fractionation trendfrom trachybasalt through basaltic tra-chyandesite to trachyandesites (Fig 4)Trace elements show a similar fractionationtrend observable only in the HFSE contentsin Figure 5 based on Zr variations as a frac-tionation index LILE do not show a distincttrend (Fig 5) this lack of a trend is thoughtto have been caused by the assimilation ofcrustal rocks or the involvement of sub-ducted sediments in the genesis of thesevolcanics as discussed below

Data plotted in a Zr-ZrY discriminationdiagram indicate a within-plate genesis forthe volcanic rocks of the Ulukiordmla Formation(Fig 6) these rocks are considered to havebeen derived directly from the uppermantle The chondrite-normalized trace-element patterns of trachybasalts indicate asignificant enrichment of LILE except for K

TABLE 1 (continued)

Sample CU382 CU392 CU393 CU394Longitude 37deg3255 37deg3225 37deg3228 37deg3230Latitude 34deg4940 34deg4945 34deg4947 34deg4948

SiO2 5263 5113 5579 5134TiO2 097 088 112 089Al2O3 1708 1623 1761 1628Fe2O3 673 676 636 678MnO 007 014 008 011MgO 478 695 164 593CaO 416 544 38 725Na2O 594 32 533 377K2O 104 469 424 244P2O5 051 036 044 041LOI 606 41 37 565

Total 9997 9988 10011 10085

Pb 7 24 21 22Rb 38 115 119 83Cs 21 2 33 48Ba 541 1810 1418 1242Sr 552 1378 939 1086Ta 1 15 14 15Nb 196 233 223 229Hf 62 59 6 61Zr 245 239 233 242Y 28 26 24 25Th 295 272 274 252U 69 61 65 51La 1252 757 72 745Ce 2202 1347 1284 1365Pr 2145 1369 1283 1349Nd 812 536 515 534Sm 123 82 84 84Eu 324 205 187 197Gd 843 668 626 656Tb 099 084 08 078Dy 527 484 461 439Ho 09 091 083 079Er 243 251 231 248Tm 039 039 033 039Yb 255 232 233 235Lu 038 04 037 04187Sr86Sr ndash ndash 0707582plusmn6 ndash143Nd144Nd ndash ndash 0512355plusmn4 ndash206Pb204Pb ndash ndash 18879plusmn0009 ndash207Pb204Pb ndash ndash 15716plusmn001 ndash208Pb204Pb ndash ndash 39157plusmn003 ndash

1Major and trace elements are given in weight percent (wt) and parts per million (ppm) respectively tFe2O3 = total iron oxide as ferric iron LOI = loss in ignition

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1031

Rb and Cs (Fig 7A) which seems to be consistentwith the crustal contribution during magma genesisThe depletions of HFSE expressed by a large Nb-Tatrough and an apparent negative Pb anomaly inFigure 7 are interpreted as resembling those ofocean-island and mid-ocean ridge basalts asdescribed by Hoffmann (1986 1988) A chon-drite-normalized REE spider diagram (Fig 7B) witha slight enrichment of LREE reveals an intimatekinship between these different rock types of theUlukiordmla Formation that are subparallel to eachother The absence of a negative Eu anomalyindicates that plagioclase fractionation has notplayed an important role during the evolution of themagma source

Variation diagrams between HFSE and LREEwere used in order to assess genetic considerationsas described by Hoffmann et al (1986) and Fitton etal (1998) For example a small variation in (LaSm)N versus ThNb ratios (Fig 8) shows that there isno relationship between Th and the degree of LREEenrichment The positive correlation between BaNbratios and those of LaNb and BaLa (Fig 9) andalso high BaNb ratios ranging from 54 to 240 areconsidered most similar to those of subduction zonevolcanic rocks (BaNb gt 28 Fitton et al 1998)

rather than those of MORB and OIB sources CePband NbU ratios of the Ulukiordmla volcanic rocks arelower than those of typical oceanic island basalts(CePb = 25 + 5 NbU = 47 + 10 Hoffmann et al1986) and more closely resemble those of typicalcontinental crust High variability in the CePb val-ues may have been caused by the mobility of Pb dur-ing hydrothermal alteration processes All thesamples have high LREEHFSE ratios (LaTa gt 50LaNb gt 3 LaNSmN gt 4) yielding some character-istic Ta and Nb troughs on chondrite-normalizedspider diagrams (Figs 7 and 9)

Pb-Sr-Nd Isotope Geochemistry

Volcanic rocks of the Ulukiordmla Formation from theCcedilamard-Ulukiordmla Basin show little scatter in their143Nd144Nd 87Sr86Sr and Pb isotope ratios (seeTable 1) Inital epsilon Nd values (calculated at 60Ma) range from ndash41 to ndash55 clearly indicating theenriched nature of the source of these volcanic rocksTCHUR ages are between 042 and 057 Ga and TDMages correspondingly vary between 101 and 123Ga This range might be representative of the age ofthe mantle source from which these volcanic rockswere derived 87Sr86Sr inital ratios vary between

FIG 3 Total alkali vs silica diagram (LeMaitre et al 1989) of the volcanic rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin Dashed line dividing the alkaline and subalkaline fields is after Irvine and Baragar (1971)Abbreviations T-B = trachybasalt B-TA = basaltic trachyandesite

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1032 ALPASLAN ET AL

070704 and 070740 and also require the contribu-tion of a radiogenic Sr component in the source Pbisotopes are characterized by 206Pb204Pb composi-tions between 18803 and 18927 with correspond-ingly very high 207204Pb ratios of 15716 to 15787and elevated 208Pb204Pb ratios between 38938 and39454 These Pb isotope data are indicative of anold continental crustal-type Pb signature in thesource region of the volcanic rocks Crustal materialcould have been assimilated during ascent of themelts through thick crustal piles or could have beenmixed with the source by previous subduction pro-cesses Nd mantle model ages might thereby delin-eate the approximate age (~1 Ga) of this componentin the source In Nd-Sr isotopic space volcanic rocks

of the Ulukiordmla Formation lie beneath (ie at lowerepsilon Nd values than) the EMII OIB end memberof Zindler and Hart (1986) in Figure 10 The lowerepsilon Nd values at given 87Sr86Sr in these volcanicrocks reflect an old continental crustal componentmixed in their source as expected in the light of theintraplate setting of the basin In Sr-Pb isotopespace the Ulukiordmla volcanic rocks plot in the EMIIfield in Figure 11 Looking at Pb only the data pointslie above the Northern Hemisphere Reference Line(NHRL) of Hart (1984) in Figure 12A and exhibithigher 207Pb204Pb ratios relative to the field of EMII(White 1985 Zindler and Hart 1986) Theirdistinct position above the average continentalcrustal growth curve of Stacey and Kramers (1975)

FIG 4 Major-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1033

implies separation of a high-mu (ie high UPb)source from average continental crust sometime inthe past Without further information it is difficult to

elaborate on the exact time when such a separationmight have taken place but because of the ~1 Ga Ndmodel ages it is likely that this event took place in

FIG 5 Trace-element variation diagrams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin using Zras differentiation index

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1034 ALPASLAN ET AL

the Late Proterozoic In the thorogenic-uranogenicdiagram the 208Pb204Pb compositions lie close tothe field of typical EMII sources (Fig 12B)

Discussion

In the following section we discuss thegeochemical data in the context of source character-

FIG 6 Zr vs ZrY discrimination diagram (Pearce andNorry 1979) of rocks of the Ulukiordmla volcanics from theCcedilamard-Ulukiordmla basin

FIG 7 REE spider diagrams of rocks of the Ulukiordmla vol-canics from the Ccedilamard-Ulukiordmla Basin A Chondrite-normal-ized multi-element (normalized values from Sun andMcDunough 1989) B Chondrite-normalized (normalized val-ues from Taylor and McLennan 1985)

FIG 8 (LaSm)N vs ThNb diagram of rocks of theUlukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin

FIG 9 BaNb vs LaNb (A) and BaNb vs BaLa (B) dia-grams of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla basin MORB and OIB fields after Sun andMcDunough (1989)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1035

istics and compare the subductional signature withresults obtained from other similar basins in Turkey

Source enrichmentCoherent major- and trace-element fractionation

trends and subparallel REE patterns suggest that

the melts evolved by fractional crystallization fromoriginal melts produced by partial melting of themantle source Primitive mantlendashnormalizedelement patterns of the volcanic rocks of theUlukiordmla Formation have some distinctive featuresincluding HFSE depletions and Ba Th U and

FIG 10 Nd-Sr isotopic space of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oceanic basaltfields from White (1985) and end-members from Zindler and Hart (1986)

FIG 11 206Pb204Pb vs 87Sr86Sr diagram of rocks of the Ulukiordmla volcanics from the Ccedilamard-Ulukiordmla Basin Oce-anic basalt fields from White (1985) and end members from Zindler and Hart (1986)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1036 ALPASLAN ET AL

LREE enrichments all of which are known to bespecial geochemical characteristics of island-arcandor crust-contaminated volcanic rocks The pres-ence of a negative Ta-Nb anomaly in Figure 7A is atypical geochemical behavior that has beenobserved in island-arc volcanic rocks andor conti-nental crustndashcontaminated volcanic rocks (Wilson1989) Because the Ccedilamard-Ulukiordmla volcanics wereextruded through a thinned continental crust aspointed out by Boztug et al (2001) the possibility ofcrustal assimilation (consequently elevated 87Sr86Sr ratios enrichments in LILE and depletions inHFSE) has to be evaluated Magmas that have beenvariably contaminated en route through the conti-nental crust are expected to show strong correlations

between their isotopic compositions and potentialcontamination indices such as RbSr ratios and SiO2concentrations The almost flat trends seen in SiO2and RbSr versus 87Sr86Sr diagrams (Fig 13) do notsupport extensive crustal assimilation Overall itcan be concluded that some crustal assimilationmay have occurred but it was not the dominantprocess accounting for the trace-element signaturesexhibited by the volcanic rocks of the UlukiordmlaFormation

In addition the negative Pb anomalies are simi-lar to those of oceanic-island and mid-ocean ridgebasalts (eg Hoffmann 1986 1988) Extremeenrichments in Ba Th and U compared to K andRb are not characteristic of island-arc volcanism

FIG 12 206Pb204Pb versus 208Pb204Pb (A) and 206Pb204Pb versus 207Pb204Pb (B) diagrams of rocks of the Ulukiordmlavolcanics from the Ccedilamard -Ulukiordmla Basin Abbreviations NHRL = Northern Hemisphere Reference Line (Hart 1984)CIM = Central Indian MORB (Mahoney et al 1989) Field for the Pasific MORB is from White et al (1987) the approx-imate fields for DMM EMI and EMII are from Zindler and Hart (1986)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1037

and crustal-contaminated volcanics Elevated BaNb and LaNb ratios which are higher than those ofthe island-arc volcanics and continental crust andpositive anomalies for Ba Th and U require aprimary source enrichment in these elements andpoint to different degrees of involvement of a sub-duction component in the genesis of the Ulukiordmlavolcanics A subduction signature in the genesis ofthese volcanic rocks has already been documentedby Clark and Robertson (2002) A possible explana-tion for these extreme enrichments is a composi-tional modification of the mantle by previoussubduction events with the involvement of modernpelagic sediments that have equally high values ofBa Th and U (Tatsumi et al 1986) Alternativelyassimilation of continental-crustal componentsduring the ascent of the magmas can explain suchenrichments Incompatible element ratios such asZrNb (10ndash18) ThLa (~018ndash032) and RbNb(~36ndash1537) are different from those of primitivemantle MORB and OIB Former subduction eventsmight have caused a large-scale recycling ofsubducted slab material During such eventssediments rich in incompatible elements (LILE)and fluids may have been assimilated into the litho-spheric mantle

EMII source Several mantle sources are commonly discussed

in the framework of magma genesis These include adepleted low 87Sr86Sr low 206Pb204Pb component(DMM) a low 87Sr86Sr but a high 206Pb204Pb com-ponent (HIMU) and two enriched components(EM-I and EM-II) among which the EMI-source haslow 143Nd144Nd low 206204Pb but an intermediate87Sr86Sr whereas EM-II is characterized by a high206Pb204Pb a high 87Sr86Sr and an intermediate143Nd144Nd isotopic composition (Zindler and Hart1986 Hart et al 1986 Sun and McDonough1989) The enriched components are also character-ized by elevated LILE concentrations as suggestedby Zindler and Hart (1986) EM-I contains portionsof either recycled oceanic crust plus a few percentpelagic sediment or metasomatized subcontinentallithosphere (McKenzie and OrsquoNions 1983) whereasEM-II involves recycled oceanic crust with a fewpercent of continent-derived sediment (Zindler andHart 1986) EMndashend member source regions arealso proposed to have been affected by subsequentelement fractionation during subduction processesby Weaver et al (1986) Hoffmann (1989) andWeaver (1991)

On the other hand continental intraplate volca-nic rocks are known to be much more complicateddue mainly to contamination from lithosphericmantle through which the magma must pass Thestudy of such volcanic products has made it increas-ingly apparent that many continental lithosphericmantle sources are characterized by low 143Nd144Nd ratios and high 87Sr86Sr ratios as well as high207Pb204Pb (Hawkesworth et al 1993)

Volcanic rocks of the Ulukiordmla Formation possessthe negative epsilon Nd values and high 87Sr86Srratios that are the indicators of an enriched mantlesource (Fig 10) High 206Pb204Pb and 87Sr86Srratios seem to be very compatible with an EM-IImantle source (Fig 11) Plots of 208Pb204Pb vs206Pb204Pb (Fig 12A) and 206Pb204Pb vs 207Pb204Pb (Fig 12B) also discriminate an EM-II-typemantle source for these volcanic rocks in theCcedilamard -Ulukiordmla Basin The combination of trace-element signatures and isotopic data indicate thatthe volcanic rocks of the Ulukiordmla Formation werederived from a EM-II-type mantle source regionThis in turn seems to support a post-collisionalextension-related origin for material coming directlyfrom the upper mantle in space and time

FIG 13 87Sr86SrndashRbSr (A) and 87Sr86SrndashSiO2 diagramsof rocks of the Ulukiordmla volcanics from the Ccedilamard-UlukiordmlaBasin

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1038 ALPASLAN ET AL

Comparision of subduction signature of the Ccedilamard-Ulukiordmla Basin with other basins in Turkey

The basaltic to andesitic lavas mainly found inEarly Tertiary basins in various parts of Turkey iethe central and northeastern part of Turkey havebeen largely misinterpreted by earlier workers asbeing related to arc magmatism on the basis of theirgeochemical compositions (for example in the stud-ied area by Oktay 1982 and Goumlruumlr et al 1998 andin northeastern Turkey by Tokel 1977 Yilmaz1981 Ercan and Gedik 1983 Akin 1985 andRobinson et al 1985) However in both areasthese investigators noted that on the basis of struc-tural evidence subduction had ended substantiallybefore magmatism and that the igneous rocks couldnot be related to arc magmatism even though theyapparently show a subduction-type geochemical sig-nature This situation has been re-evaluated andcorrected by Yilmaz et al (1997) in northeasternTurkey where it was postulated that the subductionsignature was generated by an earlier subductionprocess that modified the composition of the uppermantle material That signature was then inheritedby the volcanic rocks of the Ccedilamard-Ulukiordmla basin

Studies of volcanic rocks from other Late Creta-ceous to Early Tertiary basins (ie the Yozgat andYildizeli basins) in Central Anatolia (Fig 1BErdogan et al 1996 Alpaslan and Temel 2000Alpaslan 2000) indicate that volcanic rocks have acalc-alkaline character and formed after the colli-sion between the Tauride-Anatolide Platform(Anatolian basement) and Eurasia (Pontide base-ment) These studies strongly suggest the presenceof interaction between mantle-derived melts andcontinental crust (Alpaslan and Temel 2000Alpaslan 2000) Less-enriched patterns in LILE ofthese volcanic rocks require that the melts origi-nated from different mantle sources compared tothose of the Ccedilamard-Ulukiordmla volcanics Lack ofcomplete trace-element geochemical data and ofisotopic data in general for volcanic rocks in theseother areas prevent detailed petrological character-ization and genetic modeling of the magmas in thesebasins Ongoing studies of the volcanic rocks in theHekimhan-Divrigi sub-basin of the Sivas Basin (Fig1B) reveal similarities to the Ccedilamard-UlukiordmlaBasin in terms of LILE and LREE enrichments andof the HFSE depletions that are characteristics ofsubduction signatures Therefore an enrichedmantle source modified by an earlier subductionevent seems to be the most likely explanation for the

genesis of the Ccedilamard-Ulukiordmla basin volcanic rocksbased on the geochemical and isotopic data of thisstudy

Concluding Remarks

1 The volcanic rocks of the Ulukiordmla Formationfrom the Ccedilamard-Ulukiordmla Basin have an alkalinecharacter with modal compositions ranging fromtrachybasalt to trachyandesite

2 Incompatible-element patterns of the thesevolcanic rocks exhibit pronounced depletions in NbTa and Ti and large enrichments in Ba Rb Th Uand K Furthermore light rare-earth elementconcentrations are higher than those of primitivemantle

3 Despite their within-plate tectonic settingthese volcanic rocks show a strong subduction-zonesignature manifested in a depletion of HFSE (egNb Ta Ti) Subduction processes that occurredprior to the Late Cretaceous possibly related to theclosure of the Neotethys (Dilek et al 1999) couldhave been the cause of these geochemical signaturesin the mantle Infiltration and interaction of risingsubduction zone fluidsmelts into the overlying sub-continental lithospheric mantle prior to rifting wereresponsible for enrichmentdepletion of certainincompatible elements in the studied volcanic rocksin the Ccedilamard -Ulukiordmla Basin

4 Pb Sr and Nd isotope geochemical data arecompatible with a mantle source for these volcanicrocks that is compatible with an EMII-like reservoirsuggesting assimilation and contamination of aprimitive mantle source by recycled oceanic crustcontaining a few percent of continent-derived (pos-sibly neo-Tethyan) sediments

5 The strong relative depletion of Nb and Ta thehigh 87Sr86Sr 208Pb204Pb and 207Pb204Pb and low143Nd144Nd isotopic signatures are all consistentwith a subcontinental lithospheric source This issupported by incompatible-element patterns of thevolcanic rocks of the Ulukiordmla Formation showingthat they were derived from subcontinental mantlelithosphere modified by previous subductionepisodes

6 Trace-element and isotope geochemical datareveal an apparent EM-II-type mantle source regionfor the genesis of the volcanic rocks of the UlukiordmlaFormation which supports a post-collisional exten-sion-related geodynamic setting as alreadyproposed by Clark and Robertson (2002)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1039

Acknowledgments

This paper is the part of a research projectgranted by the Scientific and Technical ResearchCouncil of Turkey (TUBITAK) under Project NoYDABCcedilAG-100Y010 Dr Greg B Arehart (Univer-sity Nevada-Reno) read and corrected the manu-script The authors also thank Prof Selim Inan(Mersin University) for assistance in field work

REFERENCES

Akin H 1978 Geologie Magmatismus und lagers-taettenbildung im ostpontischen Gebirge-Tuumlrkei ausder Sicht der Plattentektonik Geologische Rund-schau v 68 p 253ndash283

Alpaslan M 2000 Mineralogical-petrographical andgeochemical aspects of the Pazarcik volcanics (Yildi-zeli Sivas) Geological Bulletin of Turkey v 43 no 2p 49ndash60 [in Turkish with English abstract]

Alpaslan M Boztug D Uccedilurum A and Oumlzdemir Z2003 Petrology of the PaleocenendashEocene volcanics inthe Ccedilamard-Ulukiordmla Basin and Au-potential of thehydrothermal occurences Ankara Turkey Scientificand Technical Research Council of Turkey Projectnumber YDABCAG-100Y010 115 p (in Turkishunpubl report)

Alpaslan M and Temel A 2000 Petrographic andgeochemical evidence for magma mixing and crustalcontamination in the post-collisional calk-alkalineYozgat volcanics Central Anatolia Turkey Interna-tional Geology Review v 42 p 850ndash863

Baordm H Ayhan A and Atabey E 1986 Some petrologi-cal and geochemical features of the Ulukiordmla-Ccedilamard(Nigde) volcanics Geological Engineering 26 27ndash34(in Turkish with English abstract)

Blumenthal M 1956 Geology of the northern part andwestern extensions of the high Bolkardag MineralResearch and Exploration Institute of Turkey (MTA)publication Vol D Geological map series no 7

Bozkurt E 2001 Neotectonics of Turkeymdasha synthesisGeodinamica Acta v 14 p 3ndash30

Boztug D 2000 S-I-Andashtype intrusive associations Geo-dynamic significance of synchronism between meta-morphism and magmatism in Central Anatolia TurkeyGeological Society of London Special Publication173 p 407ndash424

Boztug D Ccedilevikbaordm A Demirkol C and Oumlztunali Ouml2001 The co-existence of the crustal thickening andthinning related plutons in the Middle Taurus Moun-tains Turkey [abs] in 4th International Turkish Geol-ogy Symposium (ITGS-IV) 24ndash28 September 2001Ccedilukurova University Adana-Turkey Abstracts p207

Boztug D Jonckheere R Wagner G A and YegingilZ 2004 Slow Senonian and fast PaleocenendashLower

Eocene uplift of the granitoids in the Central EasternPontides Turkey Apatite fission-track results Tec-tonophysics v 382 p 213ndash228

Boztug D Kuordmccedilu I Erccedilin A I and Avci N 2003 Min-eral deposits associated with the pre- syn- andpost-collisional granitoids of the Neo-Tethyan conver-gence system between the Eurasian and Anatolianplates in NE and Central Turkey in Eliopoulops D etal eds Mineral exploration and sustainable develop-ment Rotterdam Netherlands Millpress p 1141ndash1144

Clark M and Robertson A 2001 Tectonic implicationsof sedimentation and volcanism in the Lower TertiaryUlukiordmla Basin south central Turkey in EUG-XI Inte-grated tectonic studies of the evolution of the Tethyanorogenic belt in the eastern Mediterranean regionStrasbourg France Terra Abstracts p 318

Clark M and Robertson A 2002 The role of the EarlyTertiary Ulukiordmla Basin southern Turkey in suturingof the Mesozoic Tethys ocean Journal of the GeologicalSociety of London v 159 p 673ndash690

Ccedilemen I Goumlncuumloglu M C and Dirik K 1999 Struc-tural evolution of the Tuzgoumlluuml basin in central Anato-lia Turkey Journal of Geology v 107 p 693ndash706

Dellaloglu A A and Aksu R 1986 Geology and petro-leum possibilities of the Ereglki-Konya-Ulukiordmla-Ccediliftehan-Ccedilamard (Nigde) surroundings Ankara Tur-key TPAO Report no 2205 (in Turkish unpubl)

Demirtasli E Bilgin A Z Erenler W Iordmiklar S SanliD Y Selim M and Turhan N 1975 Geology of theBolkar Mountains in Alpan S ed Congress of EarthSciences 50th Year of the Republic Ankara TurkeyMineral Research and Exploration Institute of Turkey(MTA) Special Publication 42 p 57

Demirtaordmli E Turhan N Bilgin A Z and Selim M1984 Geology of the Bolkar Maountains in Tekeli Oand Goumlncuumloglu M C eds Geology of the Taurusbelt Proceedings of the International Symposium onthe Geology of the Taurus Belt Ankara Turkey Min-eral Research and Exploration Institute of Turkey p125ndash141

Dilek Y Thy P Hacker B and Grundvig S 1999Structure and petrology of Tauride ophiolites andmafic dyke intrusions (Turkey) Implications for theNeotethyan ocean Geological Society of America Bul-letin v 111 p 1192ndash1216

Dirik K Goumlncuumloglu M C and Kozlu H 1999 Stratig-raphy and pre-Miocene tectonic evolution of the south-western part of the Sivas basin Central AnatoliaTurkey Geological Journal v 34 p 303ndash319

Duumlzgoumlren-Aydin N Malpas W Goumlncuumloglu M C andErler A 2001 Post collisional magmatism in CentralAnatolia Turkey Field petrographic and geochemi-cal constraints International Geology Review v 43 p695ndash710

Ercan T and Gedik A 1983 Volcanism in the PontidesGeological Engineering v 18 p 3ndash22 (in Turkish)

1040 ALPASLAN ET AL

Erdogan B Akay E and ordfirin Ugur M 1996 Geologyof the Yozgat region and evolution of the collisionalCcedilankiri Basin International Geology Review v 38 p788ndash806

Fitton J G Hardarson B S Elam R M and RofersG 1998 Sr- Nd- and Pb-isotopic compositions ofvolcanic rocks from the southeast Greenland margin at63degN Temporal variation in crustal contaminationduring continental breakup in Saunders A DLarsen H C and Wise S W eds Proceedings of theOcean Drilling Program Scientific Results v 152 p351ndash357

Goumlncuumloglu M C 1986 Geochronological data from thesouthern part (Nigde area) of the Central Anatolianmassif Mineral Research and Exploration Institute ofTurkey (MTA) Bulletin v 105106 p 111ndash124

Goumlncuumloglu M C Erler A Toprak V Olgun E YalinizK Kuordmccedilu I Koumlksal S and Dirik K 1993 Geologyof the central part of the Central Anatolian massif PartIII Geological evolution of the Tertiary Basin of thecentral Kizilirmak Ankara Turkey Turkish PetroleumCompany Report no 3313 (in Turkish unpubl)

Goumlncuumloglu M C Erler A Toprak V Yaliniz K OlgunE and Rojay B 1992 Geology of the western part ofthe Central Anatolian Masif Part II Central partAnkara Turkey Turkish Petroleum Company Reportno 3155 (in Turkish unpubl)

Goumlncuumloglu M C Dirik K Olgun E Kuordmccedilu I andKozlu H 1995 Evolution of the central KizilirmakBasin A prototype of Tertiary basins in Central Anato-lia 8th Meeting European Union of GeosciencesTerra Abstracts p 192

Goumlncuumloglu M C Toprak G M V Kuordmccedilu I Erler Aand Olgun E 1991 Geology of the western part of theCentral Anatolian Massif Part 1 Southern partAnkara Turkey METU-TPAO Project Report 140 p(in Turkish unpubl)

Goumlruumlr N Oktay F Y Seymen I and ordfengoumlr A M C1984 Paleotectonic evolution of the Tuzgoumlluuml Basincomplex central Turkey Sedimentary record of aNeotethyan closure in Dixon J E and RobertsonA H F eds The geological evolution of the EasternMediterranean Geological Society of London SpecialPublication 17 467ndash482

Goumlruumlr N and Tuumlysuumlz O 2001 Cretaceous to Miocenepalaeogeographic evolution of Turkey Implications forhydrocarbon potential Journal of Petroleum Geologyv 24 p 119ndash146

Goumlruumlr N Tuumlysuumlz O and ordfengoumlr A M C 1998 Tec-tonic evolution of the Central Anatolian basins Inter-national Geology Review v 40 p 831ndash850

Hart S 1984 A large scale isotopic anomaly in theSouthern Hemisphere mantle Nature v 47 p 753ndash757

Hart S R Gerlach D C and White W M 1986 Apossible new Sr-Nd-Pb mantle array and conse-

quences for mantle mixing Geochimica et Cosmo-chimica Acta v 50 p 1551ndash1557

Hawkesworth C J Gallagher K Hergt J M andMcDermott F 1993 Mantle and slab contributions inarc magmas Annual Review of Earth Science v 21 p175ndash204

Hoffmann A W 1986 Nb in Hawaiian magmas Con-straints on source composition and evolution Chemi-cal Geology v 57 p 17ndash30

Hoffmann A W 1988 Chemical differentiation of theEarth The relationship between mantle continentalcrust and the oceanic crust Earth and Planetary Sci-ence Letters v 90 p 297ndash314

Hoffmann A W 1989 Geochemistry and models of man-tle circulation Philosophical Transactions of the RoyalSociety of London A v 328 p 425ndash439

Hoffmann AW Jochum KP Seufert M and WhiteW M 1986 Nb and Pb in oceanic basalts New con-straints on mantle evolution Earth and Planetary Sci-ence Letters v 90 p 421ndash436

Ilbeyli N Pearce J A Thirlwall M F and MitchellJ G 2004 Petrogenesis of collision-related plutonicsin Central Anatolia Turkey Lithos (in press)

Irvine T N and Baragar W R A 1971 A guide to thegeochemical classification of the common volcanicrocks Canadian Journal of Earth Science v 8 p 523ndash548

Iordmler F 1988 Mineralogical-petrographical andgeochemical investigation of Ccediliftehan (Nigde) volca-nics Earth SciencesndashGeosound v 26 p 47ndash56 (inTurkish with English abstract)

Jaffey N and Robertson A H F 2001 New sedimento-logical and structural data from the Ecemiordm fault zoneImplications for its timing and offset and the Cenozoictectonic escape of Anatolia Journal of the GeologicalSociety of London v 158 p 367ndash378

Koccedilyigit A and Beyhan A 1998 A new intracontinen-tal transcurrent structure The central Anatolian faultzone Turkey Tectonophysics v 284 p 317ndash336

Koumlksal S Goumlncuumloglu M C and Floyd P A 2001Extrusive members of postcollisional A-type magma-tism in Central Anatolia Karahidir volcanics IdiordmDagindashAvanos area Turkey International GeologyReview v 43 p 683ndash694

Le Maitre R W 1989 A classification of igneous rocksand glossary of terms Oxford UK Blackwell Scien-tific 193 p

Lytwyn J N and Casey J F 1995 The geochemistry ofpost-kinetamic dyke swarms and subophiolitic metab-asites Pozant-Karsant ophiolite Turkeymdashevidencefor ridge subduction Geological Society of AmericaBulletin v 107 p 830ndash850

Mahoney J J Natland J H White W M Poreda RBloomer S H Fisher R L and Baxter A N 1989Isotopic and geochemical provinces of western IndianOcean spreading Journal of Geophysical Research v94 p 4033ndash4052

LATE CRETACEOUS TO EARLY TERTIARY VOLCANISM 1041

McKenzie D and OrsquoNions R K 1983 Mantle reser-voirs and oceanic island basalts Nature v 301 p229ndash231

Nazik A 1989 Stratigraphical interpretation of TertiaryUlukiordmla sequence in foraminifera and ostracod fau-nas Bulletin of the Turkish Geological Society v 32nos 1ndash2 p 89ndash95 (in Turkish with English abstract)

Okay A and ordfahintuumlrk Ouml 1997 Geology of the EasternPontides in Robinson A G ed Regional and petro-leum geology of the Black Sea and surrounding regionAmerican Association of Petroleum Geologists Mem-oir no 68 p 291ndash311

Oktay F Y 1973 Sedimentary and tectonic history of theUlukiordmla area southern Turkey Unpubl PhD thesisUniversity of London

Oktay F Y 1982 Stratigraphy and geological history ofthe Ulukiordmla and its surroundings Bulletin of the Turk-ish Geological Society v 25 p 13ndash23 (in Turkish withEnglish abstract)

Oumlzguumll N 1976 Some geological properties of the Tau-rides Geological Society of Turkey Bulletin v 19 p845ndash862 (in Turkish with English abstract)

Pearce J A and Norry M J 1979 Petrogenetic impli-cations of Ti Zr Y and Nb variation in volcanic rocksContributions to Mineralogy and Petrology v 69 p33ndash47

Poisson A Guezou J C Oumlztuumlrk A Inan S Temiz HKavak K ordf and Oumlzden S 1996 Tectonic settingand evolution of the Sivas Basin Central AnatoliaTurkey International Geology Review v 38 p 838ndash853

Robinson A G Banks C J Rutherford M M andHirst J P P 1995 Stratigraphic and structural devel-opment of the Eastern Pontides Turkey Journal of theGeological Society of London v 152 p 861ndash872

Stacey J S and Kramers J D 1975 Approximation ofterrestrial lead isotope evolution by a two-stage modelEarth and Planetary Science Letters v 26 p 207ndash221

Sun S S and McDunough W F 1989 Chemical andisotopic systematics of oceanic basalts Implicationsfor mantle composition and processes in SaundersA D and Norry M J eds Magmatism in the oceanbasins Geological Society of London Special Publica-tion 42 p 313ndash345

ordfengoumlr A M C and Natlrsquoin B A 1986 Paleotectonicsof Asia Fragments of a synthesis in Yin A and Har-rison M eds The tectonic evolution of Asia Cam-bridge UK Cambridge University Press p 443ndash486

ordfengoumlr A M C and Yilmaz Y 1981 Tethyan evolutionof Turkey A plate tectonic approach Tectonophysicsv 75 p 181ndash241

Tatsumi Y Hamilton D L and Nesbitt R W 1986Chemical characteristics of fluid phase released from asubducted lithosphere and origin of arc magmas Evi-dence from high pressure experiments and naturalrocks Journal of Volcanology and GeothermalResearch v 29 p 293ndash309

Taylor S R and McLennan S M 1985 The continentalcrust Its composition and evolution Oxford UKBlackwell

Todt W Cliff R A Hanser A and Hoffmann A W1993 Re-calibration of NBS lead standards using a202Pb + Pb double spike [abs] Terra Abstracts v 5 p396

Tokel S 1977 Eocene calc-alkaline andesites and geo-tectonism in the Eastern Black Sea region GeologicalBulletin of Turkey v 20 p 49ndash54 (in Turkish)

Weaver B L 1991 The origin of ocean island basaltend-member compositions Trace element and isotopicconstraints Earth and Planetary Science Letters v204 p 381ndash397

Weaver B L Wood D A Tarney J and Joron J L1986 Role of subducted sediment in the genesis ofoceanic island basalts Geochemical evidence fromSouth Atlantic Ocean Islands Geology v 14 p 275ndash278

White W M 1985 Sources of oceanic basalts Radio-genic isotopic evidence Geology v 13 p 115ndash118

White W M Hoffmann A W and Puchelt H 1987Isotope geochemistry of Pacific mid-ocean ridgebasalt Journal of Geophysical Research v 92 p4881ndash4893

Wilson M 1989 Igneous petrogenesis London UKUnwin Hyman 466 p

Yetiordm C 1984 New observations on the age of the Ecemiordmfault in Tekeli O and Goncuoglu M C eds Geol-ogy of the Taurus Belt in Proceedings of the Interna-tional Tauride Symposium Ankara Turkey MineralResearch and Exploration Institute of Turkey (MTA)p 159ndash164

Yilmaz Y 1981 Tectonic evolution of the western marginof the Sakarya continent IU Earth Science v 1 nos1ndash2 p 33ndash52

Yilmaz Y Tuumlysuumlz O Yigitbaordm E Genccedil S C andordfengoumlr A M C 1997 Geology and tectonic evolutionof the Pontides in Robertson A G ed Regional andpetroleum geology of the Black Sea and surroundingregion American Association of Petroleum GeologistsMemoirs v 68 p 183ndash226

Zindler A and Hart S 1986 Chemical geodynamicsAnnual Review of Earth and Planetary Science v 14p 493ndash571