Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area: Mt....

eschweizerbartxxx_ingenta

Early activity of the largest Cenozoic shield volcano in the

circum-Mediterranean area: Mt. Karacadag, SE Turkey

MICHELE LUSTRINO1,2,*, MEHMET KESKIN3, MICHELE MATTIOLI4, VLADIMIR A. LEBEDEV5, ANDREY CHUGAEV5,

EVGENII SHARKOV5 and ORHAN KAVAK6

1 Dipartimento di Scienze della Terra, Universita degli Studi di Roma La Sapienza, P.le A. Moro, 5, 00185 Roma, Italy2 CNR – Istituto di Geologia Ambientale e Geoingegneria (IGAG), c/o Dipartimento di Scienze della Terra, Universita

degli Studi di Roma La Sapienza, P.le A. Moro, 5, 00185 Roma, Italy*Corresponding author, e-mail: [email protected]

3 Department of Geological Engineering, Faculty of Engineering, Istanbul University, 34320 Avcilar, Istanbul, Turkey4 Dipartimento di Scienze Geologiche, Tecnologie Chimiche e Ambientali, Universita degli Studi di Urbino

‘‘Carlo Bo’’ Urbino, Italy5 Institute of the Ore Deposits Geology, Petrology, Mineralogy and Geochemistry, Russian Academy of Sciences,

Moscow, Russia6 Department of Mining Engineering, Faculty of Engineering and Architecture, Dicle University, Diyarbakir, Turkey

Abstract: Volcanic activity at Mt. Karacadag, SE Turkey, developed between �11 and �0.01 Ma. In this paper we investigate theoldest products (older than 2.6 Ma) that created a large volcanic plateau and a N-S aligned volcanic edifice in the form of a shieldvolcano. These igneous rocks are mildly alkaline to transitional olivine-clinopyroxene phyric basalts with minor hawaiites, basanitesand very rare differentiated lithologies (mugearites and benmoreites). The poor correlation of major elements with MgO in these lavasis qualitatively consistent with polybaric depths of magma production, variable degrees of partial melting (from �2 to �10 %),heterogeneous mantle sources and differences in the fractionating crystal assemblage. Primitive mantle-normalized patterns resembletypical anorogenic magma compositions, with peaks at HFSE (Nb, Ta, Hf, Zr) and high HFSE/LILE ratios. REE contents arecompatible with derivation of the basanites from a mixed garnet-spinel facies peridotite after�2 % partial melting. Alkali basalts arecompatible with higher degrees of melting (between 5 and 10 %) from the same type of source. Initial 87Sr/86Sr ratios range from0.70349 to 0.70522 while those of 143Nd/144Nd range from 0.512853 to 0.512659. Early-stage lavas show higher 87Sr/86Sr and lower143Nd/144Nd compared to plateau-stage lavas. The Sr-Nd isotopic variations and their relation with major and trace elements cannotbe explained by AFC-like (Assimilation and Fractional Crystallization) processes involving average crustal lithologies. More likely,the Sr-Nd isotopic ratios are related to the existence of heterogeneous mantle sources with only minor involvement of AFC-likeprocesses.

The Cenozoic lavas in a 200� 800 km area between the Karasu Valley and the Syria-Iraq-Turkey border in south-eastern Anatoliaform a distinct igneous province which can be characterised on the basis of Sr-isotope signatures. The lithospheric mantle beneath thisarea is characterized by anomalously enriched 87Sr/86Sr compositions (up to 0.7055) as well as more isotopically depleted composi-tions (87Sr/86Sr down to 0.7030).

Key-words: Turkey, Anatolia, basalt, igneous petrology, isotope geochemistry, K/Ar dating.

1. Introduction

South-eastern Anatolia is a crucial area for examiningmutual interactions among the Eurasian, Tethyan andArabian plates (e.g., Sengor & Kidd, 1979; Sengor &Yilmaz, 1981; Sengor et al., 1985; Yilmaz, 1993; Oralet al., 1995; Westaway, 2003). There, a complex magmaticresponse occurred during northward subduction of theTethys oceanic lithosphere and Eurasia-Arabia collision.This collision, which began during the Early Miocene,

induced crustal thickening in the Eurasian plate (Deweyet al., 1986) and widespread magmatism on both Eurasianand Arabian plates (e.g., Pearce et al., 1990; Notsu et al.,1995; Ekici et al., 2007). Igneous activity in the Eurasianplate occurred from Oligo-Miocene to historical times (e.g.,Yilmaz, 1978, 1990) and was dominated by large stratovol-canoes and emission of predominantly calcalkaline-typeproducts (e.g., Pearce et al., 1990; Keskin et al., 1998;Yilmaz et al., 1998; Keskin, 2007, and references therein),with minor alkaline igneous rocks (e.g., Innocenti et al.,

0935-1221/10/0022-2024 $ 9.00DOI: 10.1127/0935-1221/2010/0022-2024 # 2010 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart

Eur. J. Mineral.

2010, 22, 343–362


1976, 1980; Pearce et al., 1990; Keskin et al., 1998; Yilmazet al., 1998; Alici et al., 2001; Alpaslan, 2007; Keskin, 2007;Kurt et al., 2008). On the Arabian plate (i.e., the foreland ofthe Tethyan subduction system), extensive volcanic activitydeveloped on a 35–40 km thick crust mostly during the LateMiocene to Quaternary, with the production of largeamounts of alkaline basic rocks (Pearce et al., 1990; Ercanet al., 1991; Notsu et al., 1995; Alici Sen et al., 2004).

Detailed geochemical data and petrological modelling onMt. Karacadag (also known as Karacalidag) are nearly absentin the scientific literature, despite the fact that it is the largestvolcano (�10,000 km2; about seven times the area occupiedby Mt. Etna, Sicily, Italy) of the circum-MediterraneanAnorogenic Cenozoic Igneous Province (Lustrino &Wilson, 2007). Many aspects have not been understood yet,such as the volume of melts produced, their chemical, miner-alogical and isotopic compositions and variations with time,the tectonic setting of emplacement, the volume and compo-sition of the mantle sources, the relationship with crustallithologies, and the possible derivation from a common man-tle reservoir in the form of sub-lithospheric mantle or evendeeper sources (e.g., mantle plume-related).

With the exception of a dozen whole-rock chemicalanalyses and a couple of Sr-Nd isotopic ratios, the chemi-cal composition of Mt. Karacadag is nearly unknown. Inthis paper we present new major- and trace-element plusSr-Nd isotope data, as well as K/Ar ages for the volcanicrocks from the early activity. Our aim is to better charac-terize this igneous district, and to find answers to as manyof the above questions as possible.

2. Geological setting

The collision of the Eurasian and Arabian plates during theCenozoic resulted in the formation of a complex suturezone along a �2500 km-long curved fold-and-thrust beltknown as the Bitlis-Zagros Belt (e.g., Sengor & Kidd,1979; Yilmaz, 1993; Westaway, 2003; Fig. 1a). TheTethyan Ocean, originally separating the two continentalmasses, was subducted underneath SE Anatolia and WIran, which acted as the hanging-wall (over-riding plate)of the subduction system. The collisional stage betweenEurasia and Arabia was diachronous in different sectors ofthe orogen and may have involved poorly constrainedoceanic and continental micro-plates in SE Anatolia andIran (e.g., Dercourt et al., 1986; Dewey et al., 1986;Stampfli, 2001; Robertson et al., 2006; Omrani et al.,2008, and references therein). In eastern Anatolia themain geological units are represented, from north to south,by the Rhodope-Pontide Arc, the East Anatolia accretionarycomplex and the Bitlis-Poturge massif, characterized bysouthward tectonic transport over the northern Arabian con-tinental margin (e.g., Sengor & Yilmaz, 1981; Yilmaz,1993). After the continent-continent collision, a wideorogen (typically more than 400 km wide; Sengor & Kidd,1979; Dewey et al., 1986) developed along the Eurasia-Arabia collision zone. A large plateau (�90,000 km2),

with a relatively flat topography, a slightly thickened crust(�40–50 km), a reduced lithospheric lid thickness (�0–30km thick lithospheric mantle) and an average elevationaround 1500–2000 m a.s.l., developed in eastern Anatolia(e.g., Al-Lazki et al., 2003; Sengor et al., 2003, 2008; Anguset al., 2006).

Before, during and after the collisional stage, long-last-ing igneous activity, with subduction-related geochemicalcharacteristics, developed over large areas on the over-riding plate (Eurasia; SE Anatolia and Iran; Keskin,2007, Omrani et al., 2008, and references therein).Neogene magmatism in Eastern Anatolia comprises vol-canic rocks characterized by complex temporal geochem-ical variations (e.g., Pearce et al., 1990; Keskin et al., 1998,2003, 2006, 2007; Sengor et al., 2008). In EasternAnatolia, the oldest activity (mostly Late Miocene ande-sites, dacites and rhyolites) shows subduction-related geo-chemical features (e.g., Innocenti et al., 1982; Keskinet al., 1998; Keskin, 2003, 2007; Sengor et al., 2008).Alkali-richer lithologies (hawaiites, alkali basalts, basa-nites, sodic trachytes and phonolites, in order of abun-dance) plus rare tholeiitic basalts and basaltic andesitesoccur sporadically (e.g., Innocenti et al., 1976, 1980;Pearce et al., 1990; Alici et al., 2001; Alpaslan, 2007;Kurt et al., 2008). Temporally, these rocks follow thesubduction-related magmatic activity and show anoro-genic geochemical characteristics. Subduction-relatedigneous activity in SE Anatolia is partially contempora-neous with the latest anorogenic-type magmatism.

Mt. Karacadag is probably the least investigated from thegeochemical and petrological point of view among the‘‘anorogenic’’ volcanoes. It sits over the sedimentary forma-tions of the Arabian foreland (i.e., Arabian autochthon), whichform a thick sedimentary succession ranging in age fromPrecambrian to Late Miocene. The basement of the Arabianforeland beneath the volcano is exposed close to the town ofDerik to the SE. It is represented by the Telbesmi formationwhich belongs to the Derik group and is thought to bePrecambrian in age (Ercan et al., 1991). The Telbesmi forma-tion consists of andesitic lavas and pyroclastics alternatingwith sandstones. The Derik group is overlain by the CambrianSadan, Koruk and Sosink formations which are dominated bydetrital and carbonate sediments (Bozdogan & Erten, 1990).The Cambrian basement is in turn unconformably overlainby Cretaceous carbonates of the Mardin group(Turonian–Campanian; Perincek, 1980) and then by clay-rich limestones of the Karabogaz formation. The LateMaastrichtian-Paleocene Germav formation conformablyoverlies this unit. All these sedimentary formations are cov-ered by Eocene to Early Miocene limestones of the Midyatformation (Perincek, 1980), exposed to the SE of the volcanoand in contact with the Karacadag lavas over great distances.

3. Volcanological background

The oldest volcanic rocks of Mt. Karacadag (Fig. 1b) aredated at �11 Ma (Haksal, 1981; Ercan et al., 1990), i.e.,

344 M. Lustrino, M. Keskin, M. Mattioli, V.A. Lebedev, A. Chugaev, E. Sharkov, O. Kavak


Fig. 1. (a) Main outcrops of Cenozoic igneous rocks in SE Anatolia and the northern Arabia plate, with the location of Karacadag volcano.NAFZ, North Anatolian Fault Zone; BSZ, Bitlis Suture Zone. (b) Chrono-diagram showing the distribution of Karacadag volcanic activityduring time. The reported K/Ar ages are the new data presented in this work. (c) Simplified map of Mt. Karacadag volcano showing thedistribution of products related to early and younger activities, the main faults and sample localities.

Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area 345


almost coeval with the initiation of collision-related vol-canism on the Erzurum-Kars Plateau in the north (Keskinet al., 1998; Keskin, 2003). The youngest products eruptedup to very recent times (,0.01 Ma; Ercan et al., 1991;Notsu et al., 1995; Bridgland et al., 2007). The volcanismstarted during the Late Miocene with pyroclastic eruptionsof basic composition, fed by the fissures that cut peneplain-like plains. The volcanic activity was later dominated bythe eruption of voluminous basic lavas that built the mainedifice of the volcano at �11 Ma, immediately after therapid uplift recorded in the SE Anatolia plateau (Keskin,2003, 2007; Faccenna et al., 2006). Volcanism followedthree stages, which are divided by two quiescent periodscharacterized by widespread continental sedimentarydeposits. Ercan et al. (1990) divided the volcanism intothree stages/groups: (1) the Siverek, (2) the Karacadag, and(3) the Ovabag groups. The�700 m thick Siverek group isthe most widespread one, forming a plateau from Siverekin the West, Cermik and Viransehir in the south toDiyarbakir city in the east (Fig. 1c). The Karacadaggroup represents the main edifice of the mountain thatsits almost in the middle of the previously formed lavaplateau. It has a N-S elongated elliptical shape with numer-ous small scoria and spatter cones at the summit (Fig. 1c).Lavas of the Ovabag group, representing the last stage ofvolcanism, are exposed on the eastern flanks of the volcanoand easily recognized by their very dark, vegetation-freeappearance and still identifiable morphological features(e.g., aa and pahoehoe type flow surfaces, lava tunnels,etc.) akin to recent basaltic eruptions. Most of these havebeen derived from a number of small scoria cones locatedon the flank of the volcano. The present paper deals onlywith the early-activity volcanic rocks.

4. Analytical methods

Seventy-six samples (lavas and dykes) from the Karacadagvolcano (Fig. 1c) were investigated, and 62 chosen forwhole-rock analysis (Tables 1 and 2). Major-element ana-lyses were performed at the University of Rome LaSapienza by EMPA on glassy pearls produced by meltingof the rock powders at high T. The glassy pearls wereproduced as follows: a small amount of powder (,0.5 g)was left overnight in a furnace at 1000 �C until it wascompletely dry. Then a small fraction of it was put into ahole (5 mm in depth and 3.5 mm in diameter) drilled in avitreous carbon rod (length 5 cm, diameter 6 mm) with adiamond tip driller. This drilled rod was placed in contactwith another solid vitreous carbon rod. Electric power wasapplied at two ends and the resistance of the graphite rodsto the passage of electricity increased the temperature ofthe carbon rods and the powder. Temperature wasincreased up to�900–1000 �C within 1 and 2 min, whereasthe temperature peak (�1500 �C) was reached in tens ofseconds, in order to reduce alkali loss. The temperaturewas continuously checked with a thermocouple. The resultwas the formation of a small (�2–3 mm in diameter) glassy

pearl. The pearls were mounted in an epoxy resin andsubsequently cut and polished. After that, they were ana-lysed by a Cameca SX50 electron micro-probe at theUniversity of Rome La Sapienza (IGAG laboratory,CNR) under full WDS mode operated at 15 kV accelerat-ing voltage and 30 nA beam current. Counting time was100 s. To reduce alkali loss during glass analysis, thecounting time was decreased to 20 s and the beam wasdefocused to 15 mm. ZAF correction was applied to alldata. Every analysis is the average of 4–7 measurements.Weight loss on ignition (LOI) was determined by standardgravimetric techniques, after igniting the powder at�1100�C for 5 h. Seven international rock standards ranging incomposition from basaltic to rhyolitic (i.e., SGD1A,ST1A, BR, AGV, QLO-1, BCR-1, BHVO1) were analysedtogether with the samples. Analytical results of the stan-dard materials revealed that the relative error, compared tothe expected results, is generally lower than 3–4 %. Theresults on the international standard are listed in Table 2.

Trace-element contents (including REE) of a subset ofrepresentative whole-rock samples were analysed by an ICP-MS at Actlabs, Ancaster, Ontario, Canada (www.actlabs.com)on a different aliquot of the same powder. Precision, accuracyand detection limits are reported in Table 3 together with twointernational rock standards (DNC-1 and BIR-1).

Sr and Nd isotopic compositions of selected sampleswere measured on groundmass aliquots with a MicromassSector 54 thermo-ionization multicollector mass spectro-meter at the Institute of the Ore Deposits Geology,Petrology, Mineralogy and Geochemistry, RussianAcademy of Sciences (IGEM RAS), Moscow. The87Sr/86Sr and 143Nd/144Nd were normalized to 86Sr/88Sr¼ 0.1194 and 146Nd/144Nd ¼ 0.7219, respectively. The2s errors of the results were ,0.003 % for Sr and,0.002 % for Nd. The accuracy of the measurementswas monitored by the systematic analyses of Sr and Ndisotopic standards (SRM-987 and La Jolla, respectively).The 87Sr/86Sr of the NIST-SRM987 and 143Nd/144Nd ofthe La Jolla-standard throughout this study were 0.710246� 0.000016 (�2s, n¼ 12) and 0.51185� 0.00001 (�2s, n¼ 10), respectively. Elements for mass spectrometric ana-lysis were extracted by ion-exchange chromatographictechniques.

K/Ar radiometric dating was determined on groundmassaliquots with a MI-1201 IG mass spectrometer at IGEMRAS, Moscow. The groundmass chips (0.10–0.25 mm sizefraction) were carefully checked under a binocularmicroscope and all the altered phases were handpickedand eliminated, producing a sample with a purity level.99.9 %. The chips were cleaned with distilled waterand dried at room temperature (in order to prevent Arloss). The determination of radiogenic argon was carriedout using the isotope dilution method with 38Ar as thespike. The potassium content was determined by theflame spectro-photometry method. For age calculationsthe following international constants were used: lK ¼0.581 � 10�10 yr�1, lb- ¼ 4.962 � 10�10 yr�1, 40K ¼0.01167 (at%). The uncertainties of K-Ar age are given at�2 s level (Table 4).


http://www.actlabs.com


Table 1. Synoptic table summarizing the latitude and longitude coordinates, the altitude, the rock type (based on the TAS diagram), and themain petrographic features of the analysed Karacadag volcanic rocks.

Sample Stage

GPS

Altitude (m a.s.l.)Rock type

Texture Main Phenocrysts GroundmassLat. Long. (TAS)

3MO 44 E 54.5453 41.74983 964 Basalt (1) Ol (4), Pl þ Cpx þ Ol þ Opq3MO 48 E 54.8973 41.73996 1086 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 105 E 52.6736 41.69816 723 Basalt (1)–(2) Ol þ Cpx (5), Pl þ Cpx þ Ol þ Opq3MO 111 E 53.9872 41.33419 686 Basalt (1)–(2) Ol þ Cpx (4), Pl þ Ol þ Cpx þ Opq3MO 39 E 53.2713 41.78606 843 Basalt (1) Ol (5), Cpx þ Pl þ Ol þ Opq3MO 40 E 53.2937 41.77147 803 Basalt (1) Ol (5), Cpx þ Pl þ Ol þ Opq3MO 43 E 54.2598 41.74253 909 Basalt (1) Ol þ Pl (5), Cpx þ Pl þ Ol þ Opq3MO 53 E 55.6290 41.76870 1110 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 104 E 52.8611 41.76075 747 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 106 E 52.9121 41.63567 750 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 109 E 53.1077 41.50554 760 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 141 E 52.0720 41.68945 698 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 142 E 51.4711 41.64659 615 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 41 E 53.6160 41.76070 837 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 47 E 54.7147 41.7512 1061 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 85 E 56.1196 41.63957 1113 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 134 E 53.5468 42.11832 715 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 135 E 53.3316 42.06488 901 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 138 E 52.5212 41.88135 808 Basalt (1) Ol þ Pl (4), Pl þ Cpx þ Ol þ Opq3MO 139 E 52.7384 41.81653 778 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 143 E 50.7946 41.62664 611 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 52 E 55.3951 41.75344 1054 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 136 E 52.7363 42.01201 908 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 80 E 55.7450 41.72146 1088 Basalt (1)–(2) Ol þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 59 E 59.9677 41.80356 826 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 33 E 55.0363 41.83670 1180 Basanite (1) Ol þ Pl (4), Pl þ Cpx þ Ol þ Opq3MO 84 E 55.5461 41.53100 935 Basanite (1) Ol þ Pl (5), Pl þ Ol þ Cpx þ Opq3MO 32 E 55.2534 41.84543 1185 Hawaiite (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 35 E 54.8336 41.82643 1143 Hawaiite (5) Ol (4), Pl þ Cpx þ Opq3MO 36 E 54.3421 41.81912 1077 Hawaiite (1)–(2) Ol þ Cpx (4), Pl þ Cpx þ Opq3MO 37 E 53.7418 41.80039 951 Hawaiite (1)–(2) Ol þ Cpx (4), Pl þ Cpx þ Opq3MO 107 E 52.9845 41.62029 731 Hawaiite (1)–(2) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 38 E 53.7418 41.80039 951 Hawaiite (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 54 E 55.6754 41.75184 1095 Hawaiite (1)–(2) Ol þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 34 E 54.8336 41.82643 1143 Mugearite (1) Ol þ Pl (4), Cpx þ Ol þ Opq3MO 42 E 54.0551 41.74877 857 Benmoreite (5) Pl þ Ol (4), Cpx þ Ol þ Opq3MO 131 P 58.9978 42.16345 751 Basalt (1)–(2) Ol þ Cpx (4), Pl þ Ol þ Cpx þ Opq3MO 146 P 60.8684 41.94247 628 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 147 P 60.8492 41.95993 627 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 102 P 58.7156 41.86376 911 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 2 P 58.8479 41.94294 840 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 56 P 60.7536 41.91016 646 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 58 P 60.8238 41.84929 719 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 114 P 55.9625 41.20592 562 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 103 P 59.2402 41.90526 783 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 113 P 55.3690 41.19998 559 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 124 P 58.9447 41.20364 475 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 125 P 59.7922 41.18960 474 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 129 P 59.6650 42.09054 737 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 150 P 62.0560 41.81854 689 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 3 P 58.5667 41.95117 856 Basalt (1) Ol (5), Pl þ Cpx þ Ol þ Opq3MO 115 P 56.5670 41.20357 539 Basalt (1)–(2) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 116 P 56.8025 41.27065 638 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 119 P 57.2007 41.43513 908 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 130 P 59.2749 42.13818 719 Basalt (1) Ol þ Pl (5), Pl þ Cpx þ Ol þ Opq3MO 133 P 58.1730 42.21933 775 Basalt (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Ol þ Cpx þ Opq3MO 126 P 60.8992 41.18002 466 Basanite (1)–(2) Ol þ Cpx þ Pl (4), Pl þ Opq3MO 4 P 58.0940 41.95489 855 Basanite (1) Ol (4), Pl þ Cpx þ Ol þ Opq



5. K/Ar dating

About 20 K-Ar and Ar-Ar ages for Karacadag lavas areavailable in the literature (Sanver, 1968; Haksal, 1981;Ercan et al., 1990, 1991; Pearce et al., 1990; Notsu et al.,1995; Bridgland et al., 2007; Westaway et al., 2009). Most ofthe dated samples belong to the youngest (Pleistocene) vol-canic phase. In this paper we present five new K-Ar ages forthe older volcanic units. Two samples (3MO-42 and 3MO-142) are approximately Late Miocene (6.68� 0.15 and 6.65� 0.35 Ma, respectively), two samples (3MO-103 and 3MO-114) are approximately Early Pliocene (3.87� 0.15 and 3.95� 0.15 Ma, respectively) and one sample gives a LatePliocene age (2.72� 0.15 Ma). On the basis of the publishedliterature and our new geochronological dating results (Table4) we argue that Karacadag volcanic activity can be dividedinto at least four main phases: (1) Middle-Late Miocene(�11–10 Ma; Haksal, 1981; Ercan et al., 1990), (2) LateMiocene (�6.7 Ma), (3) Pliocene (�3.9–2.7 Ma) and (4)Pleistocene (�1.9–0.1 Ma; Ercan et al., 1991; Fig. 1). Onthe basis of morphological features, the first three phases aregrouped in the early stage of volcanic activity.

6. Geochemistry

6.1. Major elements

Chemical analyses and CIPW norms of early Karacadagrocks are given in Table 2 (the complete set on analyses isreported as electronic supplementary material, freely availablefrom the gsw website of the journal, http://eurjmin.geoscien-ceworld.org//). Loss on ignition (LOI) is generally low (,2wt%); only in very few samples LOI reaches values up to 4.5wt%. On the basis of petrography and the total alkali vs. silicadiagram (Le Bas et al., 1986; Fig. 2 and 3), most of thevolcanic rocks of early Karacadag activity are basalts (�73% of the sample population), with minor hawaiites (�15 %)and basanites (�10 %). Only one sample plots in the andesitefield with 61.5 wt% SiO2 and one sample straddles thehawaiite-mugearite-phonotephrite field. The basaltic samplesstraddle the line dividing alkaline from subalkaline composi-tion. Their petrography is typical of alkaline melts (witholivine and clinopyroxene phenocrysts), but their CIPWnorms indicate both nepheline-normative composition

(nepheline content ranging from�17.0 to 0.14 %) and SiO2-saturation (hypersthene-olivine normative). With the excep-tion of the SiO2-rich sample, no quartz-normative composi-tions have been found.

Except for the benmoreite, all the studied rocks are highTiO2 (TiO2 �1.9–4.8 wt%), mildly alkaline-to-transitionalmafic rocks with SiO2 varying from �43.3 to �52.2 wt%.They display a clear sodic character with Na2O/K2O rangingfrom 2.1 to 6.0 (average 3.2). Their Mg# values [Mg#¼Mg/(Mgþ Fe2þ), assuming Fe2O3/FeO¼ 0.15] range from 0.46to 0.75 (average 0.57). The benmoreite shows lower TiO2 (1.2wt%), lower Mg# (0.19) and lower Na2O/K2O ratio (�0.60).

Major and trace element variation diagrams are shownin Fig. 4 and 5, with MgO as the differentiation index.Among major elements, only Al2O3 (�11.8–17.8 wt%)shows a good negative correlation with MgO (R2 ¼ 0.70;Fig. 4), whereas SiO2 shows a much less defined negativecorrelation (R2 ¼ 0.35). A slight and scattered increase inCaO (�3.2–13.2 wt%), FeOtot (�6.8–15.8 wt%) and TiO2

with increasing MgO can be observed (Fig. 4). K2O(�0.5–3.9 wt%), Na2O (�2.3–5.0 wt%) and P2O5

(�0.07–1.0 wt%) show no clear correlation with MgO.The absence of clear differentiation trends is a common

feature also observed in other mafic sodic alkaline andtholeiitic rocks in neighbouring and coeval provinces ofthe Arabian plate (i.e., Syria, Israel, Palestine and Jordan)and throughout the Anatolian plate (Fig. 4). Compared tothese ‘‘anorogenic’’ rocks, the Karacadag samples cannotbe distinguished by any peculiar feature.

6.2. Trace elements

Selected trace elements are listed in Table 3 and plottedagainst MgO in Fig. 5. As observed for major elements, theKaracadag mafic rocks plot in the field of the other maficalkaline ‘‘anorogenic’’ Neogene rocks from Mashrek(Syria, Jordan, Israel, Palestine, Lebanon, northern SaudiArabia) and Anatolia. No difference exists among themagmas emplaced in these two areas.

Among Large Ion Lithophile Elements (LILE), Rb(9–23 ppm), Sr (368–1000 ppm) and Ba (162–592 ppm)show no correlation with MgO. Benmoreite shows a muchhigher concentration of Rb (101 ppm), higher Ba (592ppm) and nearly similar Sr contents (430 ppm) comparedto the mafic rocks. An interesting feature emerges when

Table 1. Continued.

Sample Stage

GPS

Altitude (m a.s.l.)Rock type

Texture Main Phenocrysts GroundmassLat. Long. (TAS)

3MO 118 P 57.2055 41.43274 925 Basanite (1) Ol þ Cpx (4), Pl þ Opq3MO 110 P 53.8948 41.41225 711 Basanite (1)–(2) Ol þ Cpx (4), Cpx þ Ol þ Opq3MO 148 P 60.9152 41.97717 648 Hawaiite (3) Ol (4), Pl þ Cpx þ Opq3MO 1 P 58.8479 41.94294 840 Hawaiite (1)–(2) Ol (5), Pl þ Cpx þ Ol þ Opq

Notes: E, Early Stage; P, Plateau Stage; (1) porphyritic; (2) glomeroporphyritic; (3) sub-aphyric to vitrophiric; (4) hypocrystalline, fine tovery fine grained; (5) holocrystalline, intergranular to sub-ophitic; Ol, olivine; Cpx, clinopyroxene; Pl, plagioclase; Opq, opaque minerals.Samples in bold contain xenoliths and/or xenocrysts.


http://eurjmin.geoscienceworld.org//

http://eurjmin.geoscienceworld.org//


Table 2. Major element (wt%) content and CIPW norm of the most representative early activity volcanic rocks of Karacadag. The complete list of the analyses (62 samples) can be requestedfrom the first author or can be downloaded from the European Journal of Mineralogy web site. Mg# and CIPW norms calculated assuming Fe2O3/FeO ¼ 0.15.

Stage Plateau Plateau Plateau Plateau Plateau Early Early Early Early Early Early Early Early International rock standards

Sample 3MO103

3MO110

3MO 114 3MO119

3MO133

3MO 135 3MO142

3MO 32 3MO 34 3MO 40 3MO42

3MO 59 3MO 84 SGD-1a SGD-1a Error % ST-1a

Rock type Basalt Basanite Basalt Basalt Basalt Basalt Basalt Hawaiite Mugear Basalt Benmor Basalt Basanite meas.val.

cert. val. meas.val.

SiO2 46.9 44.3 46.6 48.0 50.9 52.2 48.5 51.0 49.4 46.6 61.5 48.4 43.3 48.1 47.1 2.0 50.62TiO2 2.26 3.54 2.71 3.28 2.74 2.23 2.40 2.42 3.58 1.88 1.18 2.99 4.76 1.69 1.74 -2.7 1.85Al2O3 12.5 11.8 12.6 15.4 16.1 15.3 13.6 15.5 17.0 14.3 17.8 16.5 14.3 15.42 15.1 2.0 14.58FeO(tot) 12.8 13.6 12.4 13.0 10.3 10.3 13.4 6.82 9.48 11.6 8.60 11.1 15.8 10.33 10.5 �1.5 13.59MnO 0.25 0.21 0.18 0.21 0.18 0.23 0.20 0.20 0.19 0.21 0.14 0.22 0.26 0.18 0.17 6.0 0.23MgO 11.8 9.62 11.4 5.50 5.44 6.81 8.13 9.90 5.86 9.06 1.03 5.79 6.94 6.83 7.11 �4.0 5.68CaO 9.62 9.38 10.2 10.1 9.02 8.47 9.52 9.03 7.02 13.2 3.16 9.96 10.5 10.33 11.1 �7.3 10.19Na2O 2.67 4.63 2.66 3.29 3.39 3.19 3.06 3.75 5.01 2.66 2.31 3.49 2.90 2.75 2.87 �4.2 2.44K2O 0.91 1.97 0.95 0.91 1.55 1.02 0.86 1.25 2.32 0.45 3.87 1.26 0.80 2.88 3.01 �4.3 0.67P2O5 0.36 0.98 0.35 0.36 0.42 0.23 0.35 0.07 0.15 0.16 0.52 0.28 0.40 0.95 1.03 �7.7 0.19L.O.I. 1.76 0.22 0.81 0.38 2.88 4.53 0.85 2.03 0.58 3.36 2.86 1.23 0.46Mg# 0.65 0.59 0.65 0.46 0.52 0.57 0.55 0.75 0.56 0.61 0.19 0.51 0.47

CIPW NormQ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00or 5.40 4.96 9.56 4.95 11.6 5.38 8.28 9.15 9.23 8.04 6.96 5.77 3.46ab 27.6 22.1 25.4 25.4 7.74 21.6 23.2 28.7 27.7 28.3 13.8 25.4 19.8an 24.6 24.5 19.8 26.8 5.69 27.2 19.9 24.2 23.4 15.8 13.3 25.4 25.3ne 0.14 2.44 4.40 0.00 17.0 0.00 4.09 0.00 0.00 1.04 9.51 0.00 3.58di 19.1 22.4 12.8 14.0 28.1 14.4 15.9 14.6 14.9 19.7 22.1 13.7 24.2hy 0.00 0.00 0.00 9.61 0.00 5.75 0.00 8.93 13.6 0.00 0.00 9.19 0.00ol 13.8 16.6 19.7 9.59 18.4 14.5 19.2 6.37 3.85 18.1 23.8 13.2 17.3mt 2.49 2.25 2.25 2.41 2.60 2.71 2.34 1.97 2.01 2.37 2.77 2.39 2.38il 6.23 4.41 4.95 6.45 6.73 7.37 5.82 5.21 4.49 5.21 6.18 4.29 3.67ap 0.85 0.44 1.42 0.94 2.32 1.34 1.45 0.99 0.94 1.64 1.78 0.90 0.48Sum 100.2 100.2 100.5 100.2 100.2 100.5 100.4 100.2 100.4 100.6 100.2 100.2 100.2

Sample ST-1a Error % BR BR Error % AGV AGV Error % QLO-1 QLO-1 Error % BCR-1 BCR-1 Error % BHVO1 BHVO1 Error%

Rock type cert. val. meas.val.



cert.val.

meas.val.


cert.val.

SiO2 49.9 1.5 41.10 40.0 2.6 60.17 60.1 0.2 67.67 66.2 2.2 56.83 54.3 4.6 50.70 49.7 2.1TiO2 1.88 �1.6 2.87 2.73 5.2 1.14 1.07 6.7 0.56 0.63 �10.1 2.29 2.25 1.9 2.78 2.70 3.1Al2O3 14.5 0.8 10.77 10.7 0.8 18.05 17.5 3.1 16.77 16.4 2.6 14.12 13.7 3.1 14.18 13.7 3.3FeO(tot) 13.7 �0.7 11.96 11.6 3.2 6.50 6.91 �5.9 3.69 4.39 �16.0 11.97 13.5 �11.1 10.99 12.2 �9.7MnO 0.21 7.8 0.24 0.24 �0.8 0.14 0.08 0.09 �11.9 0.18 0.19 �3.4 0.19 0.17 12.4MgO 5.83 �2.6 13.42 13.9 �3.6 1.55 1.56 -0.8 0.93 1.01 �7.9 3.39 3.57 �5.2 7.07 7.19 �1.7CaO 10.4 �1.7 14.24 14.5 �1.6 5.20 5.04 3.1 3.01 3.20 �5.9 6.99 7.15 �2.2 11.45 11.3 1.0Na2O 2.53 �3.5 3.12 3.20 �2.4 3.93 4.35 �9.6 3.81 4.24 �10.1 3.03 3.28 �7.7 2.23 2.25 �1.0K2O 0.71 �6.1 1.39 1.47 �5.2 2.92 2.98 �2.2 3.61 3.63 �0.7 1.67 1.71 �2.2 0.53 0.52 2.9P2O5 0.21 �10.9 0.99 1.09 �9.2 0.47 0.51 �7.9 0.21 0.25 �16.8 0.32 0.36 �11.5 0.25 0.27 �6.9

Notes: International rock standard EMP results are also shown: meas. val., measured value; cert. val., certified value.

Early

activity

of

the

largest

Cen

ozo

icsh

ieldv

olcan

oin

the

circum

-Med

iterranean

area3

49


Table 3. Trace element (ppm) content of selected samples from early Karacadag activity.

Sample 3MO 142 3MO 134 3MO 59 3MO 84 3MO 42 3MO 114 3MO 103 3MO 118 3MO 110 Det. Lim. Reference samples.

Rock type Basalt Basalt Basalt Basanite Benmor Basalt Basalt Basanite Basanite (ppm) DNC-1 DNC-1 BIR-1 BIR-1Stage Early Early Early Early Early Plateau Plateau Plateau Plateau meas. val. cert. val. meas. val. cert. val.Rb 22 15 16 9 101 11 12 10 23 2 4 4.5 ,2 0.25Sr 368 398 599 739 430 530 459 854 1000 2 146 145 111 108Ba 178 192 162 256 592 219 258 179 332 3 117 114 7 7V 216 216 267 263 22 259 235 239 214 5 150 148 311 313Cr 340 350 150 130 – 460 400 310 180 20 280 285 390 382Co 51 47 41 49 11 65 67 67 52 1 56 54.7 52 51.4Ni 170 150 110 100 – 260 300 270 160 20 250 247 170 166Y 22 25 24 21 37 19 20 20 26 1 18 18 16 16Zr 122 123 193 147 360 139 133 219 277 5 36 41 15 16Nb 19 17 29 32 54 28 26 48 90 1 2 3 ,1 0.6La 15.0 14.8 22.6 20.7 50.3 17.9 18.8 33.2 50.9 0.1 4.0 3.8 0.7 0.62Ce 34.3 31.5 50.1 46.3 104.0 40.6 41.6 71.2 103.0 0.1 8.6 10.6 2.2 1.95Pr 4.20 3.83 5.44 5.71 10.90 4.94 4.95 8.48 11.90 0.05 1.05 1.3 0.37 0.38Nd 16.9 16.1 22.9 23.1 41.5 19.2 19.7 32.9 43.5 0.1 5.0 4.9 2.5 2.5Sm 4.3 4.3 5.8 5.7 9.9 4.8 4.7 7.3 9.7 0.1 1.4 1.38 1.1 1.1Eu 1.53 1.57 2.01 2.07 2.71 1.74 1.68 2.53 3.22 0.05 0.61 0.59 0.54 0.54Gd 4.6 4.9 5.6 5.6 8.9 4.8 4.7 6.7 8.7 0.1 2.0 2 1.8 1.85Tb 0.7 0.8 0.9 0.8 1.4 0.7 0.7 0.9 1.2 0.1 0.4 0.41 0.4 0.36Dy 4.0 4.4 4.8 4.1 7.5 3.7 3.7 4.3 5.6 0.1 2.8 2.7 2.6 2.5Ho 0.7 0.9 0.9 0.7 1.3 0.7 0.7 0.7 0.9 0.1 0.6 0.62 0.6 0.57Er 2.1 2.3 2.3 1.9 3.6 1.7 1.8 1.7 2.2 0.1 2.0 2 1.8 1.7Tm 0.28 0.31 0.3 0.24 0.48 0.22 0.24 0.2 0.26 0.05 0.34 0.38 0.30 0.26Yb 1.6 1.9 1.8 1.4 2.9 1.3 1.4 1.1 1.4 0.1 1.9 2.01 1.6 1.65Lu 0.25 0.27 0.25 0.18 0.41 0.19 0.20 0.15 0.18 0.04 0.30 0.32 0.25 0.26Th 2.6 2.5 2.6 1.5 10.3 1.7 2.2 2.7 5.3 0.1 0.3 0.2 ,0.1 0.03U 0.7 0.6 0.9 0.4 2.8 0.5 0.7 1.1 1.7 0.1 ,0.1 0.1 ,0.1 0.01Hf 3.5 3.5 5.0 4.0 9.4 3.8 3.5 5.6 7.0 0.2 1.00 1.01 0.6 0.6Ta 1.0 0.9 1.6 1.7 3.2 1.5 1.4 2.5 4.8 0.1 ,0.1 0.098 ,0.1 0.04Ga 23 24 26 25 33 22 21 27 28 1 15 15 17 16Cs – – – – 1.8 – 0.8 – – 0.5 ,0.5 0.34 ,0.5 0.005Cu 90 70 60 80 10 80 80 100 70 10 110 96 140 126Zn 170 180 200 210 150 180 210 240 200 30 80 66 100 71

Note: meas. val., measured value; cert. val., certified value.

35

0M

.L

ustrin

o,

M.

Kesk

in,

M.

Mattio

li,V

.A.

Leb

edev

,A

.C

hu

gaev

,E

.S

hark

ov

,O

.K

avak


the mafic samples are divided into two main groups as theearly- and the plateau-forming stage volcanic rocks: withthe exception of sample 3MO-59, the plateau-forminglavas (4.0–2.7 Ma) show a clear negative correlationbetween Sr and MgO (R2 ¼ �0.92; Fig. 5) in contrast tothe mafic samples of the early stage (.6.6 Ma).

Among the transition elements, Cr (130–460 ppm), Co(41–67 ppm) and Ni (100–300 ppm) show a positive cor-relation with MgO (R2¼ 0.42, 0.96 and 0.86 respectively),indicating that removal of olivine and clinopyroxene wasan important process during fractional crystallisation,which is also consistent with the petrographic results(Fig. 3 and 5). V content is roughly constant in the maficrock group (214–267 ppm). The benmoreitic sample ischaracterized by its remarkably lower Co (11 ppm) and V(22 ppm) contents whereas Cr and Ni are below theirdetection limits. No substantial difference emergesamong the early-stage and the plateau-forming stage lavas.

Taken as a whole group, the mafic rocks of Karacadagshow no correlation between High Field Strength Elements(HFSE) such as Nb (17–90 ppm), Ta (0.9–4.8 ppm), Hf(3.5–9.4 ppm) and Zr (122–277 ppm) and MgO content.However, again with the exception of sample 3MO-59, Nb,

Table 4. Results of K–Ar dating of the selected samples from early Karacadag activity.

Sample Analyzed material K, % � s 40Arrad (ng/g) � s 40Aratm, % (in sample) Age, Ma � 2s

3MO-42 Groundmass 2.97 � 0.03 1.378 � 0.007 10.7 6.68 � 0.153MO-142 Groundmass (a-magnetic) 0.73 � 0.015 0.336 � 0.006 38.4 6.65 � 0.353MO-103 Groundmass 0.90 � 0.015 0.242 � 0.003 60.2 3.87 � 0.153MO-114 Groundmass 1.12 � 0.02 0.307 � 0.005 56.0 3.95 � 0.153MO-59 Groundmass 0.89 � 0.015 0.168 � 0.005 72.9 2.72 � 0.15

2

3

4

5

6

7

8

9

10

11

12

38 42 46 50 54 58 62

SiO2 (wt%)

Na 2O

+ K

2O (

wt%

)

Picrobasalt Basalt

BasaniteTephrite

Basalticandesite

Hawaiite

Benmoreite

Andesite

Phono-tephrite

Mugearite

Alkaline

Subalkaline

Turkey

Mashrek

Fig. 2. Total alkali vs. silica classification diagram (Le Bas et al.,1986). Alkaline-subalkaline field division (dashed line) after Irvine& Baragar (1971). All the analyses have been recalculated to LOI-free basis. Literature data for Karacadag rocks from Pearce et al.(1990), Ercan et al. (1991) and Alici Sen et al. (2004). Also shownare other Neogene alkaline rocks of neighbouring volcanic districtsfrom the Arabian plate (Mashrek) and throughout the Anatolian plate(Turkey; references in Lustrino & Wilson, 2007).

Fig. 3. Photomicrographs showing the typical texture of the mainvolcanic rocks of early Karacadag activity. All photographs in plane-polarized light except for (g) and (h) which are in cross-polarizedlight. (a) Basalt with euhedral to subhedral olivine phenocrysts in aholocrystalline (intergranular to sub-ophitic) groundmass (sample3MO-113). (b) Basalt with scarce olivine and plagioclase phenocrystin a fine-grained hypocrystalline groundmass (sample 3MO-31). (c)Basalt with subhedral to skeletal olivine phenocrysts in a fine-grained hypocrystalline mesostasis (sample 3MO-44). (d)Sub-ophitic hawaiite with scarce olivine set in a medium- to fine-grained holocrystalline matrix (sample 3MO-1). (e) Porphyriticbasanite with subhedral olivine phenocrysts set in a very-fine hypo-crystalline groundmass (sample 3MO-118). (f) Mugearite sample(3MO-34) with small olivine and a hypocrystalline groundmass.(g) Sub-aphyric benmoreite sample (3MO-42) with scarce pheno-crysts of zoned plagioclase and olivine in a fine-grained, hypocrys-talline groundmass rich in granular feldspar. (h) Kinked olivinexenocryst in the basaltic sample 3MO-31.



8

10

12

14

16

FeO

tot

42

46

50

54

58

62

SiO

2

1

2

3

4

5

K2O

0.5

1.0

1.5

2.0

P2O

5

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12 14 16MgO

CaO

/Al 2O

3

1

2

3

4

TiO

2

12

14

16

18

20A

l 2O3

2

4

6

8

10

12

14

CaO

2

3

4

5

6

Na 2O

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 2 4 6 8 10 12 14 16MgO

Mg#

TurkeyMashrek

Fig. 4. Major elements, Mg# and CaO/Al2O3 ratio vs. MgO diagrams for the Karacadag lavas (analyses recalculated to LOI-free basis).References as in Fig. 2.



100

300

500

700

900

1100

Ba

20

40

60

80

Co

0

20

40

60

80

100

Nb

10

30

50

70

90

110R

b

50

100

150

200

250

300

V

0 2 4 6 8 10 12 14 16MgO

200

600

1000

1400

1800

2200

Sr

100

200

300

400

500

600

700

Cr

50

100

150

200

250

300

350

Ni

100

200

300

400

Zr

2

3

4

5

6

7

8

9

Hf

0 2 4 6 8 10 12 14 16MgO

TurkeyMashrek

Fig. 5. Selected trace elements vs. wt% MgO for the Karacadag lavas. References as in Fig. 2.



Ta, Hf and Zr of the plateau-forming stage lavas show clearnegative correlation with MgO content (R2 ¼ 0.98, 0.97,0.97 and 0.96, for Nb, Ta, Hf and Zr, respectively). Inearly-stage lavas, these elements also show a negativecorrelation with MgO but with more scatter (Fig. 5).

Among the Rare Earth Elements (REE), a clear negativecorrelation emerges, especially for L (Light) REE and M(Medium) REE (not shown) if only the plateau-forminglavas are taken into consideration. With the exception ofsample 3MO-59, the correlation factor (R2) of the plateau-forming lavas from La to Dy with MgO is always higherthan 0.96. Holmium and Er still show negative correlationwith MgO but with lower R2 values (0.80 and 0.65, respec-tively). This correlation factor decreases abruptly from Tm(R2¼ 0.17) to Yb (R2¼ 0.001). Lutetium shows a scatteredpositive correlation of MgO with low R2 (0.19). REEcontents of the early-stage lavas also show negative corre-lation with MgO but with more scatter compared to thoseof the plateau-stage lavas (not shown).

Chondrite CI-normalized REE patterns show a (La/Lu)N

ratios of �6–10 in the basalts and �12–29 in the basanites(Fig. 6). REE patterns of basalts cross those of basanites incorrespondence of Ho (MREE), reflecting slightly variableLREE/HREE ratios. All the rocks have very small positiveEu anomalies (Eu/Eu* �1.04–1.11) and a relatively low

HREE content (LuN¼ 6.1–11.0 times chondrite). Only thebenmoreite shows slight negative Eu anomaly (Eu/Eu* ¼0.88). There is no substantial difference between the early-stage and the plateau-stage lavas in terms of REE fractio-nation patterns.

Primitive mantle-normalized multi-elemental diagrams(Fig. 7) for most of the mafic samples of Karacadag showdistinct patterns, which are typical of the ‘‘anorogenic’’magmas, with bell-shaped trends peaking at Nb-Ta.Positive anomalies are present also for Zr-Hf. Two of theearly-stage alkali basalt samples (3MO-134 and 3MO-142)show negative Nb-Ta anomalies and a slightly positive Kanomaly (Fig. 7). The patterns of the early-stage lavas showless pronounced positive HFSE anomalies (maximum 41�the primitive mantle values) compared to those of the pla-teau-stage rocks (maximum 126� the primitive mantle). Allthe mafic samples show positive anomalies at Sr and Ti.

6.3. Sr-Nd isotopic ratios

Sr-Nd isotopic ratios have been determined for three pla-teau-stage lavas and two early-stage lavas. The data arepresented in Table 5 and are shown in Fig. 8. The threeplateau-stage samples (two basalts and one basanite) show87Sr/86Sr(i) ratios lower than BSE (Bulk Silicate Earth)estimate (i.e., between 0.70349 and 0.70434) and

1

10

100

1000

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu

Sam

ple/

Cho

ndrit

e

1

10

100

1000

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu

Sam

ple/

Cho

ndrit

e

Basanites

Alkalibasalts

Benmoreite

Fig. 6. Chondrite-normalized REE diagram (normalization factorsfrom Sun & McDonough, 1989) for the Karacadag lavas.

1

10

100

1000

Cs Ba U Ta La Pr P Sm Hf Ti Tb Y Er YbRb Th Nb K Ce Sr Nd Zr Eu Gd Dy Ho Tm Lu

Roc

k/P

rimiti

ve M

antle

Basanites

Alkalibasalts

1

10

100

1000

Cs Ba U Ta La Pr P Sm Hf Ti Tb Y Er YbRb Th Nb K Ce Sr Nd Zr Eu Gd Dy Ho Tm Lu

Roc

k/P

rimiti

ve M

antle Benmoreite

Fig. 7. Multi-elemental primitive mantle-normalized diagram (nor-malization factors from Sun & McDonough, 1989) for theKaracadag lavas.



143Nd/144Nd(i) higher than the ChUR (Chondritic UniformReservoir) estimate (0.512768–0.512853). Despite theirdifferent MgO content (MgO ¼ 8.13–1.03 wt%), the twoearly-stage lavas (basalt and benmoreite) analyzed for Sr-Nd isotopic ratios show similar 87Sr/86Sr(i)

(0.70505–0.70522), which are higher than those of the pla-teau-stage lavas, coupled with lower 143Nd/144Nd(i) isotopicratios (0.512659–0.512736). Compared to Karacadag litera-ture data (five samples previously analyzed for Sr-Nd iso-topes; Pearce et al., 1990; Alici Sen et al., 2004), our samplesplot at lower 143Nd/144Nd with higher 87Sr/86Sr ratios (Fig. 8).

No correlation of Sr-Nd isotopic ratios is observed withSiO2 or MgO (Fig. 9). The early-stage basalt (3MO-142;MgO ¼ 8.13 wt%) shows the most radiogenic 87Sr/86Sr(i)

ratio, coupled also with troughs at Nb-Ta in primitivemantle-normalized diagrams (Fig. 7). Interestingly, the87Sr/86Sr(i) ratio of the 3MO-142 sample is also higherthan the early-stage benmoreite (3MO-42) with muchlower MgO (1.03 wt%). The three plateau-stage lavasanalyzed in this study show roughly positive correlationbetween 87Sr/86Sr(i) and MgO and roughly negative corre-lation between 87Sr/86Sr(i) and SiO2 (Fig. 9).

7. Discussion

The origin of the anorogenic magmatic activity in south-eastern Anatolia and the northern Arabian plate (Fig. 1a) isnot well constrained. The geochemical characteristics ofthe volcanic rocks indicate derivation of the magmas fromsub-lithospheric mantle sources that have escaped significanteffects of crustal contamination during oceanic subduction.Nearly all the products of this activity crop out on the down-going plate (south-easternmost Turkey, Syria; e.g., Lustrino& Sharkov, 2006; Alpaslan, 2007; Ekici et al., 2007 andreferences therein). The origin of the intra-plate-like volcanicT

able

5.

Sr

and

Nd

iso

top

icco

mp

osi

tio

ns

of

sele

cted

Kar

acad

ag.

Sam

ple

Mg

#A

ge

Sta

ge

Rb

Sr

Sm

Nd

87S

r/8

6S

r (m

)eS

r (m

)8

7S

r/8

6S

r (i)

eSr (

i)1

43N

d/1

44N

d(m

)eN

d(m

)1

43N

d/1

44N

d(i

)eN

d(i

)

3M

O-4

20

.19

6.6

8E

arly

10

14

30

9.9

41

.50

.70

51

14�

14

þ9

.40

.70

50

50

þ8

.50

.51

27

4�

1þ

2.0

0.5

12

74

þ2

.13

MO

-14

20

.55

6.6

5E

arly

22

36

84

.31

6.9

0.7

05

23

5�

14

þ1

1.1

0.7

05

22

0þ

10

.90

.51

26

7�

1þ

0.6

0.5

12

66

þ0

.63

MO

-59

0.5

12

.72

Pla

teau

16

59

95

.82

2.9

0.7

03

49

4�

12

�1

3.6

0.7

03

49

4�

13

.60

.51

28

6�

1þ

4.2

0.5

12

85

þ4

.23

MO

-10

30

.65

3.8

7P

late

au1

24

59

4.7

19

.70

.70

43

40�

14

�1

.60

.70

43

40

�1

.60

.51

27

7�

1þ

2.6

0.5

12

77

þ2

.63

MO

-11

40

.65

3.9

5P

late

au1

15

30

4.8

19

.20

.70

37

37�

12

�1

0.1

0.7

03

73

7�

10

.10

.51

28

3�

1þ

3.8

0.5

12

83

þ3

.8

0.5124

0.5125

0.5126

0.5127

0.5128

0.5129

0.5130

0.5131

0.7025 0.7035 0.7045 0.7055 0.7065 0.7075 0.7085

87Sr/86Sr

143 N

d/14

4 Nd

Turkey

Mashrek

BS

E (

0.70

445)

ChUR (0.51264)

Fig. 8. 143Nd/144Nd vs. 87Sr/86Sr initial isotopic ratios of theKaracadag lavas. References as in Fig. 2. BSE ¼ Bulk SilicateEarth value (87Sr/86Sr ¼ 0.70445). ChUR ¼ Chondritic UniformReservoir (143Nd/144Nd ¼ 0.51264).



activity has alternatively been attributed to: (1) heat-excess inthe mantle sources, related to the presence of a hot andbuoyant mantle super-plume, whose stem is located close tothe Afar depression (Weinstein et al., 2006; Krienitz et al.,2009); (2) a fossil (ancient but still hot) mantle plume head,rheologically attached to the base of the lithosphere (Stein &Hofmann, 1992); (3) adiabatic decompression of shallowmantle as response to thinning of the lithosphere (e.g.,Lustrino & Sharkov, 2006); (4) asthenospheric sources mobi-lized (i.e., upwelled) after slab-steepening and break-off pro-cesses (e.g., Keskin, 2003, 2007; Krienitz et al., 2006; Sengoret al., 2008); and (5) the development of local graben struc-tures (e.g., the E-W extending Akcakale graben in the case ofKaracadag; Sengor & Yilmaz, 1981; Sengor et al., 1985;Elitok & Dolmaz, 2008).

7.1. Constraints from major elements

Variations in major elements compared with both SiO2 andMgO do not indicate any clear evolutionary trend for theKaracadag lavas. This has been observed also for all the other

Neogene ‘‘anorogenic’’ lavas of Turkey and Mashrek region(i.e., Syria, Jordan, Israel, Palestine, Lebanon and SaudiArabia). The absence of a clear major-element correlationcould qualitatively be linked to several processes such as: (a)variable depth of magma separation, (b) variable degrees ofpartial melting, (c) presence of heterogeneous mantle sources,(d) significant differences in the fractionating crystal assem-blages and (e) complex interaction between replenishment andfractional crystallization processes in magma chambers. Giventhe fact that a large number of variables could have beeninvolved in the magma genesis and evolution, we argue thatit is not possible to give a definite petrogenetic answer usingonly major elements. On the basis of major-element dataalone, it can be argued that the mantle sources must havebeen devoid of significant effects of modification by subduc-tion-related fluids. This is consistent with their tectonic set-ting and, above all, with their high TiO2, Na2O and Na2O/K2O values coupled with relatively low CaO (see Lustrino &Wilson, 2007 for a proposal for the definition of ‘‘anoro-genic’’ magma). Similarly, their major element compositionis compatible with a derivation from a relatively fertile peri-dotitic mantle source (i.e., not depleted in basalticcomponents).

The negative correlation between SiO2 and MgO suggestsa variable degree of fractional crystallization of a maficphase, involving initial removal of olivine as suggested bythe petrographic data (Table 1). Moreover, the roughly posi-tive correlation of FeO(tot) and TiO2 with MgO (Fig. 4),coupled with their decrease with increasing silica, impliesfractional crystallization of ferromagnesian minerals and Ti-bearing phases (i.e., olivine, clinopyroxene and Fe-Ti oxi-des). Despite the petrographic observations, which indicatethe presence of only olivine and clinopyroxene phenocrysts,the CaO/Al2O3 vs. MgO correlation indicates the involve-ment of plagioclase in the fractionating mineral assemblage.

7.2. Constraints from trace elements

Variations in LILE, HFSE and HREE with MgO for early-and plateau-stage lavas (with the exception of sample 3MO-52) show similar trends starting from different MgO con-tents. In Fig. 5, two distinguishable trace-element trends canbe observed for the rocks belonging to these two temporalgroups. The increase in incompatible trace elements (e.g.,Sr, Y, Zr, Nb, Hf, Ta, LREE, Th, U, Ga) in the plateau-stagelavas and the decrease of compatible trace elements (Cr, Co,Ni) with decreasing MgO with respect to the rest of the lavascan be interpreted as the effect of fractional crystallizationprocesses with removal of clinopyroxene, olivine and Fe-Tioxides, again consistent with petrographic data (Table 1). Aminor role of plagioclase fractionation is indicated by thenegative correlation of Sr with MgO.

The relationship between highly compatible elements(e.g., Cr) and highly incompatible ones (e.g., Th) in amagmatic system experiencing fractional crystallizationof an ultramafic (i.e., plagioclase-free or plagioclase-poor) assemblage can furnish constraints for the type ofprocess causing the spread of data. In Fig. 10 theKaracadag samples do not show any clear trend.

0.7025

0.7030

0.7035

0.7040

0.7045

0.7050

0.7055

0.7060

0.7065

0 2 4 6 8 10 12 14 16

MgO

87S

r/86

Sr

38 42 46 50 54 58 620.7025

0.7030

0.7035

0.7040

0.7045

0.7050

0.7055

0.7060

0.7065

87S

r/86

Sr

SiO2

Turkey

Mashrek

Fig. 9. 87Sr/86Sr vs. MgO and 87Sr/86Sr vs. SiO2 of the Karacadaglavas. References as in Fig. 2.



Although there are limited data for modelling this process,the linear distribution of most of the data points (trend 1) iscompatible with periodic replenishment of the evolvedmagmas (defining the FC trend) by primitive magma(with a composition similar to 3MO-114). Such a magmamixing process is unsurprising, as magma production andtapping should have been important and periodic, beneaththis huge, long-lasting volcano.

The relatively fractionated LREE/HREE patterns of themost mafic plateau-stage lavas (basanites 3MO-110 and3MO-118) suggest that the melt production was in the pre-sence of residual garnet, a phase particularly effective atbuffering HREE compared to LREE. This hypothesis isgeochemically modelled in Fig. 11, where the Sm/Yb ratiois plotted against La/Sm ratio. The bulk of the Karacadagsamples fall in a �2–10 % melting interval of a peridotiticsource containing garnet/spinel ratio ranging from 1 to�0.5.Due to the large number of variables that are difficult toparameterize (the modal and chemical composition of thesource, the dynamics of partial melting process, the mode ofphases entering the melt and the partition coefficients ofindividual minerals), this treatment can be considered onlyin a qualitative or semi-quantitative way. The basanites showrelatively high LREE and high LREE/HREE, compatiblewith low degrees of melting (�2–5 %), whereas alkalinebasalts display REE contents which are compatible withhigher degrees of melting (�5–10 %). Interestingly, themost evolved (benmoreitic) sample shows a similar LREEcontent (LaN¼ 212 times chondrite) but higher HREE (LuN

¼ 17 times chondrite) in comparison with the most maficearly-stage basanite (LaN ¼ 215; LuN ¼ 7). The REE con-tent of this evolved sample is consistent with relatively highdegrees of melting (lowering LREE abundance in the partial

melt) followed by fractional crystallization processes. SinceMg# values indicate a relatively evolved character (i.e., aretoo low to be in equilibrium with a peridotitic assemblage)the degrees of melting calculated using REE contents areonly minimum estimates. Very likely, the original degreesof melting were higher.

Incompatible trace elements can be used in theory also toconstrain the role of crustal contamination of mantle. Iffractionation and crustal assimilation (AFC; DePaolo,1981) were operational, the incompatible trace element con-tent of the melts would record such a process. Figure 12ashows Rb/Nb vs. Nb with a series of AFC curves calculatedat different r (i.e., the mass of contamination/mass of frac-tionation; DePaolo, 1981) and a bulk contamination line,using as contaminant average upper crust (Taylor &McLennan, 1985). The bulk of the Karacadag lavas clusteralong low r lines (Fig. 12a), indicating only a minor role ofcrustal contamination in magma evolution. Only two sam-ples fall along higher r values, suggesting a larger involve-ment of crustal lithologies as indicated by the troughs at Nb-Ta pairs and the higher LILE/HFSE ratios in primitivemantle-normalized patterns (Fig. 7).

0

50

100

150

200

250

300

350

400

450

500

0 1 2 3 4 5 6 7 8

3MO -114

Replenishment (mixing)

FC

?

?

?

Th

Cr

1

Fig. 10. Cr vs. Th plot. A fractional crystallization curve has beendrawn starting from the least differentiated Karacadag sample (3MO-114). Few samples plot along the fractional crystallization curve,whereas others plot along hypothetical mixing lines connecting pri-mitive and evolved compositions. Further details are in the text.

1

2

3

4

5

6

7

8

9

10

2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

La/Sm

Sm

/Yb

100% Gt

70% Gt30% Sp

50% Gt50% Sp

30% Gt 70% Sp10% Gt 90% Sp

100% Sp

F = 2%

F = 3%

F = 5%

F = 10%

F = 15%

3MO-42

Fig. 11. La/Sm vs. Sm/Yb plot showing theoretical melting curvestogether with the basic samples from Mt. Karacadag. The bachmelting equations of Shaw (1970) have been used to construct themelting model. F: weight fraction of melt produced, La, Sm and Ybinitial concentration: 4, 1.3 and 1.1 ppm, respectively. Modal miner-alogy for the starting peridotite (D): Ol:Opx:Cpx:Gt/Sp ¼0.60:0.25:0.09:0.06 (Ol: olivine, Opx: orthopyroxene, Cpx: clino-pyroxene, Sp: spinel, Gt: garnet). Modal content of the phasesentering the melt (P): Ol:Opx:Cpx:Gt/Sp ¼ �0.10:0.30:0.50:0.30.The sign minus (–) of olivine indicates that this phase is beingproduced during incongruent melting of orthopyroxene. Kdsbetween the basaltic melts and minerals given in inset have beencompiled from Irving & Frey (1978), Fujimaki et al. (1984),McKenzie & O’Nions (1991) and Rollinson (1993). Bulk partitioncoefficient (Ds) of each element have been calculated for garnet andspinel peridotite source-rock compositions by taking the modalmineralogy of these end-members into consideration.



7.3. Constraints from Sr-Nd isotopic ratios

Within the MgO range of 8–9 wt%, the 87Sr/86Sr ratio ofthe Karacadag lavas ranges from 0.7033 to 0.7053, withoutany clear trend (Ercan et al., 1990; Pearce et al., 1990;Alici Sen et al., 2004; this study). If crustal contaminationhad played an important role during the magma evolution(e.g., AFC-type process), a significant decrease in MgOcontent in the most contaminated magma should beexpected, due to thermal death of the original magmabatch. However, MgO-poor magmas (3MO-59; MgO5.79 wt%) display lower 87Sr/86Sr ratio than MgO-richmagmas (Fig. 9). This observation contrasts with thehypothesis of crustal contamination at shallow depths. Onthe other hand, the crude positive correlation between87Sr/86Sr and SiO2 (Fig. 9) led other authors (e.g., Ercanet al., 1990) to hypothesize AFC-type processes in thegenesis and evolution of Karacadag magmas. We consider

the AFC hypothesis to be unlikely for most of theKaracadag lavas because 87Sr/86Sr ratios (literature andnew data) display a large spread of composition(0.7034–0.7053) in a narrow SiO2 interval (44–48.5wt%), pointing asymptotically to SiO2 �49 wt% (Fig. 9).SiO2 concentrations of the local basement rocks exposed inthe region are not known at all. Assuming as potential meltcontaminant average upper continental crust (SiO2 �66.6wt%; Rudnick & Gao, 2003) or average total continentalcrust (SiO2 �60.6 wt%; Rudnick & Gao, 2003), withradiogenic 87Sr/86Sr composition (.0.712), AFC pro-cesses could not produce the observed asymptotic trendof Fig. 9. This interpretation is also supported by AFCmodels involving variations in trace elements (Fig. 12a)and 87Sr/86Sr (Fig. 12b). Of course, samples 3MO-134 and3MO-142 still show evidence of a stronger interaction withcrustal lithologies.

For the case of a hypothetical parental melt end-member(alkali basalt) with Zr ¼ 136 ppm, Sr ¼ 509 ppm and87Sr/86Sr¼ 0.70351 (Alici Sen et al., 2004) and a potentialcrustal contaminant with Zr ¼ 163 ppm, Sr ¼ 273 ppm(total continental crust average; Rudnick & Gao, 2003) and87Sr/86Sr¼ 0.7125 (Fig. 12b), neither a simple mixing linenor AFC calculations satisfy the isotopic variability of theKaracadag lavas. Only the benmoreite sample could beconsistent with AFC process, hypothesizing an r value ¼0.27 and F (residual melt fraction) ¼ 45 %. The most Zr-enriched mafic samples analyzed in this study (3MO-59)could be produced after �30 % fractionation starting fromthe basaltic sample of Alici Sen et al. (2004) and r ¼ 0(Fig. 12b). The Karacadag samples with Zr ,136 ppm(i.e., lower than the parental melt end-member) couldhave been produced neither by simple mixing nor byAFC-type processes, also invoking much more radiogeniccrustal contaminant. These findings indicate that: (a) theaverage crustal composition chosen as hypothetical con-taminant is not valid; (b) the AFC process was very unli-kely to have played a major role in the isotopic and traceelement variability in the Karacadag lavas. The rare pre-sence of 5–10 cm sized mantle xenoliths found in thealkaline mafic rocks (authors’ unpublished data) indicatesa rapid rise to the surface of the mantle melts, thereforelimiting isotopic and elemental interaction with crustallithologies. In conclusion, we do not exclude at all theexistence of processes of crustal contamination of mantlemelts at relatively shallow depths (AFC processes), but werelegate them to as a process of secondary importance or tofew samples (e.g., 3MO-134 and 3MO-142).

The last, but poorly constrained (and constrainable),hypothesis is to invoke the presence of a shallow heteroge-neous upper mantle. The sub-continental lithospheric mantleis classically believed to be more heterogeneous than theunderlying convecting mantle. The rigidity of the lithosphericlid permits the development of isotopic and elemental hetero-geneities. The relative isotopic and elemental homogeneity ofthe anorogenic igneous rocks of the circum-Mediterraneananorogenic Cenozoic igneous Province has been related to thepresence of a well-stirred and homogeneous sub-lithosphericmantle source (e.g., Hoernle et al., 1995; Wilson & Bianchini,

0.7020

0.7040

0.7060

0.7080

0.7100

0.7120

0.7140

0 50 100 150 200 250 300 350 400 450 500 550

Zr

87S

r/86

Sr

(b)

0

1

2

3

4

5

1 10 100 1000

Rb/

Nb

Nb

Bul

k as

sim

ilatio

n

(a)Turkey

Mashrek

Magma

r =0.85

r =0.70

r =0.50

r =0.35

r =0.25

r =0.15

r =0.10

r =0.05r =0

3MO-42

Average UC

AF

C c

urv

es

Turkey

Mashrek

DNb = 0.1DRb = 0.1

r=0.50

r =0.30

r =0.20r =0.05

r =0.40

F=0.80

F=0.70F=0.60

F=0.50

F=0.40

Fig. 12. (a) Rb/Nb vs. Nb plot displaying the results of AFC (assim-ilation–fractional crystallization) modelling using the equation of DePaolo (1981). UC ¼ upper crustal composition of Taylor &McLennan (1985); r ¼ ratio of the rate of assimilation to the rateof fractional crystallization. 3MO-42¼ Benmoreite. (b) 87Sr/86Sr vs.Zr diagram showing: mixing (bold line), fractional crystallization(dotted line) and AFC grid. Continuous lines indicate constant rvalues at varying F (residual melt aliquot); dashed lines indicateconstant F at varying r values. See text for further details.



1999; Lustrino & Wilson, 2007). The mafic Turkish andMashrek Neogene volcanic rocks plot in the isotopic field ofthe Circum-Mediterranean Anorogenic Cenozoic IgneousProvince mafic igneous rocks, but the early-stage Karacadaglavas cluster towards more radiogenic 87Sr/86Sr and less radio-genic 143Nd/144Nd. The mantle source regions of theKaracadag lavas could be alternatively lithospheric mantlevolumes or poorly-mixed sub-lithospheric volumes.Considering that the lithosphere-asthenosphere boundary isnot known in detail in the area, a definitive conclusionbetween these two possibilities cannot be drawn. Sengoret al. (2003) proposed the existence of a 40 km-thick litho-spheric mantle beneath Mt. Karacadag. This thickness,together with the 36–38 km thick crust (Gok et al., 2007),would place the lithosphere-asthenosphere boundary at adepth of ,78 km. On the other hand, Gok et al. (2007)propose the existence of a lithosphere more than 100 kmthick under the northern margin of the Arabian plate. Thespinel-garnet facies transition in the upper mantle is placedaround 80 km, therefore the source of Mt. Karacadag lavas (inequilibrium with garnet peridotite) could have been derivedfrom a shallow asthenospheric mantle or deep lithosphere.

7.4. Consideration of neighbouring Neogene volcanicprovinces

The bulk of the mafic ‘‘anorogenic’’ Neogene volcanicrocks of Mashrek and Anatolia has 143Nd/144Nd.0.51284 and 87Sr/86Sr ,0.704. About one third of theavailable 87Sr/86Sr data for Karacadag lavas are .0.704.Interestingly, most of the Mashrek lavas displaying87Sr/86Sr .0.704 are the late Pliocene alkali basalts crop-ping out in northern Syria, very close to the internationalborder with SE Turkey, only 200 km away from Karacadagvolcano (Krienitz et al., 2006, 2009). Also the mafic alka-line ‘‘anorogenic’’ lavas in Turkey with 87Sr/86Sr .0.704are mostly confined to the Karasu Valley, close to theborder with Syria (Capan et al., 1987; Alici et al., 2001).The occurrence of the most Sr radiogenic lavas in a �200� 800-km area could be interpreted as indicating an anom-alously heterogeneous shallow mantle domain feeding therecent mafic alkaline ‘‘anorogenic’’ lavas in a context of amore homogeneous upper mantle, the so-called CMR(Common Mantle Reservoir; Lustrino & Wilson, 2007).

8. Concluding remarks

Mt. Karacadag is the largest volcano of the circum-Mediterranean anorogenic Cenozoic igneous Province(Lustrino & Wilson, 2007) covering and area of �10,000km2 in SE Anatolia, close to the border between Turkeyand Syria. Its activity developed with several quiescentphases during Late Miocene to Quaternary times.Petrographic, geochemical, K/Ar and isotopic investiga-tions of the products of the early activity (.2.6 Ma) hasprovided evidence for the following characteristics:

� 58 % of the sampled lavas are mildly alkaline, SiO2-undersaturated olivine-clinopyroxene phyric rockswith sodic affinity (Na2O/K2O from 2.1 to 6.0, andup to 17 wt% normative nepheline. About 40 % ofthe sample population is represented by SiO2-satu-rated (CIPW olivine-hypersthene normative) oli-vine-clinopyroxene phyric basalts straddling thealkaline-subalkaline division line on the TAS dia-gram. On the basis of the TAS classification scheme,the rocks are basalts (�73 % of the sample popula-tion), with minor hawaiites (�15 %) and basanites(�10 %). Only one sample plot in the andesite fieldwith 61.54 wt% SiO2 and one sample straddle thehawaiite-mugearite-phonotephrite field. The ande-site sample has a mineral paragenesis typical ofsodic alkaline melts and therefore is classified asbenmoreite. Mantle xenoliths are occasionally asso-ciated with the most mafic rocks. Major elements donot show any clear correlation with MgO. Major andtrace element composition as well as petrographicfeatures are indistinguishable from neighbouring andcoeval mafic rocks from Turkey and Mashrek.� Lavas of the plateau-forming stage (�4.0–2.7 Ma)

show incompatible trace element patterns well cor-related with MgO, whereas early-stage lavas(�11–6.6 Ma) show more scattered patterns.� Trace-element variation diagrams are compatible

with a fractional crystallization of the main phasesobserved in the thin sections (i.e., olivine and clin-opyroxene plus minor Fe-Ti oxides).� 87Sr/86Sr(i) ratios range from 0.70374 to 0.70522 and

143Nd/144Nd(i) ranges from 0.512853 to 0.512659;early-stage lavas show higher 87Sr/86Sr(i) and lower143Nd/144Nd(i) compared to plateau-stage lavas.

On the basis of these features the following conclusionsmay be drawn:

� Major-element scatter is qualitatively consistent withpolybaric depths of magma separation, variable degreesof partial melting (from�2 to�10 %), the presence ofheterogeneous mantle sources and differences in thefractionating crystal assemblage. The major-elementscatter is common to all other Neogene anorogenicrocks overlying the Turkish and Arabian plates.� Primitive mantle-normalized patterns of the early

lavas resemble those of the classical anorogenicmagmas, with peaks at HFSE (Nb, Ta, Hf, Zr) andhigh HFSE/LILE ratios. Few samples show evidenceof interaction with crustal lithologies (e.g., lowerNb-Ta content). The REE content is compatiblewith derivation of the basanites from a mixed gar-net-spinel facies peridotite (garnet/spinel ratio�80:20) after �2 % partial melting; alkali basaltsare compatible with higher degrees of melting(between 5 and 10 %) from the same type of source,with spinel-richer composition (garnet/spinel ratio aslow as 50:50).



� The Sr-Nd isotopic variations cannot be fullyexplained with a process of magma contaminationwith crustal lithologies at shallow depths (AFC-likeprocesses), assuming average upper and total conti-nental crust estimates. The presence of rare mantlexenoliths testifies rapid ascent to the surface and,consequentially, low residence times at shallowcrustal depths. More likely, the differences arerelated to the existence of heterogeneous mantlesources with only minor involvement of AFC-likeprocesses.� A �200 � 800-km wide area extending throughout

southern Anatolia, from the Karasu Valley to theSyria-Iraq-Turkey border is identified for the firsttime on Sr isotopic grounds. The lithospheric mantlebeneath this area is characterized by anomalouslyenriched 87Sr/86Sr compositions (up to 0.7055) aswell as more isotopically depleted compositions(87Sr/86Sr down to 0.7030). The coexistence of thesecompositions testifies to the presence of heteroge-neous mantle regions close to the Bitlis suture zone.

Acknowledgements: The first author warmly thanksRaffaello Trigila (Rome) for designing and assemblingthe equipment to produce the glassy beads and for hiscontinued assistance during the production of the data.Marcello Serracino is thanked for his usual skilled helpduring electron micro-probe work. The manuscript wassignificantly improved after a detailed review byGianluca Bianchini (London) and an anonymous reviewer.Additional comments from the Associate Editor (CliffShaw) and the Chief Editor (Sandro Conticelli) are appre-ciated. Gillian Foulger (Durham, UK) kindly helped us inthe proofreading the manuscript. ML thanks, as usual,Enrica, Bianca and Laura for their support to the projectand the late Israel ‘‘IZ’’ Kamakawiwo’ole, now ‘‘some-where over the rainbow’’. We thank the local people fortheir warm welcome during the fieldwork. MK thanks theIstanbul University Research Fund (project # ACIP-1282)for their support during the fieldwork. This work waspartly supported by a RFBR-TUBITAK joint project(RFBR project # 09-05-91220-CT and TUBITAK project# 108Y222), by research grants from University LaSapienza (AST 2008, 2009) and from PRIN 2008 (researchgrant#: 2008HMHYFP_005).

References

Alici, P., Temel, A., Gourgaud, A., Vidal, Ph., Gundogdu, M.

(2001): Quaternary tholeiitic to alkaline volcanism in the

Karasu Valley, Dead Sea Rift Zone, Southeast Turkey: Sr-Nd-

Pb-O isotopic and trace-element approaches to crust-mantle

interaction. Int. Geol. Rev., 43, 120–138.

Alici Sen, P., Temel, A., Gourgaud, A. (2004): Petrogenetic model-

ling of Quaternary post-collisional volcanism: a case study of

central and eastern Anatolia. Geol. Mag., 141, 81–98.

Al-Lazki, A., Seber, D., Sandvol, E., Turkelli, N., Mohamad, R.,

Barazangi, M. (2003): Tomographic Pn velocity and anisotropy

structure beneath the Anatolian Plateau (eastern Turkey) and the

surrounding regions. Geophys. Res. Lett., 30, 8043, doi:

10.1029/2003GL017391.

Alpaslan, M. (2007): Early to middle Miocene intra-continental

basaltic volcanism in the northern part of the Arabian plate, SE

Anatolia, Turkey: geochemistry and petrogenesis. Geol. Mag.,

144, 867–882.

Angus, D.A., Wilson, D.C., Sandvol, E., Ni, J.F. (2006):

Lithospheric structure of the Arabian and Eurasian collision

zone in eastern Turkey from S-wave receiver functions.

Geophys. J. Int., 166, 1335–1346.

Bozdogan, N. & Erten, T. (1990): The age and effects of Mardin

uplift, Proc. 8th Petrol. Congr. Turkey. In Turkish: Mardin

yukseliminin yasi ve etkileri, GD Anadolu, Turkiye 8. Petrol

Kongresi Bildirileri, 207–227.

Bridgland, D.R., Demir, T., Seyrek, A., Pringle, M., Westaway, R.,

Beck, A.R., Rowbotham, G., Yurtmen, S. (2007): Dating

Quaternary volcanism and incision by River Tigris at

Diyarbakir, southeast Turkey. J. Quat. Sci., 22, 387–393.

Capan, U.Z., Vidal, Ph., Cantagrel, J.M. (1987): K-Ar, Nd, Sr and Pb

isotopic study of Quaternary volcanism in Karasu Valley

(Hatav), N-end of Dead-Sea Rift zone in SE Turkey.

Yerbilimleri, 14, 165–178.

DePaolo, D.J. (1981): Trace elements and isotopic effects of com-

bined wallrock assimilation and fractional crystallization. Earth

Planet. Sci. Lett., 53, 189–202.

Dercourt, J., Zonenshain, L.P., Ricou, L.E., Kazmin, V.G., Le

Pichon, X., Knipper, A.L., Grandjacquet, C., Sbortshhikov,

I.M., Geyssant, J., Lepvrier, C., Perchersky, D.H., Boulin, J.,

Sibuet, J.-C., Savostin, L.A., Sorokhtin, O., Westphal, M.,

Bazhrnov, M.L., Lauer, J.-P., Biju-Duval, B. (1986):

Geological evolution of the Tethys belt from the Atlantic to

the Pamirs since the Lias. Tectonophysics, 123, 241–315.

Dewey, J.F., Hempton, M.R., Kidd, W.S.F., Saroglu, F., Sengor,

A.M.C. (1986): Shortening of continental lithosphere: the neo-

tectonics of Eastern Anatolia – a young collision zone. in

‘‘Collision Tectonics’’, M.P. Coward & A.C. Ries, eds. Geol.

Soc. Lond. Spec. Publ., 19, 3–36.

Ekici, T., Alpaslan, M., Parlak, O., Temel, A. (2007): Geochemistry of

Pliocene basalts erupted along the Malatya-Ovacik fault zone

(MOFZ), eastern Anatolia, Turkey: implications for source charac-

teristics and partial melting processes. Chem. Erde, 67, 201–212.

Elitok, O. & Dolmaz, M.N. (2008): Mantle flow-induced crustal thin-

ning in the area between the easternmost part of the Anatolian

plate and the Arabian foreland (E Turkey) deduced from the

geological and geophysical data. Gondw. Res., 13, 302–318.

Ercan, T., Fujitani, T., Madsuda, J.-I., Notsu, K., Tokel, S.,

Tadahide, U.I. (1990): Apraisal of new geochemical, radio-

metric and isotopic data related to Eastern and Southeastern

volcanites of Neogene-Quaternary age, MTA J. In Turkish:

Dogu ve guneydogu Anadolu Neojen-Kuvaterner volkanitlerine

iliskin yeni jeokimyasal, radyometrik ve izotopik verilerin yor-

umu. M.T.A. Dergisi, 110, 143–164.

Ercan, T., Saroglu, F., Turhan, N., Matsuda, J.-I., Ui, T., Fujitani, T.,

Notsu, K., Bagirsakci, N., Aktimur, S., Can, B., Emre, O.,

Akcay, A.E., Manav, E., Gurler, H. (1991): The geology and


http://dx.doi.org/10.1029/2003GL017391

http://dx.doi.org/10.1029/2003GL017391


petrology of Karcadag Volcanites. Proc. 5th Petrol. Congr.

Turkey. In Turkish: Karacadag volkanitlerinin jeolojisi ve pet-

rolojisi, Bull. Geol. Congr. Turkey, 6, 118–133.

Faccenna, C., Bellier, O., Martinod, J., Piromallo, C., Regard, V.

(2006): Slab detachment beneath eastern Anatolia: a possibile

cause for the formation of the North Anatolian Fault. Earth

Planet. Sci. Lett., 242, 85–97.

Fujimaki, H., Tatsumoto, M., Aoki, K. (1984): Partition coefficients

of Hf, Zr and REE between phenocrysts and groundmasses.

Proc. 14th Lunar Planet. Sci. Conf., J. Geophys. Res. Suppl.,

89, B662–B672.

Gok, R., Pasyanos, M.E., Zor, E. (2007): Lithospheric structure of

the continent-continent collision zone: eastern Turkey. Geophys.

J. Int., 169, 1079–1088.

Haksal, A. (1981): Petrographie und Geochemie des Schildvulkans

Karacadag. Hamburg University, unpublished PhD thesis.

Hoernle, K., Zhang, Y.S., Graham, D. (1995): Seismic and geochem-

ical evidence for large-scale mantle upwelling beneath the eastern

Atlantic and western and central Europe. Nature, 374, 34–39.

Innocenti, F., Mazzuoli, R., Pasquare, G., Radicati di Brozolo, F.,

Villari, L. (1976): Evolution of the volcanism in the area of inter-

action between the Arabian, Anatolian and Iranian plates (Lake

Van, Eastern Turkey). J. Volcanol. Geotherm. Res., 1, 103–112.

Innocenti, F., Mazzuoli, R., Pasquare, G., Serri, G., Villari, L.

(1980): Geology of the volcanic area of Lake Van (Turkey).

Geol. Rundsch., 69, 292–393.

Innocenti, F., Kolios, N., Manetti, P., Rita, F., Villari, L., Villari, L.

(1982): Acid and basic Late Neogene volcanism in Central

Aegean Sea: its nature and geotectonic significance. Boll.

Volcanol., 45, 87–97.

Irvine, T.N. & Baragar, W.R.A. (1971): A guide to the chemical

classification of the common volcanic rocks. Can. J. Earth Sci.,

8, 523–548.

Irving, A.J. & Frey, F.A. (1978): Distribution of trace elements between

garnet megacrysts and host volcanic liquidus of kimberkitic to

rhyolitic composition. Geochim. Cosmochim. Acta, 42, 771–787.

Keskin, M. (2003): Magma generation by slab steepening and break-

off beneath a subduction-accretion complex: an alternative

model for collision-related volcanism in eastern Anatolia,

Turkey. Geophys. Res. Lett., 30, doi: 10.1029/2003GL018019.

— (2007): Eastern Anatolia: a hotspot in a collision zone without a

mantle plume. in ‘‘Plates, Plumes, and Planetary Processes’’,

G.R. Foulger & D.M. Jurdy, eds. Geol. Soc. Am. Spec. Pap., 430,

693–722.

Keskin, M., Pearce, J.A., Mitchell, J.G. (1998): Volcano-stratigra-

phy and geochemistry of collision-related volcanism on the

Erzurum-Kars Plateau, North Eastern Turkey. J. Volcanol.

Geotherm. Res., 85, 355–404.

Keskin, M., Pearce, J.A., Kempton, P.D., Greenwood, P. (2006):

Magma-crust interactions and magma plumbing in a post-colli-

sion setting: geochemical evidence from the Erzurum-Kars

Volcanic Plateau, Eastern Turkey. in ‘‘Postcollisional Tectonics

and Magmatism in the Mediterranean Region and Asia: Boulder,

Colorado’’, Y. Dilek & S. Pavlides, eds. Geol. Soc. Am. Spec.

Pap., 409, 475–505, doi: 10.1130/2006.2409(23).

Krienitz, M.S., Haase, K.M., Mezger, K., Eckardt, V., Shaikh-

Mashail, M.A. (2006): Magma genesis and crustal contamina-

tion of continental intraplate lavas in northwestern Syria.

Contrib. Mineral. Petrol., 151, 698–716.

Krienitz, M.S., Haase, K.M., Mezger, K., van den Bogaard, P.,

Thiemann, V., Shaikh-Mashail, M.A. (2009): Tectonic events,

continental intraplate volcanism, and mantle plume activity in

northern Arabia: constraints from geochemistry and Ar-Ar dat-

ing of Syrian lavas. Geochem. Geophys. Geosyst., 10, doi:

10.1029/2008GC002254.

Kurt, M.A., Alpaslan, M., Goncuoglu, M.C., Temel, A. (2008):

Geochemistry of late stage medium to high-K calc-alkaline

and shoshonitic dykes in the Ulukisla Basin (Central Anatolia,

Turkey): petrogenesis and tectonic setting. Geochem. Int., 46,

1145–1163.

Le Bas, M.J., Le Maitre, R.W., Streckeisen, A., Zanettin, B. (1986):

A chemical classification of volcanic rocks based on the total

alkali-silica diagram. J. Petrol., 27, 745–750.

Lustrino, M. & Sharkov, E. (2006): Neogene volcanic activity of

western Syria and its relatioship with Arabian plate kinematics.

J. Geodyn., 42, 115–139.

Lustrino, M. & Wilson, M. (2007): The circum-Mediterranean anoro-

genic Cenozoic igneous province. Earth Sci. Rev., 81, 1–65.

McKenzie, D.P. & O’Nions, R.K. (1991): Partial melt distribution

from inversion of rare earth element concentrations. J. Petrol.,

32, 1021–1091.

Notsu, K., Fujitani, T., Ui, T., Matsuda, D., Ercan, T. (1995):

Geochemical features of collision-related volcanic rocks in cen-

tral and eastern Anatolia. J. Volcanol. Geotherm. Res., 64,

171–192.

Omrani, J., Agard, Ph., Whitechurch, H., Benoit, M., Prouteau, G.,

Jolivet, L. (2008): Arc-magmatism and subduction history

beneath the Zagros Mountains, Iran: a new report of adakites

and geodynamic consequences. Lithos, 106, 380–398.

Oral, M.B., Reilinger, R.E., Toksoz, M.N., King, R.W., Barka, A.A.,

Kinik, I., Lenk, O. (1995): Global positioning system offers

evidence of plate motions in Eastern Mediterranean. EOS

Trans. Am. Geophys. Un., 76, 9–11.

Pearce, J.A., Bender, J.F., de Long, S.E., Kidd, W.S.F., Low, P.J.,

Guner, Y., Saroglu, F., Yilmaz, Y., Moorbath, S., Mitchell, J.G.

(1990): Genesis of collision volcanism in eastern Anatolia,

Turkey. J. Volcanol. Geotherm. Res., 44, 189–229.

Perincek, D. (1980): The effects of tectonical evolution occurring in

Northern Arabian Plate on the succession of the sedimentation.

Proc. 5th. Petrol. Congr. Turkey. In Turkish: Arabistan kitasikuzeyindeki tektonik evrimin kita uzerinde cokelen istifteki

etkileri, Turkiye 5. Petrol Kongresi Bildirileri, 77–93.

Robertson, A.H.F., Ustaomer, T., Parlak, O., Unlugenc, U.C., Tasli,K., _Inan, N. (2006): The Berit transect of the Tauride thrust belt,

S Turkey: Late Cretaceous-Early Cenozoic accretionary/colli-

sional processes related to the closure of the Southern Neothetys.

J. Asian Earth Sci., 27, 108–145.

Rollinson, H.R. (1993): Using geochemical data: evaluation, pre-

sentation, interpretation, Longman Scientific & Technical. John

Wiley Sons, New York, 344 p.

Rudnick, R.L. & Gao, S. (2003): Composition of the continental

crust. in ‘‘Treatise on Geochemistry’’, Vol. 3, H.D. Holland &

K.K. Turekian, eds. 1–64.

Sanver, M. (1968): A palaeomagnetic study of Quaternary volcanic

rocks from Turkey. Phys. Earth Planet. Inter., 1, 403–421.

Sengor, A.M.C. & Kidd, W.S.F. (1979): Post-collisional tectonics of

the Turkish-Iranian Plateau and a comparison with Tibet.

Tectonophysics, 55, 361–376.

Sengor, A.M.C. & Yilmaz, Y. (1981): Tethyan evolution of Turkey:

a plate tectonic approach. Tectonophysics, 75, 181–241.

Sengor, A.M.C., Gorur, N., Saroglu, F. (1985): Strike-slip faulting

and related basin formation in zones of tectonic escape: Turkey


http://dx.doi.org/10.1029/2008GC002254

http://dx.doi.org/10.1029/2008GC002254

http://dx.doi.org/10.1029/2003GL018019

http://dx.doi.org/10.1130/2006.2409(23)


as a case study. in ‘‘Strike-Slip Deformation, Basin Formation,

and Sedimentation’’, K.T. Biddle & N. Christie-Blick, eds. Soc.

Econ. Paleontol. Mineral. Spec. Publ., 37, 227–264.

Sengor, A.M.C., Ozeren, S., Genc, T., Zor, E. (2003): East Anatolian

high plateau as a mantle supported, north-south shortened domal

structure. Geophys. Res. Lett., 30, doi: 10.1029/

2003GL0117858.

Sengor, A.M.C., Ozeren, M.S., Keskin, M., Sakinc, M., Ozbakir,A.D., Kayan, I. (2008): Eastern Turkish high plateau as a small

Turkic-type orogen: implications for post-collisional crust-form-

ing processes in Turkish-type orogens. Earth Sci. Rev., 90, 1–48.

Shaw, D.M. (1970): Trace element fractionation during anatexis.

Geochim. Cosmochim. Acta, 34, 237–243.

Stampfli, G.M. (2001): Tethyan oceans. in ‘‘Tectonics and Magmatism

in Turkey and the Surrounding Area’’, E. Bozkurt, J.A. Winchester,

J.D.A. Piper, eds. Geol. Soc. Lond Spec. Publ., 173, 1–23.

Stein, M. & Hofmann, A.W. (1992): Fossil plume head beneath the

Arabian lithosphere? Earth Planet. Sci. Lett., 114, 193–209.

Sun, S.-S. & McDonough, W.F. (1989): Chemical and isotopic systema-

tics of oceanic basalts: implications for mantle composition and

processes. in ‘‘Magmatism in the Ocean Basins’’, A.D. Saunders &

M.J. Norry, eds. Geol. Soc. Lond. Spec. Publ., 42, 313–345.

Taylor, S.R. & McLennan, S.M. (1985): The continental crust: its

composition and evolution. Oxford, Blackwell, 328 p.

Weinstein, Y., Navon, O., Altherr, R., Stein, M. (2006): The role of

lithospheric mantle heterogeneity in the generation of Plio-

Pleistocene alkali basaltic suites from NW Harrat Ash Shaam

(Israel). J. Petrol., 47, 1017–1050.

Westaway, R. (2003): Kinematics of the Middle East and eastern

Mediterranean updated. Turk. J. Earth Sci., 12, 5–46.

Westaway, R., Guillou, H., Seyrek, A., Demir, T., Bridgland, D.,

Scaillet, S., Beck, A. (2009): Late Cenozoic surface uplift,

basaltic volcanism, and incision by the River Tigris around

Diyarbakir, SE Turkey. Int. J. Earth Sci., 98, 601–625.

Wilson, M. & Bianchini, G. (1999): Tertiary-Quaternary magmatism

within the Mediterranean and surrounding regions. in ‘‘The

Mediterranean Basins: Tertiary Extension Within the Alpine

Orogen’’, B. Durand, L. Jolivet, F. Horvath, M. Seranne, eds.

Geol. Soc. Lond. Mem., 156, 141–168.

Yilmaz, Y. (1978): Relation of Bitlis Massive/Offiolities in the

environ of Gevas (Van). Proc. 5th Petrol. Congr. Turkey. In

Turkish: Gevas (Van) dolayinda Bitlis Masifi/ofiyolit iliskisi.

Turkiye Dorduncu Petrol Kongresi. Bildiriler ve Acik Oturum,

83–93.

— (1990): Comparison of young volcanic associations of western

and eastern Anatolia formed under a compressional regime. A

review. J. Volcanol. Geotherm. Res., 44, 69–87.

— (1993): New evidence and model on the evolution of the southeast

Anatolian orogen. Geol. Soc. Am. Bull., 105, 251–271.

Yilmaz, Y., Guner, Y., Saroglu, F. (1998): Geology of the

Quaternary volcanic centers of the east Anatolia. J. Volcanol.

Geotherm. Res., 85, 173–210.

Received 7 October 2009

Modified version received 9 February 2010

Accepted 22 February 2010


http://dx.doi.org/10.1029/2003GL0117858

http://dx.doi.org/10.1029/2003GL0117858

Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area: Mt....

Documents

Transcript of Early activity of the largest Cenozoic shield volcano in the circum-Mediterranean area: Mt....