Acta Vulcanologica - Yol.7 (2) - 1995: 53 - 61

K-Ar datings of Neogene-Quaternary calc-alkaline volcanic rocksin Romania

Z. Pécskayl, O. Edelstein2, I. Seghedi3, A. Szakács3, M. KovacS2, M. Crihan2, A. Bernad2

I. Institute of Nuclear Research of the-Hungarian Ac-ademy 9[S9ielces, Bem ter 18lc, H-4001 , pÍ'51, Debrecen, Hungary

,. o",,];,íÍi{ji,,?,!TÍí?;i|,{,,,,!f!iZi,,lxÍ;#f ;i,Í33En{;,;;"x,",T35|!o.-,,,,

Abstract

Neogene-Quaternary plate convergence-related calc-alkaline magmatic rocks from Romania have been dated using theK-Ar radiometric technique. The magmatic rocks occur in the East Carpathians and the Apuseni Mts. In the

-East

Carpathians, the discontinuous magmatic arc is segmented into two main volcanic areas' Oaq-Gutái (oG) and Cálima-ni-Gurghiu-Harghita (CGH) at the extremities and an intrusive (subvolcanic) segment (Jibles-Toroiaga-Rodna-Bárgau: TTRB) in the middle. According to biostratigraphical data, volcanic activity started in the,Badenián' but theoldest rocks are dated atL3.4 Ma. The volcanic activity ceased at about 0.2Ma.

The range of apparent ages during Pannonian (9-11 Ma) in TTRB is partly coeval with that of OG, reflecting theparoxysm of the magmatic activity. The longest interval of activity was detected in the Gutái Mts. (13.5-6.9 Ma)-. Anobvious age progression along the arc was pointed out for CGH volcanic chain, enhanced along the terminal 40 km ofSouth Harghita Mts. (4.3-0.2 Ma). Preliminary data from the Apuseni Mts. suggest the Sarmatian as the main intervalfor magmatic activity in that region (13.4-12.4 Ma).

l. Introduction

This study deals with the geochronological interpreta-tion of K-Ar ages from the Romanian volcanic areasperformed at the Institute of Nuclear Research of theHungarian Academy of Sciences (ATOMKI), De-brecen. Before the earlv 1990's onlv a few radiometricages were available (Rádulescu et ál., 1972; Edelsteinet al. , 7977 ; Michailova et al. , 1983; Peltz et al. , 7987 :Lemne et al., 1983). In order to improve the knowledgeof space-time evolution of the volcanic activity, especial-ly in the East Carpathians, systematic K-Ar age deter-minations have been undertaken, starting in 1990 withinthe framework of a bilateral scientific collaboration be-tween the Romanian Academy and the HungarianAcademy of Science. At present there are more than300 age determinations on about 250 samples, coveringall the studied volcanic areas. Some of these data andtheir interpretation have already been published (Edel-stein et a|., 1992;1993; Pécskay et a|.,1994; Szakács eta I . , 1993 ) .

2. Methods

Most of the K-Ar age determinations were carried outon whole rock samples because of the mineralogy andtexture of the investigated magmatic rocks. Secondarilyaltered specimens were eliminated after microscopic in-spection of thin-sections. The samples were degassed ina conventional extraction system using induction heat-ing and were measured by mass spectrometric isotopedilution with an 'oAr spike using a mass spectrometer(magnetic sector type of 150mm radius and 90" deflec-tion) in the static mode. Recording and evolution of theAr spectrum were controlled by microcomputer. Kanalyses were made using standard flame photometrictechniques. K and Ar determinations were checked reg-ularly bv interlaboratory standards LP-6. Gl-O, HD-B1

and Asia 1/65. Atomic constants suggested by Steiger &Jager (1977) were used for calculating the age. Allanalytical errors represent one standard deviation (68%analytical confidence level). Since we base our analytic-al errors on the long-term stability of the instrumentsand on the deviation of our results obtained on standardsamples from the interlaboratory mean, the analyticalerrors are likely to be overestimated. Details of the in-struments, the applied methods and results of calibra-tion have been described elsewhere (Balogh, 1985).

K-Ar ages of suites of volcanic rocks generally are ingood agreement with geological observations. However,both Ar and K concentrations may undergo changesduring the history of the rock, due to diffusion, solutionor ion-exchange. Since misinterpretation of themeasurements because of excess Ar or diffusion de-ficiency cannot be excluded, partícularly in some of thesub-volcanic and intrusive rocks, the isochron methodwas also used. On the other hand, the long-lived andcontinuous volcanism may have caused Ai loss fromsome samples. The full significance of this phenomenonhas yet to be evaluated. In this paper, K-Ar ages areconsidered if their reality can be supported by geologi-cal, stratigraphical and petrographical arguments aswell. For stratigraphic classification, we use the interna-tionally accepted time-scale (Vass & Balogh, 1989).

3. Geologic framework

The Neogene-Quaternary volcanic activity is consideredto be a response to compressive tectonic phases postdat-ing continent-continent collision and developed alongthe inner part of the Carpathians (Sándulescu, 1.988;Royden & Burchfiel, 1989). The Neogene volcanics ofthe Carpathians are dominantly calc-alkaline and arediscontinuously distributed along the inner side of theorogenic arc forming an elongated chain runningthrough Slovakia, Hungary, Ukraina and Romania. In

53

Z. Pécskay et a|.

Romania, Neogene-Quaternary calc-alkaline volcanicsoccur in the East Carpathians and Apusení Mts. TheEast Carpathian magmatic arc consists of (1) a northernvolcanic sector: oag and Gutái Mts. (oG), (2) a centralintrusive (subvolcairic) sector: Tible;-To;oüga-Rodna-Bárgáu MtS. (TTRB) and (3) a sóuthern volcanic Sector:Cálimani-Gurghiu-Harghita Mts. (CGH) (Fig. 1).

The OG segment typically consists of calc-alkalinerock assemblages ranging from basalts to rhyolites. Aseries of isolated (in oag Mts.) or complex (in Gutái andOas Mts.) volcanic edifices and associated or isolated (inthe'Poiana Botizei area) intrusive bodies have beenbuilt-up. Medium-K pyroxene andesites are the domi-nant rock type in the Gutái Mts. (Kovacs et a|.,1992).

The TTRB segment is characterized by swarms ofsimple or complex intrusive bodies. They pierce pre-Mesozoic metamorphic rocks in the Rodna andToroiaga Mts. and Upper Cretaceous to Lower Miocenesedimentary deposits in the Tibleq and Bárgáu Mts. Thecalc-alkaline bodies mainly coísist of intermediate(andesite, diorites, monzodiorites) and acid (dacites,microgranodiorites) rocks.

The CGH segment is a ca. 160 km long continuousvolcanic chain with its width, height and volume de-creasing from north to south. Most of the chain isformed of calc-alkaline andesites, although basalts,basaltic andesite (especially in the Cálimani Mts.) anddacites are also present. A slight tholeiitic trend hasbeen identified for the early volcanic products in theCálimani area. The southernmost South-Harghita seg-ment is notable for its alons-arc variations from calc-

alkaline to shoshonitic compositions (Seghedi et al.,1986; 1987; Szakács et al., 1993).

The Neogene volcanics in the Apuseni Mts. are most-ly located along a ca. 100 km long NW-SE alignment inthe central and north-western part of the Metaliferi Mts.They extend to the north-west in the Zárand Mts. andthe adjacent Zárand Depression, and consist of andesiteand dacite lava flows, volcaniclastics and shallow intru-sions and minor rhyolitic-rhyodacitic volcaniclastics andlavas. At the south-eastern extremity of the area, in theMures Valley, an isolated rock body of shoshonitic com-position occurs in the morphologically prominent UroiuHill. A second occurrence in the northern MetaliferiMts. (Baia de Arieq-Rogia Montana-Bucium zone) con-sists mostly of anddsiticjdacitic intrusive bodies aíd t*onecks of basaltic-andesites (Detunata).

4. Results and discussion

The results of the K-Ar age determinations are given inTab. 1. For the OG and CGH segments where a largenumber of K-Ar data are available, histograms showingthe range of the ages have been constructed (Fig.2). Forthe other areas (TTRB and Apuseni), an insufficientnumber of samples have been analysed and the resultsshould be taken as preliminary. Fig. 3 shows the synth-esis of the age data, according to geographical area, andcompared with Mediterranean and Central Paratethystime-scales.

íd

.L(t

, ? '

54

K-Ar datings of Neogene-Quaternary volcanic rocks

TaP^l", l^ . K-Ar datings of Neogene-Quaternary calc-alkaline volcanics in Romania performed in ATOMKI, Debrecen, during1990-1994.

oA$ MTS.

Sanplc no. lmtity Rmk type Dttcdfnctinr

x%

fi Ar rid%

{0 Ar ndc STPIp

K.Ar4e(Me) , Rcfme

I a 4 5 6 7 I 911 797 E Sunltmrm V b i \.67 2 5 3 1.6&r l0-' l l 9 í 0 7óo5R'9l X Mcdieq Vii-(raqu N,ru R q-r 3t3 3 9 8 l-1rl lo?- I t 0 r 0 . 55.!o5 2 C leleznic Fal w.r .63 E 2 9 6 9 r 3 l 0 l O . 9 i 0 4ó0ó2 93 N Tu4 lF23ó'/416) lúDtpr q . r 2 t t 7 l t7 l ü . l 0 E i 0 ó21 565-L BatrE Vlsului Sumit w. r u z5 I 4.351 l0 l 0 7 r 0 . óte 757-9t E Sarce Hill APT w.r 4 t I l 7 5.t22 lO' l0.ó t I.2n12 A{ rurE IÚmHill v r . t 3 l 4 7593 lO l o . ó 1 0 6zz.5Tr-t9L PictÍele dc cará v API w.Í ,03 3't 6 { 2 6 4 ' l ü ' 10.6 ! 051777.E9 c) Gcarrtm Hill Ilpr v.r .T 3Z.Z 9.192 tO' l05 Í 0.5t.l 701-t9 E Iroiana $au Ap{ ltvJ. 7E 4 1 . 3 72ót ' l0.' 105 r 0.5l77E-90 Gruiului FmI Dpr 9 J 97 6ó'3 7 714 tt', lo.4 r 0.422 582-E9 L Plc|.ula HiU Diqz g.r 5ó L1.7 ó lB l lo, 1 0 . 3 i I I27 56-92L Negm tül| Aqz g.r z.@ 57.7 E2E5 lÚ' l0.Z r 0.416&{-t9 H Tlrlo\ V A4z ÚJ . tr L7 1 . |5ó3. lo. , lo.l r 0.977.s67-CZL Curturii V Aqz w.r 2.9. l3.E 9.O19. ld ' lO,0 r l.O45ót.1 c (,iltr V Ápr w.r. 2. 19 1 5 4 E..lEl . lo 9'9 Í 0.97o7ó.9l M Ghc4! Qurrrt fl\4, Dprbj g . r 2.01 zo. I 7.733 lO-' 9 . 9 i 0 722 5il -E9 L VlüoÍ tt|l.l ÁPr v.Í 2.4 5 0 5 9.399 ld' 9-7 LO.420 s Saca Mine APx w.r 2.63 2E.8 9.t52 ld' v.o t o.o60ó l -93 K Fn.in V. (GhcrF I API w.r 2.E l 129 l 'o47.tü- 9.6 r 0.419 5ó{ 9| E öllre| v' Dpr w.Í' z2t 19.3 8.14t l0-' 9.5 r 0.7

GI.JTÁI MTs.

7 E3 I,r 1.15 5.6 ó.0l0 l0. 1 3 4 r 0 . 724 00ó L Ráchi1clc V. ABpr P-r l . ó3 2 5 r t á t5 rÍ I3.3 r 0.E2ó}{.E9 Sa.E Eill Dpr w.Í 2.70 45.6 1.3E5 .lcr 13.2 + 0.69222,90E MrÍ€ v. (ciceÍhu| ABpr w-r I t o 20. I 6.624 tt l 3 . l ! 0 .925 25ó.90 Nirtru ql8rÍy ÁBpx WJ t.z9 2 5 0 ó.352 rü, 1 2 6 r 0 . 825.25b,t\ Nt'tÍü q|aÍI}' ABpr v.r t . 5 J 3 8 3 ó.z75 lo., 12. l r0.627.2 35 -O Forcubi V (Ilbat API w.r L-76 720 Ef,12 . lo-' tz.o * 0.5zauF2al Firizan gallery A4z \t.r t 7 8 252 8.103 l0-' I 1 . 7 r 0 . 7l5 792 Ee E Bu|zulrli V (Dáncoüi Dbi B i ó.6p 4 3 5 1 n t ? . l f I l ó r 0 . 5 3

2 :t 4 5 6 7 I 9tE 330-9t E LrlÍnu Pcat AAL w.Í I2ó 240 5.óó5. ld, l l 5 r 0 . 7ETrZ t'&1 }bÉna crmB Paf Aqz w.r L.T1 73, I 7-7t7 tO-' . 3 1 0 425.E.Í3 90 VáIini V w.r 2.0I 47.2 8.752 r0 .z ! 0.5975-BE U3tu0 v AAz s.r . 51 3 7 5 6.47r tO 0 * 0 5 325 050 Mlgura Mare Peat fur !Y.Í .63 5 6 8 6'xó. lü, 0.9 r 0.5 322 B-E5 PiatE Tilei Pat Aqz g.Í .6 7 4 9 70u l d ' E r 0 412.522-t9 E Íljrcm Pa} \zanptbi w.f .ó4 407 ó909 . lü E i 0 . 5t 9 5 l { GutiDul!i v i nBpr q. r .q 247 5.197 . l0 ' 0 . t ! 0 75590 M $uror C4nrrt ÁBPx g.Í .39 32.7 5'7tó 10.. 7 ! 0 . 527 E23-t3 Gorlieb v ADÍ w.r . 4 1 t7.3 5 ' t 32 ' } ü C.6 r 0.92 4 m 5 L Piatm Tirci ItaI A4z lv.r 5 l 497 ó.70l lü l I 4 r 0 . 5z7 ffi793L Chicem ftal ABpr lY. r 2t 3ó.5 5t59. rO 15 i 0.5529ó-9l Bud.{ti QuarÍ} ABpr v.f .@ l B 8 {.390. rd I1.2 r O.9t717,8t E Rotudu Sumir APX gÍ. 5 l .13 3 6.W1 . tt 10.3 r 0.520.E20 L srur v AtbI w.r .43 3ó.0 s . rn . t t ' 10.3 r 0.5 37999-&4. E Tumu Ars V ÁBpr w-r 26 59.9 5.O3A. r0 102 r 0.15óto Á.t3 E Hi8é EaI Apr w.r 53 1 . 7 ó.o5o. lü, l0 . l r 0.55Tt9-C2C Jióovn V Apxsm ÍlJ. l9 3 ó 3 .1565. rO 9.9 r 0.525 t2.+-s Brlze suÍÍrrrrit Dtnpx w.r. 1 7 7 r.05E.rf lO .0 r04 J

z7 562-vZL HolrrÜt Pcat APx 9J. 45 47.5 i583 ro 9.9 r 0.1z7 561-.12 L srlniloÍ sumií Apr w,r .82 55,.r 6 .ym' rÍ , 9 . 8 r 0 4 t

14.593 L MoÍo.á sumit ÁBortÍn w.r. 0.7E .í3.o z.9o3 . lü' 9 5 r O r ll6m-t1 E Bngr Fcal .4pxÍÍ'bi w.Í L-W 657 6',ltE. Iü, 9-3 r 0.467t4-FB2 lgDrq Smit Apr w.r 1.94 4 r 7.063. lü' 9.3 i 0.625.t99-t9 Gutei Sumit Ápnnüi v.Í z2z 4 3 4 7.998 rO' 9 . 3 r O 4 J

25.E79-E9 Gurii Sumit ApErÍü' w,r z.& 3 E 4 t .6ó7. td ' 9 . 3 + 0 467l3 Á.90 F IÍnirsmil APx w.Í 1.62 49.0 5.773. r( f ' 9.1 r o.4 I

ó7 l3 .9o F Ignr{ Smil Apr W.r 1.94 70.6 6.827 lO'' 9 . O r O 4 I15.103^E9 E GÜlfu snTÍniÍ Ápx!ÍÍtb' lvÍ 2.52 35.2 t . t l s . l 0 9 . O r O 4 326 106 90 vidÍ8 v w,r 0.Eo 1 5 6 z767 '1Ú, E.E I O,E5&7-0).t Bf,ii v B,f. . l ó 2 0 ó 3.595. l0'' 7.9 r 0.620 4-9ZE w.Í 5a 50.9 3.X7 lO 7.7 r 0.325.256 90 ts€Ídu v v.r 3t 1 5 7 3.t7 l . ld 7 .6 rO7 z20 943-90 E Rmcului \r Bpx tv,r 3't 2,Í.8 ' lÍ I 7.O ! O.4 z

55

Z. Pécskay et a|.

Table I (continued).

POIANA BOTIZEI STTBVOLCAMC ZONE

z J 4 5 6 I 9l l t(n E7 E Rlmati ferl mDrpr w.Í 1 4 3 18.0 ó 282 l0. IJ * O.9

2437-A7 B KOUr V. ÁpI 1{.Í ' l.5o t < ) 6.52l ' lü , t 1 . l i 0 . 74293-E7 M lllrnului V mDrpr B - t l . t 2 25.E 4.572 l0' l0.4 + o.ó7557-A7 H bimn V Ápl 9 . t l .4b 1t.9 5 9(}5 r0', 10.3 t 0526029-E7 bgului V MDipx s.Í. 1.79 37.1 7. lE t0 10.3 r 0525.E98-87 hiráccle Pat DbiaÍpl g.Í. 2 6 3 .12.6 9 9 3 lo ' 9.7 r 0.4IE EI7 .E7 L Rmalr Fal Dbnnpr q.t 227 ól .0 t 2 t0' 9.3 10 .425 40ó A.E7 PÉrrms PEat QDrpr qJ- 1.9ó 33..1 7.ffi lo 9.3 r o.5309r,t7 H Izvtrul l(uqulur V DPx'rói w.Í. 234 19.1 E .2 t3 , t d 9.O r 0.4

TIBLE$ MTS.

26 073-89 stcaoÍa Fcal ODrpr gJ , .19 37.9 6.6n.r6', l15 r 0526 072-t9 Stegime Surrrnit Qhpr w.t 35 47.b 5.358' |ü lo.9 r 05l9 767-92 E Hudict Feel Dbx v.Í t 3 zz5 rt.76 lo 10.6 r 0.719767 A-CZE Hrdiet Smit Drpx gJ . .4t 50.7 5.609 10', lo2 + o.,{15.E8GE9 E AÍter &rrÍrru| API g.Í 50 L7 -'t 5 96ó ' rd, 102 1 0.823,978-E9 L Iludrn Surrrnil ÍtGD!bánbr w.Í. 26 53.8 r.r3l ld' lo.o * o.49Eó Aric{ubi V mGDibianpx B.r. 221 44.0 E.6ol lü, 10.0 i 0.4x'o9ÍJ7-9zE AÍccr F]'l.ry MDipt v.Í 279 29.1 l'oóE.rcr 9.E r 059E5 cücad.loÍ v MDipr SJ 1 5 t .1O.0 5 óóó. r0 9.ó + 0.4zgz-89 a GÍobot D.rÍPx g.Í. l 5E 14.6 5.El.í t0., 9.1+O.920 9(}5-92. E ÁrceÍ Pe.l Ápr w.Í l.ó9 3 6.2t7 tt' 9.4 r 0.6zo90ó,92E AÍcd sutrmi| ÁPx s.Í' t-42 33.0 8.262 rd' Ü.7 * o.420 908-92 E AÍctr cÁllffl MDipx w.r 220 34.1 7 078 10" t.3 a o.4

TOROIOAGA MTS.

19,316-9t E S6ulu.i v. 6Dibi bi ó'ó9 51;t 2..497.ttr' 9.6 !0 .1

19 316-91 E Secului V. GDibi Íp t . I9 30.t 4.5(n lü 9.7 r 0.526 1ff) 9l E TmicgESmil Abi íp o.T7 zz5 ) <ü ln. 9.0 r o'ó

RODNA MTS.

RI-3 | tumcu

RD-s I Cmii DriED I i Tumuri

10,4 ! 0.t9-9 t O.7

CÁLIMAMMTs.

CL -61 DoÍni{cra QlEfr' ABPI g.r 05r lo.4 3.r90 lo 11.9 r l . fC L - 6 E DoÍm v Ápt v.r o.79 32.4 3 ' z T2 , |Ü lo.r ! 05

vL6 stánca'i Qnrry ABpr w.Í. l , 3 r 232 4.96 tü, 9.O ! U.O

CL -57 ttl.lm (JualÍ. Áam g.Í t.47 38.3 5.38ó. r0 9.4 tO.4

cL - 4't Bofordniq Qurry Dam g J 2.76 65.7 9.ósó ' ld, 9.0 * 0.4C L - 4 2 Cica Mim Surrmit Árm w.Í, 0.73 20z 2..ó5 l0 E-7 r 0.6c L - 1 4 N€aíÍa v Apnm v.Í t59 .|ó.3 5.2qt to E5 r 0.4CL -TZ Budacu V, Á!m w.Í 0.95 23.7 3 ró5 |0, Ü J t u J

c L - 1 6 aqlilhtj \j. AaÍpI w.Í t . t t za.9 6 ol' l . lO E2 10.4

CL -76 sc8unul suÍÍrÍrit API vJ. t.Tz 62.t 5.45r, ld ' E2 ! O.3

C L . 9 TopÜciora V Á'm w-r 'óo 55.9 5.050. tü 8.1 r o.3337-I hrulüi v ABpx w.Í 1.43 54.E 4.527 'tt E.l + o.3c L - r o Ilipon V ABpx w.Í 0.E0 9.0 z-48a. tÜ E.0 r 1.2CL- T5 ouÍo llaitci Aprem v.Í l .19 !9.4 3 & 4 . | Ú , 7 . 9 L O 1

C L ' ó B Neooiu RorÍtnerc Peal MDrpxrm Ü.Í' 0,3| 3.|ó 3{).t 9 '6E5. lü 7.9 !O-4

C L . 1 Vevojeera V Dam g,r l . l E 16.2 3.623 lO' 7.9 r O.7C L - 3 8 Pictricehl FeaI Dbianpx m.dÍn 0.ló l .7t z 1.8 3' l9 l , |Ü 75 Í o.5C L - 6 A Nepoiu RorrÉner FeaI MDipxam E.r 0 .31 3'|ó 30.5 9.127 .16 ' , 7 4 r O . 4JJO) trver Rrdce Apx w.t 2 4 8 79.8 7 .138 . I d 7 4 r 0 . 3q - - 5 Netoiu RonÉnerc PeaL Dbianpr w.Í t-92 17.7 {28 . lO 7 . 3 t 0 6

56

K-Ar datings of Neogene-Quaternary volcanic rocks

Table I (continued).

t 3 { 5 6 I 9c L - 3 PielÍicclx| P€al Dbnnpr E. r 0 .16 l.5ó ó1-5 4 4{n l0- 7 . 2 i 0 3

c L - 3 Á Pietricclul Feal Dbiarnpr mÍm 0.|ó 224 tz.7 ó 2 E 2 ' r d 7 . 2 ! O 4cL- 2 fi Rrtitis PeaL ÁpI Ü.r z.t7 14.7 ó 039 lo 7 . 1 r 0 3C L - 4 4 Bátcqu| Qxl!rr'. ApI Iry'Í L T I 35.8 4 tEo l0 ' 7 . 1 ! 0 . 334 l3 Tamita Ridge Danpx wJ. t.4'l 25.3 3 995 lü 7.O + 0.133óó Llvci fudce AaÍnDxbi q.r z.z3 7r.6 6 033 I0 ' 6 . 9 r 0 3c L - l hrtumul V ÁpI w.Í z.tz 31.0 6.203. t0 ' 6.9 r 0,1

Rltit$ PaL ApI wJ . 2 .17 53.2 5.7U t6', 6 . E r 0 3c L - 4 Ncqoiu RgÍilcr Fa} ÁDr w.r z.o5 2 t . E 5.377 tO- 6 . 7 r 0 5

GURGHIUMTS.

39t9 MlcuE dc Sur v Á!m w.Í 0.71 z1 .E 2.5.6. r0" 9.2 ! O.TG - 8 3 ZarpezcL Fcal Bpxol w.Í l.0t I T . L 3.714 lO' E . t r 0 7G H . 5 3 Salrrd V Armpx l.Í 124 4t2 4 . tE3 . t d ' t .7 r 0.4G - l ó l Mtgm lrtarc Ral WJ l .0r 3.í.l 3 . 3$ . r ü t.6 Í 0.,to H - 5 7 Itlael v Á!m E.Í 0.E? 20.2 L.73É. rt ' Ü.) : l0 'o39ú Piciorul Fopii-Jina Ápr w.Í o9z , 1 ) 2.988. l0- E. l i 0 .56 H - 7 0 sobrá v. ÁpI g.r. 1.39 t9J .í.435 ' I0., E.2 r 0.63914 Fámel Fcat APrlm w.r. 0.94 4 t 2.9Eó rd E.2 r O..lG B - s r *D€8 v ÁpI v.Í 0.9r 5t.4 2.tóE rü E l r 0 . 3G H - 5 6 FBnccl V Aprlm w,r. l . Ir 2 3.5fi IÜ E 0 + 0 . 46It 59 r8nccl v ABprol * J o.76 210 2.3ó3' ld, t.0 + 0.5G H - 1 3 . { t|oru-Sácüdat V Apram 9.Í. l .m 37.4 3.(}zl lü, 7.E Í 0 '4GH.74 Bótráná Rilge Aprm w.r l '4ó 59.4 4.2C7 lc.' 5 r O . 3GH -,+8 |JACta Á!m w.r, 1.34 70.9 3 t95 r0', 7.5 ! 0.36 H - 6 1 Gurphirlui \', Árm w.r 1.@ t.6 2.994 lO"' 5 r O 9G H - í ) Fu8cQuÍry€orod Ápm w,t l , l 3 42.3 3.264 10', 7.,t r 0.3GH- 35 Brcin hss Apx w.r. I l l 58.0 3.095 r0', 2 + O . 3G t I . Í } Drumul uü GotTiIá Y' Árm v .Í , I . I E 62.9 3.243. td ' , 7 1 i 0 . 3

G H - 6 2 North guca Smit ÁPlam WJ 124 30.2 3.399 l0-' 7 0 r 0 . . 1cH ' ó{ . Iubül ouErn' ÁBplrm w.Í. 0.E9 53.1 2 433 l0'' 7 '0 Í 0 '3G H - 4 1 Bscts v Á!ÍTpx v.Í. 1.32 I I .0 3.608. ld ' 7.0 Í 0.9G Z O Miguncea Sunrnrir Aam w l t .30 31.0 3.520. t0 7 o Í o 4G H - 6 1 Iuhodul Dmcului V Apnm v.r. t 2 l 2ó'6 3.255 lü, 6 . 9 r 0 4GH - blr Bc'rzont Sumit Apx q.Í 0 E l 20.t 2 l.l2 l0 6 E i 0 . 5

*.rw.Í

135i sfruoul v Al'xam 27.9

NORTH HARGHITA l\{TS

l.r2 I ls.s' . I i - l_ 1íJ

-

3.213 tO" i 1,4 ! 0.3

I 0o I 41 .74 l 1 9 l ü ,

2 .407. lO" | 6 .2 I O.3 i1íÉl llo=]---T- 6., i o.4---T-

2 231 lü

t IR- t Iobf f ia tüsur rmt Arnpr W.r I rlt 32.9 3 628 . lü. 6 3 r 0 . 3l,ok v Ampr w.r 1.39 472 3',t('. rü 6.3 * 0.3

BC - tol Citr B..in lmlEn16 ADT v,r 1.03 25.3 z 162 ' |Ü, 6.2 ! 0.4

I l v o V Aplam w.r LEO 30.r rl'z18 lü 6 .010 .3Bc lft.ó\ Citr'B8rin l@Ylll4 Ápx w.r t 4 t 2 4 4 3. lE2 Iü , 6.0 r 0.1TIR 32 ciM8c QurrÍ}' ÁPl w.Í L.TI 20.6 4.@5 r6'. 5 9 r 0 4t I R . 3 Rsczt.bÉl v l.tsm s,r 2. ló ffi.7 4.917 Iü, 5.E r O.2IIR - 28 Rácbi|io smEnit Dam w.r 35.6 5.374 16'. 5 . E r 0 3H R - 3 8 TüÍEtti Atr w.r t .12 z l . { 2.540 Id' 5.E t 0 .4

IIR - 30 sr'Éu v ÁPÉm w-r 2 . t l 5 5 3 4.735. lü 5.t r 0.2vL- lm4 Filio 1 ÁfI w.r z.gz zo.7 4.505 . tfÍ, 7 ! O . 4

I t R - 3 3 st' BuÍnjte| suÍÍÍÍu. Apr w.r 1.97 ló.4 4 3 5 l ' t ü , 5.7 r 0.5H R 4 MtdáÍa{ v QErrJ' APr *.Í l . 3a z7 -o 2 877 l0 ' ).o t u.J

w ,307 Ií'rgbln Mrd' s.lmil Apx w.t 0.98 5t. r 2.o&1 tÚ, 5.6 r 0.2Mádán{ sat QErÍ'' ÁPr g.Í 5ó 32-O 3.290 Iü, 5.4 * 0.3

HR -.1o W Dtoe0ti ÁPx s.r. 39 t7.0 2.v26 r0" 5 4 + 0 . 4l l l , - 1E{ BoÍtz v Apr WJ .20 zz5 z.4Tt ta 5,3 r 0.3! L . 2 0 9 E }Lr'hlla Bái Apxam w.Í I9 t i .9 2.t73 16 5 . 1 a 0 . 6

L ! - 8 s v aÍv Dam w-r 't9 52.9 ] 448 lC 5.0 t o.2w , 1 1 2 2 Filic'V Aan{tx w.r 35 .18.0 4.504 t0- 4.9 ! .O.2

57

Z. Pécskay et aI.

Table I (continued).

I 2 3 4 ! 6 7 I 9H R - 4 1 Rscu I APx WJ t23 42.9 2.353 10" 4.9 r 0.2H R . tI Bái Driu lo55/lo5 API w.r l . 5E ) ) ) 3 m4 lÍ, 4.9 i 0 .3LV - I55.4 Tolvaios V ÁDx 159 20 I 2.985 . tü 4.8 r O.3V L - O U v8r.scrhcE RrdÍ'e ApI WJ t 1 5 23 I 2 m4 . l d ' 4.5 I 0 .3w - 8 8 E llanhito Ciccu Darnpxbi v .Í z-o't I 1 . 3 353 l ü , 4.1 r 0.5

SOIJTH HARGHITA MTS.

tIR - tá Bibortcúi API uJ. 0-9t E.3 z,71! ' |Ú ' 5 . 9 r l 0I { R - l l Bib.'rFÜ Apr w.r, 0.t9 1.7 1.93,1 tO' 5 . 6 r L 7vL- &51 Tolnios hss Ápx q.Í 73 2 1.2 z.x)l t6' 4 . 3 Í 0 3B C - 3 8 CiE E3uo LW1274 ÁpEm w.Í 35 3 I . I z.263 |Ú, 4 3 r 0 . 2BC - t { Cir B$in lml/234 Áanprbi g.Í .69 lz.4 2.óló Id 4 . O + 0 4ITR .6 S lrzo Rrdqe Apt B.r. 42 t1.'1 ) rn1 l?I 3.7 * 0.3n x - conc|ü v Apram w.Í 1.t.0 2.39I td ' J.O * 0.O

c - l m w cucu R|dÍc ,qlmpr w.Í 3 l 39.E r .(26. lO z.E r 0. l 1c - 3 V.lca MtrE V Álmpl 9Í. 1.39 39.3 r.504 rd' 2.8 * 0, 1

- !r! )r(it-i V ABPT q J I.35 n 4 l '33ó lü 2.5 r 0.3 1c . u 5 DL FotruJui smit Áamrbi w.r. z.6L 5 8 3 r.556 rO 2.5 Í 0.I 4

I I R - 8 Crxu Pal ÁÁnpI w.r t.14 15.9 4m td 2.5 r 0.2 4c - l 19 Xrput Sunmit Áan5ipr VJ 1.79 3E2 Á'6 |fÍ 2 . 3 r 0 4c - u N' cru Rldí( A!npr w.Í /ó tló.0 '@ |Ú z.3 Í 0. 4c . ó t Velca Mrrc rptinfs DÜnbi w.r tvt ű'7 .fió rÜ 2 . 2 * 0 4

P - Z t,tüt.í sllnrÍnÍt Dambt Bioritf b.4z t9.5 5.233 lü 1.1 + 0.TIR .9 Pilipa Ridp Áámbi w.r. t .E0 z7.4 t 3{I2. lü I . t i 0 .

H R . T O Pilirco RjdÍ€ Á!Íbi Biottt 6.Tl 20.6 3 943 lü 1 .5 +0H R - 1 3 B Balvanyos Drmbi w-r z.b 9 , I 9úz |Í" 1.0 r 0.2I I R . 1 3 A Balvmyoa Darnbi w'Í z .# ó 9 t.l8Í lo 0 . 9 r 0 2A M . 4 3 A Ilanml lvlre Sunrnit Danüi v,r 2 3 0 5.7 5.2m rC 0 . r 10 .2AM ,35 Kovcs Font Sunrnil Dambi Biotilc 7-33 7 n r 59A. tO' 0.5 + 0.1 .l

Álví - 2 s ]]l$cd Böl Quary Drmbi BrolrL r:6 4 . t l .3u ld 0.5 10.0A M - S Z N cioÍrndul Dambi 1r.f , z.u 5 o 2 270 rd 0 . 2 ! O 0 4

ZARÁND tl.ÍTs.

Z' 117 i liouth'lblagiu I _|ry-7 , - 51E6 lD rm i I r y*m

48.6

t b 26 ó 2 3 l 0 , I l ] 4 l o ó i

1 3 4 ! 1 2 i3.r 7 6 . t 95 10 " I l 3o i 0 . 7-5'E97_'lo.]---r_

'z E ] oó _

ó . l 4 4 . ' o . - I t 2 4 + o ?

5 293 IO

METALTFERJ MTS.

MM 2352 Curechi Afrz w.Í I . l t 6 .757 tO 14 1 ! 1 .7MM 222t Bucium cÍ.Ío HilI Á!rlm s.Í l 2 l t2.E 6 916 to' 14,6 r 1 .6MM 795 Brazi D w.r 1.25 t7.5 6.5E3 lü 3 5 ! l . lM M , t 9 3 Crraciu Álmpx q. r o97 54 4 7t4 Itr ' 12 5 10 .6MM - 4220 BaÍza . Bmd Apxam w.r 1.44 t4 .4 6.9n W 1 2 4 Í l . 2MM - 426 Brrd D w.r l-2,2 54.4 5.096 I0 ' l o 7 . 0 4MM. 776 ZlEbriF ÁPx'ÍÍbt 1{-f z'{ó 6 t7 I.ou . l0* l o 5 1 0 . tM M - E l Rotunda Arnpr 9.r 4 33.7 5.095 ld 9.3 r o.5MM 7I8 DctÜút8 ÁB *-r r r < 3.óo2 lü 7 . 1 ! O . 4MM 29 _4 timiu Hil'l SH q. r 3 3 E zt-o 1 . 6 i 0 I

Abreviations: B:Basalts; AB:basaltic andesites; A:andesites; D:dacites; R:rhyolites; SH:shoshonites; T:tuffs; Di=diorites;MDi=monzodiorites; mDi:microdiorites; QDi=quartz diorites; 6pi:granodiorites; mGDi=microgranodiorites; px:pyroxene;am:amphibole; bi:biotite; qz:quartz; ol=olivine; w.r. =whole rock; fp=feldspar; medm=medium magnetic fraction;mostm:most magnetic fraction; 0.31' 0'ló:below 0.31, 0.16 granulometric fractions.References: 1 : Edelstein eta|. (L992);2: Edelstein et al. (1993);3 = Pécskay etaI. (|994);4: Szakács et al. (1993).

OG segment

According to biostratigraphical data, acidic volcanicactivity took place within the OG segment during theBadenian and the early Sarmatian. However, acidic vol-canic rocks have not yet been dated by radiometricmethods because no suitable sample has been found sofar. Regarding the intermediate volcanic activity, mostof the K-Ar dates show a good agreement with the bios-tratigraphy (mainly for the Sarmatian and the Panno-

58

nian). However, they do not prove the biostratigraphi-cally defined Pontían-Pliocene volcanic activity.

Despite the fact that in the adjacent areas (TokajMts., Vihorlat Mts. and Gutái Mts) Sarmatian in-termediate volcanism is present (Pécskay et al., 1986)'in the Oas Mts. only Pannonian intermediate volcanicshave been recorded. Rapid and continuous evolution ofthe volcanic activity in Oag Mts. between 11.9 and 9.5Ma is obvious' In íhe Gutái Mts. the intermediate vol-canism was initiated during the Middle Miocene around

K-Ar datings of Neogene-Quaternary volcanic rocks

cALD.{.r Nt F x XenOxrrr-'l r r !

oUROHtu-; F-+-__ S. HARcHtTA________i

77D citrisr l.,Zjl

ffi -*",u 1a. !7)

$1."-or,r^ 1n. 25;

$ls xmoxrre (n . 2 l l

rutim

t a . 2 t I

í i . r ' l

oA?

GUla l

Fig.2 - Statistical distribution of K-Ar ages for OG and CGH segments based on data listed in Tab. 1. Frequencies of age intervalsof 0.5 Ma are given in percent for each of the volcanic areas separately (n is the number of analyses taken into account for each area;samples HR-l1 and HR-LA, from Biborleni, South Harghita have not been considered because they could belong either to a localvent or to a debris-avalanche deposit coming from a North-Harghita edifice).

E A s Í ( ^ R P A T l { | A N s )ERSANI lPusEtl

r ..1c6tÍol .r..X9l'{ 1 . " + C.írtrol rubvol(ohi. aQó . n l sdüm Elo|!

0or 6u tol Ti bl.r Tocogo Rodno Brí9öu ó l|óoi l 'mhI t ó ANAND

2

7

6

I

0

í

o -

.ó'9N I

N I

alt ln . 5

n = 4 ?

.N;,N-n . t N"t

Nu.t

W,N:

n3?

aii,,n . 2 5

7)0?Y)

A z t^a::

W:r

El lóh s ' l

VWn. t

- J 1 -

Ál{tEAx

- 5 3 -

- l t -

)^crAN

- 5 . ó -

- ó 5 --1.O-

-lJ ó-

^0o{|ÁN

1r71 2 SSSI

Fig. 3 - The space-time distribution of the Neogene/Quaternary volcanicsParatethys chronostratigraphic scales. 1 : volcanics and volcaniclastics; 2

in Romania, according to Mediterranean and Central= intrusive ísubvolcanic) bodies.

the Badenian/ Sarmatian boundary, and continued untilca. 9 Ma. Basaltic intrusive activity followed after aperiod of about 1 Ma of quiescence (Edelstein et al.,1993). The K-Ar and Ar-Ar datings performed on adu-laria (Lang et al.,1994) and illite (Bonhomme, unpub-lished data) of the hydrothermal mineral assemblage are

fully consistent with the ages obtained on fresh volca-nics. The paroxysm of the volcanism in Gutái Mts. be-longs to the Pannonian. The ages of the isolated subvol-canic bodies in Poiana Botizei area aÍe similar to themain Pannonian volcanic activity in Gutái (11-9Ma).

t .+ 0 A S +t l

59

Z. Pécskay et a|.

TTRB segment

In the light of the available data, it can be suggested thatthe subvolcanic magmatism from this segment belongsmostly to the Pannonian (Tibles Mts 8.3-11.5Ma,Toroiaga 9.0-9.7Ma, Rodna Mts 8.6-l0.6Ma and Bár-gáu Mts 10.6-11.9Ma) and is partly coeval with volcanic-ism in the OG segment.

CGH segment

Magmatism consisting of intrusive activity in the rangeI2-9.5Ma began at the northwestern periphery of theCálimani Mts. as the southeastern extension of the sub-volcanic zone of the Bárgáu Mts. (TTRB segment). Inthis segment, the oldest volcanics are located in the east-eÍn part of the Cálimani MtS. (9.3 Ma) and are repre-sented by dacitic rocks (Peltz et al., 1987). A long coevalperiod of volcanic actívity was observed for the Cálima-ni and Gurghiu Mts. (8.4-6.8 Ma). The K-Ar ages sug-gest that volcanic activity started at approximately thesame time in the Cálimani and Gurshiu areas but itlasted ca. 1.5Ma longer along the latler segment (Fig.z).

There is a slight overlap between the final volcanismin the Gurghiu Mts. and the onset of North Harghitavolcanicity (6.3-5.9 Ma; Fig. 2). It is notable thaioneNorth Harghita volcano and the northernmost SouthHarghita volcano were simultaneously active (Fig. 2).Following a period of waning activity of about 0.7 Ma,volcanism resumed vigorously along the rest of SouthHarghita and an enhanced southward migration isobserved for the three main volcanoes (Cucu, Piliscaand Ciomadul) of the chain-terminus segment, rangí.'gfrom 2.8 to 0.15 Ma. Ciomadul is the vounsest volcanoof the East Carpathians.

Apuseni Mountains

In the Apuseni Mountains, 7 samples from the Meta-liferi Mts. range in age between 14.7-9.3 Ma. One sam-ple from an intrusive body at Bucium (Northern Meta-liferi) gave the oldest K-Ar age for the Apuseni Moun-tains Neogene volcanism (I4.7 Ma). One of rhe twosmall-volume basaltic andesite outcrops at Detunatayielded 7 .3 Ma The shoshonitic rocks of Uroiu Hill (1.6Ma, Fig. 1) are coeval with the Southern Harghitashoshonites (1,.4-2.4 Ma, Michailova et al., 1983, Peltzet a l . , 1987).

5. Conclusions

Compared with West Carpathian calc-alkaline volcan-ism (Slavik et al., 1976; Durica et al. ' |978 Hámor etal., 1987), the Romanian East Carpathian chain is youn-ger. The southward migration of volcanicity along theEast Carpathian volcanic arc as a whole (Rádulescu etal., 1972) has been confirmed by geochronological data.However, within the northern volcanic sesments inRomania (OG and TTRB) no clear evidenie of ageprogression was confirmed. The longest interval ofactivity occurred in the Gutái Mts. (13.5-6.9 Ma). Theparoxysm of the magmatism in the OG and TTRB seg-ments belongs to the Pannonian (11-9 Ma) whereas themagmatism in the Apuseni Mountains is essentiallySarmatian. An obvious short-distance age-progression isseen along the southernmost South Harghita segment.

60

Acknowledgements

K-Ar age determinations were sponsored by the Hunga-rian National Scientific Research Fund (OTKA), Pro-ject No. T 7278. We are grateful to the following institu-tions for supporting in various ways the accomplishmentof the Project: Institute of Nuclear Research of theHungarian Academy of Sciences (ATOMKI), De-brecen, Hungary; Geological Institute of Romania,Bucharest; <Cuart> S.A. Company, Baia Mare, Roma-nia. We thank Drs. A. $tefan and E. Rogu of the Geolo-gical Institute of Romania for providing us with samplesfrorn the Apuseni Mountains. We are indebted to N. J.Snelling (Universidad Complutense de Madrid, Spain)for his suggestions improving the early version of themanuscript.

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