GEOL. CROAT. ZAGREB 1998 Upper Cretaceous - Palaeogene Tholeiitic Basalts of the Southern Margin of the Pannonian Basin: Pozeska gora Mt. (Croatia) Mirko BELAK', Josip HALAMIC', Vesna MARCHIG2 and Darko TIBLJAS3 Key words: Tholeiitic basalts, Upper Cretaceous­ Palaeogene, Upper mantle, Pannonian Basin, Poze­ ska gora MI., Croatia. Abstract According 10 the geological relationsh ips in the region of Poze­ ska gora MI. (the southern margin of the Pannonian Basin, nOrlhern Croatia), basic erupti ve rock s are considered to be of Upper Creta­ ceous - Palaeogene age. Detailed petrographic examination, based on phys iographic descri ption, th e chemical composition of major and trace elements, rare earth elements and stable isotopes, indicates that (hese primary tholei it ic basalts have variable structural-textural chara­ cterist ics, and we re postmagmatically affected by metamorphic processes . Tholeiitic basalts originated from the upper mantle, and were placed in the form of subaquatic effusions in the extensional zones withi n continental crust. 1. INTRODUCTION Pozeska gora Mt. is located in the transitional zone between the Tis ia tectonic megaunit and the Inner Dinarides (Fig. 1; KovAcs et aI., 1989; HAAS et aI. , 1990; SIKH:, 1995; HERAK et aI. , 1990). Basic rocks represent part of the magmatic complex of the NE part of the Pozeska gora Mt. , which is also composed of alkal i-feldspath ic granites and rhyolites (Fig. 2). Petrograph ic examination s of the basic magmatic rocks of the Pozeska gora Mt. have prev iously been incomplete, compri s ing part of investigation of the magmatic complex as a whole (KOCH, 1917; TUCAN, 1919; BARIC & TAmER, 1942; TAmER, 1947, 1955, 1959; SPARICA et aI., 1979, 1980; MAJER & TAmER, 1982). PAMIC ct a1. (l990) concluded that basal t magmas originated from the upper mantle, and that they are connected with continental areas. They included basic rocks within the bimodal volcanic asso­ ciation. I Inst itute of Geology, Sachsova 2, P.O.Box 268, HR- lOOOO Zagreb, Croatia. 2 Bundesanstalt fUr Geowissensehaften und Rohstoffe, Hannover, Germany. ~ Faculty of Science, department of Geology , Insti tute for Mineralogy and Petrology. Horvatovac bb, HR-1 0000 Zagreb, Croatia. On the basis of geological data KOCH ( 19 17,1919), TAKSIC (1944) and SPARICA et a1. (1979, 1980) determined that the volcanic rocks are of Tertiary age. However, discovery of "scaglia" limestone layers with­ in the basalts led PAMIC & SPARICA (1983) to their conclusion of an Upper Cretaceous age. HALAMIC et al. (1990) interpreted these limestone occurrences as enclaves, which together with structural measurements, was used as an argument for a Post-Maastrichtian, i.e. Post-Laramian age for the basic volcanic rocks of the Pozeska gora. However, MAJER & T AJDER (1982) proposed that these rocks represen t an allochtonous block, and that they are, according to their similarity with the rocks in the other parts of the Dinarides, of Tri­ assic age. Isotopic K-Ar analyses undertaken by PA· MIC et a1. (1988) determined the age of the acid mag· matic rocks withi n the bimodal volcanic association as 71.5 ± 2.8 Ma, thus reaffirming an Upper Cretaceous age. 2. BASIC GEOLOGICAL DATA The magmatic complex of the Pozeska gora is bounded on the northern margin by Neogene and Qua­ ternary sediments, in a partly tectonic and partly ero­ sional -tectonic contact (Fig. 2). Their southern margin is characterised by a tectonic contact with Upper Creta­ ceous deposits (Fig. 2). Acid eruptive rocks, which are the major part of the magmatic rocks, are represented by alkali-feldspathic granites, i. e. alaskitcs and alkali ­ feldspathic rhyolites (PAMIC, 1988; PAMIC et a!., 1990). Basic rocks mostly occur southeas t of Pozega, between the Vidovci and Komusina vil1ages, where along the northern margin they are in the contact with rhyolites and rhyolitic tuffs, and to the south are cov­ ered by Neogene sediments (Fig. 2). FurthellTIorc, these rocks have been found southwest of Pozega, south of Drskovci vil1age, where they are in tectonic contact with granites and rhyolites. A major part of the basalt body is composed of more or less altered basalts of different stmctural and textural vari eties , which are presented as a singl e unit on the geological map, since it was not possible to divide them into units appropriate for geological mapping. At some localities pillow lavas have been found, proving that the 164 Geologia Croatica 51n MARIBOR ........ NOVO ." MESTO " N A 10 o 30km Fig. 1 Tectonic scheme of the basement in the SW part of the Pannonian basin (from SIKIC, 1995). basaltic rocks originated from subaquatic effus ions (Fig, 3a), The second group of basic rocks of the Poze­ ska gora is composed of hypoabyssaI rocks, i.c. diabas­ es and subordinate gabbrodiabases. They arc rather fre­ quently represented as veins in granites (Fig. 4a) and rhyolites (Fig. 4b). Diabase veins have also been found in thc Uppcr Cretaccous sediments north of Bod lis (Fig. 2). In addition basic effusives and vein rocks, volcanic agglomerates, and basic tuffs have been discovered. In the basaltic body there are several occurrences of reddish to gray-reddish pelagic limestones which are up to 1.5 m thick, and of restricted lateral extent (Fig. 3b). These rocks are mostly sandy biomicri tes, micrites and sparites. Non-carbonate detritus comprises quartz gra­ in s, fine-grained muscovite, opaque minerals and a clayey-haematitic substance . Findings of globotrun­ canid foraminifera indicate their Upper Cretaceous age (pAMIc & SPARICA, 1983) . At several localities al ­ ong the Nakop creek, limestones are accompanied by acid tuffs. Boundaries between sedimentary rocks and basaltic lavas are almost always sharp and without load casts, and reactional boundaries are characterized by the recrystallization of limestones and loss of their haematitic component, as well as a decrease in grain size of the basalts ("frozen margin") . On this basis we may conclude that these limestones were enclaved dur­ ing effusion of lava on the sea bottom , and that the basic effusives are younger than the sediments. 3, PETROLOGY The analysed samp les were collected during work on Ihe Geological map of the Republic of Croatia (scale 1 :50.000) during 1989 and 1990. The modal composition was determined by optical and X-ray diffraction methods. Major elements were analysed in the Institute of Geology, Zagreb, by gra- Belak. Halmn ic. Marchig & Tibljas: Upper Cretaceous - Palaeogene Tholeiitic Ba.~a lts .. , ~' '. " .. ] ... ~ ~ M ~ '" ~ ~ ;:: lSJ <:> ~ ~ ~ ~ '" lSJ ~ D '" D . . ~ ~ ... M 165 Fig. 2 Geo logica l map of the magmalic complex of Poie­ ska gora M I. Legend: I ) ba­ salt s: 2) diabase veins; 3) rhyolites: 4) granites; 5) Up­ per Crc taceous sedimentary rocks; 6) Teni ary sedimen­ tary rocks: 7) Quaternary: 8) di scordant boundary; 9) bo­ undary of effusive volca nic body; 10) faul t: normal. tra­ nsc urrent: I I) reverse faul t: 12) gravitational sli ding: 13) re lat ive ly subsided block; 14) gravitat ional overth rust. 166 Geolog ia Cro:llica 5 [/2 Fig. 3 a) Pillow lavas in the Nakop quarry: b) enclaves of Upper Cretaceous pelagic limestones in basalts in the Pako quarry. vimctry, spectrophotometry and flame photometry, and some of the samples were analysed by XRF allhe Bun­ desanslall fUr Geowissensehaflen lind Rohsloffe (BGR) in Hannover (Table 1). Trace elements were de tcnnined al Ihe Ruder Boskovic Inslilule in Zagreb , and at BGR in Han nover by XRF (Table 2). Thc accuracy of the determinations was tes ted with international standards and was in all cases better then ±5%. Rare earth con­ tent s were determined by inductively coupled plasma mass spectrometry (ICP-MS) al BGR Hannover (Tabl e 3) . The accuracy of these analyses is also bette r than ±5%. The d iag ram s o f STRECKEISEN (1967, 1978) were used [or class ification of the basic volcanic rocks. Three diffe renl basic rocks were determined: a) basalts, b) diabases and gabbrodiabascs, and c) volcanic agglo­ merates and basic tuffs. a) Basalts arc composed of basic plagioclase (la­ bradorite), alb ite and pyroxene. Secondary components, besides albite, are chl orite, epidote, calcite, prehnite, pumpell yite, sericite, quartz and zeolite, and accessory are ilmenite, magnetite and apatite. Basic plagioclase is completely altered into acid plagioclase in approxi­ male ly 80% or the analysed rocks, while in 20 % of basalts basic plagioclase is preserved, but rarely unalte­ red, because of prehnitization and sericit ization. On the basis of structural and textu ral characteristics basalt s a re di v ided into several g roups: fin e-grained , medium-grained, coarse-grained , porphyritic and vesic­ ular. Fine-grained basalts with grain s up to 0.5 mm in size most ly have typical o phitic texture, while those wi th subophitic, intergranular, di vergent-radial , skele­ tal -arborescent and hyalopillitic texture are not so fre­ quent. Their structure is homogeneous and ves icular. Medium -grained basalts arc composed of grain s ranging in size from 0.5 - 1 mm. Their texture is ophitic, intergranular and subophiti c, and stru cture ho moge­ neous, infrequently vesicular. Coarse-grained varieties have grains coarser than 1 mm, ophitic texture and homogeneous structure. Porphyritic basalts are characterized by porphyrit ic texture and a homogeneous or ves icular structure. In the fine-g rai ned matrix, composed of any of these textural va riet ies of fine-grained basalts , are phenocrysts of pla­ gioclase and clinopyroxene, up to 3 mm in size, wh ich are present either as isolated grains or as agglomerates. Vesicular basalts are characterized by their vesicular structure, which is macroscopically visible. Vesicles are 0. 15-3 mm in size, usually of circular or slightly e ll ipti­ cal shape. Monomineralic vesic les are fi lled with cal­ c ite, infrequently with chlorite and very rarely with quartz. Polymineralic vesicles are fill ed with the mlner- Fig. 4 ..; 0-= ~, c ~ () a i ;J .,- i o g g; ~. ~ f ~ ~ 168 Geologia Croatiell 51/2 1 2 3 4 5 9 10 11 12 13 14 16 17 19 (NG8') (NJ5') (35') (755) (2810) (VDA2) (74') (782) (MG') (1318A) (PG1) (VDA4) (KB1) (845) Ba 124 164 111 154 112 107 81 78 238 136 282 175 165 354 Co 38 45 40 26 Cr 67 160 140 189 Cu 28 18 24 27 Ga 30 28 23 26 HI 18 18 18 18 Mo 4 4 4 4 Nb 20 21 19 12 Ni 23 26 34 23 Rb 14 28 35 27 5 5 15 12 32 27 5 9 5 23 Sn 30 35 39 36 31 52 49 29 35 50 31 41 30 29 Sr 175 147 202 199 165 234 139 181 251 181 265 206 225 353 V 341 337 315 198 300 159 238 150 266 196 73 174 238 92 Y 37 48 39 20 41 34 17 26 31 21 23 37 21 18 Zn 111 123 108 96 119 113 34 114 11 1 80 84 120 99 64 Zr 214 235 189 78 205 227 105 97 182 180 114 194 120 66 Table 2 Trace elements contcnls (in ppm). Table 1 is the numeration key for samples. al association ± calcite ± chlori te ± epidote ±quartz ±pre­ hnite ± pumpcIlyit ± haematite ± zeolite. b) Diabases and gabbrodiabases only occur as dy­ kes and s ill s which cut both the entire magmatic com ­ plex, and sed imentary rocks of Upper Cretaceous age. Diabases have ophitic texture, a homogenous structure, and could be divided, on the basis of their textural and structura l charac teris tics into medium-grained, coarse­ grained and weakly- porphyrit ic lypes. Major mineral components are basic plagioclase or albite and clinopy­ roxene. Secondary components include albite, chlorite, epi dote, calcite, prehni Le and sericite, while accessory components are opaque minerals and apat ite. 74 NG8 NJ5 35 La 6.8 16 17 15 Ce 16 38 43 35 Pr 2.2 5 5.7 4.7 Nd 11 23 27 22 Sm 33 6.1 7.6 6.5 Eu 1.2 2 1.9 1.6 Gd 2.9 6.2 7.1 5.7 Tb 0.52 0.96 1.2 0.96 Dy 3.9 6.9 8.3 6.9 Ho 0.69 1.3 1.6 1.3 Er 2.1 31 4.78 3.8 Tm 0.33 0.56 0.72 059 Yb 2.4 4.3 5.3 4.4 Lu 0.35 0.61 0.80 0.64 Table 3 Rare earth clements contents (i n ppm). Table I is the Ilumc- ration key for samples. Gabbrodiabases are characterized by hypidiom or­ phic texture and homogeneous structure. The major mineral components are plagioclase and hornblende, secondaries include chlorite, epidote and calcite, while magnetite and apatite are accessories. c) Volcanic agglomerates and basic tuffs occur much more infrequently than other types of basic rocks. Volcanic agglomerates have psephitic texture and mas­ sive st ructure. C lasts of different textural-structural ty­ pes of basalis, or subordinate rhyolite, are 10-100 em in size. The matrix is composed of weakly cemented tuffaceous materiaL Basic tuffs are represented by thinner beds within the success ion of basalts and volcanic agglomerates. They were divided into vi trocrystalline, crys talldvitro­ phitic and vitrophitic types. 4. MI NERALOGY Plagioclase (labradorite) has a prismatic shape, is usually prehni tized or sericitized, only infrequently fre- sh. Its modal component in basalt and diabase is appro- ximately 55 %. The mean content of anorthi te was det- ermined by optical measurement as 57.9 %. The mean normative composition of pl agioclase is 52 .8% an (Table 1). Therefore, optical and normative values indi- cate that the p lag ioclase is a labrador ite, what is a lso confirmed by roentgen analysis indicating neutral to basic plagioclase. The clinopyroxene (augite) is of short -pri smat ic, a rticulated or feat her- like form. It is one of the major mineral components of basalt and diabase, with a modal content of up to 30 %. l3c1ak. HalamiC. Marchig & Tibljas: Upper Cretaceous - Palaeogene Tholeii tic Basalts". 169 Hornblende is the major mineral co mponent of gabbrodiabase dykes, while only in one type of basalt it does represent a late-magmatic m ineral. lImclJitc, magnetite and apatite are accessory minerals in all basic effusive rocks of Poieska gora Mt. Albite is the most important mineral in a ltered ba­ salts and diabases, since there are almost no samples of basic magmatic rocks showing no evidence of albitiza­ tion. It is most frequentl y of prismatic, twig-like an d needle -like form, and is inhomogeneou s, with inclu­ sions of epidote/cl inozois ite and chlori te . The mean anorthite compo nent dctcrmined by optical measure­ ments is 5.5 %, and by roentgen diffract ion it was deter­ mined as acid to neutral plagioclase. The mean value of normative composition is 34.4 % an (Table J). Norma­ tive values arc not in concordance with the results of optical determinations. Thi s could be explained by inc­ luding one part calcium from the postmagmatic miner­ als epidote, prehn ite and pumpelly it e into nonnative plagioclase. Also, there is a possibi lity that the alb it iza­ tion process is not complete, but it was not possible to prove this optically because of the very small number of plag ioclase grai ns appropri ate for theodol it ic mea ­ surements. C hlorite was fou nd in all samples of the basic rocks. It is present in small veins, vesicles or in inter­ granu lar spaces in the form of very fine aggregates. The approximate formula of chlori te which occurs in vein­ lets in basalts from Nakop c reek was calcul ated from X-ray powder diffrac tion data fo ll ow ing the procedure proposed by NIETO (1997). Accordiog to the obt ai ned formula (Mg,,,Pe rnAI I. I) ) (S iJ.07 Alo.OJ) ° III(OH)8 200°C) sea water­ basalt alteration at reducing conditions and medium to low water/rock ratios. However, it shou ld be pointed Qut that secondary minerals albite, chlorite, epidote, prchnitc, sericite, pumpellyite and zeolite are also typ i­ cal for the very low degree of regional metamorphism (WINKLER, 1979). Gathered K-Ar ages of basic rocks from the Pozeska gom Mt. rangc from 66-48 Ma (from the Upper Creta­ ccous/Palaeocene boundary to the Middle Eocene) (PAMIC, 1993). The posi tion of the magmatic body is presen ted on the geolog ical map (Fig. 2); it is dis­ cernible that veins of basic rocks cut the Upper Creta­ ceOtls granite-rhyo li te complex, as well as Upper Creta­ ceous clast ic rocks. FUl1hennore, within the basalt body numcrous decimelre-metre size outcrops of pelagic limestones and shales occur (Fig. 3), and some of these were de termined as being of Upper Cre taceous age (Uppcr Santonian to Lower Maastrichtian - PAMIC & SPARfCA, 1983). These rocks show no signs of more intense contact-metamorphic changes, except recrystal­ lization, probably because of the more abrupt cooling of lava dur ing submari ne effusion. S ince contact planes between basalts and sediments arc sharp , without load casts, it may be supposed that these sediment s were enclavcd aftcr lithification. However, the poss ibility that some sedimentary rocks represent layers between two elTusional events , cannot be excluded. On the basis of aforementioned, compatible geo logical and isotopic data, we may conclude that the basic rocks of the Pozeska gora Mt. are of Upper Cretaceous - Palaeogene age, and that they arc younger than the granite- rhyolite complex and Upper Cretaceous clastic rocks. Subduction processes during the Early Cretaceous, together with the Eoalpi ne orogenesis (BELAK et aI. , 1995) had caused cmersion in the marginal part of the Nort hern Dinaridcs; therefore in this area there are no deposits of this age. Subduction was e ithe r minimized during the Uppe r Cretaceous, or was completed, i.c. thcre was a closure of Tethys in th is part of the Dinar­ ides. Postsubd uction tectonic processes (continen tal rifting or pseudorifting) have caused rhyolite volcanism along deep faults. Rift ing or pscudorifting-extensional processes caused the Upper Cretaceous transg ression, which was registered in all marginal parts of the Dina­ rides (SPARICA et aI., 1980), and formation of the Uppcr Crctaceous - Palaeogene marginal basin. Basic rocks of thc Pozeska gora MI. are, therefore, a consequence of cxtensional processes during the Upper Cretaceous and Palaeogene along the northern margin of the Dinarides. On the basis of geologica l and iso­ topic data it may be concluded that the first process was effusion of the rhyolites, and crystalliza tion of smallcr masses of its iIllrusive equivalents. Rhyolite magma was formed by partial melting of the continenta l crus t (PAMfC ct a I. , 1990). Partial melting, which produced acid crustal magma, was faeilitatcd by positioning o f Geologia Croatica 5 1/2 high-temperature basic magma in higher levels of the lithosphere (SUNESON & LUCCHITTA , 1983). Simi ­ lar geodynamicaJ evoluti on o f some areas in the west­ ern part of the USA, resulting in bimodal volcanic asso­ ciation , was proposed by LIPMAN (1980). By the Upper Cretaceous bas ic volcanism occurred in deeper parts of the already form ed basin, and las ted until the c losure of the basin (Pyrenean tectoni c phase in the Eocene) . In the geodynam ic inte rpretation of these areas it should be stated that rhyolites were placed along the marginal parts of the Upper Cretaceous­ Palaeogene basi n, si nce they were not genetically relat­ ed to the sediment s in this basin , while basalts were placed in the deeper parts of the basin. Consequent ly, acid and basic volcanic rocks were, during effu sion , spatially separatcd, and were posit ioned in their present mutual position by tangential tectonic transport during the Tertiary. Acknowledgements T he authors are indebted to Dr. 1. PAMIC for the critical reading and improvement of the manuscript. We also thank Dr. V. MAJER and Dr. P. ARKAI for their thoughtful rev iews and useful comments. 7. REFERENCES BARIC, Lj. & TAJDER, M. (1942): Petrografsko prou­ cavanje PozeSke gore (Pre thodni izvjcStaj ).- Yjest­ nik Hrv. drz. gco!. zavoda i Hrv. drz . geo!. muzeja, 1,22-26, Zagreb. BELAK, M., PAM IC, J., KOLAR-JURKOVSEK, T ., PECKAY, Z. & KARAN, D. (1995): Alpinski regi­ onalnometamorfni kompleks Medvednice.- 1st Cro­ atian Geological Congress, Opatija, Proceedings, 1, 67 -70, Zagreb. CABANIS, B. & LECCOLLE, M. (1989): Le diagra­ mme La/iO - Y/15 - Nb/8: un outil pour la discrimi­ nat ion des series volcan iques et la mise en evidcl'tce des processus de melange ello u de co nt aminati on crusta lc.- C.R. Acad. Sci. SeL II , 309, 2023-2029. CA RBONIN, S. & MOLIN, G. (J 980): Crystal-chcmi­ cal considerat ions on e ight metamorphic epidotes.­ Neues Jahrbuch Miner. Abh., 139/2,205-215. ERZINGER, J. (J 989): Chem ical alteration of the oce­ anic crust.- Gcol. Rundschau, 78/3, 73 1-740. HAAS , J., csAszAR, G., KovAcs, s. & VOROS, A. (J990): Evolution of the Western Part of the Tethys as reflected by geological formations of Hungary. ­ Acta Geod. Gcoph. Mont. Hung., 25/3-4, 325-344. HALAM IC, 1. , BELAK, M. & JAM ICIC, D. (1990): Gcolosko-petrografski prikaz bazicnih stijena Poze­ ske gore (Slavonija/Hrvatska).- Zbornik rad ova XIII Kongr. geol. Jugos l. , II , 456-465 , Ohrid. Belak. HalamiC. Marchig & Tibljas : Upper Cretaceuus - Palaeogene Tholeiitic 8asalts... 173 HERAK, M., JAMICIC, D., SIMUNIC, A. & BUKO- southern part of the Pannonian basin, Yugoslavia.- VAC, J. (1990): The northern boundary of the Acta Geologica, 18/2, 13-39, Zagreb. Dinarides.- Aeta geologica, 20, 5-27, Zagreb. KOCH, F. (19 17): Prilog geoloskom poznavanju Poze­ ske gore.- Foldtani intozct (1916) Evi Jelentesebol, 702-712, Budapes t. KOCH, F. (1919): Grundlinien der Geologie von West­ Siavonien.- Glasnik Hrv. prir. drustva , XXXI/I-4, 217-236, Zagreb. KOV Acs, S., csAszAR, G., GALACZ, A., HAAS, J. , NAG Y, E. & VOROS, A. (1989): The Tisza Supcrunit was originally part of the North Tethyan (European) Margin.- Mcmoires de la Soc. Geol. de France, 4,81- 100. LIPMAN , P.W. (1980): Cenozoic volcanism in the Wcstern United States: Implications for continental tectonics.- Re print from "S tudi es in geophysics: con tinental tectonics", USA Acad . Sci., 161- 174, Washington. MAJER, V. & TAJDER, M. (1982): Osnovne karakte­ ristike spilit -kc ratofirnog magmatizma Slavonije.­ Acta geol., 12/1 , 1-22, Zagreb. MANTOVANI, M.S.M., MARQUES, L.S., DESOU­ SA, M.A., CIVETTA, L., ATALLA, L. & INNO­ CENTI, F. (1985): Trace element and strontium iso­ tope constraints on the origin and evolution of Pa­ rana co ntinental f lood basalts of Santa Catarina Statc (Southern Brazil).- J. Petrol., 26, 187-209. MESCHEDE, M. (1986): A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb - Zr - Y dia­ gram.- Chern. Geol., 56, 207-2 18. NEWMAN, A.C.D. & BROWN, G. (1987): The chemi­ ca l const itution of clays.- In: NEWMAN, A.C.D. (cd): Chem istry of Clays and Clay minerals. Miner­ alogical Society Monograph, 6, 1-128. NIETO, F. (1997): Chemical composition of meta­ pelitic chlorites: X-ray diffraction and optical prop­ erty approach. - European 10urnal of Mincralogy, 9, 829-841. PAMIC, J. (1988): Mladoalpinski alkalijsko-fcldspatski graniti (a ljaskiti) Pozcske gore u Slavoniji.- Geolo­ gija,30, 183-205, Ljubljana. PAMIC, J. (1993): Late Cretaccous volcanic rocks from some oil we lls in the Drava depress ion and adjacent mountai ns of the Sou the rn parts of the Pannonian Basin (North Croatia).- Nana, 44, 203-2 10, Zagreb. PAMIC, J. & SPARICA, M. ( 1983): Staros t vulkanila Pozcske gore.- Rad JAZU, 404/19, 183-198 , Za­ greb. PAMIC, J., LANPHERE, M. & McKEE, E. (1988) : Radiometric ages or metamorphic an d associated igneous rocks of the Slavonian mountains in the PAMIC, J., INJUK, J. & JAKSIC, M. (1990): Prilog geokemijskom poznavanju gornjokredne bimodalne vulkanske asocijacije Pozeske gore u Slavonij i (sje­ verna Hrvatska, Jugoslavija).- Gcologija, 31-32, 415 -435, Ljubljana. PEARCE, J.A. (1983): The ro lc of sub-continental l ithosphere in magma genesis at destructive pl ate margins. - In: HAWKESWORTH, C.J. & NORRY , MJ . (cds): Continental basal t and mantle xenoliths. Nantwieh, Shiva, 230-249. PEARCE, J.A. & CANN, J.R. (1973): Tectonic setting of basic volcan ic rocks determi ned using trace cle­ ment analyses.- Earth and Plan . Sci . Letters, 19, 290-300. SHERVAIS, J.W. (1982): Ti -V plots and the petroge­ nesis or modc rn and ophiolitic lavas. - Earth and Planet. Sci. Letters, 59, 203-212. SPOONER, E.T.C., BECKI NSALE, R.D., FYFE, W .S. & SMEWING, J.D. (1974): 180 enriched ophiolitic me tabasic rocks from E. Liguria (Ttaly), Pindos (Greece), and Troodos (Cyprus).- Contrib. Mincral. Pctrol. , 47,41-62. STRECKEISEN, A. (1967): Classification and nomen­ clature of igneous rock.- Neues 1ahrb.Miner. Abh., 107/2-3, 144-240. STRECKEISEN, A. (1978): Classification and nomen­ clature of volcanic rocks, lamprophyres, carbona­ tites and mel iIi tic rocks.- Neues 1ahrb. Abh ., 134, 1- 14. SUNESON, N.H. & LUCCHITTA, 1. ( 1983): Origin of bimodal volcanism, Southern Basin and Range pro­ vince, West-Central Arizona.- Geol. Soc. Amer. Bull., 94,1005-1019. SIKIC, K. (1995) : Prikaz geoloske grade Medvedniee.­ In: SIKIC, K. (ed.) : Geoloski vodic Mcdvcdnicc, 7- 30, Zagreb. SPARICA, M., JURISA , M. , CRNKO, J., SIMUNIC, A., JOVANOVIC , C. & ZIVANOVIC, D. (1979): Osnovna geoloska karta SFRJ I: 100.000. Li st Nova Kapela L33-1 08.- Inst. za geol. istraz. Zagreb, Geol. zavod sarajevo (1966-1972), Say. gcol. zavod, Beo­ grad . SPARICA, M., J URI SA, M., CRNKO, J., SIMUNIC, A., JOVANOVIC, C. & ZIV ANOVIC , D. (1980): Osnovna gcoloska karta SFRJ 1: 100.000. Tumac za li st Nova Kapela L33-108 (Geology of the Nova Kapc la sheet). - Ins!. za geol. istraz. Zagrcb, Sav. gcol. zavod, Beograd, 55 p. TAJDER, M. (1947): Albitski dolcrit iz Nakop potoka u PozcSkoj gori. - Geol. vjesnik, I, 182-189. TAJDER, M. ( 1955): Istrazivanja Papuka i Poieske gore.- Ljetopi s JAZU , 60, 307-308, Zagreb. 174 T AJDER; M: (1959): Petrografsko proueavanje Poie­ ske gore.- Ljetopis JAZU, 63, 383-387, Zagreb. TAKSIC, A. (1944): 0 tektonici i morfologiji iztoenog dicla Poieske gore (Prethodni izvjestaj).- Vjestnik Hrv. drz.. geo!. zavada i Hrv. drz. geo!. muzcja, II/IIl, 28-36, Zagreb. TAYLOR, H.P. & SHEPARD, S.M.F. (1986): Igneous rocks: processes of isotopic fractionation system at­ ics. - In: VALLEG, J.W., TAYLOR, H.P. & O'NE­ IL, J.R. (cds.): Stable Isotopes.- Miner. Soc. Amer., 16,227-272. THOMPSON, R.N. (1982): Magmatism of the British Tert iary Volcanic Province.- Scott. J. Geol., 18,49- 107. Geologia Croalica 5 [/2 TUCAN, F. (1919): Sitan prinos poznavanju krista li­ nicnog kamenja Pozeske gore.- Glasnik Hrv. priro­ dosl. drustva, XXXI/l-4, 98-105, Zagreb. WILSON, M. (1989): Igneous petrogenesis - a global tectonic approach.- Unwin Hyman, London, 455 p. WINCHESTER, J.A. & FLOYD, P.H. (1977): Geoche­ mical discrimination of different magma series and their differentiation products using immobile e le­ ments.- Chem. Geol., 20, 325-343. WINKLER, H.G.F. (1979): Petrogenesis of metamor­ phic rocks.- Springer Verlag, Berlin, 348 p. Manuscript received March 10, 1997. Rev ised manuscript accepted November 23, 1998.