j ourna l homepage: www.e lsev ie r.com/ locate / l i thos
The Eastern Carpathians “ophiolites” (Romania): Remnants of a Triassic ocean
Volker Hoeck a,b,1, Corina Ionescu b,a,⁎,2, Ioan Balintoni b,2, Friedrich Koller c,3
a University of Salzburg, Geography and Geology Department, 34 Hellbrunner Str., A-5020 Salzburg, Austriab Babeş-Bolyai University, Geology Department, 1 Kogălniceanu Str., RO-400084 Cluj-Napoca, Romaniac University of Vienna, Department of Lithospheric Research, 14 Althanstrasse, A-1090 Vienna, Austria
ated rocks in the Eastern Carpathians occur in three areas, from north to south:Rarău, Hăghimaş and Perşani Mts. They are found as blocks ranging from few metres to a few kilometers insize and as centimetre-sized in breccias, most likely embedded in the Late Barremian–Early Albian Wildflyschformation. Compositionally, they range from lherzolites and harzburgites to mafics such as FeTi gabbros,dolerites, basalts, and to andesites. The volcanics comprise highly-depleted basalts/andesites to enriched-type mid-ocean ridge basalts; additionally they include ocean island basalts and calc-alkaline basalts/andesites and trachytes. Based on paleontological evidence, their age is Middle to ?Late Triassic. They can beclearly compared with remnants of the Meliata–Hallstatt Ocean in the Western Carpathians, but do notmatch the Jurassic ophiolites and island arc volcanics in the Mureş Zone of the Southern Apuseni Mts. Wepropose a Triassic ocean connected with the Meliata–Hallstatt Ocean, between (a) the Bucovinian/Sub-Bucovinian continental crust, (b) the Infrabucovinian and finally (c) the Northern Apuseni microcontinents.This ocean closed in the Late Triassic to Early Jurassic causing close juxtaposition of all three microcontinents.An ophiolite complex together with ocean island basalts and calc-alkaline basalts/andesites remained fromthis ocean and was subsequently eroded and transported as blocks of different size into the Lower CretaceousWildflysch basin, together with blocks and clasts of limestones similar to the Mesozoic sedimentarysequences in the Northern Apuseni realm. The Wildflysch formation was thrust as an independent unitduring the Albian over the Bucovinian Nappe in the Eastern Carpathians and the Northern Apusenicontinental crust, respectively.
The Eastern Mediterranean realm, including the Alpine–Car-pathian chain as well as the Dinaric–Hellenic orogen, comprisesophiolites which are believed to have mainly formed in three differentperiods: Mid-Triassic, Jurassic and Late Cretaceous. The Mid-Triassicophiolites are assigned to the so-called Meliata–Hallstatt Ocean in theWestern Carpathians (Kozur, 1991; Harangi et al., 1996; Channell andKozur, 1997; Ivan, 2002; Faryad et al., 2005) and possibly in theEastern Carpathians (Hoeck and Ionescu, 2007). Triassic magmaticsare also described from the Dobrogea area in eastern Romania (Savuet al., 1980; Seghedi and Szakacs, 1994; Saccani et al., 2004) andDinarides (Trubelja et al., 2004). Jurassic ophiolites are found in the
Penninic Ocean in the Eastern Alps (Koller and Höck, 1990), and itspossible extension into the Eastern Carpathians as the Pieniny Klippenbelt (Săndulescu et al., 1982; Hovorka et al., 1984). The mostwidespread and complete Jurassic ophiolite sequences are confinedto the Pindos and the Vardar Ocean (eastern branch and westernbranch) respectively in the Dinarides and Hellenides (for a review, seeRobertson, 2002 and citations therein). Ophiolites and associatedisland arc volcanics (IAV) from the Southern Apuseni Mountains(SAM) are most likely a continuation of the Eastern Vardar Ocean(Anđelković and Lupu, 1967; Saccani et al., 2001; Bortolotti et al.,2002). Jurassic island arc volcanics are also found in the basement ofthe Transylvanian Depression (TD) as an eastern continuation ofthe SAM ophiolites and IAVs (Ionescu and Hoeck, 2006; Ionescuet al., 2009-this issue). Upper Cretaceous ophiolites are widelydistributed in Turkey, Cyprus and further to the east (see alsoRobertson, 2002). Recently, some small occurrences were alsoreported from the “Western Vardar branch” (Karamata et al., 2000;Pamić et al., 2002).
In the Eastern Carpathians (EC) fragments ofMesozoic “ophiolites”,i.e. ultramafics (UM), and mostly basalts to andesites respectively arenot completely understood in the stratigraphic framework given
above.Wewill use the widely-applied term “ophiolite” for the EasternCarpathians UMs and magmatics only based on the fact that somebasalts originated obviously in an ocean basin (see below). The EC“ophiolites” are believed (Săndulescu, 1984) to have been formedbetween Mid-Triassic and Mid-Cretaceous, in a branch of the VardarOcean, the Main Tethyan Suture zone, being thus partly time-equivalent to the SAM Jurassic ophiolites and island arc volcanics.Săndulescu (1984) considered the “ophiolites” of the “Transylvaniannappes” (“TN”) as being emplaced on the top of the EC during mid-Cretaceous orogenic events. Schmid et al. (2008) also connect the EC“ophiolites” to the SAM area. By contrast, a Triassic age of the EasternCarpathians “ophiolites” and a separation from the SAMophiolites andIAVs were postulated by Kozur (1991) and Channell and Kozur (1997).
We present here for the first time evidence that the UMs and themagmatic rocks in the Eastern Carpathians formed in variousgeotectonic environments and that most of them are associatedwith Mid-Triassic sediments and show no connection with the SAMJurassic ophiolites and IAVs. The new petrological, geochemical andstratigraphical evidence for the EC Mesozoic “ophiolites” are the basisof an alternative view on their origin.
2. Geological setting
For an investigation and interpretation of the Mesozoic magmaticrocks from the “Transylvanian nappes” in the Eastern Carpathians (Fig.1), a comparison with the ophiolites and IAVs from the SouthernApuseni Mountains is necessary. Equally important is the comparisonwith the Mesozoic IAVs found in the basement of the TransylvanianDepression (Ionescu et al., 2009-this issue). Thus, we will brieflyreview the ophiolites and island arc volcanics from the SAM, thegeology of the Transylvanian Depression basement and finally theEastern Carpathian geology.
a. The Southern Apuseni Mountains. The Southern Apuseni tectonicunits are a sequence of nappes called the Mureş Zone (Bleahu,
Fig. 1. Simplified tectonic map of the Eastern Carpathians. The insert in the upper right showBleahu (1976), Burchfiel (1976) and Săndulescu (1984). More detailed maps for each area (R
1976; Burchfiel, 1976) or “Transylvanides” (Săndulescu, 1984). Inthis paper we will use the terms Mureş Zone and/or SouthernApuseni Mountains ophiolites in order to avoid confusionwith the“Transylvanian nappes” from the Eastern Carpathians. The MureşZone of SAM consists of ophiolites, island arc volcanics andWildflysch sediments, all of Jurassic and Cretaceous age, respec-tively. Numerous papers present the geological, petrographical,and geochemical characteristics of the SAM ophiolites and IAVs(calc-alkaline rocks), e.g. Savu (1996), Saccani et al. (2001), Nicolaeand Saccani (2003), Bortolotti et al. (2002). The ophiolitic sequencestarts with ultramafic cumulates at the base, followed by gabbros(layered, isotropic and FeTi gabbros). The transition from theplutonic to the volcanic sequence is marked by a sheeted-dykecomplex. The volcanics consist of massive lava flows, pillow basaltsand pillow breccias. Callovian to Oxfordian radiolarites (Lupu et al.,1995) occur only occasionally. The calc-alkaline rocks display acomplete sequence ranging from basalts, basaltic andesitesto rhyolites. Based on the petrography, mineral chemistry andwhole-rock chemistry, Bortolotti et al. (2002) consider theophiolites as a normal oceanic crust profile, with some gabbrosand basalts showing a high-Ti affinity. The calc-alkaline sequence isinterpreted as a remnant of an island arc developed above oceaniccrust. The SAM ophiolites are intruded by Oxfordian–Kimmer-idgian granites, granodiorites and diorites (152–156 Ma U/Pb acc.to Pană et al., 2002) according to Bortolotti et al. (2002) as theplutonic equivalent of the calc-alkaline island arc sequence. Thewhole complex is assigned to the Vardar Zone (Anđelković andLupu, 1967; Săndulescu, 1984).
b. The Transylvanian Depression adjoins the Mureş Zone of theSouthern Apuseni Mountains to the west and the SouthernCarpathians to the south. Towards north and east, the TD bordersthe Neogene volcanics, the “Transylvanian”, Bucovinian (Uhlig,1907) and the flysch nappes (Săndulescu, 1984) of the EasternCarpathians. The geological and tectonic history of the TD startedin the Late Cretaceous and continued with breaks until the
s the position of the map within the Romanian territory. The major tectonic units afterarău, Hăghimaş and Perşani Mts.) are presented in Figs. 2–4.
Fig. 2. Simplified geological map with the distribution of Mesozoic ultramafics (UM) and magmatics in the Rarău area, based on references (Joja et al., 1968; Mutihac, 1969;Săndulescu, 1973; Kräutner et al., 1975) and our own field data.
153V. Hoeck et al. / Lithos 108 (2009) 151–171
Pannonian (Ciupagea et al., 1970). The basement of the TD wasstrongly tectonized during Mid-Cretaceous times (Săndulescu,1984). At the beginning of the Cenozoic, the Mesozoic formationsincluding the metamorphics and Jurassic volcanics were folded. Inthe Cenozoic, the TD underwent a relatively slow sedimentation,which lasted until the Middle Oligocene. In the Miocene an intensesubsidence led to the accumulation of almost 5000m of sediments.Based on geological and geophysical data, the basement of the TDhas been interpreted in various ways. For simplicity, we willdiscuss only Săndulescu's version since it is relevant to our study.According to Rădulescu and Săndulescu (1973) and Săndulescu(1984), the nappes of the Major Tethyan Suture occurring in theSAMextend eastwards into the basement of the TD and continue tothe east, forming the so-called “Transylvanian nappes” on top ofthe EC. The authors postulated that the roots of both the MureşZone from the SAM, and the“Transylvanian nappes” from EC, arelocated at the western end of the TD. They stated also that themetamorphics drilled in the eastern part of the TD prove thepresence of the central nappes of the Eastern Carpathians (i.e.Bucovinian, Sub-Bucovinian and Infrabucovinian (IB) nappes)beneath the TD. These ideas about the SAM, the TD basementand the EC structure have in particular dominated all modelsdeveloped so far. Kozur (1991), Nicolae and Saccani (2005), Saccaniand Nicolae (2005), Hoeck et al. (2006), Hoeck and Ionescu (2006,2007) expressed their doubts regarding a connection of theMesozoic magmatics from the EC (“Transylvanian nappes”) withthe SAM ophiolites and IAVs.
c. The Eastern Carpathians. In this short reviewwe follow the conceptof Săndulescu (1984). Structurally, the EC contain, from top tobottom, various nappes, starting with the “TN” and the Bucoviniannappes s.l. The latter are divided into the Bucovinian Nappe s.s., theSub-Bucovinian Nappe and the Infrabucovinian nappes. Towards
the east, the Bucovinian nappes s.l. are thrust over several flyschnappes (Black Flysch unit, Baraolt and Ceahlău nappes).
The term “Transylvanian nappes” is a generic term for all tectonicunits above the Bucovinian Nappe s.s. Subordinate terms are HăghimaşNappe, Perşani Nappe and Olt Nappe. These terms have been usedincoherently and in different ways (Patrulius et al.,1966; Popescu,1970;Popescu et al., 1975, 1976; Peltz et al., 1983; Săndulescu, 1984).Independently from this nomenclature, the “Transylvanian nappes”occur in the area of Rarău (RA) in the north (Fig. 2), Hăghimaş (HAG) inthe centre (Fig. 3), and the Perşani Mts. (PM) in the south (Fig. 4) of theEastern Carpathians.
In 1907 Uhlig discovered the nappe structure of the EC and calledthe deeper unit above the flysch “Bucovinische Decke” and the higherone “Siebenbürgische Decke” (i.e. Bucovinian Nappe and Transylva-nian Nappe respectively). He realized that volcanics and serpentiniteswere associated with Mesozoic sediments with a similar facies foundin “Siebenbürgen” (Apuseni Mts.?).
The “Transylvanian nappes” consists of Mesozoic “ophiolitic”material (UMs and magmatics) and/or Mesozoic (pre-Cenomanian)sedimentary deposits that have no crystalline basement. The“ophiolites” include lherzolitic and harzburgitic ultramafics, raregabbros, doleritic dykes and basalts to andesites. Additionally,trachytes are restricted to the PM. According to Russo-Săndulescu etal. (1983), basalts are derived either from MOR processes or from hotspot activity. The assumed time span from Mid-Triassic to EarlyCretaceous (Săndulescu, 1976) is explained with an original positionwithin the north-eastern part of the Vardar Ocean (Săndulescu, 1984).
The basement of the Bucovinian Nappe s.s. is covered withsandstones, limestones and dolomites ranging stratigraphically fromthe Lower to theMiddle Triassic. Jurassic limestones locally covering theTriassic sequence are in turn overlain by Callovian to Oxfordian jaspers
Fig. 3. Simplified geological map with the distribution of Mesozoic volcanics (basalts) in the Hăghimaş area based on references (Alexandrescu et al., 1968; Săndulescu, 1975) and ourown field data.
154 V. Hoeck et al. / Lithos 108 (2009) 151–171
(Băncilă and Papiu, 1953; Popescu and Patrulius, 1964; Mutihac, 1969;Dumitrica, 1981, 1994). In the Ladinian, the crystalline basement of theBucovinianNappewas intruded by theDitrăuComplex (Dallmeyer et al.,1997; Pană et al., 2000).
The Upper Barremian to Lower Albian Wildflysch (WF) formationin the EC is regarded as the highest stratigraphic formation4 of theBucovinian Nappe s.s. According to Săndulescu (1975) it is mainlycomposed of non-stratified clastic sediments such as clays and silts,with conglomerates and breccias. At several levels, better-stratifiedsediments may occur. Our own field observations have revealed forlarge areas a more regular stratification, with well-bedded shales,sandstones, turbidites and rare conglomerates. The same is true forthe Cretaceous Wildflysch in the SAM.
The name wildflysch might suggest a close relation to a tectonicmélange, which is indeed the case in the Western Alps, where manyunits which weremapped as wildflysch, are now regarded as mélange(compare Hsü and Briegel, 1991). In this case, the wildflysch should behighly deformed, with a chaotic structure. The Wildflysch in the ECand in the Apuseni Mts. is better comparable with the characteristicsgiven by Marschalko (1964) for wildflysch. It should consist of “…
homogeneously bedded, medium-grained sandstones, coarse-grainedsiltstones, with abundant claystone fragments. The amount ofirregular bedding is very small. Huge slide bodies should occur, witha composition different from the flysch sequences”. Such anappearance is not typical for a tectonic mélange.
4 The arguments to separate an individual “Wildflysch” Nappe will be presented inthe last chapter of this paper.
Olistoliths of various sizes, between decametres and hectometresoccur throughout theWildflysch. The olistoliths consist of Triassic andJurassic sediments, as well as of ultramafics andmagmatics. The larger(2–4 km sized) occurrences of “ophiolites” forming parts of the“Transylvanian nappes” as well as those from the Wildflysch areassumed to be structurally and compositionally equivalent to theMureş Zone ophiolites and IAVs from the SAM. Consequently, the“ophiolites” from the EC should have formed in the same Jurassicocean as those from the SAM, from where they were overthusttowards east, as “Transylvanian nappes” (Săndulescu, 1984).
By contrast, Popescu-Voiteşti (1929) supposed that the roots of the“Transylvanian nappes” from the EC are in “the region presentlyoccupied by the Pannonian Depression”. The author envisaged aneastward and southward movement of the “TN”, up to the EasternCarpathians and to the Perşani Mts., respectively. Thus, they“travelled” over the crystalline basement of the Apuseni Mts. andover the region occupied now by the Transylvanian Basin. Popescu-Voiteşti (1929)mentioned “diabases, porphyrites and porphyries” thatwere emplaced “during the overthrusting of the TN”.
3. Samples and methods
For this study, 215 samples (ultramafics, magmatics and sedi-ments) from the Eastern Carpathians were collected, and documentedby GPS coordinates. Out of these 89 samples (48 from the Rarău area,15 from the Hăghimaş area and 26 from the Perşani Mts.) wereanalyzed for major, minor, trace and RE elements. Twenty micro-paleontological analyses were made of thin sections and bulk samples(radiolarites) respectively. For the paleontological identification of the
Fig. 4. Simplified geological map with the distribution of Mesozoic ultramafics and magmatics in the Perşani Mts. based on references (Patrulius et al., 1967; Săndulescu et al., 1968;Popescu, 1970) and our own field data.
155V. Hoeck et al. / Lithos 108 (2009) 151–171
radiolarian assemblages, the samples were prepared by grinding andrepeated attacks with HF.
Electron microprobe analyses were carried out on polished thinsections coatedwith carbon, at 15 kV accelerating voltage, 40 nA beamcurrent intensity and5 μmelectron beamdiameter,with a Jeol XA8600(Salzburg University) equipped with four wavelength dispersivespectrometers (WDS) and a Si(Li) energy-dispersive spectrometer(EDS). As standards, wollastonite (for Ca), apatite (for P), rutile (for Ti),KCl and adularia (for K), FeO and Fe metallic (for Fe), MnO (for Mn),NaCl and jadeite (for Na), quartz and adularia (for Si), synthetic Al2O3
(for Al), synthetic MgO (for Mg) were used.For mineral identification, especially alteration products such as
vesicle and veins infilling, transmission electronmicroscopy and X-raypowder diffraction were performed (Babeş-Bolyai University Cluj-Napoca). The BF 450-TESLA Brno operated at 30 kV on Cu or Au-coatedsamples. The DRON 3 X-ray diffractometer operated at 40 kV and45mA, with CuKα radiation (λ=1.5406 nm). The scan speedwas 0.02°/step, from 2 to 64° 2θ.
Part of the samples were crushed in an agate mill and chemicallyanalyzed for major, minor, trace and RE elements at the AcmeAnalytical Laboratories Ltd. Vancouver (Canada). For SiO2, Al2O3,Fe2O3, CaO, MgO, Na2O, K2O, MnO, TiO2, P2O5, MnO, Cr2O3, Ba, Ni, Scanalyses by ICP-ES (Spectro Ciros Vision) the samples underwent aLiBO2/Li2B4O7 fusion in a graphite crucible at 980 °C and weredissolved afterwards in HNO3 (5% concentration). The ICP-MS analyses(Perkin-Elmer-Elan 6000/9000) for REE and incompatible elementswere done by LiBO2/Li2B4O7 fusion in a graphite crucible at 980 °C andsubsequently dissolution in HNO3 (5%). This procedurewas applied forCo, Cs, Ga, Hf, Nb, Rb, Sn, Sr, Ta, Th, U, V, W, Zr, Y, La, Ce, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The precious and base metals2+ (Mo,Cu, Pb, Zn, Ni, As, Cd, Sb, Bi, Ag, Au, Hg, Tl) were digested in aqua regiaand also analysed by ICP-MS. Loss of ignition (LOI) was determined byweight loss after ignition at 950 °C for 90min. The Ctot was determinedby a LECO furnace at 1650 °C.
The trace elements, REE and precious and base metals weremeasured with the laboratory standard DS4 which was calibrated
Table 1Distribution of Mesozoic ultramafics and magmatics in the Eastern Carpathians
Rock type Rarău Hăghimaş Perşani
Lherzolites X Missing X?Harzburgites X X XFeTi gabbros X Missing MissingHDBA Missing X XDMORB X Missing MissingNMORB X Missing MissingEMORB X X MissingOIB Missing X XCABA X X XTrachytes Missing Missing X
For the abbreviations see the text.
156 V. Hoeck et al. / Lithos 108 (2009) 151–171
against CANMET Reference Materials TILL-4, LKSD-4 and STSD-1 forthese elements. The major elements were measured with standardSO-18 which was calibrated against CANMET SY-4 and USGS AGV-2,BCR-2, GSP-2 and W-2.
4. Petrography and mineral chemistry
Mesozoic magmatics and ultramafics in the EC occur almostexclusively as individual, well-defined blocks, which were partlyconsidered as olistoliths in the WF, partly as tectonic klippen derivedfrom so-called “Transylvanian nappes” (Săndulescu, 1984). They showa wide variety of lithologies. The UM include mainly lherzolites andsubordinate harzburgites. The magmatic sequence comprises FeTigabbros, microgabbros, dolerites, and basalts to andesites. They areoften found as clasts in a carbonate matrix. A detailed petrologicanalysis of these rocks is beyond the scope of this paper and will be
Table 2aSelected microprobe analyses for orthopyroxene (opx) and olivine (ol) from ultramafics in t
FeTOT as FeO; Mg#=100×Mg/(Mg + Fe2+). Pyroxene end members and Fe3+ are calculaterecalculated to 100%. Abbreviation: nd—not determined.
presented elsewhere. Here we will deal only with the aspects ofpetrology and geochemistry relevant for the origin, age andpaleogeographic setting of the Eastern Carpathians “ophiolites”.
The ultramafic and magmatic rocks were separated into tengroups: lherzolites, harzburgites, FeTi gabbros, highly-depletedbasalts/andesites (HDBA), depleted MOR basalts (DMORB), normalMOR basalts (NMORB), enriched MOR basalts (EMORB), ocean islandbasalts (OIB), calc-alkaline basalts/andesites (CABA) and trachytes.The grouping is more based on geochemistry than petrography. Ajustification of the grouping will be highlighted in the Section 5. Thevarious rock types are unevenly distributed among the three areasRarău, Hăghimaş and Perşani Mts., as displayed in Table 1. Onlyharzburgites and calc-alkaline basalts are found in all three areaswhereas the other rock types are present only in one or two areas. Asingle remnant of a sheeted-dyke complex was found in PM(Sărmanului Quarry). Breccias, particularly in RA and HAG arefrequent. Pillow lavas occur in RA and PM. Gabbros are almostabsent.
Alteration is severe in almost all samples. The most commonalteration products are chlorite and calcite, which very often formpseudomorphs after clinopyroxene with a perfectly preserved shape.Plagioclases changed to a large extent into albite. Furthermoresmectite, illite, celadonite, glauconite, pumpeyllite and prehnite mayoccur as alteration products. It should be noted that the amount of clayminerals is subordinate, compared with chlorite and calcite. Spinelsare often transformed into Fe-oxides.
4.1. Ultramafics
Petrographically, the ultramafics are mainly represented bylherzolites and rarely by harzburgites (Table 1). In general, lherzolites
FeTOT as FeO. Mg#=100×Mg/(Mg+Fe2+). Pyroxene end members and Fe3+ are calculated based on charge balance according to Cawthorn and Collerson (1974). Wo+En+Fsrecalculated to 100%.
157V. Hoeck et al. / Lithos 108 (2009) 151–171
are better preserved than harzburgites, which are serpentinized to ahigh degree. The latter are concentrated in HAG and PM where onlyone occurrence of lherzolites(?) was identified so far. Lherzolites arerestricted to a relatively large body in the north of the Rarău syncline,NW of Breaza (Fig. 2). It was mapped by Săndulescu (1973) as aremnant of the “TN”.
Table 2cSelected microprobe analyses for spinel from ultramafics (UM), depleted basalts (DMORB) a
Mg#=100×Mg/(Mg+Fe2+), Cr#=100×Cr/(Cr+Al). Atomic proportions are calculated on 3 ca
Tables 2a, 2b and 2c display the mineral chemistry of orthopyr-oxene, olivine, clinopyroxene and spinel respectively, in the ultra-mafics. Lherzolites consist of two generations of minerals. The olderones form large porphyroclasts of orthopyroxene and rarer clinopyr-oxene, of mantle origin. Orthopyroxene shows 3 to 10 μm thickexsolution lamellae of clinopyroxene vice versa clinopyroxene
tions. FeO and Fe2O3 recalculated on the basis of ideal structural formula.
Fig. 5. a) BSE image of lherzolite from Rarău (Tătărcuţa Valley): olivine (Ol) and clinopyroxene (Cpx) overgrow exsolved orthopyroxene (Opx). Srp for serpentine minerals. b)Brecciated EMOR basalt from Rarău. Abbreviations: Pl for plagioclase, Chl for chlorite. N+. c) BSE image of the inner part of basaltic pillow lava from the Tătărcuţa Valley (Rarău), withclinopyroxene phenocrysts (Cpx) entirely replaced by calcite and some chlorite. Quenched structure of the groundmass, with plagioclase laths. d) Microphoto of Perşani Mts. trachyte(Topul Valley). Zoned K-feldspar phenocryst (Kfs) and deposition of calcite (Cal) in voids. N+.
158 V. Hoeck et al. / Lithos 108 (2009) 151–171
exhibits exsolution of orthopyroxene. The Mg# of orthopyroxenevaries from 90.42 to 93.24 (Table 2a). The Al2O3 content ranges from~1 to slightly over 4 wt.%. The forsterite content, from 90 to 90.5 wt.%,is relatively low for UM but high for magmatic olivines. Together witholivine, a younger generation of small, probably magmatic, clinopyrox-
Table 2dSelected microprobe analyses and calculated structural formulae for plagioclase from FeTi g
Calculations on 8 O basis according to Deer et al. (1966). FeTOT as FeO. Abbreviations: σ for
ene formed. So far there is no significant difference discernable betweenthe pre-existing clinopyroxene porphyroclasts and the newly-formedclinopyroxene. The composition of these clinopyroxenes (Table 2b) isfairly constant in respect to Mg and Ca, but variable in Al2O3 (3–6 wt.%),Na2O (0.4–1wt.%), and TiO2 (0.3–1wt.%). Cr2O3 is generally high, around
abbros (Rarău) and OIBs (Hăghimaş and Perşani Mts.)
1 wt.%. In terms of the quadrilateral endmembers, clinopyroxenes fromultramafics classify as diopside to augite. The jadeite component issignificant due to a relatively high Na2O content. Spinel has a very highAl content and consequently a low Cr#. The TiO2 content is very low(Table 2c), indicating that spinels belong to residual abyssal peridotites(Kamenetsky et al., 2001).
Both relict minerals are overgrown by ubiquitous olivine as shownin Fig. 5a. These textures argue for a two-stage origin inwhich an olderrefractory peridotite assemblage consisting of orthopyroxene, clin-opyroxene and probably spinel, was refertilized by the precipitation ofolivine and clinopyroxene from a percolating melt (Piccardo et al.,2004). A more thorough study of these lherzolites is in progress.
4.2. FeTi gabbros
Gabbros are extremely rare and were not described so farconvincingly. There are only short notes by Russo-Săndulescu et al.(1982) for RA and Cioflica et al. (1965) for PM. We found small blocks
Table 3aBulk rock chemistry for selected samples of ultramafics in Rarău, Hăghimaş and Perşani Mt
Major elements in %; minor, trace and RE elements in ppm. Mg#=100×MgO/(MgO+FeOTOT
of FeTi gabbro only in Fundu Pojorâta (Fig. 2). It consists mainly of Fe-rich clinopyroxene with low Mg content. Al2O3 and Cr are also low.Clinopyroxenes show extremely fine lamellae (1–2 μm thick) ofprobably amphibole, growing along the cleavage planes. At a moreadvanced stage of amphibole growth only parallel-oriented relics ofclinopyroxene can be seen. Plagioclase (Table 2d) has a wide variety ofcompositions, with a maximum An content of ~50%. Plagioclase ishighly altered and transformed to oligoclase and albite. Despite thesevere alteration, slight normal zoning is still preserved. Most of theTiO2 is confined to ilmenite and titanite. The FeTi gabbros underwentintense alteration where pyroxene transformed to Fe-rich amphibole,also to epidote and Fe-rich chlorite. Additionally, calcite occurs as wellas alteration product.
4.3. Dolerites, basalts to andesites
DMORBs andNMORBs are oftenpillowed; theOIBs are almost totallypillowed, whereas the EMORBs occur preferentially as breccias and
). FeTOT as Fe2O3. Abbreviations: Lz—lherzolites, Hz—harzburgites, σ—FeTi gabbros.
160 V. Hoeck et al. / Lithos 108 (2009) 151–171
brecciatedmassive lavas. Andesite is common inCABAswhere it appearsasmassive lava. The dykes in serpentinites e.g. in the Sărmanului Quarry(near Vârghiş, in PM; Fig. 4) are doleritic but they also display anandesitic chemistry (HDBA). Other dolerites (NMORB, EMORB) occur-ring as blocks might be derived from dykes.
The texture of basaltic rocks ranges from aphyric, sparsely phyric tohighly porphyritic (mainly in CABA), and rarer glomeroporphyritic.Some massive basalts are holocrystalline (Fig. 5b). Plagioclase andclinopyroxene form phenocrysts. The groundmass consists mainly ofsmall clinopyroxene, plagioclase and Fe-oxides. Some basalts showquenched structures, with radially growing acicular laths of plagio-clase (Fig. 5c), whereas the more coarse-grained basalts display asubophitic to intersertal structure. Dolerites are characterized byintergranular fabric. Only doleritic dykes (Sărmanului Quarry) containa large amount of amphibole formed on the expense of clinopyroxene.
The OIBs in Hăghimaş and in the Perşani Mts. are all vesicular, mostof them highly vesicular. This contrasts with the remainder of basalts,which show only rarely small vesicles. The vesicles are mainly filled
Table 3bBulk rock chemistry for selected samples of MOR-type basalts in Rarău, Hăghimaş and Perş
Major elements in %; minor, trace and RE elements in ppm. Mg#=100×MgO/(MgO+FeOTOT
with calcite and/or chlorite; some have a rim of Fe-oxide. Rarely, thevesicles are filled with adularia.
All of the basalts are severely altered. The groundmass andphenocrysts are transformed mainly to chlorite, calcite, some quartzand Fe-oxides or Fe-hydroxides. Remnants of original phenocrysts, inparticular plagioclase, are rare but the crystallographic shape ispreserved (as for example clinopyroxene in Fig. 5c). Apart from thesemajor alterationminerals, clay minerals such as illite, smectite, possibleceladonite and glauconite also occur.
Of the fewpreserved clinopyroxenes in FeTi gabbros and basalts, someare listed in Table 2b. These classify as diopside to augite inthe quadrilateral diagram and contain variable amounts of TiO2 andNa2O, but only a small amount of Cr2O3. In the various discriminatingdiagrams (Nisbet and Pearce, 1977; Beccaluva et al., 1989) they are notgeotectonically classified, but are compatiblewith clinopyroxenes derivedfromMORbasalts. Plagioclases arehighlyaltered anddisplayawide rangeof compositions, from labradorite to pure albite. Labradorite (An50–65)forms the magmatic core of plagioclase, whereas the andesine
composition represents themagmatic rims.More acidic compositions aredue to the alteration. Only themost basic compositions of plagioclases arelisted in Table 2d.
Spinels occur rarely, where preserved they are good petrogeneticindicators (Allan et al., 1988; Kamenetsky et al., 2001). Two groups ofspinels can be distinguished, one from DMORB and another one fromCABA. The former have a high Mg#, around 70, and an intermediateCr#, around 50. On the other hand, the CABA spinels are extremelypoor in Mg and rich in Cr, reflected by Cr# between 70 and 80 andMg# below 20, respectively (Table 2c). Spinels from the DMORB showalsomoderate TiO2 content, thus plotting in the TiO2 vs. Al2O3 diagramin the MORB field, as outlined by Kamenetsky et al. (2001). On theother hand, the CABA spinels are very high in TiO2 and plot close to theLIP (Large Igneous Provinces) field. This would indicate a formation ofspinels from a fertile mantle source and high PT melting (Kamenetskyet al., 2001).
Trachytes are confined to the Perşani Mountains (Cioflica et al.,1965; Nicolae and Saccani, 2005; Saccani and Nicolae, 2005), where
Table 3cBulk rock chemistry of selected samples of volcanics in Rarău, Hăghimaş and Perşani Mts.
Major elements in %; minor, trace and RE elements in ppm. Mg#=100×MgO/(MgO+FeOTOT
theyweremapped as large bodiesmainly in the surroundings of Racoş(Fig. 4). They are often associated with Triassic limestones. Smalloutcrops and blocks reveal massive trachytes or trachytic brecciaswith angular components in a very fine-grained matrix. The latter isstructureless and consists of amixture of crystalloclasts, mainly quartzand K-feldspar and tiny fragments of trachytes. The components ofbreccias and themassive trachytes show a typical trachytic fabric, withtightly parallel-oriented laths of K-feldspar, albite with relatively highcontent of K, and occasionally pure albite (Fig. 5d). Quartz and K-feldspar form phenocrysts. Trachytes are intensely altered, as shownmainly by large-scale calcitization and chloritization. Carbonate fillsthe fissures and impregnates the matrix of the breccia.
5. Geochemistry
Selected data on UM and basic to intermediate rocks are listed inTables 3a, 3b and 3c. The alteration is reflected in the variation ofLIL elements, in particular the alkalies, Ba and to a certain extent Sr.
Fig. 6. Spider diagrams for the Mesozoic basic to intermediate volcanics in the Eastern Carpathians.
162 V. Hoeck et al. / Lithos 108 (2009) 151–171
Their variation is highlighted in the spider diagrams (Fig. 6) where therelative concentration of Ba, Rb and K range sometimes over a factor of10. Sr is in general enriched but shows some variation to a much
Fig. 7. a) The plot of EC basic to intermediate rocks into the TAS diagram by Cox et al. (1979). bFor abbreviations see text.
smaller extent. Other elements might be only slightly changed byalteration processes. The HFSE as well as the REE show no significantvariation. The high content of LOI, larger than 10%, affects some major
) The Th–Hf–Ta diagram of basic to intermediate rocks from EC (diagram byWood,1980).
163V. Hoeck et al. / Lithos 108 (2009) 151–171
elements but has no effect on trace element ratios. Consequently, ourdiscussion of the geochemical grouping of the rocks is based onimmobile trace and RE elements.
The geochemical TAS classification is based on recalculatedchemical analyses on a LOI-free basis (Fig. 7a). The bulk of thevolcanics (DMORBs, NMORBs, EMORBs and OIBs) plot in the basalt andbasaltic andesite fields, whereas the HDBAs and the CABAs range frombasalts to andesites. The more alkali-rich OIBs partly classify ashawaiites. The apparently low-silica content of some of the basalts(below 45 wt.%) is mainly due to an admixture of carbonate.
The Ti/Zr ratio allows an initial classification. It shows that theCABAs have a lower Ti/Zr ratio (~40) than the other basalts, i.e. HDBAswith around 50, OIBs with around 80 and the MORB groups with a Ti/Zr ratio around 100. At the same time, the HDBAs have the lowest Tiand Zr contents. The Zr/Y ratio is higher than 4 in the CABAs and OIBs.The other basalts and andesites exhibit Zr/Y ratio between 2 and 4. Thehigh Nb content (N20 ppm) separates out the OIBs with a Zr/Nb ratioof about 4 from the rest of volcanics with Zr/Nb ratio between 35 and50. Only in the CABAs is it slightly lower (around 20).
For the Ta/Yb and Th/Yb ratios, the OIBs and CABAs are clearlyseparated from the other lithologies. The OIBs form a linear array withthe DMORBs as shown by Pearce (1982), whereas the CABAs and the
Fig. 8. REE diagrams for the Mesozoic basic to inte
EMORBs are offset from this array to higher Th/Yb ratios. In a similarway, the Th–Hf–Ta diagram (Wood, 1980) uses the Th/Ta ratiocombined with Hf. It separates out (Fig. 7b) the OIBs, which plot inthe field of WPB (Within Plate Basalts). The CABAs plot in the field ofthe Destructive Plate Margin Basalts. The MORB-type rocks plot in orclose to the MORB field, the EMOR-types rocks being shifted awayfrom the Ta apex, into the supra-subduction zone (SSZ) field. TheHDBAs plot between the IAV field and the EMORB field.
The final separation of the basalts groups was determined usingspider (Fig. 6) and REE diagrams (Fig. 8). The OIB and CABA groups showRE patterns with enriched LREE over HREE, with an enrichment factor(LREE) between 70 and 300 for the OIBs, and from 50 to 100 for theCABAs respectively. The spider diagrams were normalized againstNMORB,with normalizing data taken from Sun andMcDonough (1989).The OIBs show a continuous decrease from the incompatible elementstowards themore compatible elements. Ba and K show awider range ofnormalized values than the other elements, according to alteration. TheCABAs display a more irregular pattern, with a positive Th anomaly, anegative Nb anomaly, and high La and Ce values compared with Zr andHf. These suggest a strong influence of a subduction zone component.The relatively high values of La, Ce, Sr and Nd as well as the high Zr/Yratio could be due to an intraplate component. This is supported by the
rmediate volcanics in the Eastern Carpathians.
164 V. Hoeck et al. / Lithos 108 (2009) 151–171
field data which shows that the CABAs are closely associated withTriassic limestones (Botuş Quarry, Fig. 9a).
The separation among the HDBA, DMORB, NMORB and EMORB isnot so clear and to some extent arbitrary, since the groups grade intoeachotherwithout any sharp boundaryas shown in Figs. 6 and8, also inFig. 7. Despite the partly severe alteration, HSFE and REE (Figs. 6 and 8)seem to be at most only slightly affected and can be used with cautionfor a preliminary classification. This grouping is mainly shown for thesake of clarity. An attempt to draw possible petrogenetic inferencesfrom the grouping is beyond the scope of this paper. However, there aresome differences between these four groups, as highlighted in thespider and REE diagrams (Figs. 6 and 8).
The HDBAs have highly-depleted LREE and a spoon-shapedpattern. In the spider diagram they are the most depleted and show,apart from some anomalies, U-shaped patterns with the lowestnormalized values among the slightly incompatible elements. TheHDBAs have high Mg, Cr and Sr values. Most of these highly-depletedbasalts/andesites are found as dykes in serpentinites of the Sărmanu-lui Quarry, in PM. Those from the HAG area (Fig. 3) are extrusives.
The DMORBs show also low values of LREE but a clear overallenrichment compared with HDBAs. In the spider diagram they exhibitan almost flat pattern, but slightly depleted compared with averageMORB. There is a significant negative Nb anomaly and a weak positiveSr anomaly, and a wide range of values in K, Rb and Ba. The NMORBshave the same shape of the REE patterns as the DMORBs but areslightly more enriched. On the spider diagram, the HFSE plot close tounity, apart from Sr which shows a positive anomaly. Ba, Rb and Kshow irregular patterns. The EMORBs finally have a convex-upwardsREE pattern, with an enrichment of the MREE and the highest overallenrichment factor. Additionally, they display a small but significantnegative Eu anomaly. In the spider diagram, they plot slightly aboveunity and display only a small negative Nb anomaly. The LILE againhave an irregular pattern.
Except for theOIB, all groups display somesigns of a subduction zonecomponent, such as depletion in Nb, or high Sr values, and in the case ofCABA, a positive Th anomaly. They also deviate in their Th/Yb ratio from
Fig. 9. Field evidence for basalts associated with Triassic limestones. a) The Botuş quarry sequand Anisian massive limestones (Aml). The Werfenian sandstones and shales on top of basalposition. b) Primary contact of basalts (β) and red limestones (Lm) in the Rarău Peak area. c)Valley near Vârghiş).
the MORB-OIB array towards higher values. Additionally, all containrelatively highU and Pbvalueswhichwould result in a positive anomalyin spider diagrams. In particular the last two elements are thought to berelated with sediments in the down-going slab (Plank and Langmuir,1993; Pearce and Peate, 1995).
Summarizing, six groups of volcanic rocks with basaltic toandesitic chemistry could be distinguished, from which at least two,the OIB and CABA are not related with the otherMORB-type rocks. TheMORB-type rocks have a wide variety of composition and range fromstrongly depleted to enriched, compared with NMORB. Nevertheless,they show some slight differences which can be found in each of thesegroups. All have a small but distinct supra-subduction zone signature.
6. Discussion
6.1. Are they all ophiolites?
An ophiolite consists of a pseudostratigraphic rock sequence ofmantle tectonites, ultramafic and mafic cummulates, gabbros, sheeteddykes, basic extrusives (pillow lavas or massive lava flows) and finallysiliceous and/or calcareous sediments on the top. One or severalmembers may be missing. In the EC several members of an ophioliticsequence can be found: presumed mantle tectonites (lherzolites orharzburgites), FeTi gabbros, traces of sheeted dykes and extrusivessimilar to MORB with a wide range of compositions. Additionally thereare CABAs and OIBs, which are not related in any case to a possibleophiolite sequence. Apart from the serpentinized harzburgites, whichare intruded by highly-depleted basaltic dykes, and the associatedblocks of sheeted dykes, all other rock types occur as isolated blocks orslivers of variable size (Figs. 2–4). This ranges from some kms indimension for lherzolites from Tătarca and Tătărcuţa valleys (Rarău) orthe OIB pillow basalts in the Lupşa Valley (Perşani Mts.) to knockers oftens to one hundred metre size consisting of massive basaltic brecciaswith clasts between1and20cm.Nodirect geologicalfield relation couldbe established among the isolated occurrences. Thus, it is difficult toassignUMs, FeTi gabbros and basalts to a coherent ophiolite assemblage.
ence, in the Rarău area. From top to bottom: basalts (β), Anisian nodular limestones (Anl)ts are behind the hill in the left side of the image. The sequence is overturned in actualPrimary contact of basalts (β) and white limestones (Lm) in the Perşani Mts. (Hăghimaş
165V. Hoeck et al. / Lithos 108 (2009) 151–171
On the other hand, several basalt groups indicate an oceanic origin, thusjustifying the use of the term “ophiolites”.
6.2. Age of the Eastern Carpathians “ophiolites”
The age of magmatics and ultramafics in the Eastern Carpathians isstill a matter of debate. In the past, they have been regarded as Permian,Triassic and Late Cretaceous (Ilie, 1957), Triassic (Preda, 1940; Cioflicaet al., 1965), Triassic to Early Cretaceous (Savu, 1968; Săndulescu, 1976;Săndulescu and Russo-Săndulescu, 1981), and Early Jurassic (Turculeţ,1991) in age.
Our approach towards the age estimation of the EasternCarpathians “ophiolites” is based on clear primary interfaces betweenvolcanics and sediments, such as radiolarites and limestones, and onoccurrences where the volcanics are sandwiched between datedsediments (for example Botuş Quarry, in Fig. 9a). Besides our owninvestigations, we used only those literature data showing a clearconnection between volcanics and sediments. The most promisingamong the sediments are red, grey or greenish radiolarites as well asred and white limestones found both in the RA and the PM.
6.2.1. RadiolaritesIn the Rarău area, radiolarites form two main age groups, one of
Triassic and the other of Middle to Late Jurassic (Callovian–Oxordian)age. The Triassic radiolarites (Băncilă and Papiu, 1953; Dumitrica, 1981)occur as dispersed blocks in the Cretaceous Wildflysch and are oftendirectly associated with volcanics (Fundu Pojorâta and Seacă Valley inthe southern part of the Rarău area; Fig. 2). The Late Jurassic radiolarites(Băncilă and Papiu,1953;Mutihac,1969; Dumitrica,1994)weremappedas an almost continuous band on the western, southern and south-eastern slopes of the Rarău synclinewhere they belong to the sedimentsof the Bucovinian Nappe. They overlie a paleorelief formed in MiddleJurassic on the surface of the Anisian dolomites (Dumitrica, 1994).
From the olistoliths in the RA (Fundu Pojorâta; Fig. 2) Dumitrica(1981, 1994) described several radiolarian assemblages of Triassic age,ranging from Late Anisian to Carnian. In the Rarău Peak zone,Dumitrica identified an Upper Ladinian (Longobardian) assemblage,with Falcispongus rostratus (Dumitrica), Falcispongus calcaneus (Dumi-trica), Falcispongus falciformis (Dumitrica), Spongoserrula rarauana(Dumitrica), Pterospongus patrulii (Dumitrica), Pterospongus alatus(Dumitrica), Baumgartneria retrospina (Dumitrica), Baumgartneriacurvispina (Dumitrica), Zhamoidasphaera latispinosa (Kozur andMostler), Dumitricasphaera sp., Vinassaspongus subsphaericus (Kozurand Mostler), Baloghisphaera kovacsi (Kozur and Mostler), Emiluvia?cochleata (Nakaseko and Nishimura) a.o. In an olistolith in theWildflysch on the Pojorâta Valley (Rarău syncline), the red cherts ofLower Carnian age [with Spongoserrula rarauana (Dumitrica), Pteros-pongus undulatus (Dumitrica), Falcispongus rostratus (Dumitrica)] arein direct contact with basaltic rocks (EMORB).
Red-brownish cherts outcropping in the Rarău area at the springsof the Cailor Brook (Fig. 2) form amassive Fe-deposit (Walter, 1876), inclose vicinity to basaltic pillow lavas (NMORB). The radiolarite samplecontains volcanic ash remnants. Despite the poor preservation offossils, some indicator radiolarians could be identified5: Archaeoce-nosphaera (a genus known in the Ladinian–Carnian) and Oertlispongussp. (a genus characteristic to the Lower Ladinian but which ranges upto Upper Ladinian). The assemblage suggests a Ladinian age, alreadyassumed by Paul (1876). The tunnel used for the Fe explorationshowed clearly (Walter, 1876) that the radiolarites and the associatedvolcanics are blocks in the Wildflysch.
On the eastern slope of the Pojorâta Valley, SE of the Pojorâtavillage (Fig. 2), red cherts occur on the top of an ophiolite olistolith(EMORB). Radiolarians are poorly to moderately preserved; most of
5 The identification of the radiolarians is due to Dr. Paulian Dumitrica (University ofLausanne).
them represent spongy-shelled species. The following species havebeen identified4: Bogdanella praecursor (Kozur and Mostler), Dumi-tricasphaera sp., Hungarosaturnalis multispinosus (Kozur and Mostler),Muelleritortis cochleata (Nakaseko and Nishimura), Muelleritortisexpansa (Kozur andMostler), Pseudostylosphaera imperspicua (Bragin),Spongoserrula rarauana (Dumitrica), Scutispongus latus (Kozur andMostler), Tritortis dispiralis (Bragin), Tubospongopallium gracile(Tekin and Mostler). This assemblage is characteristic for the“Muelleritortis cochleata radiolarian zone”, the Spongoserrula rarauanasubzone respectively and indicates a Middle Longobardian (LateLadinian) age.
The cherts south of Câmpulung Moldovenesc, on the Seacă Valley(Fig. 2) are also associated with basalts (EMORB). They have a red-violet colour and contain a high amount of calcium carbonate.Radiolarians are frequent and most of them are represented byspherical moulds, which could be assigned to the Archaeocenosphaerasp. A single spherical specimen could be tentatively assigned to thegenus Octostella Tekin and Mostler, described from the Late Long-obardian of the Dinarides (Octostella pulchra)5. Thus, we consider theage of this sample as Late Ladinian–Early Carnian.
In the Perşani Mts. (Sărmanului Valley, near Vârghiş—Fig. 4),Dumitrica (1981) identified also a Lower Ladinian–Upper Anisian(?)radiolarians assemblage, with Falcispongus falciformis (Dumitrica),Baumgartneria bifurcata (Dumitrica), Baumgartneria trifurcata (Dumi-trica), Falcispongus calcaneum (Dumitrica). The highly-depletedbasalts (HDBA) from Sărmanului area are in close vicinity to theseradiolarites.
6.2.2. LimestonesSeveral papers describe limestones in direct contact with UM or
volcanics in the Rarău area (Fig. 2). Turculeţ (1987) provides evidencefor a stratigraphic range from Ladinian to Early Jurassic for smallblocks of variegated limestones included together with volcanics in apolymictic breccia from theMacieşHill (Timoi Valley). These volcanicsare EMORB. Mutihac (1969) described Norian red limestonesassociated with basic rocks in the same area, while Săndulescu(1976) mentioned altered basic rocks overlain by Barremian–Aptian(Urgonian) limestones on the Seacă Valley.
In the Botuş quarry, on the eastern slope of the Moldova Valley inthe RA, a succession of basalts, sandstones, shales and limestonesoccurs (Fig. 9a). The normal sequence starts with Werfeniansandstones and shales, overlain by basalts to andesites (CABA).Above basalts are Anisian thin-bedded nodular limestones followedby massive limestones. The whole sequence is overturned andrepresents an olistolith embedded in the Cretaceous Wildflysch.According to Kräutner et al. (1975), the age of the sediments in theBotuş quarry is Campilian–Anisian. In the limestones from Botuş,Săndulescu and Tomescu (1978) cited Earlandia (Aelisaccus) ampli-muralis Pantić, Earlandia (Aelisaccus) gracilis Elliott together withBaccanella floriformis, characteristic forms for Upper Anisian–LowerLadinian. The same association, with Earlandia (Aelisaccus) amplimur-alis Pantić and Earlandia (Aelisaccus) gracilis Elliott is described in theTriassic limestones of the Infrabucovinian Nappe from Iacobeni and inthe olistoliths embedded in the Wildflysch formation in the RarăuPeak area by Popescu and Popescu (2005, 2004 respectively).
North of Rarău Peak we found an occurrence of basalts (EMORB)closely associated-interbedded with red limestones (Fig. 9b). Thesediments are bioclastic lime-wackestone with crinoid fragments andrare nodosariacean foraminifera, indicating a hemipelagic facies. Thesediments are slightly dolomitized. No strict indication on the agecould be provided, but the facies is characteristic of Triassic (?Middle–Upper Triassic).6 Not far away, Săndulescu (1976) also mentionedUpper Triassic jaspers and limestones with Daonella indica, at the base
6 The identification of the fossil remnants is due to Dr. Ioan I. Bucur (Babeş-BolyaiUniversity Cluj-Napoca).
166 V. Hoeck et al. / Lithos 108 (2009) 151–171
of the Piatra Zimbrului klippe (Rarău Peak area). Popescu and Popescu(2004) described a Ladinian–Lower Carnian fauna in the PiatraŞoimului klippe from the Wildflysch in the same Rarău Peak area(see Fig. 2).
In the PM, the Mid-Triassic sediments from the Olt Defile are redshales and red nodular limestones with cherts (Mutihac, 1990).Recently, a torrential creek opened an outcrop on the northern slopeof the Hăghimaş valley, opposite to the Vârghiş Quarry in PM (Fig. 4),exposing a direct contact of basaltic rocks and limestones (Fig. 9c). Thewhole profile starts at the bottom with shales, marls and sandstonesbelonging to the Cretaceous Wildflysch formation. The upper part ofthe flysch level, containing basaltic fragments is overlain by massivebasalts (OIB). In the lower part, basalts are associated with thin layersof siliceous sediments. Basalts are aphyric, slightly vesicular and arehighly brecciated. The apparent thickness of the basalts is about 30 m.In the upper part of the basaltic layer, several decimeters-thick layersof red and white limestones and limestone breccias with basalt-clastsoccur. These are different limestones each displaying a faciescharacteristic of the Late Triassic,6 such as intraclastic grainstones,mudstones/wackestones/packstones and microbreccias with stroma-tolitic elements connected by laminitic fenestrate with siltic sedimentin the fenestre. The limestone microbreccias contain small clasts ofbasalts.
Săndulescu and Russo-Săndulescu (1981) considered four local-ities as evidence for a wide time range of the formation of the“ophiolites”, fromAnisian–Ladinian to Neocomian. These includes (a)Deremoxa creek, where a Kimmeridgian limestone overlie ultra-mafics (Săndulescu, 1976), (b) Cailor Brook, where basalts lie onWerfenian sandstones, (c) Seacă Valley, with Urgonian limestones overbasalts, and finally (d) the Bicaz Gorges, where tectonically emplacedbasalts occur beneath the Kimmeridgian limestones of the Hăghimaş.Unfortunately, none of these places displays clear primary interfacesbetween basalts and sediments. In the Seacă Valley, which wasconsidered asevidence for theLate Jurassic, evenNeocomian, volcanism,we could show that EMOR-type basalts are associated primarily withMid-Triassic radiolarites (see above). In all cases where we observedinterfaces with basalts, the sediments proved to be Triassic.
When combining the basalts ages with the geochemical grouping, itis clear that at least one or more samples from the following groups areTriassic: OIB, CABA, and EMORB. For the NMORB and HDBA this is alsoprobable sinceMid-Triassic radiolarites (Dumitrica,1981) were found inclose vicinity (Cailor Brook in RA and Sărmanului Quarry area in PMrespectively). No stratigraphic assignment can bemade for themomentfor the UMs, FeTi gabbros and theDMORBs, but none of these shows anyclose connection to Jurassic or Lower Cretaceous sediments. Taken allthe arguments together, it is highly probable that a vast majority of themagmatic rocks, maybe even all, are of Triassic age.
6.3. Comparison with Southern Apuseni Mts. and Meliata ophiolites
Some of the EC ophiolites and other basic rocks were thought bySăndulescu (1984) to be part of the “Transylvanian nappes”. Theblocks of unquestionable sedimentary emplacement in theWildflyschwere believed to be derived from the approaching “TN”. The origin ofthe “Transylvanian nappes” was located by Săndulescu (1984) in theso-called Main Tethyan Suture Zone (exposed nowadays in SAM), inwhich the Vardar Ocean disappeared. Thus, both the SAM ophiolitesand IAVs and the EC “ophiolites” should come from the same VardarOcean. It was envisaged that upon the closure of this ocean, its easternbranch was thrust towards the east forming the “Transylvaniannappes” in the EC. In the same time, the western branch is thrust ontothe crystalline basement of the Apuseni Mts. to the north, giving riseto the SAM ophiolites and the associated IAVs.
In our opinion, it is very difficult to accept that the SAM and the EC“ophiolites” are the result of an emplacement mechanism in twoalmost opposite directions from a single subduction zone. It is also
difficult to reconcile the origin of the EC Triassic “ophiolites” with theEastern Vardar Ocean (see also Kozur,1991; Channell and Kozur,1997).
The SAM ophiolites are entirely of Jurassic age but in the EC allauthors, including Săndulescu, agree on the Triassic age of a substantialpart of “ophiolites” (Cioflica et al., 1965; Patrulius et al., 1966;Săndulescu,1976; Săndulescu and Russo-Săndulescu,1981; Săndulescu,1984). The latter assumed a time span for the generation of basalts fromMid-Triassic to Late Jurassic/Early Cretaceous. He explained the Triassicage of many EC basalts as remnants of an older Triassic stage of theopening of the Vardar Ocean, which was obviously not preserved in theSAM ophiolite.
Starting from this concept, it is worthwhile to compare the EasternCarpathians “ophiolites” with those from the Southern ApuseniMountains. The first and most obvious difference between the SAMand the EC occurrences is the geological appearance. The SAMophiolitesform a huge and coherent assemblage extending over 60 km, asdiscussed in Section 2. Apart from the mantle tectonites, the SAMophiolites typically contain all ophiolite members. By contrast, there isno coherent body of a complete ophiolitic assemblage throughout theEC. The largest individual bodies are 1 to 3 km-extending fromlherzolites in the RA to pillow basalts in the PM. The majority of basaltsand ultramafics (lherzolites+harzburgites) occur as breccias andolistoliths in the Wildflysch. Gabbros, which constitute a voluminousand important part of the SAM ophiolites, are missing in the EC,excepting a small occurrence of FeTi gabbros. Only one small occurrenceof remnants of a sheeted-dyke complex could be found in PM, but it ispossible that somemore coarse-grained dolerites occurring throughoutthe area in separate blocks and components in breccias may be derivedfrom a more extensive sheeted-dyke complex. Contrary to the SAMbasalts, the ECbasalts displayawidevariety of composition,with severaltypes of MOR-like basalts, OIBs, and CABAs. Furthermore, alteration inthe SAMophiolite is dominated by the occurrence of saponite, smectite,chlorite and glauconite/celadonite and zeolites,whereas in the ECcalciteand chlorite are predominant.
Secondly, only MOR-type basalts and CABA occur in the SAMophiolite, OIBs have never been described so far. Comparison ofgeochemistry can therefore be restricted to the former rock types. Thecomparison is based partly on the data published by Bortolotti et al.(2002), Nicolae and Saccani (2003), Saccani et al. (2001) and partly onour own analyses from the SAM ophiolites, which are in goodagreement with their results. Most prominent differences can beobserved with the HDBA and the DMORB group. Compared with MORbasalts from SAM, they show high contents in Cr, but low values of Nb,Zr, LREE. The Ce/Yb ratio is low and the Zr/Nb ratio high (N50),compared with the SAM basalts, where the majority of the Zr/Nbratios is smaller than 35. The EC NMORB and EMORB groups are moreclose to the SAM basalts but also they show higher Zr/Nb ratios andalso higher Ce/Nb ratios, compared with the SAM.
The calc-alkaline basalts to andesites from the EC can be comparedwith the relevant rocks of the island arc sequence on top of theophiolites in the SAM. Here the differences between the two groupsare evenmore conspicuous than in the MOR-type basalts. The EC calc-alkaline basalts to andesites have significantly higher concentrationsin LREE, trace elements such as Zr and Nb and also Ti. Additionally,their Zr/Nb ratios are lower and the Zr/Y ratios higher.
Third, the age problems of the EC “ophiolites” have beenextensively discussed above and we could show that from the mostimportant geochemical groups, at least one is of Triassic age. On theother hand, the SAM ophiolites and IAVs are undoubtly of Middlle toLate Jurassic age, as indicated by the sediments and the intrusion ofthe granitoids respectively (Lupu et al., 1995; Pană et al., 2002).
Considering the age data, a comparison with occurrences of theTriassic ophiolitic fragments of theMeliata–HallstattOcean (MHO) sensuKozur (1991) can be confirmed. Hewas the first to suggest a connectionbetween the Meliata–Hallstatt Ocean and the “Transylvanian” Ocean inthe Eastern Carpathians, continuing through the Strandzha Zone into the
7 The Bucovinian plus Sub-Bucovinian units will be trated as one entity (BSB).
167V. Hoeck et al. / Lithos 108 (2009) 151–171
Pontides. The assumption is reasonable not only because of the age butalso based on the close similarity of the various Triassic limestone blocksin theWilflysch with the Triassic limestones in the Eastern Alps and theWestern Carpathians (Uhlig, 1907; Turculeţ, 1991). However, we restrictour comparison to the remnants of theMeliata ophiolites in Slovakia andN Hungary. They occur in several regions: in the Jaklovce Formation,Meliata Formation, Bôrka Nappe, Bodva Valley Formation, Darnó HillFormation (Ivan, 2002; Faryad et al., 2005) and in the E Bükk area(Harangi et al., 1996). Similar to the EC, the Meliata ophiolites occur assmall and incoherent blocks in a Jurassic mélange, in which they wereemplaced tectonically or as olistoliths. Additionally, they also occur asclasts in the Upper Cretaceous Dobšinská Ladová Jaskyňa conglomerate.Lithologically, they are very similar, including lherzolites and harzbur-gites, gabbros, dolerites and basalts. Whereas gabbros are abundant inthe Bodva Valley Formation, the Darnó Hill Formation and in the UpperCretaceous conglomerate, they are, as in the EC, almost totally absent inthe Jaklovce Formation, the Meliata Formation and the Bôrka Nappe.Where the original mineralogy is preserved, basalts and dolerites showthe same features as those in the EC, such as phenocryst assemblageswith plagioclase and clinopyroxene and the composition of thegroundmass. TheMeliata ophiolitic remnants are partlymetamorphosedin HP/LT (blueschist facies) or LP/LT (greenschist facies) conditions.
Regarding the geochemistry, variousMOR-typebasalts andOIBs arecommon in the Meliata–Hallstatt Ocean. Unfortunately, the data baseis relatively small and incomplete. The comparison is based on thepublished analyses by Harangi et al. (1996), Ivan (2002), Faryad et al.(2005). Nevertheless, a wide range of compositions can be observed,ranging fromnormal to enrichedMORB. In the Bodva Valley FormationNMORB types occur, whereas in the Darnó Hill Formation and JaklovceFormation EMORB types prevail. OIBs are found in the Bôrka Nappeand in the E Bükk area. Some of basalts in the Bôrka Nappe exhibit asupra-subduction signature. The REE distribution patterns, theelement concentrations and the element ratios are similar withthose depicted in Figs. 6 and 8 respectively.
The comparisonof the EC ultramafics and eruptives shows that theyare more close to the Meliata ophiolites than to the SAM ones. Theirlithology, their mineralogy and their geochemistry match very wellthose of the ophiolitic fragments of the Meliata–Hallstatt Ocean. Wesuggest here, in agreement with Burchfiel (1976) and Kozur (1991),that the Eastern Carpathians “ophiolites” represent the eastwardcontinuation of the former Mid-Triassic Meliata–Hallstatt Ocean.
6.4. The Wildflysch problem
Uhlig (1907) assigned for the first time the limestone blocks ofTriassic and Jurassic age, occurring in and on the Wildflysch togetherwith eruptive rocks, to the “Siebenbürgische Decke” (i.e. Transylva-nian Nappe). The source area of limestones remains unknown.Săndulescu (1984) elaborated on nappe concept, whereas Burchfiel(1976), in close cooperation with Bleahu, considered most of theblocks as olistoliths and only the larger ones, like the 20 km-longUpper Jurassic limestone in Hăghimaş area as tectonic klippe.Nevertheless he suggested also for this, emplacement by gravitysliding. The close connection of the “TN”with theWildflysch raises thequestion whether the latter is autochthonous or allochthonous inrespect to the underlying Bucovinian crystalline and sediments.
Popescu (1970), following Preda (1940) regarded the Wildflysch asan allochthonous formation. By contrast, Săndulescu (1975, 1984)considered the Widlflysch as a syn-tectonic formation on top of theBucovinian sequence, formed during the eastward movement of the“TN” and collecting material from the latter as olistoliths. Balintoni(1997) argued again in the favour of an allochthonous origin of theWildflysch. His major arguments were:
1. The lower stratigraphic parts of the WF show a rapidly-changingdevelopment of different facies. This includes material from both,
the Bucovinian Nappe, in some places, and the “TN”, in other places.Such a composition is not consistent with formation on top of theBucovinian sequence.
2. The pelitic–siltic matrix of the WF cannot originate from the “TN”,which would consist of carbonate rocks and ophiolites. Thesediments of the WF are intensely deformed at the base and insome places foliated, mirroring a strong shearing.
3. The WF is emplaced above a deformed basement and additionallythere is a stratigraphic gap over wide areas ranging from the LateJurassic to Barremian.
4. The WF unconformably overlies Triassic, Jurassic and ?EarliestCretaceous sediments and it cuts Lower Cretaceous local thrustplanes in the Bucovinian sediments.
5. In the Perşani Mts. the WF is directly thrust as an independenttectonic unit onto the Ceahlău Flysch Nappe (Lower Cretaceous),the highest unit within the Eastern Carpathian Flysch.
Based on these arguments, we propose a tectonic emplacement ofthe Wildflysch as a separate nappe, called theWildflysch Nappe. At thesame time, we suppose, in agreement with Burchfiel (1976), that the“Transylvanian nappes” should be interpreted as a series of olistoliths,megaolistoliths and klippen formed by gravity gliding.
It should be noted that Wildflysch sediments of the same age (LateBarremian–Early Albian) including olistoliths are known in theSouthern Apuseni Mts. (Burchfiel, 1976; Săndulescu, 1984). These arethrust onto the crystalline basement and the Mesozoic sediments ofthe Northern Apuseni nappes. The thrusting of the Wildflysch in theApuseni Mts. in the Late Albian was probably contemporaneous withthe Wildflysch thrusting in the EC. In both areas Cenomanian clasticsediments form post-tectonic cover.
6.5. Hypothetical Mesozoic evolution of the Eastern Carpathians andApuseni Mts
A model describing the development of the inner part of theEastern Carpathians has to take into account several facts:
a) TheMid-Triassicmagmatic activity, leading to the formation ofMOR-type basalts (Cioflica et al., 1965; Patrulius et al., 1966; Săndulescu,1984);
b) The occurrence of Mid-Triassic calc-alkaline basalts (Hoeck andIonescu, 2006; Hoeck et al., 2006; Hoeck and Ionescu, 2007);
c) The Early Mesozoic sedimentary evolution in the Bucovinian/Sub-Bucovinian realm, Infrabucovinian, and Apuseni Mts. (Bleahu,1976; Săndulescu, 1976, 1984);
d) The development of the Wildflysch with limestone clasts andolistoliths comparable with sediments from the Apuseni Mts.(Uhlig, 1907; Săndulescu, 1984);
e) The composition of the basement of the Transylvanian Depression(Ionescu et al., 2009-this issue);
We assume that an ocean branch, in connection with the Meliata–Hallstatt Ocean opened in the Eastern Carpathians during Early toMiddle Triassic (Fig. 10a), as postulated by Savu (1980; “Siret Ocean”)and Kozur (1991). To trace the location of the MHO in the EC is a verydifficult task since no suture zone is preserved. Several authors (e.g.Săndulescu, 1984; Csontos and Vörös, 2004) connected MHO with theVardar Zone. Our findings, in accordance with Kozur (1991), Channelland Kozur (1997) and Stampfli and Borel (2004) do not support thisconnection but argue for a separate oceanic realm. This ocean mighthave been situated between three continental domains, which showdifferent sediment sequences during Early Mesozoic (Uhlig, 1907;Popescu and Popescu, 2005). These are the Northern Apusenicontinental crust, the Infrabucovinian and the Bucovinian/Sub-Bucov-inian units7 (Fig. 10a). The reason to suggest the existence of an ocean
Fig. 10. a,b,c. Hypothetical evolution of the Eastern Carpathians and the Apuseni Mountains (Early Triassic–Late Jurassic). d,e. Hypothetical evolution of the Eastern Carpathians andthe Apuseni Mountains (Barremian–Albian).
168 V. Hoeck et al. / Lithos 108 (2009) 151–171
between Infrabucovinian on one side and the BSB on the other side ismainly based on the differences of the lithological and stratigraphicevolution of these units, including their crystalline basements (Berciaet al.,1975; Burchfiel, 1976; Balintoni,1997). The crystalline basement ofthe BSB consists mainly of the Rebra and the Tulgheş Complex,metamorphosed in amphibolite and greenschist facies respectively. Onthe other hand, the Bretila Complex (amphibolite facies) forms thebasement of the Infrabucovinian. The BSB has a Low to Mid-Triassicsedimentary cover consisting of Werfenian siliciclastic and Anisiandolomites and limestones. Radiolarites on top are already Oxfordian inage. Locally, Lower Jurassic calcareous sandstones and Upper JurassicAptychus limestone grade into lowermost Cretaceous facies. TheInfrabucovinian is characterized by a similar Werfenian lithology butcontains Anisian bituminous dolomites followed by ?Upper Triassicvariegated limestones, with red, green, violet and grey colours(Săndulescu, 1975; Burchfiel, 1976; Grasu et al., 1995; Popescu andPopescu, 2005). Further in the north-west, in theMaramureş area, Mid-Triassic basic volcanics occur in the IB (Săndulescu, 1984).
In this respect, the olistolith of the Botuş Quarry is of major interestfor three reasons. First, it consists ofWerfenian sandstones, Mid-Triassiccalc-alkaline basalts and andesites, andAnisian limestones including rednodular limestones (Fig. 9a). This facies resembles that of theInfrabucovinian (Popescu and Popescu, 2005). Second, basalts and
andesites clearly have a SSZ signature, which requires a subductingocean nearby. Third, both facts strongly support an origin of the BotuşQuarry olistolith from the IB realm, since only in the IB Mid-Triassic arevolcanics known outside the Wildflysch.
The remnants of this ocean can be found now as olistoliths in theWildflysch of the EC. The supra-subduction signature of MOR basaltssuggests a possible back-arc basin nature for this ocean branch in thevicinity of the Paleotethys (Stampfli and Borel, 2004).
The DitrăuMassif, whichwas dated asMid-Triassic (Dallmeyer et al.,1997; Pană et al., 2000) was intruded into the Bucovinian basementprobably during the opening of this ocean. Similarly, Mid-Triassicalkaline intrusions are also common in the Southern Alps (Castellarinet al., 1982) and the Dinarides (Pamić, 1984).
Soon after its opening, this ocean already started to subductbeneath the Infrabucovinian unit, generating some basic volcanicsembedded in Ladinian sediments. In the Late Triassic to Early Jurassicthe oceanic basin closed when the opening of the Vardar Ocean began(Fig.10b). The subductionwas probably directed beneath the NorthernApuseni continental crust and the Infrabucovinian continent.
In the Mid- to Late Jurassic (Fig. 10c) the north-directed oceanicbranch in the EC closed and formed a suture among these threecontinental units, leavinganophiolite bodyasa remnantof this oceanontop of the suture. This scenario predicts a close spatial connection of the
169V. Hoeck et al. / Lithos 108 (2009) 151–171
Northern Apuseni Mts. (Tisia) with the IB plus BSB domains after theMid-Late Jurassic suturing. In this respect, our model is consistent withsome aspects of the paleogeographic reconstructions by Plašienka(2000) and Csontos and Vörös (2004).
The Eastern Vardar Ocean only opened later and eventuallydeveloped a back-arc basin and intra-oceanic island arc above asubduction zone, generating what is known today as SAM ophiolitesand island arc volcanics (for details see Ionescu et al., 2009-this issue).During the closure of the Vardar back-arc basin, the Wildflysch basindeveloped in the Barremian–Albian (Fig. 10d), between the remnantsof the back-arc basin on one side and the Northern Apusenicontinental crust (Tisia) and the Bucovinian/Sub-Bucovinian crust onthe other side. The Wildflysch basin was filled in with clasticsediments and olistoliths—mainly limestones, which originated fromthe Northern Apuseni continent, from the IB, also from the BSB, andwith “ophiolitic” clasts from the remnants of the Triassic ocean. Theformer IAVs (SAM) possibly provided material to the Wildflysch basinas well. The sedimentation ended in the Early Albian and theWildflysch was subsequently overthrusted onto the Northern Apusenicontinent and the Bucovinian continent (Fig. 10e).
This model accounts for a number of facts but nevertheless, severalquestions remain to be answered, e.g. the connection of the MHOOcean with Dobrogea and the Küre Ocean (compare Stampfli andBorel, 2004) or the relation between the Vardar Ocean and thePenninic Ocean, and finally the post-Early Cretaceous evolution.
The present position of the EC is fundamentally different from theMesozoic situation. The Eastern and Southern Carpathians as well asthe Transylvanian Depression most likely rotated some 60° clockwisetogether with the Apuseni Mts. during Miocene (Pătraşcu et al., 1994;Márton et al., 2007).
7. Conclusions
This investigation of ophiolitic remnants and the related volcanicsin the Eastern Carpathians led to results, which support a new modelof the Mesozoic evolution of the inner EC, which differs substantiallyfrom that developed by Săndulescu (1984), and can be summarized asfollows:
1. The Eastern Carpathians “ophiolites” display a wide range ofgeochemical compositions, from HDBA, D- and NMORB andrelatively enriched MORB, to CABA and OIB. Lherzolites, harzbur-gites and trachytes occur as well.
2. We regard all the Eastern Carpathians Mesozoic magmatics asoccurring as components of breccias or isolated blocks, includinglarger blocks, as olistoliths and megaolistoliths respectively, in theBarremian–Albian Wildflysch formation. A series of newly foundsediments showing a clear depositional contact with volcanicswere paleontologically dated. For most of the geochemical groupsof “ophiolites” a Triassic age is established. Up to now noconvincing Jurassic ages have been proved.
3. We compared the Eastern Carpathians “ophiolites”with theMiddleto Upper Jurassic SAM ophiolites and IAVs andwith the remnants ofthe Triassic Meliata–Hallstatt Ocean in the Western Carpathians.Apart from the age, we could show that there are other significantdifferenceswith the Southern ApuseniMts. ophiolites. The latter donot display such a wide variety of compositions, e.g. the OIBs andDMORBs are missing. Even those which are on first sightcomparable basalts and andesites show significant differences. Onthe other hand, the Meliata remnants are in a similar way to theEastern Carpathians “ophiolites”, fragmented into small blocks anddisplay, besides MORBs, serpentinites and gabbros, also OIBs.Together with our age-dating, this suggests a close connectionamong the Meliata and the Eastern Carpathians ophiolites.
4. We assume that the Wildflysch was not deposited transgressivelyon top of Jurassic to Lower Cretaceous sediments of the Bucovinian
Nappe s.s. but rather in an independent basin during Barremian toEarly Albian. The Wildflysch sediments of the Apuseni Mts. coverthe same time interval, possible in the same basin. The source areaof the limestone olistoliths and clasts in the Wildflysch wasprobably the Mesozoic cover of the Northern Apuseni Mts. andpossibly the Mesozoic sediments from IB and BSB. The UM andmagmatic blocks were derived from the remnants of the Triassicocean in the EC. Presumably, volcanic olistoliths in the Wildflyschsediments in the Apuseni Mts. were derived from the Jurassic IAVs.
Based on these facts, a new model was developed, which accountsfor the Triassic age of the “ophiolites” in the Eastern Carpathians, fortheir origin in a Triassic ocean (Meliata–Hallstatt Ocean), unrelated tothe Vardar Ocean, for a separate basin of the Wildflysch and for thepossible origin of the Triassic–Jurassic limestone blocks in the Wild-flysch, from the Northern Apuseni area and possible from IB and BSB.
In a recent study, Ionescu et al. (2009-this issue) showed, based ondrill cores and reflection seismic data, that in the basement of theTransylvanian Depression island arc volcanics, and probably ophiolitesbeneath, which are the continuation of the Southern Apuseni Mts., arein direct contact along a steep fault (Târnava Fault) with meta-morphics (Infrabucovinian? Bucovinian?). All of our findings do notsupport a model invoking the “Transylvanian nappes” as originating inthe Eastern Vardar Ocean (Main Tethyan Suture Zone) i.e. thebasement of the Transylvanian Depression.
Acknowledgments
The authors are grateful to Dr. Hans-Georg Kräutner, Dr. TudorBerza, Dr. Cestmir Tomek and Prof. Alastair Robertson for theircomments which helped to improve the manuscript. The paperbenefited by the Dr. P. Dumitrica and Dr. Ioan I. Bucur identification ofradiolarians and other microfossils respectively. Many thanks are dueto Prof. Alastair Robertson and Otis Crandell for the English review ofthe manuscript and to Mrs. Monica Mereu for the computer-assisteddrawings. The study was financially supported by Grant 1337 funds(CNCSIS - Romanian Ministry of Education).
References
Alexandrescu, Gr., Mureşan, G., Peltz, S., Săndulescu, M., 1968. Geological Map ofRomania, 1:200,000; Topliţa Sheet. Geological Institute Bucharest.
Allan, J.F., Sack, R., Batiza, R.,1988. Cr-rich spinels as petrogenetic indicators:MORB-type lavasfrom the Lamont seamount chain, eastern Pacific. American Mineralogist 73, 741–753.
Anđelković, M.Z., Lupu, M., 1967. Die geologie der Šumadija- und Mureş- zone:stratigraphische gliederung, fazies, magmatismus, tektonik. Carpatho-BalkanGeological Association VIII Congress, Belgrade, Reports, Geotectonics, pp. 15–28.
Balintoni, I., 1997. Geotectonics of the metamorphic terrains from Romania. EdituraCarpathica, Cluj-Napoca, 176 pp. (in Romanian).
Băncilă, I., Papiu, C.V., 1953. Les jaspers triasique de Pojorâta. Buletin Ştiinţific alAcademiei, Secţia Biologie Agronomie Geologie Geografie V 4, 675–694 (inRomanian).
Beccaluva, L., Macciotta, G., Piccardo, G.B., Zeda, O., 1989. Clinopyroxene composition ofophiolite basalts as petrogenetic indicator. Chemical Geology 77, 165–182.
Bercia, I., Bercia, E., Săndulescu, M., Szasz, I., 1975. Geological Map of Romania, 1:50,000;Vatra Dornei Sheet. Institute of Geology and Geophysics Bucharest.
Bleahu, M., 1976. Structural position of the Apuseni Mountains in the Alpine system.Revue Roumaine de Géologie, Géophysique et Géographie. Serie de Géologie 20 (1),7–19.
Bortolotti, V., Marroni, M., Nicolae, I., Pandolfi, L., Principi, G., Saccani, E., 2002.Geodynamic implications of Jurassic ophiolites associated with Island-ArcVolcanics, South Apuseni Mountains, Western Romania. International GeologicalReview 44, 938–955.
Burchfiel, B.C., 1976. Geology of Romania. Geological Society of America Special Paper,vol. 158. 82 pp.
Castellarin, A., Lucchini, F., Rossi, P.L., Sartori, R., Simboli, G., Sommavilla, E., 1982. Notegeologiche sulle intrusioni di Predazzo e dei M. Manzoni. In: Castellarin, A., Vai, G.B.(Eds.), Guida alla geologia del Sudalpino Centro-Orientale. Guide Geol. Reg. SocietaGeologica Italiana, Bologna, pp. 211–219.
Cawthorn, R.G., Collerson, K.D., 1974. The recalculation of pyroxene end-memberparameters and the estimation of ferrous and ferric content from electronmicroprobe analyses. American Mineralogist 59, 1203–1208.
Channell, J.E.T., Kozur, H.W., 1997. How many oceans? Meliata, Vardar, and Pindosoceans in Mesozoic Alpine paleogeography. Geology 25 (2), 183–186.
Cioflica, G., Patrulius, D., Ionescu, J., Udubaşa, G., 1965. The Triassic ophiolites from thePerşani Mts. Studii şi Cercetări de Geologie, Geofizică, Geografie. Seria Geologie 10 (1),161–182 (in Romanian).
Ciupagea, D., Pauca, M., Ichim, T., 1970. Geology of the Transylvanian Depression.Editura Academiei, Bucharest. 254 pp. (in Romanian).
Cox, K.G., Bell, J.D., Pankhurst, R.J., 1979. The Interpretation of Igneous Rocks. GeorgeAllen & Unwin, London, Concord MA. 450 pp.
Csontos, L., Vörös, A., 2004. Mesozoic plate tectonic reconstruction of the Carpathianregion. Palaeogeography, Palaeoclimatology, Palaeoecology 210, 1–56.
Dallmeyer, D.R., Kräutner,H.G., Neubauer, F.,1997.Middle-Late Triassic 40Ar/39Ar hornblendeages for early intrusion within the Ditrău alkaline massif, Romania: implications forAlpine rifting in the Carpathian orogen. Geologica Carpathica 48 (6), 347–352.
Deer, W.A., Howie, R.A., Zussman, J., 1966. An Introduction to Rock Forming Minerals.Longmans Group Ltd., London. 528 pp.
Dumitrica, P., 1981. Triassic Oertlisponginae (Radiolaria) from Eastern Carpathians andSouthern Alps. Dări de Seamă Institutul de Geologie şi Geofizică LXVII (3), 57–74(1979–1980).
Dumitrica, P., 1994. Biostratigraphy of the radiolarites at Pojorîta (Rarău syncline, EastCarpathians). Mémoires Géologique (Lausanne) 23, 907–914.
Faryad, S.W., Spišiak, J., Horváth, P., Hovorka, D., Dianiška, I., Józsa, S., 2005. Petrologicaland geochemical features of the Meliata mafic rocks from the sutured Triassicoceanic basin, Western Carpathians. Ofioliti 30 (1), 27–35.
Grasu, C., Cătană, C., Turculeţ, I., Niţă, M.,1995. The Petrography of theMesozoic from the“External Marginal Syncline”. Editura Academiei, Bucharest. 192 pp. (in Romanian).
Harangi, Sz., Szabo, Cs., Józsam, S., Szoldán, Zs., Árva-Śos, E., Ball, M., Kubovics, I., 1996.Mesozoic igneous suites in Hungary: implications for genesis and tectonic setting inthe northwestern part of Tethys. International Geological Reviews 38, 336–360.
Hoeck, V., Ionescu, C., 2006. Basic and intermediate volcanics in the Eastern Carpathians(Rarău; Romania): are all of them ophiolites? In: Sudar, M., Ercegovac, M., Grubić, A.(Eds.), Proceedings of XVIII Congress of the Carpathian–Balkan GeologicalAssociation, Belgrade, pp. 219–221.
Hoeck, V., Ionescu, C., 2007. Mesozoic ophiolites from the Eastern Carpathians: what arethey and where are they coming from? Geophysical Research Abstracts, 9, 01515,2007, SRef-ID: 1607-7962/gra/EGU2007-A-01515.
Hoeck, V., Ionescu, C., Koller, F., 2006. Do the Eastern Carpathians ophiolites originatefrom the Vardar Ocean? Proceedings of International Symposium MesozoicOphiolite Belts of the Northern Part of the Balkan Peninsula, pp. 49–52.
Hovorka, D., Jaroš, J., Kratochvíl, M., Mock, R., 1984. The Mesozoic ophiolites in theWestern Carpathians. Krystalinikum 17, 143–157.
Hsü, K.J., Briegel, U., 1991. Geologie der Schweiz. Birkhäuser Verlag, Basel. 219 pp.Ilie, M., 1957. Geological research in the Rarău-Câmpulungul Moldovei-Pârâul Cailor
area. Anuarul Comitetului Geologic XXX, 108–211 (in Romanian).Ionescu, C., Hoeck, V., 2006. Mesozoic volcanics in the Transylvanian Depression
basement: the north-eastern end of the Vardar Ocean. Proceedings of InternationalSymposium Mesozoic Ophiolite Belts of the Northern Part of the Balkan Peninsula,pp. 53–57.
Ionescu, C., Hoeck, V., Tomek, C., Koller, F., Balintoni, I., Beşuţiu, L., 2009. New insightsinto the basement of the Transylvanian Depression (Romania). Lithos 108, 172–191(this issue). doi:10.1016/j.lithos.2008.06.004.
Ivan, P., 2002. Relics of theMeliata Ocean crust: geodynamic implications ofmineralogical,petrological and geochemical proxies. Geologica Carpathica 53 (4), 245–256.
Joja, T., Alexandrescu, Gr., Bercia, I., Mutihac, V., Dimian, M., 1968. Geological Map ofRomania 1:200,000; Rădăuţi Sheet. Geological Institute Bucharest.
Kamenetsky, V.S., Crawford, A.J., Meffre, S., 2001. Factors controlling chemistry ofmagmatic spinel: an empirical study of associated olivine, Cr-spinel and meltinclusions from primitive rocks. Journal of Petrology 42 (4), 655–671.
Karamata, S., Olujić, J., Protić, Milovanović, D., Vujnović, L., Popević, A., Memović, E.,Radovanović, Z., Resimić-Šarić, K., 2000. The western belt of the Vardar zone—theremnant of a marginal sea. In: Karamata, S., Jancović, S. (Eds.), Proceedings ofInternational Symposium Geology andMetallogeny of the Dinarides and the Vardarzone, pp. 131–135.
Koller, F., Höck, V., 1990. Mesozoic ophiolites in the Eastern Alps. In: Malpas, J., Moores,E.M., Panayiotou, A., Xenophontos, C. (Eds.), Ophiolites. Oceanic Crustal Analogues.Proceedings of the Symposium “Troodos 1987, pp. 253–263.
Kozur, H., 1991. The evolution of the Meliata–Hallstatt Ocean and its significance for theearly evolution of the Eastern Alps and Western Carpathians. Palaeogeography,Palaeoclimatology, Palaeoecology 87, 109–135.
Kräutner, H.G., Kräutner, F., Săndulescu, M., Bercia, I., Bercia, E., Alexandrescu, Gr.,Ştefănescu, M., Ion, J., 1975. Geological Map of Romania, 1:50,000; Pojorâta Sheet.Geological Institute Bucharest.
Lupu, M., Antonescu, E., Avram, E., Dumitrica, P., Nicolae, I., 1995. Comments on the ageof some ophiolites from the north Drocea Mts. Romanian Journal of Tectonics andRegional Geology 76, 21–25.
Marschalko, R., 1964. Sedimentary structures and paleocurrents in the marginallithofacies of the Central-Carpathian flysch. In: Bouma, A.H., Brouwer, A. (Eds.),Turbidites. Elsevier Publ. Co., Amsterdam, pp. 106–126.
Márton, E., Tischler, M., Csontos, L., Fügenschuh, B., Schmid, S., 2007. The contact zonebetween the ALCAPA and Tisza-Dacia mega-tectonic units of Northern Romania inthe light of new paleomagnetic data. Swiss Journal of Geosciences 100, 109–124.
Mutihac, V., 1969. Geological structure of the external marginal syncline, north of theMoldova Valley. Dări de Seamă Comitetul Geologic LIV (3), 213–225 (1966–1967)(in Romanian).
Mutihac, V., 1990. Geological Structure of Romania. Editura Tehnică, Bucharest. 419 pp.(in Romanian).
Nicolae, I., Saccani, E., 2003. Petrology and geochemistry of the Late Jurassic calc-alkalineseries associated to Middle Jurassic ophiolites in the South Apuseni Mountains
(Romania). Schweizerische Mineralogische und Petrographische Mitteilungen 83,81–96.
Nicolae, I., Saccani, E., 2005. Preliminary geochemical data on volcanic rocks from theOlt Nappe (Transylvanian nappes, Romania): implication for their origin in theTransylvanides. Ofioliti 30 (2), 103–106.
Nisbet, E.G., Pearce, J.A., 1977. Clinopyroxene composition in mafic lavas from differenttectonic settings. Contributions to Mineralogy and Petrology 63, 149–160.
Pamić, J., 1984. Triassic magmatism of the Dinarides in Yugoslavia. Tectonophysics 109,273–307.
Pamić, J., Tomljenović, B., Balen,D., 2002.Geodynamic andpetrogenetic evolutionofAlpineophiolites from the central and NW Dinarides; an overview. Lithos 65, 113–142.
Pană, D., Balintoni, I., Heaman, L., 2000. Precise U–Pb zircon dating of the syenite phasefrom the Ditrău alcaline igneous complex. Studia Universitatis Babeş-Bolyai,Geologia XLV (1), 79–89.
Pană, D., Balintoni, I., Heaman, L., Erdmer, P., 2002. An alternative tectonic model for theCarpathian–Pannonian system. Studia Universitatis Babeş-Bolyai Special Issue 1,265–277.
Pătraşcu, St., Panaiotu, C., Şeclăman, M., Panaiotu, C.E., 1994. Timimg of rotationalmotion of Apuseni Mountains (Romania): paleomagnetic data from Tertiarymagmatic rocks. Tectonophysics 233, 163–176.
Patrulius, D., Dimian-Popa, E., Popescu-Dimitriu, I., 1966. The autochthonous Mesozoicseries and the Transylvanian Detachement Nappe in surroundings of Comana(Perşani Mts.). Anuarul Comitetului Geologic XXXV, 397–444 (in Romanian).
Patrulius, D., Gherasi, N., Săndulescu,M., Popescu, I., Popa, E., Bandrabur, T.,1967.GeologicalMap of Romania, 1:200,000; Braşov Sheet. Geological Institute, Bucharest.
Paul, K.M., 1876. Grundzüge der Geologie der Bukowina. Jahrbuch der Kaiserlich-Königlichen Geologischen Reichsanstalt Wien 26 (3), 263–330.
Pearce, J.A., 1982. Trace element characteristics of lavas from destructive plateboundaries. In: Thorpe, R.S. (Ed.), Andesites. John Wiley & Sons, pp. 526–548.
Pearce, J.A., Peate, D.W., 1995. Tectonic implications of the composition of volcanic arcmagmas. Annual Review of Earth and Planetary Sciences 23, 251–285.
Peltz, S., Popescu, I., Ştefănescu, M., Patrulius, D., Seghedi, I., Ţicleanu, N., Mihăilă, N.,Peltz, M., Ştefănescu, M., Popescu, A., 1983. Geological Map of Romania, 1:50,000;Băile Chirui Sheet. Institute of Geology and Geophysics, Bucharest.
Piccardo, G.B., Müntener, O., Zanetti, A., Romairone, A., Bruzzone, S., Poggi, E., Spagnolo,G., 2004. The Lanzo South peridotite: melt/preidotite interaction in the mantlelithosphere of the Jurassic Ligurian Tethys. Ofioliti 29 (1), 37–62.
Plank, T., Langmuir, C.H., 1993. Tracing trace elements from sediment input to volcanicoutput at subduction zones. Nature 362, 739–743.
Plašienka, D., 2000. Paleotectonic controls and tentative palinspastic restoration of theCarpathian realm during theMesozoic. Slovak Geological Magazine 6 (2–3), 200–204.
Popescu, D., Popescu, L., 2004. Microfacies of the Triassic limestones in the PiatraŞoimului klippe (Transylvanian nappes, Rarău syncline, Eastern Carpathians,Romania). Studia Universitatis Babeş-Bolyai, Geologia XLIX (1), 87–105.
Popescu, D., Popescu, L., 2005. Microfacies of the Middle Triassic carbonates in theInfrabucovinian nappes. Analele Universitāţii “Ştefan cel Mare”. Secţiunea Geo-grafie XIV, 1–16 (in Romanian).
Popescu, Gr., Patrulius, D., 1964. Stratigraphy of the Cretaceous and the exotic klippes ofMount Rarău (Eastern Carpathians). Anuarul Comitetului Geologic XXXIV (II),73–130 (in Romanian).
Popescu, I., 1970. Geological Map of Romania, 1:50,000; Perşani Sheet. Institute ofGeology and Geophysics, Bucharest.
Popescu, I., Ştefănescu, M., Mihăilă, N., 1975. Geological Map of Romania, 1:50,000;Baraolt Sheet. Institute of Geology and Geophysics, Bucharest.
Popescu, I., Mihăilă, N., Peltz, S., Ţicleanu, N., Andreescu, I., 1976. Geological Map ofRomania, 1:50,000; Racoş Sheet. Institute of Geology and Geophysics, Bucharest.
Popescu-Voiteşti, I.P., 1929. Aperçu synthétique sur la structure des regions Carpathi-ques. Revista Muzeului de Geologie—Mineralogie al Universităţii Cluj III (1), 7–40.
Preda, D.M., 1940. Les basalts du versant ouest des Monts Perşani. Comptes rendus desséances — Institut Géologique de Roumanie XXIV, 90–98.
Rădulescu, D.P., Săndulescu, M., 1973. The plate tectonics concept and the geologicalstructure of the Carpathians. Tectonophysics 16, 155–161.
Robertson, A.H.F., 2002. Overview of the genesis and emplacement of Mesozoicophiolites in the Eastern Mediterranean Tethyan region. Lithos 65 (1–2), 1–67.
Russo-Săndulescu, D., Udrescu, C., Medeşan, Al., 1982. Petrochemical characteristics ofthe Mesozoic ophiolites of the Rarău-Hăghimaş marginal syncline. Dări de SeamăInstitutul de Geologie şi Geofizică LXVI (1), 153–185 (1979).
Russo-Săndulescu, D., Săndulescu, M., Udrescu, C., Bratosin, I., Medeşan, Al., 1983. Lemagmatisme d'Âge Mésozoïque dans les Carpathes Orientales. Anuarul InstitutuluiGeologie şi de Geofizică LXI, 245–252.
Saccani, E., Nicolae, I., 2005. Does the South Apuseni Mts. ophiolitic nappe extendeastward up to the East Carpathians? New data on volcanics from the TransilvanianDepression and Transylvanian nappes (Romania). Abstr. Vol. GEOITALIA—FIST,Spoleto, 21–23 Sept. 2005, p. 29.
Saccani, E., Nicolae, I., Tassinari, R., 2001. Tectono-magmatic setting of the Jurassicophiolites from the South Apuseni Mountains (Romania): petrological andgeochemical evidence. Ofioliti 26 (1), 9–22.
Saccani, E., Seghedi, A., Nicolae, I., 2004. Evidence of rift magmatism from preliminarypetrological data on Lower Triassic mafic rocks from the North Dobrogea orogen(Romania). Ofioliti 29 (2), 231–241.
Săndulescu, M., 1973. Contributions to the knowledge of the geological structure of theRarău syncline. Dări de Seamă Institutul de Geologie şi Geofizică LIX (5), 59–92(1972) (in Romanian).
Săndulescu, M., 1975. Geological study of the central and northern parts of theHăghimaş syncline (Eastern Carpathians). Anuarul Institutului de Geologie şiGeofizică XLV, 5–200 (in Romanian).
171V. Hoeck et al. / Lithos 108 (2009) 151–171
Săndulescu, M., 1976. Contributions to the knowledge of the stratigraphy and tectonicposition of the Mesozoic series from the upper basin of the Moldova Valley (EastCarpathians). Dări de Seamă Institutul de Geologie şi Geofizică LXII (5), 149–176 (inRomanian).
Săndulescu, M., 1984. Geotectonics of Romania. Editura Tehnică, Bucharest. 336 pp.(in Romanian).
Săndulescu, M., Russo-Săndulescu, D., 1981. The ophiolites from the Rarău andHăghimaş synclines—their structural position, age and geotectonic evolution.Dări de Seamă Institutul de Geologie şi Geofizică LXVI (5), 103–114.
Săndulescu, M., Tomescu, C., 1978. New contributions to the knowledge of theTransylvanian series from the Rarău syncline, East Carpathians (Botuş-Tătarcazone). Dări de Seamă Institutul de Geologie şi Geofizică LXIV (5), 141–151 (inRomanian).
Săndulescu, M., Vasilescu, Al., Popescu, A., Mureşan, M., Arghir-Drăgulescu, A.,Bandrabur, T., 1968. Geological Map of Romania, 1:200,000; Odorhei Sheet.Geological Institute, Bucharest.
Săndulescu, M., Neagu, Th., Antonescu, E., 1982. Contributions à la connaissance desklippes de type Pienin de Poiana Botizei (Maramureş). Dări de Seamă Institutul deGeologie şi Geofizică LXVII (4), 79–96 (1979–1980).
Savu, H., 1968. Considerations on stratigraphical relations and petrology of Mesozoicophiolites in Romania. Anuarul Comitetului Geologic XXXVI,111–141 (in Romanian).
Savu, H., 1980. Genesis of the Alpine cycle ophiolites from Romania and their associatedcalc-alkaline volcanics. Anuarul Institutului de Geologie şi Geofizică LVI, 55–77.
Savu, H., Udrescu, C., Neacşu, V., 1980. Structural, petrological and genetic study of theophiolites from the Niculiţel Zone (North Dobrogea). Dări de Seamă Institutul deGeologie şi Geofizică LXV (1), 41–64 (1977–1978).
Schmid, S.M., Bernoulli, D., Fügenschuh, B., Maţenco, L., Schefer, S., Schuster, R., Tischler,M., Ustaszewski, K., 2008. The Alpine–Carpathian–Dinaridic orogenic system:correlation and evolution of tectonic units. Swiss Journal of Geosciences 101 (1),139–183.
Seghedi, I., Szakacs, Al., 1994. A model for Mesozoic volcanism and tectonic evolution inNorth Dobrogea, Romania. Studii şi Cercetări de Geologie, Geofizică, Geografie. SeriaGeologie 39, 21–34.
Stampfli, G.M., Borel, G.D., 2004. The TRANSMED Transects in Space and Time:Constraints on the paleotectonic evolution of the Mediterranean domain. In:Cavazza, W., Roure, F., Spakman, W., Stampfli, G.M., Ziegler, P.A. (Eds.), TheTRANSMEDAtlas—TheMediterranean Region from Crust to Mantle. Springer, BerlinHeidelberg, pp. 53–80.
Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes. Magmatism in the OceanBasins. Geological Society London Special Publication, vol. 42, pp. 313–345.
Trubelja, F., Burgath, K.-P., Marchig, V., 2004. Triassic magmatism in the area of theCentral Dinarides (Bosnia and Herzegovina): geochemical resolving of tectonicsetting. Geologia Croatica 57 (2), 159–170.
Turculeţ, I., 1987. Bio-stratigraphic data about Neotriassic white limestones associatedto the diabases from the Rarău syncline (Bucovina). Analele Muzeului JudeţeanSuceava, Seria Ştiintele Naturii IX, 27–34 (in Romanian).
Turculeţ, I., 1991. Geological considerations on the ophiolites from Măcieş Hill (Rarăusyncline, Eastern Carpathians). Studii şi Cercetări de Geologie, Geofizică, Geografie.Seria Geologie 36, 19–27 (in Romanian).
Uhlig, V., 1907. Über die Tektonik der Karpathen. Sitzungsberichte Kaiserliche Akademieder Wissenschaften in Wien, Mathematische-Naturwissenschaftliche Klasse CXVI (I),871–982.
Walter, B., 1876. Die Erzlagerstätten der südlichen Bukowina. Jahrbuch der Kaiserlich-Königlichen Geologischen Reichsanstalt Wien 26 (4), 343–426.
Wood, D.A., 1980. The application of Th–Hf–Ta diagram to problems of tectonomag-matic classification and to establishing the nature of crustal contamination ofbasaltic lavas of the British Tertiary volcanic province. Earth and Planetary ScienceLetters 50, 11–30.
