The effect of early Alpine thrusting in late-stage extensional tectonics: Evidence from the Kulidzhik nappe and the Pelevun extensional allochthon in the Rhodope Massif, Bulgaria

The effect of early Alpine th the Kulidzhik nappe and t Rhodope Massif, Bulgaria Nikolay Bonev a,⁎, Richard Spiking a Department of Geology and Paleontology, Sofia Universi b Department of Mineralogy, University of Geneva, CH-12 c Department of Geochemistry and Petrology, Geological I a r t i c l e i n f o Article history: Received 12 August 2008 Received in revised form 21 December 2009 Accepted 4 January 2010 Available online 11 January 2010 154.23±0.66 Ma and 156.70±0.81 Ma, respectively, which reflect cooling following the greenschist-facies Tectonophysics 488 (2010) 256–281 Contents lists available at ScienceDirect Tectonophysics .e lsev ie r.com/ locate / tecto event below ∼350 °C, during shallow crustal level thrust emplacement and exhumation of the Kulidzhik allochthon. The hanging-wall Pelevun extensional allochthon preserves an internal NNE-directed ductile tectonic transport trend, but is underlain by a SSW-directed ductile–brittle extensional detachment and has experienced NE-SW brittle extension on high-angle normal faults. An amphibole 40Аr/39Аr inverse isochron age of 156.58±0.60 Ma constrains a Late Jurassic upper greenschist-facies tectono-metamorphic event, whereas a white mica plateau age of 39.66±0.47 Ma provides evidence for Middle Eocene cooling and exhumation of the Pelevun extensional allochthon in the hanging wall of the detachment. We relate the Kulidzhik nappe to Late Jurassic crustal deformation during arc-continental margin collision that involved NNE-directed nappe staking and metamorphism of continental margin basement and island arc units. The nappe shares a tectono-metamorphic history with the nappes of the adjacent Strandzha Massif, implying a region-wide early Alpine orogenic system. Our results reveal a record of early Alpine thrust tectonics and show the significance of crustal accretion-related assembly for the tectonic evolution of the RhodopeMassif. Both the Late Jurassic thrusting event and the subsequent Cretaceous thrusting event thickened the Rhodope crust ⁎ Corresponding author. E-mail address: [email protected]fia.bg (N. Bonev). 0040-1951/$ – see front matter © 2010 Elsevier B.V. A doi:10.1016/j.tecto.2010.01.001 tectono-metamorphic units and the nappe surface indicate top-to-the NNE tectonic transport. Deformation evolved fromductile to brittle conditions coevallywith a progressive decrease from lower amphibolite toweak greenschist-faciesmetamorphism towards the structural top. Two klippen gave plateau 40Аr/39Аr mica ages of Keywords: Early Alpine thrusting Tertiary extensional tectonics Geochemistry 40Ar/39Ar geochronology Rhodope Massif Bulgaria rusting in late-stage extensional tectonics: Evidence from he Pelevun extensional allochthon in the s b, Robert Moritz b, Peter Marchev c ty “St. Kliment Ohridski”, 1504 Sofia, Bulgaria 13 Geneva, Switzerland nstitute, 1113 Sofia, Bulgaria a b s t r a c t In the northeastern Rhodope Massif, the Kulidzhik nappe exposes a unique juxtaposition of a high-grade basement allochthon onto a low-grade Mesozoic unit, and the counterpart Pelevun extensional allochthon belonging to the same unit. The Kulidzhik nappe tectonostratigraphy comprises structurally upward: (i) a lower unit consisting of high-grade basement orthogneisses; (ii) a low-grade greenschist-phyllite unit consisting of Jurassic extrusive rocks andmetasedimentary rocks; (iii) the nappe allochthon built by the lower high-grade basement unit orthogneisses; and (iv) Eocene sedimentary rocks and Oligocene volcanic cover rocks. The Pelevun extensional allochthon is heterogeneous, and consists of Mesozoic low-grade unit marbles and greenschists and the upper high-grade basement unit. We have combined structure and kinematics, with lithological information and 40Аr/39Аr geochronology to constrain the tectonic evolution and regional significance of the Kulidzhik nappe and the Pelevun extensional allochthon.Mineral chemistry reveals igneous phases of the granitic protolith of the allochthonous orthogneisseswith textures related to ductile deformation andmetamorphismhigher than 500 °C. Their trace element patterns are indistinguishable from the high-grade basement orthogneisses in the eastern Rhodope. Mineral chemistry of the metamorphic assemblage in the underlying greenschists is consistent with medium-grade greenschist-facies metamorphism at temperatures well below 450 °C, whose geochemistry defines transitional MORB to IAT affinities with a strong arc imprint. The greenschist's composition is extremely similar to the composition of a supra-subduction zone Jurassic arc extrusive suite that occurs in the low-grade unit of the eastern Rhodope. The structural elements in all of the creating crustal instability, which influenced Terti ll rights reserved. j ourna l homepage: www ary crustal extension. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The Rhodope Massif extends over a large part of southern Bulgaria and northern Greece and represents a major tectonic zone in the Alpine chain of the Eastern Mediterranean region (Fig. 1, inset). Earlier works traditionally considered the Rhodope Massif to be a Precambrian cratonic block within the Alpine orogen (Jacobshagen et al., 1978; Kozhoukharov et al., 1988). Several subsequent studies have shown that it was actively involved in the Alpine orogeny, with deformations related to Mesozoic nappe stacking and crustal thickening, and Tertiary syn- and post-orogenic extension (Koukou- velas and Doutsos, 1990; Burg et al., 1990, 1996; Dinter, 1998; Kilias et al., 1999; Krohe and Mposkos, 2002; Bonev, 2006a; Bonev et al., 2006a; Bonev and Beccaletto, 2007). The Rhodope Massif is regarded as a S-directed, syn-metamorphic nappe complex, generated by ductile thrusting in the hanging wall of a north-dipping Cretaceous subduction system located in the Vardar Zone in Greece (Ricou et al., 1998). This subduction system gave birth to the Late Cretaceous Sredna Gora continental volcanic arc behind the Rhodope Massif (Fig. 1, inset), with magmatic activity between 92 and 78 Ma (Von Quadt et al., 2005). The magmatism migrated southwards across the Rhodope Massif, with latest Cretaceous (ca. 80–69 Ma, Peytcheva et al., 1999; Marchev et al., 2006) and Eocene (ca. 53–40 Ma, e.g. Ovtcharova et al., 2003) late- to post-tectonic granitoid plutons. These intrusions constrain a pre-latest Cretaceous minimum age for southward ductile thrusting, with an unknown lower age limit for this main tectono-metamorphic event. The tectono-metamorphic history of the Rhodope Massif has been largely defined as Mesozoic– and g Ev 257N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Fig. 1. Tectonic map of the eastern Rhodope–Thrace region in the southern Bulgaria structures, the high-grade basement units, and the Mesozoic low-grade unit includin extension (dashed) of the Circum-Rhodope Belt (CRB). Boxed: map area of Figs. 2 and 10. northern Greece (adapted from Bonev and Stampfli, 2008) showing the large-scale ros ophiolite. Inset: The Alpine tectonic framework around the Aegean domain and 258 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Cenozoic in age. It is bracketed between the radiometric constraints for the Jurassic–Early Cretaceous age of the metaophiolites in the adjacent Serbo-Macedonian Massif (ca. 163–110 Ma, e.g. Dixon and Dimitriadis, 1984; Spray et al., 1984), which are also widespread within the Rhodope Massif, and the stratigraphic ages of the Tertiary sedimentary cover sequences (e.g. Zagorchev, 1998; Boyanov and Goranov, 2001). Recent U–Pb conventional and SHRIMP zircon geochronology has revealed Late Proterozoic–Early Paleozoic and Triassic to post-Triassic ages for the sedimentary precursors in the metamorphic pile (Liati and Gebauer, 2001), and unequivocal evidence for the involvement of Variscan igneous basement within the Alpine orogeny (Peytcheva and Von Quadt, 1995; von Peytcheva et al., 2004; Liati, 2005; Turpaud, 2006; Bauer et al., 2007). Dates obtained by the same methods were also reported from a Late Jurassic–Early Cretaceous continental arc- related intrusive suite in the metamorphic complex (ca. 152–149 Ma, Ovtcharova et al., 2004; ca. 163–134 Ma, Turpaud, 2006) and analogous age (ca. 149–117 Ma) for the first stage (ultra-) high- pressuremetamorphism (Liati et al., 2002; Liati, 2005), whose onset is placed in pre-Middle Jurassic time (ca. 170–160 Ma, Bauer et al., 2007). All these radiometric data question the timing of early Alpine igneous and tectono-metamorphic events, which lack time-integrated structural and kinematic supports for the orogenic build-up of the Rhodope Massif. In the eastern Rhodope–Thrace region of southern Bulgaria and northern Greece (Fig. 1), the low-grade to weakly metamorphosed Mesozoic (i.e. Middle Triassic–Early Cretaceous) unit is regarded as an extension of the Circum-Rhodope Belt from the Chalkidiki Peninsula in northern Greece (Kauffmann et al., 1976; Kockel et al., 1977; Papanikolau, 1997; Fig. 1, inset). The intra-oceanic, arc-related Early– Middle Jurassic ophiolites within the low-grade unit (Magganas et al., 1991; Bonev and Stampfli, 2008, 2009), together with associated sedimentary successions that enclose reworked latest Paleozoic and Triassic clastics, were interpreted as a Jurassic–Early Cretaceous subduction-accertionary assemblage that bears evidence for N-directed tectonic emplacement (Bonev and Stampfli, 2003). Therefore, the age, oceanic affinity and kinematic directions are different from that associated with the S-directed Rhodope syn-metamorphic nappe complex, and are features that render the Mesozoic low-grade unit a key element to improve our understanding of the Alpine tectonic his- tory, and offers a unique opportunity to examine pre-Late Cretaceous tectonics of the Rhodope Massif. We focused our attention on the northernmost outcrop area of the low-grade unit along the Kulidzhik River Valley in the northern side of the eastern Rhodope Massif (Fig. 2), where the unit forms part of the Kulidzhik nappe (Boyanov, 1969), together with the Pelevun extensional allochthon belonging to the same unit in the central Byala reka extensional dome. This paper aims to provide evidence for early Alpine thrust tectonics in the Rhodope Massif, and an overprint by Tertiary extensional tectonics. We present new structural and kinematic data, geochemistry and 40Ar/39Ar ages, which document a Late Jurassic tectono-metamorphic event and Tertiary extension- related deformation. Finally, we discuss its significance for the Rhodope Massif, and compare it with the temporally constrained evolution of adjacent tectonic zones that were involved in the early Alpine orogeny. We also analyse the effect of the Late Jurassic thrusting event to crustal thickening that significantly influenced late- stage extensional tectonics in the Rhodope region. 2. Geological framework To the north, the RhodopeMassif is separated by theMaritsa dextral strike-slip fault from the Sredna Gora Zone that represents a Late Cretaceous volcanic arc. To the southwest, together with the more internal crystalline Serbo-MacedonianMassif, it is limited by the Vardar (Axios) Suture Zone against the innermost zones of the Hellenides (Fig. 1, inset). The Rhodope Massif mainly consists of a metamorphic basement comprising pre-Alpine and Alpine (e.g. Lips et al., 2000; Liati, 2005) units of continental and oceanic affinities. The basement is intruded by Late Cretaceous to Early Miocene granitoids (Soldatos and Christofides, 1986; Del Moro et al., 1988; Dinter et al., 1995; Peytcheva et al., 1999). Paleocene toMiocene sedimentary rocks (Ivanov andKopp, 1969; Boyanov and Goranov, 2001) and voluminous Late Eocene– Oligocene volcanic and volcanic-sedimentary successions (Innocenti et al., 1984; Harkovska et al., 1989) represent cover sequences. The tectonostratigraphy of the eastern Rhodope–Thrace region, from the base to the top, includes the following units (Fig. 1, Table 1, Bonev, 2006a; Bonev and Beccaletto, 2007): (i) a lower high-grade basement unit of continental affinity composed mainly of orthog- neisses with Carboniferous protolith ages, (ii) an upper high-grade basement unit of continental-oceanic affinity consisting of intercalat- ed metasedimentary and metaigneous rocks, with numerous metao- phiolite slivers. The metaophiolites have arc tholeiitic and boninitic affinities (Haydoutov et al., 2004), with a signature transitional between oceanic ridge and supra-subduction type ophiolites (Bonev et al., 2006c). Their age is inconclusive, with reported Neoproterozoic protolith ages, with a Variscan metamorphic overprint (∼300– 350 Ma), and a Permian protolith age (Carrigan et al., 2003; Bauer et al., 2007), (iii) a low-grade unit consisting of Mesozoic rocks (Jaranov, 1960; von Braun, 1968; Kopp, 1969) that includes the Evros ophiolites (Magganas et al., 1991), and (iv) a sedimentary and volcanogenic unit of Paleocene–Miocene syn- and post-tectonic cover sequences related to Tertiary extension. Both high-grade basement units are limited by ductile thrusts and are mainly separated by Tertiary extensional detachments. The detachments bound the Kesebir–Kardamos dome and the Byala reka–Kechros dome, whose extensional structures dominate the regional tectonic pattern (Bonev, 2006a). The dominant amphibolite-facies, eclogite-facies relics and ultrahigh-pressure assemblages in the high-grade basement reveal a complex Alpine tectono-metamorphic history. 40Ar/39Ar ages be- tween 45 and 36 Ma define the cooling history of the high-grade basement units that accompanied their extensional exhumation (Lips et al., 2000; Mukasa et al., 2003; Bonev et al., 2006b). The Mesozoic low-grade unit is uppermost in the metamorphic pile and occupies the hanging wall of the detachments (Fig. 1). This unit crops out in scattered locations within the eastern Rhodope– Thrace region, and tectonically lies on the high-grade basement as remnants of a former region-wide nappe (Gočev, 1979; Boyanov et al., 1990) that has been reworked by Tertiary extensional tectonics (Bonev and Stampfli, 2003; Bonev and Beccaletto, 2007). It is exposed in two areas of the eastern Bulgarian Rhodope, which are along the Kulidzhik River Valley in the north, and in the Mandritsa area in the south. In the Mandritsa area, the low-grade sequences have been correlated with the Makri and Drimos–Melia units of the Thrace area (Boyanov and Russeva, 1989; Papadopoulos et al., 1989). The general stratigraphy and ages of the low-grade unit in the region are summarized as follows (see Table 1). Marbles, greenschists and phyllites occur at the base, and are overlain by the basic extrusive suite of the Evros ophiolites, which in turn is overlain by non- metamorphic flysch-like sedimentary rocks at the top. The intrusive suite of the Evros ophiolites is represented by gabbros, plagiogranites and associated dykes (Biggazzi et al., 1989; Bonev and Stampfli, 2009). Apatite fission-track data obtained from the gabbros reveal cooling between 120 and 60 °C between 140 and 161 Ma, with gabbro crystallization at 169±2 Ma (Biggazzi et al., 1989; Koglin et al., 2007). The fossil ages, both in coherent strata and detrital fragments, span from Late Permian up to Early Cretaceous. Campanian fossils were only reported in the uppermost levels of the low-grade unit in the Mandritsa area (Boyanov et al., 1982). Structurally allochthonous, the low-grade unit is considered to form a thrust sheet with an inferred displacement towards the north (Boyanov et al., 1990; von Braun, 1993). Preliminary structural and kinematic data in the Mandritsa 259N. Bonev et al. / Tectonophysics 488 (2010) 256–281 area have documented a strong internal deformation with a top-to- the NW-NE-directed shear fabric in the greenschists that was related to thrust emplacement during the accretion and obduction of the low- grade unit onto the Rhodope margin (Bonev and Stampfli, 2003). Fig. 2. Geological map of the Kulidzhik River Vall Boyanov (1969) and Boyanov et al. (1969) describe the metamor- phic sequences exposed in the Kulidzhik River Valley. Boyanov et al. (1969) subdivided the pre-Eocene sequences into a lower crystalline complex consisting of retrogressed amphibolite-facies rocks of assumed ey (by the use of data from Boyanov, 1969). 260 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Precambrian age, which in turn is unconformably overlain by an upper greenschist-facies complex, known as the Paleozoic diabase-phyllitoid Formation (Ivanov, 1961;Boyanovet al., 1963). This Formationhas been subdivided into a basal greenschist series and an overlying phyllite series. The diabase-phyllitoid Formation represents the Mesozoic low- grade unit in the Kulidzhik River Valley. The argillaceous shales in the phyllite series yielded Early Cretaceous radiolarians (Boyanov and Lipman, 1973) that have been re-evaluated as Jurassic (Boyanov et al., 1990). The Kulidzhik nappe places high-grade amphibolite-facies rocks of the lower crystalline complex over the diabase-phyllitoid Formation, and theE-NE-directed thrust emplacementof thehigh-grade allochthon was inferred from fold asymmetry (Boyanov, 1969). Retrogression in greenschist-facies rocks of the lower crystalline complex was assigned to progressive metamorphism of the diabase-phyllitoid Formation, or spatially linked to the post-Precambrian faults (Boyanov et al., 1969). Preliminary work of Bonev (2006b) in the Kulidzhik Valley obtained an island arc signature from the greenschists, which reveal evidence for NE-directed tectonic emplacement. 3. Tectonostratigraphy of the Kulidzhik nappe The field data, petrographic and structural observations of the high- and low-grademetamorphic successions in the Kulidzhik Valley reveal in a structurally ascending order, a tectonostratigraphic section which includes (i) a high-grade basement orthogneiss unit, (ii) an overlying greenschist-phyllite unit of Mesozoic age, (iii) the alloch- thon of the Kulidzhik nappe consisting of high-grade basement orthogneisses, and (iv) Eocene–Oligocene sedimentary-volcanic cover sequence (Figs. 2 and 3a). The relatively autochthonous high-grade basement unit is repre- sented by restricted exposure of orthogneisses in the northern part of the study area, and consists of leucocratic equigranular and augen orthogneisses. The equigranular orthogneisses show local textural variations with banded orthogneisses, whereas the augen orthog- neisses contain up to 5 cm long feldspar porphyroclasts (Fig. 3b). Both orthogneiss types have experienced at least lower amphibolite-facies metamorphism and ductile shear deformation. They host a largely preserved mineral assemblage of the granitic protolith including quartz-alkali feldspar–plagioclase–muscovite, with retrogressive chlorite after mica. These orthogneiss types are abundant in the lower high-grade basement unit of the eastern Rhodope (Bonev, 2006a), and thus are considered as equivalent. The overlying greenschist-phyllite unit is juxtaposed against the orthogneiss unit with poorly exposed ductile thrust that is deduced from shear deformation at the contact. This unit includes both the lower crystalline complex and the overlying diabase-phyllitoid Formation in the original subdivision of Boyanov (1969). Based on the mineral assemblages, chemical composition, metamorphic grade and contacts, we do not distinguish lithologies that may belong to the lower crystalline complex, which has been assigned to the high-grade metamorphic basement. Instead, we extend the greenschist series down metamorphic section and maintain the extent of the phyllite series of Boyanov (1969). The greenschist-phyllite unit is composed of metasedimentary andmetavolcanic lithologies, which reveal an up-section decrease in the metamorphic grade. At the base, the greenschists series starts with chlorite–actinolite–white mica–plagioclase±biotite±garnet schists, which show compositional layering of alternating quartz- feldspar and chlorite–actinolite bands (Fig. 3c). Quartz–chlorite schists and chlorite-actinolite−white mica±epidote±calcite schists dominate upwards in the section, where the metavolcanic rocks are represented by thin sheets of massive mafic lavas, and dolerite and microgabbro sheets occur at the top of the series. The lavas show pyroxene-phyric and amygdaloidal textures, with a greenschist-facies overprint expressed by common chlorite and actinolite crystallizations after phenocryst phases and within the groundmass (Fig. 3d). These extrusive rocks are interstratified with tuffaceous volcaniclactic layers with varying content of sedimentary components (e.g. Bonev, 2006b). Thebulkprotolith-dependentmetamor- phic mineral assemblage in the greenschist series of quartz–plagioclase– chlorite–muscovite–actinolite–biotite–epidote–garnet–calcite suggests medium- to upper-grade greenschist-facies metamorphism. The phyllite series depositionally overlies the greenschist series, and consists of phyllites and black shales interbeddedwith up to 3 m-thick layers of laminated limestones that show transitions to calcareous shales (Fig. 3e). The primary sedimentary features are discernible in this series. The mineral assemblage in the phyllite series includes quartz–chlorite–white mica–calcite, which qualitatively indicates lower grade, greenschist-facies metamorphism, compared to the greenschist series. The overlying allochthon of the Kulidjik nappe consists of both facial rock types in the high-grade basement orthogneiss unit and occurs as numerous klippen. The allochthon is separated from the underlying greenschist-phyllite unit by a (semi-)ductile–brittle thrust surface. In the uppermost section, strata of polygenic conglomerates and sandstones that reworked the metamorphic lithologies, lie uncon- formably on all underlying units or in faulted contacts. The composition of these sedimentary rocks corresponds to the Middle– Late Eocene clastic sedimentary successions found elsewhere in the eastern Rhodope (Boyanov and Goranov, 2001), although no detailed evidence for their stratigraphic age is available from the Kulidjik Valley. These clastics are depositionally overlain by the magmatic products of the Oligocene Madjarovo paleovolcano, whose lavas yield 40Ar/39Ar ages of 32.7–32.2 Ma (Marchev and Singer, 2002). Collec- tively, these sequences represent the sedimentary and volcanic cover of the metamorphic units. 4. Geochemistry of the units in the Kulidzhik nappe 4.1. Mineral chemistry Electron microprobe mineral analyses were obtained using a JEOL 8200 Superprobe instrument at the University of Lausanne (Switzer- land). Operating conditions were 10 nA beam current at 15 kV accelerating voltage with 5 μm spot-size analysis with 30 s for peak and background counting, using natural standards and PAP correction. Selected chemical compositions and structural formula of the mineral phases are listed in Tables 2 and 3. Plagioclase in the orthogneisses from the high-grade basement unit is albite (Ab98.3-97.8) and alkali feldspar is orthoclase (Or97.1-96.2). In the orthogneisses of the allochthon, the plagioclase is albite (Ab99.3-97.6). In the greenschist series, the feldspar in the garnetiferous schists is oligoclase (Ab88.2), whichmay also be considered as albite-oligoclase because of some loss shownby the analysis.Micas aremuscovites in the orthogneisses, both in the high-grade basement unit and the allochthon, and muscovite and biotite in the greenschists (Table 2). In the greenschists, the garnet porphyroblasts are rich in almandine (Alm66.4-48.1) and the amphibole in the microgabbroic sheet is magnesio-hornblende (Table 3). 4.2. Whole-rock geochemistry Previous geochemical analyses of the greenschists revealed their arc-related signature, which is similar to the ophiolitic extrusive sequence in the Mandritsa and Thrace areas, and the continental affinity of the orthogneisses in the allochthon (Bonev, 2006b, location of previous samples used for geochemistry is shown in Fig 2). In this study, additional samples were analyzed for major and trace elements by XRF using a Philips PW 2400 spectrometer at the University of Lausanne (Switzerland), and the analyses were calibrated against both international and internal standards. The chemical compositions are ts 261N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Table 1 Summary of data for the distinct units of the eastern Rhodope–Thrace region and study Unit/area Protoliths, stratigraphic ages Structure, fabrics, metamorphism Contacts Lower Mostly granitoids SSW-directed Ductile thrus of analyzed samples are given in Table 4, and sample locations are shown in Fig. 2. The two metamafic samples Ku-159 (microgabbro) and Ku-8-3 (diabase) have a characteristic basaltic compositionwith SiO2 b50 wt.% and high TiO2, Fe2O3,MgO, relatively high Al2O3 and lowalkali contents. The greenschist sample Ku-8-1 shows comparable to the microgabbro high-grade basement unit amphibolite facies fabric Amphibolite facies Pb8 kbar T=560–620 °C SSW-directed LT fabric, ductile/semi-ductile shear zones Low-angle detac high-angle faults Upper high-grade basement unit Mafic rocks sediments SW-directed syn- metamorphic fabric Ductile thrust UHP relics PN26 kbar TN900 °C HT, eclogite relics PN13.5–16 kbar T=750–775 °C Amphibolite facies PN10 kbar T=600–650 °C Low-angle detac high-angle faults Mesozoic low-grade unit IAT-boninitic-CA lavas, sediments Greenschist-facies, prehnite–pumpellyite, non-metamorphic Low-angle detac IAT-CA gabbro Nappe complex Detrital clastics Permian Triassic N-directed shear in greenschist-facies SSW-directed LT fabricIn-situ strata Middle–Upper Triassic bivalves Lower Jurassic radiolarians Middle–Upper Jurassic/Lower Cretaceous ammonites Sedimentary- volcanogenicunit Sediments Paleocene– Miocene Non-metamorphic undeformed to brittlely deformed Syn-tectonic to p tectonic deposits Volcano- sedimentary, volcanic rocks Late Eocene–Oligocene Post-tectonic Kulidjik area Sediments, arc-related rocks Nappe N-directed thrus Lower Cretaceous radiolarians Abbreviations: UHP, ultrahigh-pressure, HP, high-pressure, HT, high-temperature, LT, low- hornblende, wm, white mica, bt, biotite, zr, zircon. a. Tectonic events Radiometric age constraints References Cretaceous nappe stacking 319–305 Ma U–Pb, zr Peytcheva & Quadt, and diabase major oxide concentrations, whereas the garnet-bearing chlorite–biotite schist (sample Ku-33) yields an evolved composition (Table 4). The trace element patterns of the microgabbro, diabase and greenschist samples normalized to N-MORB show high LILE/HFSE ratio and HFSE depletion relative to N-MORB (Fig. 4a). The green- schist samples present negative Nb anomalies, which are absent in the 1995, Liati, 2005 Burg et al. 1996 Mposkos&Liati 1993 Lips et al. 2000 hments, Paleocene–Eocene extensional faulting 42–36 Ma 40Ar/39Ar, wm, bt Bonev, 2006a Bonev et al. 2006b Cretaceous nappe stacking 572 Ma 288 Ma U–Pb SHRIMP, zr Carrigan et al. 2003 Bauer et al. 2007 Burg et al. 1996 (Pre-Maastrichtian) 69 Ma granites U–Pb, zr Marchev et al. 2006 Mposkos & Kostopoulos, 2001 160, 149–69 Ma U–Pb SHRIMP, zr Mposkos & Liati, 1993 Liati, 2005, Bauer et al. 2007 Bonev, 2006a 45–39 Ma 40Ar/39Ar, wm, hbl hments, Paleocene–Eocene extensional faulting Mukasa et al. 2003 hment Late Jurassic–Early Cretaceous thrusting Tertiary extension 170 Ma U–Pb SHRIMP, zr 140–161 Ma, AFT Magganas et al. 1991 Bonev & Stampfli 2008, 2009 Koglin et al. 2007 Biggazzi et al. 1989 Boyanov et al. 1990 Bonev & Stampfli, 2003 Trifonova & Boyanov, 1986 Bonev, 2005 Boyanov & Bodurov, 1979 Dimadis et al., 1996 Tikhomirova et al. 1988 Trikkalinos, 1955; Dimadis & Nikolov 1997 ost- 35–27 Ma 40Ar/39Ar, K/Ar, wm, bt, hbl Boyanov & Goranov 2001 Lilov et al. 1987 ts 157–159 Ma 40Ar/39Ar, wm Bonev, 2006b, this study Boyanov, 1969 Boyanov & Lipman, 1973 temperature, IAT, island arc tholeiite, CA, calk-alkaline, AFT, apatite fission-track, hbl, 262 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 microgabbro and diabase samples. All samples show a significant compositional overlap with the previous analyses of the greenschists and compositions of the Mandritsa mafic lavas and greenschists, implying a homogeneous composition for the extrusive sequence (Fig. 4b, c). Thus, the major and trace element compositions of the metamafic rocks and greenschist samples suggest these mafic lavas and Fig. 3. a) Tectono-stratigraphic column in the Kulidzhik River Valley, eastern Rhodope, b) porphyroclasts and S/C fabrics, c) banded gernetiferous chlorite–biotite schist from the gree layer intercalated between black shales in the phyllite series. volcaniclastics evolved via an arc-related petrrogenesis, with a transitional IAT to MORB signature. Sample Ku-214a reveals a composition that is characteristic for a calc-schist (Table 4). The analyzed orthogneiss samples were all taken from the alloch- thon of the Kulidzhik nappe. They have uniformly high SiO2 N73 wt.%, variable Al2O3 and total alkali concentrations and low TiO2, Fe2O3, MgO augen orthogneisses from the high-grade basement unit showing σ-type K-feldspar nschist series, d) microphotograph of mafic lavas in the greenschist series, e) limestone ulidz -41 n .82 .43 7 4 .05 9 0.49 95 96 02 02 16 05 .335 85 80 s. Ab 263N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Table 2 Representative microprobe analyses of the feldspars and micas in the rocks from the K Sample Ku-214 Ku-215 Ku-39 Ku-24a Ku-24b Ku-26 Ku-45 Ku Mineral fs fs fs fs fs fs fs fs Rock type egn egn egn agn agn egn agn eg SiO2 68.19 67.89 67.80 63.38 66.53 67.33 67.71 68 TiO2 0.01 – 0.03 – – – 0.01 – Al2O3 20.13 19.92 19.33 18.21 19.28 20.33 20.13 19 Cr2O3 – – – – – – – – Fe2O3 0.03 – 0.08 0.04 0.03 0.02 0.02 0.0 FeO – – – – – – – – MnO – – – – – – – – MgO 0.01 – – 0.01 0.02 – – – CaO 0.50 0.33 0.16 0.01 0.43 0.27 0.27 0.0 Na2O 11.23 11.62 11.95 0.32 11.84 11.75 11.68 12 K2O 0.10 0.06 0.06 16.31 0.03 0.06 0.04 0.0 H2O – – – – – – – – Total 100.20 99.83 99.41 98.27 98.16 99.75 99.86 10 Si 2.973 2.973 2.985 2.988 2.971 2.954 2.965 2.9 Ti – – 0.001 – – – – – AlIV 1.034 – 1.003 1.011 1.015 1.051 1.039 0.9 AlVI – – – – – – – – Cr – – – – – – – – Fe3+ 0.001 – 0.003 0.001 0.001 0.001 0.001 0.0 Fe2+ – – – – – – – – Mn2+ – – – – – – – – Mg 0.001 – – 0.001 0.001 – – – Ca 0.024 0.016 0.008 – 0.020 0.012 0.013 0.0 Na 0.949 0.987 1.020 0.029 1.025 1.000 0.991 1.0 K 0.006 0.003 0.003 0.981 0.002 0.003 – 0.0 OH – – – – – – – – xMg Ab 97.024 98.116 98.922 2.859 97.877 98.444 98.525 99 An 2.403 1.551 0.411 0.025 1.945 1.227 1.246 0.1 Or 0.573 0.334 0.337 97.116 0.178 0.328 0.229 0.4 Structural formula based on 22 and 32 oxygen atoms respectively for micas and feldspar contents (Table 3), which are characteristic for a normal igneous differentiation trend towards granitoid acid compositions. Chondrite- normalized trace element patterns of the orthogneisses display frac- tionated profileswith high LILE concentrations, depletion in someHFSE, and possess negative Nb anomalies (Fig. 4d). Compared to the augen and equigranular orthogneisses in the lower high-grade basement unit in the cores of extensional domes (see Fig. 1), they all present similar overlapping major and trace element patterns. Similarly, the orthog- neisses show an affinity to a volcanic arc (VAG) or within-plate (WPG) tectonic setting that is analogous to the well-defined continental arc setting for the orthogneisses of the lower high-grade basement unit (Fig. 4e, e.g. Bonev et al., 2010). Briefly, the geochemistry of the diabase, microgabbro and greens- chists in the greenschist series displays arc-related transitional IAT- MORB affinity that is comparable to the ophiolitic extrusive suite (e.g. Mandritsa area), with consistent chemical compositions along a N–S traverse along the Kulidzhik River Valley (see Fig. 2). The orthog- neisses in the klippen reveal a continental arc affinity that is indistin- guishable from the orthogneisses of the lower high-grade basement unit found elsewhere in the eastern Rhodope, which further strength- ens the interpretation, that they belong to this unit. 5. Structural record in the Kulidzhik nappe The structurally lower high-grade basement orthogneisses display a well-developed gneissic foliation defined by the planar arrangement of quartz-feldspar and micaceous aggregates in the equigranular gneiss type or flattened feldspar porphyroclasts in the augen orthogneises. The foliation strikes NW-SE to E-W with gentle dips to the S-SW (Fig. 2). A mineral stretching lineation, defined by elongated quartz-feldspar aggregates and alignment of feldspar porphyroclasts on foliation planes, trends NE-SW and gently plunges (∼20°) to the fs, feldspar; bt, biotite; Ms, muscovite. hik River Valley. For location of some samples see Fig. 2. Ku-33 Ku-214 Ku-215 Ku-39 Ku-24 Ku-26 Ku-41 Ku-33 Ku-35 fs ms ms ms ms ms ms bt ms grsch egn egn egn egn egn egn grsch grsch 61.56 48.15 47.59 46.95 46.72 47.59 45.13 35.33 46.71 0.02 0.78 0.43 0.85 0.53 0.98 0.69 1.62 0.51 20.68 26.59 27.67 25.58 28.18 24.67 26.64 16.45 29.43 – – – – – – – 0.04 0.06 – – – – – – – – – – 5.59 5.04 5.90 4.38 4.86 5.45 17.98 2.63 – 0.06 0.05 0.02 0.08 – 0.01 0.20 0.04 – 2.42 2.32 2.39 2.36 3.07 2.60 11.18 2.36 2.40 – 0.01 – – – – 0.20 – 10.38 0.28 0.14 0.26 0.21 0.31 0.23 0.11 0.20 0.08 10.70 10.66 10.54 10.95 10.21 11.00 7.57 10.64 – 4.36 4.34 4.26 4.32 4.24 4.30 3.80 4.33 95.12 98.93 98.25 96.93 97.72 95.94 98.06 94.48 96.91 2.857 6.624 6.569 6.614 6.485 6.723 6.528 5.582 6.463 0.001 0.080 0.450 0.090 0.056 0.104 0.075 0.193 0.053 1.131 1.376 1.431 1.386 1.515 1.277 1.472 2.418 1.537 – 2.936 3.062 2.861 3.096 2.831 2.903 0.645 3.262 – – – – – – 0.01 0.005 0.06 – – – – – – – – – – 0.643 0.581 0.696 0.508 0.574 0.678 2.376 0.304 – 0.007 0.006 0.004 0.009 – 0.01 0.027 0.004 – 0.497 0.477 0.538 0.488 0.646 0.540 2.633 0.487 0.119 – 0.001 – – – – 0.034 – 0.934 0.074 0.036 0.082 0.055 0.086 0.063 0.034 0.053 0.005 1.879 1.876 1.885 1.939 1.840 1.958 1.525 1.878 – 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 0.436 0.451 0.436 0.490 0.529 0.443 0.526 0.615 88.274 11.287 0.439 breviations: egn, equigranular orthogneiss; agn, augen orthogneiss; grsch, greenschist; SW (Fig. 5). Associated sense-of-shear indicators reveal a top-to-the NE tectonic transport (Figs. 3b, 5 and 6a). Ductile shear flow in the orthogneisses which experienced relatively high-temperature defor- mation conditions (N500 °C) is deduced from recrystallization of the feldspar porphyroclasts andmicas in their pressure shadows, together with a quartz texture that consists of discontinuous ribbon grains rimmed by recrystallized subgrains (Fig. 6a). These deformational features suggest ductile shearing occurred within at least lower amphibolite-facies grade metamorphic conditions. In the greenschist-phyllite unit, the planar fabrics represent a schistosity that is defined by phyllosilicates or compositional layering delineated by alternating actinolite–chlorite–micaceous and quartz- rich layers, at various scales. This generally flat-lying foliation strikes NW-SE to NE-SW with moderate to low dips (10–40°) in both oppo- site directions (Figs. 2 and 5). A stretching lineation on the foliation planes is defined by actinolite laths or white mica and chlorite aggre- gates, and trends NNE-SSW to NE-SW with gentle plunges in both opposite directions (Fig. 5). Associated shear-sense criteria, such as ductile shear bands, asymmetric porphyroclasts andmica fishes in the greenschists unequivocally demonstrate top-to-the NNE tectonic transport, which is parallel to the lineation (Figs. 5 and 6b, c, d). Intense folding at various scales has produced folds with NW-SE to NE-SW oriented axes that moderately to gently plunge mainly to the NE or ESE (Fig. 5). These are usually decimetre-scale, NE-E vergent close to tight folds (Fig. 6e) that are occasionally isoclinal (Fig. 6d, f) and lie oblique, but mostly parallel to the kinematic direction shown by the stretching lineation. The relationships of metamorphic crystal- lizations, e.g. chlorite and white mica, within the shear bands and garnet porphyroblast growth in the foliation demonstrate the syn- kinematic nature of the shear deformation under greenschist-facies conditions (Fig. 6j, h). Recrystallization of the quartz grains is limited to lower temperature conditions involving a mechanism of bulging 264 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Table 3 Representative microprobe analyses of the garnet and amphibole in the greenschist series rocks from the Kulidzhik River Valley. For samples location see Fig. 2. Sample Ku-8-1 Ku-33 Ku-35 Ku-159 Mineral grt grt grt amph Rock type grsch grsch grsch mgb SiO2 35.90 36.45 35.09 45.23 TiO2 0.09 0.15 0.09 1.03 Al2O3 21.04 20.53 20.53 10.45 Cr2O3 0.01 0.06 0.02 0.04 Fe2O3 1.85 0.76 2.68 4.48 FeO 26.55 25.06 20.22 10.07 MnO 3.56 7.88 7.27 0.31 MgO 2.44 0.88 2.22 11.67 CaO 6.64 7.11 8.20 11.46 Na2O – – – 1.34 K2O – – – 0.14 H2O – – – 2.02 Total 98.08 98.88 96.32 98.23 Si 2.927 2.977 2.908 6.698 Ti 0.006 0.009 0.006 0.115 AlIV 0.073 0.023 0.092 1.302 AlVI 1.948 1.953 1.912 0.521 Cr 0.001 0.004 0.001 0.005 Fe3+ 0.114 0.047 0.167 0.499 Fe2+ 1.810 1.712 1.401 1.247 Mn2+ 0.246 0.546 0.510 0.038 Mg 0.297 0.107 0.274 2.575 Ca 0.580 0.622 0.728 1.819 Na – – – 0.384 K – – – 0.026 OH – – – 2.000 recrystallization into the large old grains, and the development of subgrains. The most important tectonic contact in the study area is the Kulidjik nappe, which has juxtaposed the high-grade basement orthogneisses onto the greenschist-phyllite unit in the metamorphic pile. The thrust surface is generally flat-lying, with variable dips at low angles at different sites (Fig. 7a). The thrust surface is associated with cataclasites that have been extensively developed at the expense of the orthogneisses in the allochthon. Locally, wedge-shaped fractures are developed orthogonal to the slip lineation, which trends NNE-SSW with gentle NNE plunges on cataclastic ledges (Fig. 5). Shear fabrics in the cataclasites show the development of low-angle NNE-dipping shear bands marked by intense grain-size reduction of mineral phases, with calcite and secondary white mica growth at the expense of the feldspar clasts which display a strong asymmetry, whose structures indicate top-to-the NNE brittle displacement (Fig. 8a). Tectonic mixing, slicing and intense folding of lithologies from both the relative autochthon and the allochthon occur in the 10 to 25 m- thick thrust zone in between, where floating fault blocks and clasts interfinger with the cataclasites and fault gauges (Fig. 7c). The associated east-facing tight folds have NNE-SSW trending axes that are parallel to the slip lineation on the nappe surface. The structurally overlying high-grade basement allochthon con- sists of klippen that control the topographic highs on both sides of the Kulidzhik Valley (Fig. 7b). In the klippen, the planar–linear structural elements of the orthogneisses have a similar morphological expres- sion as in the structurally lowermost high-grade basement unit. The foliation varies in attitude in each klippen, mainly following that of Py 10.114 3.570 9.406 Alm 61.731 57.321 48.097 Sp 8.373 18.267 17.511 And 5.491 2.310 8.001 Uv 0.039 0.197 0.070 Gro 14.252 18.335 16.915 xMg 0.141 0.059 0.164 0.625 Structural formula based on 23 and 24 oxygen atoms respectively for amphiboles and garnets. Abbreviations: grsch,greenschist;mgb,microgabbro; grt, garnet; amph, amphibole. the thrust surface, and contains a shallow plunging, NNE-SSW oriented stretching lineation (Fig. 5). Small-scale folds have NNE- SSW oriented axes that are parallel to the stretching lineation (Fig. 5). Internal ductile deformation is revealed in the gneissic mylonites that are structurally above the nappe contact, by recrystallization of quartz, and bending of feldspar and mica grains. The kinematics of ductile shearing in the allochthon orthogneisses are shown by asymmetry of the shear bands, muscovite “fishes” and σ-type feldspar porphyroclasts, which reveal a top-to-the NNE shear sense (Fig. 8b). A local top-to-the S-SSW shear was described by Bonev (2006b) at the base of the allochthon in a folded domain that immediately overlies the Kulidzhik thrust zone. This backward flow can be related to shear instability that was probably driven by a rheologic contrast between the sliced allochthonous and the autochthonous rocks, leading to partitioning of the local flow direction at the base of the allochthon. However, a top-to-the NNE shear in the allochthon unequivocally prevails (Fig. 5). The deformation mechanisms evolved from ductile flow to brittle fracturing. This is particularly well-expressed in the deformation of the feldspars that show a kinematic continuity of distinct stages of recrystallization and lattice bending, deformational lamellae and crack propagation that ultimately resulted in the development of brittle fractures, which were filled by feldspar alteration products and late fine-grained quartz (Fig. 8b–d). This implies that the temperature during the shear deformation in the allochthon progressively de- creased from ∼550–600 °C to well below 450 °C, which is the lower temperature limit for feldspar ductile behaviour (e.g. Tullis and Yund, 1985, 1987). However, these deformational features spatially vary in the klippen, from ductile/semi-ductile in the south to brittle in the north, implying that distinct klippen expose different structural levels across the ductile–brittle transition between the relative autochthon and the allochthon of the Kulidzhik nappe. In summary, the deformational pattern and kinematics in the tectono-metamorphic section of distinct units from the structurally lowermost levels up to the top of the allochthon indicate a coherent structural paragenesis that reveals a consistently a top-to-the NNE tectonic transport direction, within a zone of decreasingmetamorphic grade, from lower amphibolite-facies to weak greenschist-facies con- ditions, involving mechanisms from ductile to brittle shear flow to- wards the structural top. Steeply dipping NW-SE, NE-SW to E–W trending faults and brittle shears (Figs. 2 and 9) occurred subsequent to the nappe structures. These normal faults truncate the allochthon, bound the cover unit against the allochthon, and limit theKulidzhik area at the northernflank of the extensional Byala reka dome. Sedimentary strata show both northern and southern low dips toward the faults, revealing almost symmetric brittle stretching at a shallow crustal level. This feature suggests that the faults were nearly concomitant with sedimentation. The faults in the Kulidzhik area have an attitude that is similar to the faults that limit a supra-detachment half-graben in the central part of the Byala reka dome, to the south (Fig. 1). The hanging-wall position of the Kulidzhik nappe in the northern flank of the Byala reka exten- sional dome (see Fig. 1), suggests the faults superimposed on the nappe occurred during Tertiary extension. These extensional structures have contributed to brittle attenuation of the hanging wall of the extensional system. 6. Structural record in the Pelevun extensional allochthon The units of the high-grade basement in the central part of the Byala reka dome are juxtaposed along a brittle tectonic contact that is referred to as the Pelevun thrust (Ivanov, 1961; Boyanov et al., 1963). The studies by Bonev and Stampfli (2003), Bonev (2006a) and Bonev et al. (2006b) in the central Byala reka dome and its eastern flank below the Mesozoic low-grade unit provided the first structural and kinematic evidences that the inferred Pelevun thrust represents a ples U-4 gn 3.19 .20 4.59 .87 .02 .36 .32 .99 .45 .11 .d. .d. .60 9.69 1 4 3 09 43 39 9 6 2b 9 9 265N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Table 4 Major and trace element analyses of the rocks from the Kulidzhik River Valley. For sam Sample KU-214 KU-215 KU-39 KU-41 K Rock type egn egn egn egn a SiO2 78.75 73.98 73.77 77.25 7 TiO2 0.09 0.52 0.16 0.32 0 Al2O3 11.92 13.15 9.64 12.65 1 Fe2O3 1.37 2.38 2.13 1.18 0 MnO 0.02 0.03 0.03 0.01 0 MgO 0.59 0.91 1.56 0.60 0 CaO 0.18 0.28 2.77 0.48 0 Na2O 4.35 3.46 2.69 5.13 3 K2O 1.71 2.96 1.63 1.29 5 P2O5 0.02 0.11 0.02 0.06 0 Cr2O3 n.d. n.d. n.d. n.d. n NiO n.d. n.d. n.d. n.d. n LOI 0.95 1.80 4.77 1.18 0 Total 99.95 99.57 99.18 100.15 9 Nb 11 27 21 17 1 Zr 57 280 201 145 9 Y 14 59 56 32 1 Rb 80 113 47 38 1 Sr 69 40 130 38 1 Ba 152 356 200 230 7 U b2b 4 3 b2b 2 Th 18 31 34 15 1 Pb 4 7 b2b b2b 2 Hf 7 8 7 7 5 Sc 8 8 8 5 2 Cr 12 30 b2b 7 b V 21 54 13 31 1 Ni 4 7 6 4 3 Ga 15 22 19 19 1 region-wide SW-directed ductile–brittle extensional detachment, named the Byala reka detachment. The most important contractional structures in the central Byala reka dome are SW-directed ductile thrusts related to syn-metamorphic (with respect to the main amphibolite-facies metamorphism) Late Cretaceous nappe stacking that sliced the lower high-grade basement unit orthogneisses with themetaophiolite slivers (Fig. 10; e.g. Burg et al., 1996; Bonev, 2006a). We describe the tectonically intercalated units, and the extensional structural pattern and kinematics of the segment of the Byala reka detachment that coincides with the original Pelevun thrust, which is hereafter referred to as the Pelevun extensional allochthon. The footwall consists of banded and augen orthogneisses of the lower high-grade basement unit. The hanging wall that is located east of the village of Rozino consists of a thin lid of finely laminated porcelain- like marbles that are locally overlain by thin layers of greenschists, and both are considered to belong to the Mesozoic low-grade unit, based on the lithologies, textures, deformational structures and ages (see below). West of the village of Rozino, the hanging wall is com- posed of intercalated schists, gneisses, amphibolites and medium- to coarse-grained marbles from the upper unit of the high-grade base- ment, which are in turn intruded by the Late Cretaceous Rozino granite (U–Pb zircon age of 68±15 Ma,Marchev et al., 2006) (Fig. 10). In the south, the hanging wall is limited by the fault-bounded Byala reka supra-detachment half-graben that is filled by Eocene–Oligocene clastic sedimentary rocks (Boyanov and Goranov, 2001). The regional foliation S1 in the immediate footwall is flat-lying, and becomes a mylonitic foliation Sm that contains a NE-SW oriented mineral stretching lineation Lstr in the shear zone that underlies the brittle detachment. The shear zone ductile–brittle mylonites reveal an Zn 25 41 26 15 18 Cu 13 12 9 3 b2b Co 5 6 4 2 b2b La 7 53 81 30 20 Ce 20 106 127 65 73 Nd 5 47 50 19 19 Major elements (wt.%), trace and rare earth elements (ppm) determined by XRF. Abbreviatio microgabbro; csch, calc-schist; sch, schist; grt-sch, garnetiferous schist; n.d. not determined location see Fig. 2. 5 KU-214a KU-159 KU-8-3 KU-8-1 KU-33 csch mgb bas sch grt-sch 18.21 47.86 49.88 49.62 74.54 0.26 1.26 2.25 1.41 0.43 6.00 14.01 13.21 12.98 9.02 2.40 11.94 15.90 11.04 7.63 0.11 0.18 0.26 0.18 0.52 2.02 7.73 6.18 6.23 2.12 37.45 11.21 7.19 10.68 1.62 0.21 2.71 3.05 3.37 1.16 1.42 0.16 0.16 0.35 0.97 0.05 0.10 0.22 0.15 0.09 0.01 0.04 0.02 0.04 0.01 n.d. 0.01 0.01 0.01 0.01 31.15 2.92 1.71 4.02 0.94 99.29 100.13 100.03 100.08 99.06 5 6 9 7 13 214 64 122 88 68 9 28 39 29 26 38 7 5 7 39 1464 118 73 144 107 276 b9b b9b 20 216 2 b2b b2b b2b b2b 9 b2b b2b 3 10 b2b 6 b2b b2b 12 b1b b1b 3 b1b 7 b2b 52 86 39 14 51 285 118 308 77 47 369 512 347 145 17 73 52 67 45 7 18 24 18 13 intense top-to-the SSW non-coaxial shearing direction involving biotite retrogression to chlorite and deformation mechanisms that indicate a temperature drop to well below 450 °C (Fig. 10, 11a,b; e.g. figs. 5 and 9 in Bonev, 2006a). The NE-SW ductile–brittle kinematic direction of the shear zone is analogous to the NNE-SSW kinematic direction derived from the slickensides in cataclasites and fault breccias-defined low-angle (30°–18°) detachment that shows top-to- the SSW-directed brittle tectonic transport. The foliation S1 in the hanging wall is flat-lying, and hence is similar to the footwall and exhibits a N–S to NNE-SSW trending mineral lineation (Fig. 10, stereoplots). The foliation S1 is parallel to the bedding S0 in the mar- bles or it represents compositional layering in the lithologies of the upper high-grade basement unit. The marbles are sub-isoclinally folded into minor recumbent folds with W–E to WNW-ESE oriented hinges, with local folds that show a fanning axial-planar cleavage S2 (Fig. 12a). The cleavage S2 morphology and preserved sedimentary bedding in the marbles coupled with chlorite–white mica±epidote assemblage in the greenschists are indicative for metamorphic grade not higher than upper greenschist-facies conditions. It is noteworthy that these lithologic-textural type marbles have no analogue in the high-grade basement units, and fully correspond to the marbles at the base of the Mesozoic low-grade unit that occur 3 km to the east (see Fig. 10). Decametre-scale, inclined close to tight folds with NE-SW to ENE-WSW trending axes without a developed axial-planar cleav- age are often parasitic to the map-scale folds in the hanging wall (Fig. 12b). Because these ESE-vergent folds occur close to the detach- ment, they are presumably related to subsequent fold generation that was associated with deformation linked to the displacement along the detachment. These latter larger foldswere considered to be detachment 35 110 160 125 63 19 36 43 19 23 11 45 47 38 24 18 5 7 10 26 46 8 15 9 23 24 7 5 5 8 ns: agn, K-feldspar augen orthogneiss; egn, equigranular orthogneiss; bas, basalt; mgb, . 266 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 surface corrugation folds that are parallel to the extension direction (Bonev and Stampfli, 2003; Bonev, 2006a). Associated shear-sense indicators in the hanging-wall marbles and greenschists demonstrate a Fig. 4. Discrimination diagrams and trace elements patterns of the rocks from the Kulidzhik Compositional envelope of greenschists samples in Bonev (2006b) is shown for comparison. b) Mandritsa area after Bonev and Stampfli (2008), c)MnO–TiO2–P2O5 diagram (afterMullen, 198 (2008), d) Chondrite-normalized diagram for the orthogneisses in the Kulidzhik allochthon. Sam fromBonev et al. (2010), e) Rb/Nb+Ydiagram (after Pearce et al., 1984) for the orthogneisses in unit is after Bonev et al. (2010). Normalization values from Sun and McDonough (1989). prevailing top-to-the N-NNE ductile shear deformation, as well as sym- metric to slightly asymmetric boudinage that reveals conspicuous top- to-theS ductile shear (Fig. 11c–f). Rare top-to-theNE-directedkinematic River Valley. a) N-MORB normalized spider diagram of the greenschists series samples. Th–Hf/3–Nb/16 diagram (afterWood, 1980) of the greenschist series samples. Data for the 3) for greenschist series samples. Data for theMandritsa area are after Bonev and Stampfli ples of the orthogneisses in the lower high-grade basement unit are taken for comparison the Kulidzhik allochthon. The field of the orthogneisses in the lower high-grade basement 267N. Bonev et al. / Tectonophysics 488 (2010) 256–281 indicators were reported in the hangingwall to thewest of the village of Rozino (Bonev et al., 2006b), although top-to-the SSW-directed ductile shear in the upper high-grade basement unit prevails in that location. The brittle detachment surface is lacking in this western fragment of the extensional allochthon, and theextensional zone is tracedby structurally Fig. 5. Structural and kinematic maps of the Kulidzhik napp lower shear zone ductile mylonites. Brittle deformation of the hanging wall is defined by a predominant set of NW-SE trending high-angle normal faults. These faults limit the supra-detachmenthalf-garben to the south and also occur within the hanging-wall marbles (Fig. 12c and the photograph). A set of N–S to NE-SW trending faults is developed at the e. Stereoplots: lower hemisphere equal-area projection. Fig. 6. Field and microphotographs of structures and kinematics in the high-grade basement orthogneiss unit and greenschist-phyllite unit. a) Texture and asymmetry of porphyroclast systems in the orthogneisses. Quartz recrystallization in subgrains is indicated by arrows (sample Ku-24, b) asymmetrically boudinaged quartz vein and associated shear bands in a chlorite schist (sample Ku-8-1), c) shear bands andmica “fishes” in garnet-muscovite schist. Bulging recrystallization of quartz is indicated by arrows, d) asymmetric folds and σ- and δ-type quartz porphyroclasts in a phyllite, e) close to tight folds in a calc-schist, f) shear band and tight to isoclinal microfolds in a chlorite–muscovite schist, j) shear band and quartz recrystallization in subgrains in a muscovite–epidote schist, h) garnet porphyroblast with foliation continuous straight inclusions of quartz and feldspar from the matrix (sample Ku-33). 268 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 western half-graben, where they host hydrothermal mineralization of the Rozino prospect. The dominant fault set defines NE-SW brittle extension direction in the hanging wall that is parallel to the ductile– brittle fabrics in the footwall shear zone beneath the detachment, implying a consistent kinematic direction from the ductile to brittle field during extension-relateddeformation. Thepredominant southerlydipof Fig. 7. a) A cross-section along the Kulidzhik valley indicated in Fig. 2, b) field view of the Kulidzhik allochton. The “observer” Niko Froitzheim kindly provides the scale, c) the fault zone of the Kulidzhik nappe. Dark blocs are from the footwall greenschists and the light ones from the hanging-wall orthogneisses. 269N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Fig. 8. Microphotographs of the fault zone and the allochthon rocks of the Kulidzhik nappe with clast-anastomosing shear bands materialized by matrix grains, secondary white mica pressure shadows and ductile bending (sample Ku-45), c) deformational lamellae (arrow) in also Fig. 2 for sample locations. . a) Cataclasite showing strong clast fragmentation and grain-size reduction associated and calcite, b) asymmetric plagioclase porphyroclast showing recrystallization in the plagioclase (sample Ku-39), d) brittle fracturing of the plagioclase (sample Ku-45). See 270 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 thebeddingof clastic sediments close to the half-grabenbounding faults, and decrease in dip angles northwards indicates that sedimentation accompanied high-angle faulting that was imposed on the hangingwall. Overall, we interpret the structural pattern in the Pelevun exten- sional allochthon as testifying for the ‘frozen’ greenschist-facies N- directed tectonic emplacement similar to the sense, kinematic direction andmetamorphic conditions recorded in the Kulidzhik nappe, followed by SSW-directed extension-related ductile–brittle shear fabrics and brittle high-angle faulting associated with the low-angle detachment and accompanying hanging-wall sedimentation in a half-graben. Fig. 9. Brittle extensional structures superimposed on the Kulidzhik nappe. a) Fault attitudes, lower hemisphere projection. b) Micro-faults in marbles. c) Micro-faults cross- cutting the ductile fabrics in quartz–chlorite schist. Note asymmetric clasts indicating the shear sense of previous thrusting event. 7. 40Ar/39Ar geochronology The timing of activity of the Kulidzhik nappe is broadly defined by stratigraphic ages for the deposition of radiolarian-bearing shales in the phyllite series, and an unconformable clastic cover succession as post- Jurassic to pre-Late Eocene. For the Pelevun extensional allochthon (see Fig. 12), a plateau white mica 40Ar/39Ar age of 40.26±0.22 Ma was reported by Márton et al. (2009), indicating the timing of cooling of the detachment hanging wall through ∼350 °C. Additionally, adularia 40Ar/39Ar plateau ages of ∼36–36.46±0.26 Ma constrain the timing of hydrothermal alteration related to low-sulfidationmineralization at the Rozino prospect in the hanging wall, while biotite extracted from sub- volcanic rhyolite body in the north yielded a plateau 40Ar/39Ar age of 32.88±0.23 Ma (Marchev et al., 2003). Awhitemica 40Ar/39Ar age of 39±1 Ma was reported by Mukasa et al. (2003) in the schists inter- calated with metaophiolites from south of the Pelevun extensional allochthon towards the core of the Byala reka dome. To improve the precision of timing of displacement of the Kulidzhik nappe and provide temporal constraints on its evolution, 40Ar/39Ar dating was conducted on muscovites extracted from the klippen orthogneisses. Two samples Ku-214 (Lat. N 41°38′23″, Long. E 25°47′ 44.1″) and Ku-215 (Lat. N 41°36′53.6″, Long. E 25°46′34.2″) of equigranular orthogneisses were analyzed (location is shown in Fig. 2). Themuscovites were aligned flakes in thin layers that define the foliation in the rock. Muscovites were separated from a 250–400 μm sieve fraction using conventional magnetic and heavy liquid methods and the concentrateswerepurifiedbyhandpicking under amicroscope. A single sample Br-06-01 (Lat. N 41°28′09.7″, Long. E 26°00′25″) of an amphibole-micaceous intercalation in the marbles of the Pelevun extensional allochthon was also dated (location is shown in Fig. 12). 40Ar/39Ar analyses were performed on coexisting amphibole and white mica in concentrates handled in the manner described above. The 40Ar/39Ar incremental-heating experiments consisted of 14–25 individual steps and were conducted at the University of Geneva. The 40Ar/39Ar laboratory at the University of Geneva consists of an Argus (GV Instruments), multi-collector mass spectrometer, equipped with four high-gain (10E12 Ω) Faraday collectors for the analysis of 39Ar, 38Ar, 37Ar and 36Ar, as well as a single Faraday collector (10E11Ω) for the analysis of 40Ar. The automated, UHV stainless steel gas extrac- tion line incorporates one SAES AP10 getter, and one SAES GP50- ST707 getter, and the extracted gas from alunite grains was cooled to ∼−150 °C by a Polycold P100 cryogenic refrigeration unit mounted over a cold finger. Several mineral grains were step-heated using a defocused 30 W, MIR10 IR (CO2) laser that was rastered over the samples to provide even-heating of the grains. Samples were mea- sured on the Faraday collectors and time-zero regressions were fitted to data collected from twelve cycles. Peak heights and blanks were corrected for mass discrimination, isotopic decay of 39Ar and 37Ar and interfering nucleogenic Ca-, K- and Cl-derived isotopes. The high stability of the Faraday baseline measurements renders it unneces- sary to record baselines during each analysis. Error calculations in- clude the errors onmass discriminationmeasurement, and the J value. 40Ar, 39Ar, 38Ar, 37Ar and 36Ar blankswere calculated before every new sample and after every three heating steps. 40Ar blanks were between 6.5E−16 and 1.0E−15 mol. Blank values for m/e 39 to 36 were all less than 6.5E−17 mol. Age plateaus were determined using the criteria of Dalrymple and Lamphere (1971). The automated analytical process uses the software ArArCalc. The sampleswere irradiated for 15 h in the Oregon State University, CLICIT facility, and J values were calculated via the irradiation of Fish Canyon Tuff sanidines, whichwere separated by distances of b1 cm, throughout the columnar irradiation package. The analytical results of incremental-heating experiments on dated concentrates are listed in Table 5 and 40Ar/39Ar age spectra are shown in Fig. 13. Muscovite Ku-214 yielded a 40Ar/39Ar plateau age of 154.23± 0.66 Ma from seven conjugate steps that represent ∼47% of 39Ar re- leased, which overlaps with the inverse isochron age of 153.28± Fig. 10. Structural map of the Pelevun extensional allochthon. Stereoplots: lower hemisphere projection. 271N. Bonev et al. / Tectonophysics 488 (2010) 256–281 272 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 1.28 Ma (Fig. 13a). Muscovite Ku-215 gave a 40Ar/39Ar plateau age of 156.70±0.81 Ma from the flattest part of the age spectrum, which overlaps with the inverse isochron age of 160.06±2.65 Ma (Fig. 13b). Amphibole Br-06-01 yielded a highly discordant 40Ar/39Ar age spectrum with a total fusion age of 203.12±6.05 Ma and an inverse isochron age of 156.58±0.60 Ma (Fig. 13c). In the same sample, muscovite yielded a 40Ar/39Ar plateau age of 39.66±0.47 Ma, which is indistinguishable from its inverse isochron age of 40.40±4.24 Ma (Fig. 13d). The textural relationships of the mineral assemblage in the dated orthogneiss samples suggest that the analyzed muscovites recrystal- Fig. 11. Shear structures and kinematics of the Pelevun extensional allochthon. a) Field aspec beneath the detachment. Sm=mylonitic foliation. Half arrows depict shear bands. Coin for sc brittle mylonites. Sm = mylonitic foliation; S1 = regional foliation. Half arrows depict shea below 450 °C consistent with biotite alteration to chlorite within the shear zone. c) Field asp the foliation S1 and top-to-the N shear bands (half arrows). d) Microphotograph of the hang bands (half arrows). Note low-temperature (ca. 300–400 °C) deformation of quartz indicate indicating top-to-the N shear sense in greenschist-facies. e) Asymmetric top-to-the S bo boudinage in the hanging-wall marbles. Lens cap for scale=6 cm. Abbreviations: Fs, feldsp lized during lower amphibolite-facies metamorphism at tempera- tures above their closure temperature range for 40Ar (350±30 °C, e.g. McDougall and Harrison, 1999). Therefore, their 40Ar/39Ar ages dating the time of cooling of the orthogneisses ∼350 °C, following peak metamorphism of the allochthon that was probably related to thrust- related exhumation and tectonic emplacement in the hanging wall of the Kulidzhik nappe, when the deformation proceeded from ductile to brittle conditions. The disturbed age spectrumof amphibole in the sample Br-06-01may result either fromthe incorporationof excess argonand/or heterogeneous t of the footwall ductile–brittle mylonitic orthogneisses in the SSW-directed shear zone ale=2 cm. b) Microphotograph of top-to-the SSW shear fabrics in the footwall ductile– r bands. Note brittle fracturing of the feldspars, implying temperature of deformation ect of the hanging-wall marbles showing preserved sedimentary bedding S0 parallel to ing-wall greenshists (quartz–white mica–chlorite schists) showing top-to-the N shear d by bulging recrystallization and deformational bands. Half arrows depict shear bands udinage of amphibolite-micaceous layer in the hanging-wall marbles. f) Symmetric ar; Ms, muscovite; Qtz, quartz. 273N. Bonev et al. / Tectonophysics 488 (2010) 256–281 amphibole composition in the sample. The Late Jurassic inverse isochron age of the amphibole is plausible upper greenschist-facies metamorphic age, which age overlaps 40Ar/39Ar ages obtained for the Kulidzhik nappe allochthon. The white mica plateau age clearly indicates Middle Eocene cooling of argon isotopic system below ∼350 °C in the hanging-wall Pelevun extensional allochthon. Fig. 12. a–b) Fold style and orientation, and c) brittle extension through high-angle faul 8. Discussion and interpretation 8.1. Tectono-metamorphic evolution and implications Combined field and geochemical data has allowed intercalated tectono-stratigraphic units in the metamorphic pile of the Kulidzhik ts in the Pelevun extensional allochthon. Stereoplots: lower hemisphere projection. metamorphism is Middle Jurassic–earliest Late Jurassic in age, 274 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 nappe to be distinguished. The newly subdivided area in the lower high-grade basement orthogneiss unit presents continental affinity, largely preserving igneous mineral phases and granitoid composition. These orthogneisses are lithologically and compositionally similar to those in the lower high-grade basement unit, elsewhere in the eastern Rhodope, thus representing its extension in the Kulidzhik Valley (Figs. 3b, 4d, e; see Fig. 1). The unit also forms the allochthon of the Kulidzhik nappe. Greenschists and mafic lavas in the greenschist-phyllite unit yield a geochemical signature that is transitional between MORB and IAT extrusive products, with a strong arc imprint and are similar to the arc-related extrusive suite of the Mesozoic low-grade unit in the Mandritsa area (e.g. Bonev, 2006b; Fig. 4b, c). This unit shows a clear oceanic affinity, with arc-related magmatic products and an associ- ated sedimentary pelitic succession, with intercalated carbonaceous horizons (Fig. 3). Based on deformational microstructures of the lower high-grade basement orthogneisses, a metamorphic temperatures higher than 500 °C can be inferred, implying that they experienced at least lower amphibolite-facies metamorphic grade. The greenschists show a bulk metamorphic assemblage of quartz+chlorite+muscovite+albite+ epidote+biotite+calcite+garnet+actinolite+hornblende that is typical for low- to medium-grade metabasites and metapelites in metamorphic conditions reaching the biotite–garnet zone of greens- chist-facies metamorphism. The higher-grade biotite and garnet-in zone in the greenschist series occur spatially and structurally close to the contactwith the orthogneiss unit, whichprovides additional support for the inferred range of metamorphic temperatures in the latter unit. The metamorphic mineral assemblage varies, depending on bulk rock com- position of the greenschist precursors. It is characteristically of lower metamorphic grade with quartz+chlorite+calcite paragenesis in the phyllite series. Mineral chemistry indicates the prevalence of albite plagioclase and almandine garnet in the greenschist series, whose phases are common in medium-grade greenschist-facies metamor- phism. In rocks with high MnO and CaO contents, such as the greenschists (Table 4), the appearance of garnet in the rocks is limited below 450 °C (e.g. Spear, 1993), which is supported by molecular spessartine-richgarnets (Table 3). The temperatures experiencedby the greenschists did not significantly exceeded 400 °C. These textural and qualitative metamorphic data indicate a progressive decrease in metamorphic grade upwards within the Kulidzhik nappe section, from lower amphibolite to weak greenschist-facies metamorphism. Structural and kinematic results for the Kulidzhik nappe reveal a rather uniform deformational pattern with consistent top-to-the NNE tectonic transport. Geometries and attitudes of the structural elements are compatible with a single deformational event that is recorded equally in all units, and evolved in ductile to brittle con- ditions towards the structurally shallow levels. The structural pat- tern is consistent with thrust-related emplacement with a NNE kinematic direction and coeval higher crustal level exhumation of the nappe pile. Relationships between metamorphic crystallization and concomitant shear structures fit this deformational pattern and the coeval greenschist-facies metamorphism. The Kulidzhik nappe NNE kinematic direction and tectonic transport in greenschist- facies are similar to the internal deformational pattern, tectonic transport and metamorphic grade of the hanging-wall marbles and greenschists in the Pelevun extensional allochthon, which is how- ever underlain by an extensional detachment providing evidence for the Tertiary extensional overprint. The 40Ar/39Ar geochronological results reveal rapid cooling of the orthogneisses in the allochthon of the Kulidzhik nappe between 157 and 154 Ma. These ages indicate a pre-Late Jurassic age of amphibolite- faciesmetamorphism for the orthogneisses in the allochthon, together with metamorphism in the corresponding grade for the greenschists in the relative autochthon, and also constrain a Late Jurassic age for thrust-related emplacement of the Kulidzhik nappe. encompassing the time interval between 170 and 154 Ma. 40Ar/39Ar geochronology in the hanging-wall marbles of the Pelevun exten- sional allochthon also shows a record of the same grade Jurassic metamorphism. There, the Jurassic tectono-metamorphic event is subsequently affected by thermal re-equilibration in the Late Cretaceous–Eocene, which was probably related to syn-metamorphic nappe stacking and extensional deformation. The tectono-metamorphic record of the Kulidzhik nappe has deep implications for the tectonic evolution of the Rhodope Massif because it reveals an early Alpine thrust tectonics that relate to subduction– accretion and orogenic crustal assembly. A simplified tectonic scenario for arc–margin collision and subsequent accretion is proposed in Fig. 14, and accounts for the data obtained for the Kulidzhik nappe, the Pelevun extensional allochthon and their Tertiary extensional tectonic overprint. Following the Late Paleozoic, the Variscan igneous base- ment of the Rhodope promontory is shown by the continental affinity orthogneiss unit that consists of volcanic arc-related, calc-alkaline intrusions (Table 1, Bonev et al., 2010), which basement in terms of magmatic intrusion ages is indistinguishable from the pre-Mesozoic basement of the StrandzhaMassif (Okay et al., 2001) (see Fig. 1). In the Tethyan realm, adjacent to the Rhodope promontory, the Triassic period encompasses an important phase of rifting (Dimitriadis and Asvesta, 1993; Ferrière and Stais, 1995; Georgiev et al., 2001), which graded to post-Middle Triassic sea-floor spreading in several back-arc basins, which formed subsequent to the closure of the Paleotethys (Stampfli and Borel, 2002; 2004; Stampfli and Kozur, 2006). The ophiolitic suites of the low-grade unit in the Mandritsa area, and the Evros ophiolites in the Thrace area were interpreted as an intra- oceanic Jurassic island arc magmatic assemblage that formed during southward subduction of the oceanic lithosphere of a back-arc basin, referred to as the Maliac/Meliata Ocean. Subduction of the Maliac/ Meliata crust established the supra-subduction Vardar Ocean in a back-arc setting (Bonev and Stampfli, 2003, 2008). Following the cessation of activity of this eastern Rhodope–Evros arc system (Fig. 14a), which did not occur significantly earlier than the formation of the back-arc Samothraki ophiolites at ∼155±7 Ma (Tsikouras et al., 1990; Tsikouras and Hatzipanagiotou, 1998), then the arc system collided with the Rhodope margin in Late Jurassic time. The collision drove the imbrication and emplacement of the island arc and orthogneiss basement units found in the Kulidzhik nappe, together with the Pelevun marble precursors that may represent near margin, shallow-water carbonates (Fig. 14b). In this sense, we consider the Kulidjik nappe to be an∼1 km thick fragment of the thrust system that has its origin in the subduction-accretionary arc-continental margin collision setting. Continental margin-derived, latest Paleozoic and Triassic clastics found in the Madritsa area within the subduction- accretionary complex are consistent with this tectonic setting. 8.2. Regional implications The Late Jurassic record of the Kulidzhik nappe and the low-grade unit in the Pelevun extensional allochthon also has an important regional implication for the extent of the early Alpine orogen, close to the Rhodope Massif i.e. the relationships with the Strandzha Massif, although it also has significance for early Alpine evolution of the With regard to the age of greenschist-facies metamorphism of the greenschist-phyllite unit, and respectively for theMesozoic low-grade unit as a whole, the new 40Ar/39Ar results allow its precision. Meta- morphism occurred after the eruption of mafic lavas that are intercalated with Early Jurassic (latest Pliensbachian to pre-Bajocian) radiolarian-bearing layers in the Mandritsa area and the intrusion of the Petrota gabbro (170 Ma), and was coeval with Late Jurassic thrust emplacement of the Kulidzhik allochthon. Thus, the greenschist-facies Balkan thrust–fold belt to the north (Fig. 1, inset). Table 5 40Ar/39Ar analytical results for dated samples in the study. Laser 40Ar/39Ar ±1σ 37Ar/39Ar ±1σ 36Ar/39Ar ±1σ 40Ar*/39Ark ±1σ 40Ar (mol) 40Ar* (%) 39Ark (%) K/Ca Age ±2σ Power (W) KU-214 muscovite 1.2 18.44474 0.11557 0.02730 0.06640 0.02499 0.00401 11.060847 1.18780 3.781E−16 59.97 0.08 15.753 81.86 17.19 1.4 18.64146 0.09590 0.00000 0.05922 0.01349 0.00222 14.653343 0.65993 6.045E−16 78.61 0.13 0.000 107.67 9.41 1.7 21.92684 0.03060 0.00000 0.00805 0.00683 0.00034 19.907699 0.10520 3.895E−15 90.79 0.69 0.001 144.76 1.47 2.0 21.97825 0.03060 0.00000 0.00591 0.00203 0.00017 21.378778 0.05762 8.363E−15 97.27 1.47 0.002 155.01 0.80 2.2 22.32613 0.02837 0.00000 0.00196 0.00191 0.00009 21.761712 0.03757 1.949E−14 97.47 3.37 0.004 157.67 0.52 2.4 21.96044 0.02971 0.00000 0.00228 0.00097 0.00009 21.674057 0.03964 1.926E−14 98.70 3.39 0.004 157.06 0.55 2.6 22.09464 0.03082 0.00000 0.00285 0.00082 0.00008 21.851517 0.03904 1.912E−14 98.90 3.34 0.004 158.29 0.54 2.8 22.25378 0.02086 0.00000 0.00259 0.00083 0.00010 22.006206 0.03580 1.444E−14 98.89 2.51 0.003 159.36 0.50 3.1 22.31326 0.02377 0.00000 0.00289 0.00130 0.00013 21.927187 0.04378 1.141E−14 98.27 1.98 0.003 158.81 0.61 3.4 22.42227 0.02468 0.00000 0.00179 0.00101 0.00009 22.123464 0.03513 2.094E−14 98.67 3.61 0.005 160.17 0.49 3.8 22.27874 0.02171 0.00000 0.00258 0.00081 0.00011 22.039678 0.03923 1.651E−14 98.93 2.86 0.004 159.59 0.54 4.1 22.18895 0.02167 0.00000 0.00265 0.00074 0.00011 21.969244 0.03913 1.763E−14 99.01 3.07 0.004 159.11 0.54 4.4 22.10045 0.02340 0.00000 0.00238 0.00056 0.00009 21.933480 0.03532 2.132E−14 99.24 3.73 0.005 158.86 0.49 4.7 22.22428 0.02370 0.00000 0.00224 0.00094 0.00009 21.944968 0.03654 2.134E−14 98.74 3.71 0.005 158.94 0.51 4.9 22.23627 0.02353 0.00000 0.00208 0.00075 0.00008 22.013869 0.03291 1.832E−14 99.00 3.18 0.004 159.41 0.46 5.2 22.19776 0.02355 0.00000 0.00184 0.00063 0.00008 22.010892 0.03381 2.118E−14 99.16 3.69 0.005 159.39 0.47 5.5 22.25383 0.02704 0.00000 0.00492 0.00062 0.00022 22.068204 0.06943 8.332E−15 99.17 1.45 0.002 159.79 0.96 5.9 22.25486 0.01214 0.00000 0.00114 0.00093 0.00005 21.978129 0.01874 3.426E−14 98.76 5.95 0.008 159.17 0.26 6.1 22.23390 0.01275 0.00000 0.00130 0.00060 0.00005 22.056952 0.01980 2.974E−14 99.20 5.17 0.007 159.71 0.27 6.4 22.42123 0.01157 0.00000 0.00107 0.00026 0.00004 22.344470 0.01600 5.580E−14 99.66 9.61 0.013 161.70 0.22 6.6 22.36098 0.01168 0.00000 0.00071 0.00023 0.00002 22.291688 0.01368 5.224E−14 99.69 9.03 0.012 161.34 0.19 6.8 22.32937 0.01172 0.00000 0.00071 0.00022 0.00003 22.264187 0.01446 5.249E−14 99.71 9.08 0.012 161.15 0.20 7.1 22.25169 0.01169 0.00000 0.00113 0.00010 0.00004 22.219878 0.01685 4.498E−14 99.86 7.81 0.010 160.84 0.23 7.3 22.17910 0.01138 0.00000 0.00119 0.00000 0.00004 22.178095 0.01138 3.290E−14 100.00 5.73 0.007 160.55 0.16 7.7 22.23133 0.01299 0.00000 0.00178 0.00000 0.00006 22.230315 0.01299 1.994E−14 100.00 3.47 0.004 160.91 0.18 8.5 22.31151 0.01516 0.00000 0.00265 0.00022 0.00011 22.246560 0.03689 1.110E−14 99.71 1.92 0.002 161.03 0.51 KU-215 muscovite 1.4 22.04482 0.07342 0.00427 0.02005 0.02942 0.00091 13.351988 0.27194 1.992E−15 60.57 0.53 100.795 98.13 3.89 1.4 22.46171 0.05771 0.01912 0.01668 0.01017 0.00060 18.597619 0.18496 3.051E−15 86.62 0.83 22.489 135.27 2.59 1.7 22.95291 0.02237 0.00000 0.00438 0.00516 0.00016 20.481627 0.07692 8.672E−15 93.35 2.30 0.010 148.42 1.07 2.0 22.99221 0.02114 0.00000 0.00249 0.00265 0.00014 21.229493 0.07494 1.758E−14 96.60 4.66 0.020 153.62 1.04 2.2 22.77122 0.02289 0.00000 0.00227 0.00179 0.00007 21.260735 0.06694 2.125E−14 97.68 5.69 0.023 153.84 0.93 2.5 22.74153 0.02293 0.00000 0.00185 0.00183 0.00010 21.221502 0.07000 1.848E−14 97.62 4.95 0.020 153.56 0.97 2.9 22.70269 0.01821 0.00000 0.00399 0.00162 0.00012 21.243881 0.07098 1.287E−14 97.89 3.46 0.014 153.72 0.98 3.4 22.82495 0.01258 0.00000 0.00156 0.00055 0.00005 21.661559 0.06383 3.165E−14 99.28 8.45 0.035 156.61 0.88 4.0 22.86996 0.01170 0.00000 0.00109 0.00058 0.00005 21.695578 0.06392 3.885E−14 99.24 10.35 0.043 156.85 0.89 4.7 22.92180 0.01164 0.00000 0.00115 0.00043 0.00004 21.787769 0.06353 4.382E−14 99.44 11.65 0.049 157.49 0.88 5.3 22.67984 0.01165 0.00000 0.00115 0.00053 0.00005 21.527681 0.06325 4.079E−14 99.30 10.96 0.045 155.69 0.88 6.0 22.73163 0.02016 0.00000 0.00244 0.00092 0.00008 21.468296 0.06719 2.070E−14 98.80 5.55 0.022 155.28 0.93 7.2 22.72073 0.01169 0.00000 0.00111 0.00035 0.00003 21.618693 0.06264 4.672E−14 99.54 12.53 0.051 156.32 0.87 8.5 22.82824 0.01180 0.00000 0.00071 0.00021 0.00002 21.759617 0.06282 6.772E−14 99.72 18.08 0.077 157.29 0.87 BR-06-01 hornblende 27.19627 0.08205 249.64042 26.58103 0.08945 0.00039 24.324795 2.55053 6.933E−15 74.41 4.24 0.001 161.64 32.42 24.47046 0.09357 347.61969 37.70509 0.09076 0.00049 31.942588 1.06726 9.769E−15 100.00 6.12 0.001 209.42 13.21 24.67166 0.10171 502.77137 54.26648 0.08686 0.00043 37.287925 2.06662 1.230E−14 100.00 6.60 0.001 242.20 25.12 26.47756 0.10784 431.61450 48.33781 0.09164 0.00042 37.316374 1.72035 1.321E−14 100.00 7.09 0.001 242.37 20.91 22.56964 0.07368 277.97729 30.90485 0.07026 0.00034 27.762609 0.71734 1.637E−14 100.00 11.80 0.001 183.35 9.01 20.36779 0.06623 295.62941 32.71785 0.06188 0.00019 25.425623 0.70475 1.534E−14 100.00 12.07 0.001 168.62 8.92 20.07482 0.07232 334.99901 36.75437 0.06148 0.00027 25.917175 0.83439 1.390E−14 100.00 10.73 0.001 171.73 10.55 22.26834 0.08280 501.05575 54.81326 0.07475 0.00031 33.596896 1.87577 1.498E−14 100.00 8.93 0.001 219.63 23.09 21.62441 0.08407 600.89879 65.79060 0.07124 0.00036 36.306228 2.70485 2.116E−14 100.00 11.66 0.000 236.22 32.99 21.41038 0.07323 580.06040 63.03267 0.07015 0.00030 35.119889 2.44840 1.961E−14 100.00 11.17 0.000 228.98 29.98 24.41220 0.05896 341.42611 38.38552 0.07865 0.00067 31.694081 1.06706 2.229E−15 100.00 1.41 0.001 207.88 13.22 22.22159 0.09317 331.70242 35.70631 0.06857 0.00041 28.606886 0.89496 5.690E−15 100.00 3.98 0.001 188.65 11.21 20.21931 0.04019 209.18824 22.33094 0.05672 0.00027 23.018648 2.06939 4.939E−15 97.82 4.20 0.002 153.31 26.43 BR-06-01 white mica 20.07111 0.06667 337.87292 35.71688 0.06601 0.00044 25.977265 0.81409 4.086E−15 100.00 0.78 0.001 173.39 10.36 18.20800 0.06104 279.63346 30.15975 0.05378 0.00046 22.427977 0.56669 4.995E−15 100.00 1.11 0.001 150.66 7.30 10.11056 0.03149 92.51843 9.86948 0.01777 0.00011 10.780887 0.08389 1.288E−14 99.99 5.93 0.004 73.99 1.13 7.62836 0.03213 31.34577 3.47416 0.00860 0.00007 7.692800 0.28007 7.334E−15 98.72 4.67 0.013 53.11 3.81 7.49069 0.02979 33.03787 3.82455 0.00750 0.00008 7.660020 0.03669 6.540E−15 99.99 4.24 0.013 52.88 0.50 7.19917 0.01964 23.46451 2.66238 0.00586 0.00006 7.313671 0.02407 8.602E−15 99.99 5.84 0.018 50.53 0.33 6.98116 0.02385 17.85173 2.05263 0.00518 0.00006 6.925397 0.16519 1.156E−14 98.01 8.12 0.024 47.88 2.25 6.86075 0.01730 13.87455 1.61587 0.00446 0.00006 6.687702 0.12976 8.341E−15 96.57 5.98 0.031 46.26 1.77 6.70112 0.02284 5.38803 2.85160 0.00342 0.00009 6.130920 0.22604 3.100E−15 91.16 2.29 0.080 42.45 3.09 6.88569 0.01899 11.19868 1.36986 0.00439 0.00005 6.509311 0.11038 1.151E−14 93.82 8.23 0.038 45.04 1.51 6.63207 0.01210 3.45629 0.98414 0.00317 0.00003 5.978862 0.07856 1.320E−14 89.94 9.85 0.124 41.41 1.08 6.53087 0.01787 0.27215 0.71533 0.00283 0.00003 5.692364 0.05898 1.129E−14 87.16 8.58 0.005 39.45 0.81 6.53309 0.01648 0.28444 1.05094 0.00266 0.00003 5.746040 0.08384 1.195E−14 87.95 9.08 0.005 39.81 1.15 (continued on next page) 275N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Some earlier workers used general considerations to suggest the Jurassic eastern Rhodope nappes and the Strandzha nappes were connected (Gočev, 1979). A recent study on the Strandja Massif identified igneous ages of the Variscan basement and Late Jurassic– Early Cretaceous N-directed thrusting that involves the basement and its Triassic–Jurassic sedimentary cover (Okay et al., 2001). Furthermore, the timing of this tectonism with the same kinematic direction in the Strandzha Massif was constrained by 40Ar/39Ar ages to have occurred during 165–157 Ma, and by Rb–Sr ages to have occurred between 162 and 140 Ma that are also associated with epidote–amphibolite or greenschist-facies metamorphism (Natal'in et al., 2005). It is worth noting that Jurassic shallow-water sedimentation in the Strandzha Massif had terminated by the Middle Jurassic (Bathonian; Chatalov, 1988), implying overprinting tectonic inversion of the related Jurassic sedimentary basin. Data from the Strandzha Massif and the Kulidzhik nappe in the eastern Rhodope Massif indicate that both areas share a common age-constrained tectono-metamorphic history. The similar style of thrusting in bothmassifs involves the basement thrust slices, but differs in the intercalated arc unit (eastern Rhodope) and near con- tinentalmargin shallow basin (Strandzha), which could be attributed to the crustal heterogeneity of early Mesozoic transtensional setting (e.g. Banks and Robinson, 1997) or complex microplate boundaries (e.g. Natal'in et al., 2005). This patternwas inherited in the connection of the eastern Rhodope–Evros arc and the Strandzha Triassic–Jurassic basin along the active Rhodope–Strandzha continentalmargin during the Late Jurassic evolution. We propose that the eastern Rhodope Kulidzhik and Strandzha nappes were related in foreland N-directed nappe staking during Late Jurassic orogenesis. Nappe staking lead to the emplacement of the thrust slices onto the Rhodope–Strandzha margin, thus contributing to early Alpine orogenic build-up and crustal growth at the south Eurasian plate by the accretion of an arc system and basinal sequences derived from the Rhodope–Strandzha continental margin. The same orogenic event contributed to the first stage of the Late Jurassic–Early Cretaceous evolution of the Balkan thrust–fold belt located to the north (see Fig. 1), where advancing Strandzha nappes drove inversion of the Triassic and Jurassic sedimentary sequences in a fore-deep basin at the southern margin of the Moesian platform (e.g. Banks, 1997; Georgiev et al., 2001). 8.3. Extensional structures in the Rhodope Massif Subsequent to the Late Cretaceous Rhodope nappe stacking in the hanging wall of the closing northwards Vardar Ocean, and the cessation of activity of the Sredna Gora arc (Fig. 14c), the Tertiary evolution of the Rhodope Massif was governed by extensional tectonics through low- angle extensional detachments and related hanging-wall sedimentation and footwall deformation. Syn-orogenic crustal extension started in the Table 5 (continued) Laser 40Ar/39Ar ±1σ 37Ar/39Ar ±1σ 36Ar/39Ar ±1σ 40Ar*/39Ark ±1σ 40Ar (mol) 40Ar* (%) 39Ark (%) K/Ca Age ±2σ Power (W) BR-06-01 white mica 6.52247 0.01462 0.23733 0.84846 0.00256 0.00002 5.763709 0.06800 1.340E−14 88.37 10.20 0.005 39.94 0.93 6.66788 0.01175 0.38174 0.72863 0.00323 0.00003 5.711753 0.05862 2.033E−14 85.66 15.13 0.005 39.58 0.80 Data are corrected for blanks, interfering nucleogenic reactions and decay of 37Ar and 39Ar. 39Ar/37Ar 6.73E−4, 36Ar/37Ar 2.64E−4, 40Ar/39Ar 1.01E−3, 38Ar/39Ar 1.138E−2. 276 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Fig. 13. 40Ar/39Ar age spectra of dated samples in the stu dy. For location and sample numbers see Figs. 2, 12. Fig. 14. Tectonic scenario for the emplacement of the Kulidzhik nappe and the extensional tectonic overprint. 277N. Bonev et al. / Tectonophysics 488 (2010) 256–281 278 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 eastern Rhodope Massif in the Paleocene–early Eocene, and is con- strained by stratigraphic ages of syn-tectonic sediments in the detachment hanging wall, while ductile thrusting was still active at depth (Bonev et al., 2006a; Bonev, 2006a). Ductile thinning of the previously thickened crust was an effective mechanism to unroof the Alpine orogenic nappe stack, with ductile–brittle extension localized in shear zones located beneath the extensional detachments that bound the metamorphic core complex-style footwall gneiss domes (Fig. 1, Bonev, 2006a). The kinematic framework in the Kesebir–Kardamos and the Byala reka–Kechros domes of the eastern Rhodope reveals a regionally consistent NNE-SSW to NE-SW direction of ductile, followed by brittle extension (Fig. 1, Bonev2006a;BonevandBeccaletto, 2007). Extension in the Kesebir–Kardamos dome was NNE-directed, and was SSW-directed in the Byala reka–Kechros dome where the kinematic direction was inherited from the nappe stacking phase. The extension, including the north Aegean region (Bonev and Beccaletto, 2007), continued into the Oligocene–Miocene and overlapped with well-documented post-oro- genicAegeanextension,which ismanifested in thewesternand southern RhodopeMassif by Late Eocene–Oligocene toNeogene sedimentaryfill in supra-detachment grabens above the Mesta and Strymon Valley detachments (Dinter, 1998; Burchfiel et al., 2003), and southward younging of 40Ar/39Ar cooling ages in the basement between 35 and 19Ma (Lips et al., 2000). In the eastern Rhodope, the extensional stage accompanied interplaybetween temporally close tectonic,magmatic and hydrothermal processes during ca. 40–34 Ma, as shown by 40Ar/39Ar geochronology (Bonev et al., 2006b; Bonev et al., 2009). 8.4. Significance for Tertiary extensional evolution of the Rhodope Massif The thrust tectonics of the Mesozoic low-grade unit containing Jurassic intra-oceanic arc and associated sedimentary successions, together with a fragment of underlying unit of the continental basement described herein, has relevant implication for the Rhodope Late Alpine crustal evolution that relates to syn- and post-orogenic extension (Bonev, 2006a; Bonev and Beccaletto, 2007). The Late Jurassic thrusting event has contributed to the initial Alpine thickening of the Rhodope crust prior to further crustal stacking and high-grade metamorphism associated with the development of syn- metamorphic nappe complex (Burg et al., 1996), which latter additionally thickened this crust obviously from the Early Cretaceous to pre-latest Late Cretaceous times. Both thrusting events caused a significant crustal thickening within the Rhodope Cretaceous orogenic wedge in the convergent region between the closing Vardar Ocean in the south, and the continental domain of Sredna Gora Zone–Balkan chain–Moesian platform to the north (see Fig. 1, inset). The progressive Alpine crustal loading by nappe stacking created an overthickened and unstable orogenic wedge that gravitationally adjusted by late-stage extensional collapse of the nappe stack. The crustal thickening initiated an orogenic welt that was apparently underlain by hot crust leading to its thermal weakening substantially facilitated by the intrusion of Late Cretaceous (80–68 Ma) and early Paleogene (53 Ma) granitoids in the central and eastern RhodopeMassif (Peytcheva et al., 1999; Ovtcharova et al., 2003; Marchev et al., 2006). This tectono-magmatic feature may well witnesses for a significant crust–mantle interaction in the collisional and extensional stages of development of the orogen. The dispersed regional outcrop extent of the Mesozoic low-grade unit always in hanging wall position of the detachments (see Fig. 1), implies that later the Late Jurassic thrust sheet belonging to this unit has been progressively excised during the Tertiary extension. This unit assisted unloading of the metamorphic nappe stack during the late-stage orogenic collapse of the thickened Rhodope crust. The structural record in the Pelevun extensional allochthon provides evidence for ductile–brittle and brittle SSW-directed extension in the central Byala reka dome. The SSW kinematic direction of syn- metamorphic ductile thrusting associated with the amphibolite metamorphism maintained through the extensional stage, however, in lower metamorphic grade and under ductile–brittle and brittle deformational conditions. The inheritance of the ductile thrusting sense and kinematic direction during the extensional deformation is obvious in the western Pelevun extensional allochthon, where is present in the footwall, the hanging and the boundingmylonitic shear zone. The hanging-wall marbles and greenschists of the Mesozoic low-grade unit recording Late Jurassic upper greenschist-facies metamorphism and NNE-directed tectonic emplacement are directly juxtaposed via the Byala reka detachment against the footwall lower unit of the high-grade metamorphic basement. This superposition accounts for an extensional omission of the upper high-grade basement unit at the detachment contact near the village Pelevun. Our 40Ar/39Ar white mica age of 39.66 Ma, together with the similar age of 40.26 Ma reported by Márton et al. (2009) in the hanging wall, unequivocally constrain the Middle Eocene cooling history below ∼350 °C and shallow crustal level exhumation of the Pelevun extensional allochthon at 40 Ma. This latter age is consistent also with the younger age of 39±1 Ma south of the extensional allochthon, implying likely subsequent footwall cooling in between half-graben bounding faults. The high-angle fault mode brittle extension that persisted into the Late Eocene assisting the sedimen- tation in the hanging wall is temporally indicated by the fault zones- filling hydrothermal rocks in the Rozino prospect at 36–36.5 Ma. Therefore, the excisement was controlled by ductile and brittle stretchings that thinned the nappe stack by removing parts of the hanging wall of the extensional detachment fault system (Figs. 14c, 15a). The style of upper crustal brittle extension dominated by high- angle faulting in the studied areas is related to the supra-crustal, shallow level position of the low-grade unit inherited from previous Late Jurassic thrusting event. The process of brittle removal parts of the hanging wall was region-wide, operating on both sides of the large-scale extensional Byala reka–Kehros dome (see Fig. 1). In the southern flank of this dome, in continuum with the Kulidzhik and the Pelevun areas, the similar style of brittle faulting affected the low- grade thrust sheet in the hanging wall of the extensional system (Fig. 15b). Because at this flank the low-grade unit dissected by high- angle faults in the detachment hanging wall occurs in direct contact with the footwall lower high-grade basement unit in a shear zone (Bonev and Beccaletto, 2007), there the extension also documents tectono-stratigraphic omission and deformation progression from ductile to brittle field up crustal section. The brittle extension on high- angle faults continued south of the Byala reka–Kechros dome, with normal and strike-slip faulting in the Oligocene times (Karfakis and Doutsos, 1995), and persisted into the Miocene–Present related to the development of the South Rhodope Basin System in the northern Aegean region (Koukouvelas and Aydin, 2002). 9. Conclusions We reached the following conclusions for the Kulidzhik nappe and the Pelevun extensional allochthon and their significance for the Alpine thrust and extension-related tectonics in the eastern Rhodope Massif: 1) Continental-type lower amphibolite-facies orthogneiss unit is sliced in the nappe with greenschist-facies unit consisting of arc-related volcanic products and sedimentary succession.When compared, the orthogneisses are indistinguishable from those in the lower high- grade basement unit of the eastern RhodopeMassif, thus represent- ing an extension of this unit in the study area. The greenschists originated from precursor basic lavas and pyroclastic rocks of transitional MORB-IAT signature with strong arc imprint. Composi- tions of the Kulidzhik greenschists are fully comparable to arc extrusive suite in the Mandritsa area, implying that the Kulidzhik mafic suite represents an extension of the supra-subduction zone Early–Middle Jurassic east Rhodope–Evros island arc magmatic assemblage. 279N. Bonev et al. / Tectonophysics 488 (2010) 256–281 2) Mineral chemistry of the orthogneisses reveals phases of the granitoid protolith, whereas textures relate to the ductile deforma- tion and lower amphibolite-facies metamorphism of temperatures higher than 500 °C. Metamorphic assemblage of the greenschists is typical for medium-grade greenschist-facies metamorphism, with late albite and almandine garnet suggesting metamorphic tempera- tures b450 °C. In the overlying phyllites and shales, the weak meta- morphic conditions of lower-grade greenschist-facies are revealed by dominant chlorite–white mica assemblage. These features imply upward decrease in metamorphic grade in the tectonostratigraphic section of the Kulidzhik nappe. The hanging-wall marbles and the greeschists of the Pelevun extensional allochthon exhibit litholog- ical–textural features of comparable upper greenschist-facies meta- morphic grade. 3) Structural pattern and kinematics demonstrate top-to-the NNE transport within the Kulidzhik nappe, with shearing that evolved from ductile to brittle conditions accompanied by decrease in metamorphic grade towards the structural top. This deformation pattern relates to single tectonic event responsible for the imbrica- tions of the units within the nappe at shallow crustal level. 40Ar/39Ar 157–154 Ma mica ages constrain cooling of the allochthon coeval with the greenschist-facies metamorphism and nappe emplace- Fig. 15. Regional-scale pattern of brittle extension in the flanks of the extensional Byala rek northern flank of the dome. b) The southern flank of the dome in Greece (low-grade unit lo grade schists, and sedimentation nearly concomitant to faulting. ment. Basedon ages, affinities and tectono-metamorphic pattern,we relate the Kulidzhik nappe to crustal deformation intercalating continental margin basement and island arc units during an arc– margin collision. The hanging-wall Pelevun extensional allochthon records similar to the Kulidzhik nappe internal NNE-directed ductile transport, whereas it is underlain by SSW-directed footwall extensional ductile–brittle shear zone and brittle detachment. 40Ar/39Ar hornblende inverse isochron age of 154 Ma is likely upper greenschist-facies metamorphic age, whereas white mica age of ca. 40 Ma indicates cooling and extensional exhumation of the allochthon above the detachment following post-Late Jurassic re- equilibration of argon isotopic system apparently resulting from the Late Cretaceous–Tertiary tectono-thermal overprint. 4) A comparison of the temporal and tectono-metamorphic pattern of the Kulidzhik nappe in the eastern Rhodope Massif with the time- constrainedhistoryof the adjacent StrandzhaMassif shows that they display analogous Late Jurassic tectonic evolution. We therefore consider both as tectonic elements of the same early Alpine orogenic system. The same Late Jurassic–Early Cretaceous tectonic event caused also the known first orogenic stage of the Balkan thrust–fold belt northwards, implying a regionally consistent orogenic build-up and crustal growth at Eurasian plate during the Late Jurassic time. a–Kechros dome. a) Panoramic view of the Kulidzhik Valley showing the faults in the cation southeast of Kardamos in Fig. 1) showing faults separating tilted blocks of low- 280 N. Bonev et al. / Tectonophysics 488 (2010) 256–281 5) The Late Jurassic thrusting event and subsequent Cretaceous thrusting event collectively caused overthickening of the Rhodope crust, thus creating instability within the Alpine orogenic wedge. These crustal thickening events largely influenced widespread Tertiary crustal extension in the Rhodope Massif. In the case of the Kulidzhik nappe and the Pelevun extensional allochthon were affected by brittle extension in the hanging wall of detachment system. Acknowledgments Thisworkwas supported byNSF (Bulgaria) contract no. VU-NZ02/06 and SNSF (Switzerland) SCOPES grant no. IB7320-111046/1. References Banks, C.J., 1997. Basins and thrust belts of theBalkancoast of theBlackSea. In: Robinson, A.G. (Ed.), Regional and Petroleum Geology of the Black Sea and Surrounding Region, 68. American Association of Petroleum Geologists Memoir, pp. 115–128. Banks, C.J., Robinson, A.G., 1997. Mesozoic strike-slip back-arc basins of theWestern Black Sea region. In: Robinson, A.G. (Ed.), Regional and Petroleum Geology of the Black Sea and Surrounding Region, 68. American Association of Petroleum Geologists Memoir, pp. 53–65. Bauer, C., Rubatto, D., Krenn, K., Proyer, A., Hoinkes, G., 2007. A zircon study from the Rhodope metamorphic complex, N-Greece: time record of a multistage evolution. Lithos 99, 207–228. Biggazzi, G., Del Moro, A., Innocenti, F., Kyriakopoulos, K., Manetti, P., Papadopoulos, P., Norelliti, P., Magganas, A., 1989. The magmatic intrusive complex of Petrota, west Thrace: age and geodynamic significance. Geologica Rhodopica 1, 290–297. Bonev, N., 2005. Foraminifers from the exotic Late Permian limestone pebbles in the Mesozoic low-grade sequence of the eastern Rhodope, Bulgaria: paleogeographic and paleotectonic consequences. Neues Jahrbuch für Geologie und Paläontologie Monatschefte 7, 385–403. Bonev, N., 2006a. Structural and geochemical studies on amphibolite and greenschist- facies rocks in theKulidjik river valley, eastern Rhodope, Bulgaria: preliminary results. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 239 (2), 161–181. Bonev, N., 2006b. Cenozoic tectonic evolution of the eastern Rhodopemassif (Bulgaria): basement structure and kinematics of syn- to postcollisional extensional deforma- tion. In: Dilek, Y., Pavlides, S. (Eds.), Postcollisional Tectonics andMagmatism in the Mediterranean Region and Asia, 409. Geological Society of America Special Paper, pp. 211–235. Bonev, N., Beccaletto, L., 2007. From syn- to post-orogenic Tertiary extension in the north Aegean region: constraints on the kinematics in the eastern Rhodope– Thrace, Bulgaria–Greece and the Biga Peninsula, NW Turkey. In: Taymaz, T., Yilmaz, Y., Dilek, Y. (Eds.), The Geodynamics of the Aegean and Anatolia, 291. Geological Society of London Special Publication, pp. 113–142. Bonev, N., Stampfli, G., 2008. Petrology, geochemistry and geodynamic implications of Jurassic island arc magmatism as revealed by mafic volcanic rocks in the Mesozoic low-grade sequence, eastern Rhodope, Bulgaria. Lithos 100, 210–233. Bonev, N., Stampfli, G., 2009. Gabbro, plagiogranite and associated dykes in the supra- subduction zone Evros ophiolites, NE Greece. Geological Magazine 146, 72–91. Bonev, N., Burg, J.-P., Ivanov, Z., 2006a. Mesozoic–Tertiary structural evolution of an extensional gneiss dome— the Kesebir–Kardamos dome, eastern Rhodope (Bulgaria– Greece). International Journal of Earth Sciences 95, 318–340. Bonev, N.,Marchev, P., Singer, B., 2006b. 40Ar/39Ar geochronology constraints on theMiddle Tertiary basement extensional exhumation, and its relation to ore-forming and magmaticprocesses in theEasternRhodope(Bulgaria). GeodinamicaActa19, 267–282. Bonev, N., Peychev, K., Nizamova, D., 2006c.MOR- vs. SSZ-origin ofmetamafic rocks in the upper high-grade basement unit of the eastern Rhodope: geochemical diversity and tectonic significance. Proceedings of Annual Conference of the Bulgarian Geological Society, “Geosciences 2006”, pp. 181–184. Bonev, N., Márton, I., Moritz, R., Spikings, R., Marchev, P., 2009. Tectonic, Magmatic and Hydrothermal Processes associated with Tertiary Crustal Extension in the Basement Domes of Southeastern RhodopeMassif, Bulgaria. Geophysical Research Abstracts 11, paper EGU2009-5304, 2pp. Bonev, N., Moritz, R., Márton, I., Chiaradia, M., Marchev, P., 2010. Geochemistry, tectonics, and crustal evolution of basement rocks in the Eastern Rhodope Massif, Bulgaria. International Geology Review 52, 269–297. Bonev, N.G., Stampfli, G.M., 2003. New structural and petrologic data on Mesozoic schists in the Rhodope (Bulgaria): geodynamic implications. Comptes Rendus Geoscience 335, 691–699. Boyanov, I., 1969. Notes on the Kulidjik nappe. Bulletin of the Geological Institute of Bulgarian Academy of Sciences, series Geotectonics 18, 159–165. Boyanov, I., Lipman, P., 1973. On the Lower Cretaceous age of the low-crystalline metamorphic complex in the East Rhodopes. Comptes Rendus de l'Academie Bulgare des Sciences 26, 1225–1226. Boyanov, I., Bodurov, K., 1979. Triassic conodonts in carbonate breccia within the low- grade metamorphic rocks of the East Rhodopes. Geologica Balcanica 9, 97–104. Boyanov, I., Russeva, M., 1989. Lithostratigraphy and tectonic position of the Mesozoic rocks from the East Rhodopes. Geologica Rhodopica 1, 22–33. Boyanov, I., Goranov, A., 2001. Late Alpine (Palaeogene) superimposed depressions in parts of Southeast Bulgaria. Geologica Balcanica 31, 3–36. Boyanov, I., Mavrudchev, B., Vaptsarov, D., 1963. On the structural–formational features in part of East Rhodopes. Bulletin of the Geological Institute of Bulgarian Academy of Sciences, Series Geotectonics, Stratigraphy and Lithology 12, 125–186. Boyanov, I., Kozhoukharova, E., Kozhoukharov, D., 1969. Relations between the Pre- Cambrian high-crystalline base and the diabase-phyllitoid formation in the Eastern Rhodope. Review of the Bulgarian Geological Society 30, 113–122. Boyanov, I., Russeva, K.M., Dimitrova, E., 1982. First find of Upper Cretaceous foraminifers in East Rhodopes. Geologica Balcanica 12, 20. Boyanov, I., Russeva, M., Toprakcieva, V., Dimitrova, E., 1990. Lithostratigraphy of the Mesozoic rocks from the Eastern Rhodopes. Geologica Balcanica 20, 3–28. Burchfiel, B.C., Nakov, R., Tzankov, T., 2003. Evidence from the Mesta half-graben, SW Bulgaria, for the Late Eocene beginning of Aegean extension in the central Balkan Peninsula. Tectonophysics 375, 61–76. Burg, J.-P., Ricou, L.-E., Ivanov, Z., Godfriaux, I., Dimov, D., Klain, L., 1996. Syn- metamorphic nappe complex in the Rhodope Massif. Structure and kinematics. Terra Nova 8, 6–15. Burg, J.-P., Ivanov, Z., Ricou, L.-E., Dimor, D., Klain, L., 1990. Implications of shear-sense criteria for the tectonic evolution of the Central Rhodope Massif, southern Bulgaria. Geology 18, 451–454. Carrigan, C., Mukasa, S., Haydoutov, I., Kolcheva, K., 2003. Ion microprobe U–Pb zircon ages of pre-Alpine rocks in the Balkan, Sredna Gora and Rhodope terranes of Bulgaria: constraints on Neoproterozoic and Variscan evolution. Journal of Czech Geological Society 48, 32–33. Chatalov, G.A., 1988. Recent developments in the geology of the Strandzha zone in Bulgaria. Bulletin of the Technical University Istanbul 41, 433–465. Dalrymple, G.B., Lamphere, M.A., 1971. 40Ar/39Ar technique of K–Ar dating: a comparison with the conventional technique. Earth and Planetary Science Letters 12, 300–308. Del Moro, A., Innocenti, F., Kyriakopoulos, C., Manetti, P., Papadopoulos, P., 1988. Tertiary granitoids from Thrace (northern Greece): Sr isotopic and petrochemical data. Neues Jahrbuch für Mineralogie Abhandlungen 159, 113–135. Dimadis, E., Nikolov, T., 1997. An ammonite find in theMakri unit (Berriasian, southeast Rhodopes, northeast Greece). Comptes Rendus de l'Academie Bulgare des Sciences 50, 71–74. Dimadis, L., Papadopoulos, P., Goranov, A., Encheva, M., 1996. First biostratigraphic evidence for the presence of Triassic at Melia (Western Thrace, Greece). Geologica Balcanica 26, 37–40. Dimitriadis, S., Asvesta, A., 1993. Sedimentation and magmatism related to the Triassic rifting and later events in the Vardar–Axios zone. Bulletin of the Geological Society of Greece 28, 149–168. Dinter, D.A., 1998. Late Cenozoic extension of theAlpine collisional orogen, northeastern Greece: origin of the north Aegean basin. Geological Society of America Bulletin 110, 1208–1230. Dinter, D.A., Macfarlane, A.M., Hames, W., Isachsen, C., Bowring, S., Royden, L., 1995. U–Pb and 40Ar/39Ar geochronology of Symvolon granodiorite: implications for the thermal and structural evolution of the Rhodope metamorphic core complex, northeastern Greece. Tectonics 14, 886–908. Dixon, J.E., Dimitriadis, S., 1984. Metamorphosed ophiolitic rocks from the serbo- macedoniean Massif, near lake Volvi, North-east Greece. In: Dixon, J.E., Robertson, A.H.F. (Eds.), The Geological Evolution of the Eastern Mediterranean, 17. Geological Society of London Special Publication, pp. 603–618. Ferrière, J., Stais, A., 1995. Nouvelle interprétation de la suture téthysienne vardarienne d'après l'analyse des séries de Péonias (Vardar oriental, Hellénides internes). Bulletin of the Geological Society France 166, 327–339. Georgiev, G., Dabovski, C., Stanisheva-Vasileva, G., 2001. East Srednogorie–Balkan rift zone. In: Ziegler, P.A., Cavazza, W., Robertson, A.H.F., Crasquin-Soleau, S. (Eds.), Peri-Tethys Memoir 6: Peri-Tethyan Rift/Wrench Basins and Passive Margins, 186. Mémoires du Muséum National d'Histoire Naturelle Paris, pp. 259–293. Gočev, P., 1979. The position of Strandja in the Alpine structure of the Balkan Peninsula. Review of the Bulgarian Geological Society 40, 27–76. Harkovska, A., Yanev, Y., Marchev, P., 1989. General features of the Paleogene orogenic magmatism in Bulgaria. Geologica Balcanica 19, 37–72. Haydoutov, I., Kolcheva, K., Daieva, L., Savov, I., Carrigan, Ch., 2004. Island arc origin of the variegated formations from the east Rhodope, Bulgaria — implications for the evolution of the Rhodope massif. Ofioliti 29, 145–157. Innocenti, F., Kolios, N., Manetti, P., Mazzuoli, R., Peccerillo, A., Rita, F., Villari, L., 1984. Evolution and geodynamic significance of Tertiaryorogenic volcanism innortheastern Greece. Bulletin of Vulcanology 47, 25–37. Ivanov, R., 1961. Stratigraphy and structure of the crystalline in the Eastern Rhodope. Works on the Geology of Bulgaria, Series Geochemistry and Ore Deposits, Bulgarian Academy of Sciences 2, 69–119. Ivanov, R., Kopp, K.O., 1969. Das Alttertiär Thrakiens und der Ostrhodope. Geologica et Paleontologica 3, 123–153. Jacobshagen, V., Durr, S., Kockel, F., Kopp, K.O., Kowalczyk, G., Berckhamer, H., Buttner, D., 1978. Structure and geodynamic evolution of the Aegean region. In: Cloos, H., Roeder, D., Schmidt, K. (Eds.), Alps, Apennines, Hellenides, Stuttgart, pp. 537–564. Jaranov, D., 1960. Tectonics of Bulgaria. Technica, Sofia. 283 pp. Karfakis, I., Doutsos, T., 1995. Late orogenic evolution of the Circum-Rhodope belt, Greece. Neues Jahrbuch für Geologie und Paläontologie Monathschefte H5, 305–319. Kauffmann, G., Kockel, F., Mollat, H., 1976. Notes on the stratigraphic and paleogeographic position of the Svoula formation in the Innermost Zone of the Hellenides (Northern Greece). Bulletin de la Societé Géologique de France 18, 225–230. Kilias, A., Falalakis, G., Mountrakis, D., 1999. Cretaceous–Tertiary structures and kinematics of the Serbomacedonian metamorphic rocks and their relation to the exhumation of the Hellenic hinterland (Macedonia, Greece). International Journal of Earth Sciences 88, 513–531. Kockel, F., Mollat, H., Walther, H.W., 1977. Erlauterungen zur geologicschen karte der Chalkidiki und angrenzender Gebiete 1/100.000 (Nord Griechenland): Bundesan- periphery of the Central Rhodopean Dome, Bulgaria. Geochimica and Cosmochimica Acta 66, A573. Papadopoulos, P., Arvanitidis, N., Zanas, I., 1989. Some preliminary geological aspects on the Makri unit (phyllite series), Peri-Rhodope zone. Geologica Rhodopica 1, 34–42. Papanikolau, D., 1997. The tectonostratigraphic terranes of the Hellenides. Annales 281N. Bonev et al. / Tectonophysics 488 (2010) 256–281 Koglin, N., Reischmann, T., Kostopoulos, D., Matukov, D., Sergeev, S., 2007. Zircon SHRIMP ages and the origin of ophiolitic rocks from the NE Aegean region, Greece. Geophysical Research Abstracts 9, paper 06848. Kopp, K.-O., 1969. Geologie Thrakiens VI: Der Çoban Dağ (Frenk Bunar) westlich von Alexandroupolis. Geotektonische Forschung 31, 97–116. Koukouvelas, I., Doutsos, T., 1990. Tectonic stages along a traverse crosscutting the Rhodopian Zone (Greece). Geologische Rundschau 79, 753–776. Koukouvelas, I.K., Aydin, A., 2002. Fault structure and related basins of the North Aegean Sea and its surroundings. Tectonics 21, 10-1–10-17. Kozhoukharov, D., Kozhoukharova, E., Papanikolaou, D., 1988. Precambrian in the Rhodope massif. In: Zoubek, V., Cogné, J., Kozhoukharov, D., Kräutner, H.G. (Eds.), Precambrian in Younger Fold Belts — European Variscides, the Carpathians and Balkans. John Willey and Sons, Chichester, pp. 723–778. Krohe, A., Mposkos, E., 2002. Multiple generations of extensional detachments in the Rhodope Mountains (northern Greece): evidence of episodic exhumation of high- pressure rocks. In: Blundell, D.J., Neubauer, F., von Quadt, A. (Eds.), The Timing and Location of Major Ore Deposits in an Evolving Orogen, 204. Geological Society of London Special Publication, pp. 151–178. Liati, A., 2005. Identification of repeated Alpine (ultra) high-pressuremetamorphic events byU–PbSHRIMPgeochronologyandREE geochemistry of zircon: theRhodopezoneof Northern Greece. Contributions to Mineralogy and Petrology 150, 608–630. Liati, A., Gebauer, D., 2001. Palaeozoic as well as Mesozoic sedimentation and polymetamorphism in Central Rhodope (N. Greece) as inferred from U–Pb SHRIMP- dating of detrital zircons. European Union of Geosciences XI, paper LS03, p.315. Liati, A., Gebauer, D., Wysoczanski, R., 2002. U–Pb SHRIMP-dating of zircon domains from UHP garnet-rich mafic rocks and late pegmatoids in the Rhodope zone, (N Greece). Chemical Geology 184, 281–299. Lilov, P., Yanev, Y., Marchev, P., 1987. K–Ar dating of the Eastern Rhodopes Paleogene magmatism. Geologica Balcanica 17, 49–58. Lips, A.L.W., White, S.H., Wijbrans, J.R., 2000. Middle–Late Alpine thermotectonic evolution of the southern Rhodope Massif, Greece. Geodinamica Acta 13, 281–292. Magganas, A., Sideris, C., Kokkinakis, A., 1991.Marginal basin-islandarc originofmetabasic rocks of the Circum-Rhodope belt, Thrace, Greece. Mineralogy and Petrology 44, 235–252. Marchev, P., Singer, B., 2002. 40Ar/39Ar geochronology of magmatism and hydrothermal activity of theMadjarovo base-preciousmetal ore district, easternRhodopes, Bulgaria. In: Blundell, D.J., Neubauer, F., von Quadt, A. (Eds.), The Timing and Location of Major Ore Deposits in an Evolving Orogen, 204. Geological Society of London Special Publication, pp. 137–150. Marchev, P., Singer, B., Andrew, C., Hasson, S., Moritz, R., Bonev, M., 2003. Characteristics and preliminary 40Ar/39Ar and 87Sr/86Sr data of theUpper Eocene sedimentary-hosted low-sulfidation gold deposits Ada tepe and Rosino, SE Bulgaria: possible relationwith core complex formation. In: Eliopoulos, D.G. (Ed.), Mineral Exploration and Sustainable Development, Millpress, Rotterdam, 2, pp, pp. 1193–1196. Marchev, P., von Quadt, A., Peytcheva, I., Ovtcharova, M., 2006. The age and origin of the Chuchuliga and Rozino granites, Eastern Rhodopes. Proceedings of Annual Conference of the Bulgaria Geological Society “Geosciences 2006”, pp. 213–216. Márton, I., Moritz, R., Spikings, R., 2009. Application of low-temperature thermo- chronology to hydrothermal ore deposits: formation, preservation and exhumation of epithermal gold systems from the Eastern Rhodopes. Bulgaria. Tectonophysics. doi:10.1016/j.tecto.2009.10.020. McDougall, I., Harrison, T.M., 1999. Geochronology and Thermochronology by the 40Ar/39Ar Method. Oxford University Press, Oxford, Second Edition. 269 pp. Mposkos, E., Liati, A., 1993. Metamorphic evolution of metapelites in the high-pressure terrane of the Rhodope zone, northern Greece. Canadian Mineralogist 31, 401–424. Mposkos, E.D., Kostopoulos, D.K., 2001. Daimond, former coesite and supersilicic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established. Earth and Planetary Science Letters 192, 497–506. Mukasa, S., Haydoutov, I., Carrigan, C., Kolcheva, K., 2003. Thermobarometry and 40Ar/39Ar ages of eclogitic and gneissic rocks in the Sredna Gora and Rhodope terranes of Bulgaria. Journal of Czech Geological Society 48, 94–95. Mullen, E.D., 1983. MnO/TiO2/P2O: a minor element discrimination for basaltic rocks of oceanic environments and its implications for petrogenesis. Earth and Planetary Sciences Letters 62, 53–62. Natal'in, B., Sunal, G., Toraman, E., 2005. The Strandja arc: anatomy of collision after long- lived arc-parallel tectonic transport. In: Sklyarov, E.V. (Ed.), Structural and Tectonic Correlation across the Central Asia Orogenic Collage: North-Eastern Segment. Guidebook and Abstract Volume of the SiberianWorkshop IGCP-480, Irkutsk, Russia, pp. 240–245. Okay, A.I., Satir, M., Tüysüz, O., Akyüz, S., Chen, F., 2001. The tectonics of the Strandja Massif: late-Variscan and mid-Mesozoic deformation and metamorphism in the northern Aegean. International Journal of Earth Sciences 90, 217–233. Ovtcharova, M., Quadt, A.V., Heinrich, C.A., Frank, M., Kaiser-Rohmeier, M., Peycheva, I., Cherneva, Z., 2003. Triggering of hydrothermal ore mineralization in the Central Rhodopean Core Complex (Bulgaria)—insight from isotope and geochronological studies on tertiary magmatism and migmatisation. In: Eliopoulos, D.G. (Ed.), Mineral Exploration and Sustainable Development, 1. Millpress, Rotterdam, pp. 367–370. Ovtcharova, M., Quadt, A.V., Cherneva, Z., Sarov, S., Heinrich, C.A., Peytcheva, I., 2004. U–Pb dating of zircon andmonazite from granitoids andmigmatites in the core and eastern géologiques des Pays Hellenique 37, 495–514. Pearce, J.A., Harris, N.B.W., Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic setting of granitic rocks. Journal of Petrology 25, 956–983. Peytcheva, I., Quadt, A.V., 1995. U–Pb zircondating ofmetagranites fromByala Reka region in the east Rhodopes, Bulgaria. Geological Society of Greece Special Publication 4, 637–642. Peytcheva, I., Kostitsin, Y., Salnikova, E., von Quadt, A., Kamenov, B., Klain, L., 1999. Alpine evolution of themagmatism in theWest-Rhodopes: Rb–Sr and U–Pb isotope data. Journal of Conference Abstracts 4, 470. von Peytcheva, I., Quadt, A., Ovtcharova, M., Handler, R., Neubauer, F., Salnikova, E., Kostitsin, Y., Sarov, S., Kolcheva, K., 2004. Metagranitoids from the eastern part of the Central Rhodopean Dome (Bulgaria): U–Pb, Rb–Sr and 40Ar/39Ar timing of emplacement and exhumation and isotope-geochemical features. Mineralogy and Petrology 82, 1–31. Ricou, L.-E., Burg, J.-P., Godfriaux, I., Ivanov, Z., 1998. The Rhodope and Vardar: the meta- morphic and the olistostromicpairedbelts related to theCretaceous subductionunder Europe. Geodinamica Acta 11, 285–309. Soldatos, T., Christofides, G., 1986. Rb–Sr geochronology and origin of the Elatia Pluton, Central Rhodope, North Greece. Geologica Balcanica 16, 15–23. Spear, F.S., 1993. Metamorphic Phase Equilibria and Pressure–Temperature–Time Paths. Mineralogical Society of America Monograph, Book Crafters, Inc., Chelsea, Michigan, USA, 789pp. Spray, J.G., Bébien, J., Rex, D.C., Roddick, J.C., 1984. Age constraints on the igneous and metamorphic evolution of theHellenic–Dinaric ophiolites. In: Dixon, J.E., Robertson, A.H.F. (Eds.), The Geological Evolution of the Eastern Mediterranean, 17. Geological Society of London Special Publication, pp. 619–627. Stampfli, G.M., Borel, G.D., 2002. A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons. Earth and Planetary Science Letters 196, 17–33. Stampfli, G.M., Borel, G., 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. (Eds.), TheTRANSMEDAtlas: theMediterranean Region from Crust to Mantle. Springer Verlag, Berlin, pp. 53–90. Stampfli, G.M., Kozur, H.W., 2006. Europe from the Variscan to the Alpine cycles. In: Gee, D.G.W., Stephenson, R.A. (Eds.), European Lithosphere Dynamics, 32. Geological Society of London Memoirs, pp. 57–82. Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in the Ocean Basins, 42. Geological Society of London Special Publication, pp. 313–346. Tikhomirova, L.B.,Boyanov, I., Zagorchev, I., 1988. Early Jurassic radiolarians fromtheEastern Rhodopes: a revision of the age of Dolno-Lukovo Formation. Geologica Balcanica 18, 58. Trifonova, E., Boyanov, I., 1986. Late Permian foraminifers from rock fragments in the Mesozoic phyllitoid formation of the East Rhodopes, Bulgaria. Geologica Balcanica 16, 25–30. Trikkalinos, J.K., 1955. Über das Alter der vortartiären Schichten des Gebietes von Alexandropoulis-Didymotichon,Westthrazien.Annales géologiquedesPaysHellenique 6, 81–82. Tsikouras, B., Pe-Piper, G., Hatzipanagiotou, K., 1990. A new date for an ophiolite on the northeastern margin of the Vardar Zone, Samothraki, Greece. Neues Jahrbuch für Mineralogie Monatschefte 11, 521–527. Tsikouras, B., Hatzipanagiotou, K., 1998. Petrogenetic evolution of an ophiolite fragment in an ensialic marginal basin, northern Aegean (Samothraki Island, Greece). European Journal of Mineralogy 10, 551–567. Tullis, J., Yund, R.A., 1985. Dynamic recrystallization of feldspar: amechanism for ductile shear zone formation. Geology 13, 238–241. Tullis, J., Yund, R.A., 1987. Transition from cataclastic flow to dislocation creep of feldspar: mechanisms and microstructures. Geology 15, 606–609. Turpaud, P., 2006. Characterization of igneous terranes by zircon dating: implications for UHP relicts occurrences and suture identification in the Central Rhodope, Northern Greece: PhD thesis, Johannes Gutenberg University, Mainz, 107pp. Von Braun, E., 1968. Die mesozoischen Hüllgesteine der SE-Rhodopen in Westthrazien (Griechenland). Geologisches Jahrbuch 85, 565–584. Von Braun, E., 1993. The Rhodope question viewed from eastern Greece. Zeitschrift der deutschen geologischen Gesselschaft 144, 406–418. VonQuadt, A.,Moritz, R., Peytcheva, I., Heinrich, C., 2005.Geochronology and geodynamics of late Cretaceousmagmatism and Cu–Aumineralization in the Panagyurishte region of the Apuseni–Banat–Timok–Srednogorie belt, Bulgaria. Ore Geology Reviews 27, 95–126. Wood,D.A., 1980. The application of a Th–Hf–Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of theBritish Tertiary volcanic province. Earth and Planetary Science Letters 50, 11–30. Zagorchev, I.S., 1998. Pre-Priabonian Paleogene formations in southwest Bulgaria and northern Greece: stratigraphy and tectonic implications. Geological Magazine 135, 101–119. stalt für Geowissenschaften und Rohstoffe, Hanover, 119pp. The effect of early Alpine thrusting in late-stage extensional tectonics: Evidence from the Kul..... Introduction Geological framework Tectonostratigraphy of the Kulidzhik nappe Geochemistry of the units in the Kulidzhik nappe Mineral chemistry Whole-rock geochemistry Structural record in the Kulidzhik nappe Structural record in the Pelevun extensional allochthon 40Ar/39Ar geochronology Discussion and interpretation Tectono-metamorphic evolution and implications Regional implications Extensional structures in the Rhodope Massif Significance for Tertiary extensional evolution of the Rhodope Massif Conclusions Acknowledgments References