A Review of the Plate Convergence History of the East Anatolia-Transcaucasus Region During the Variscan: Insights from the Georg

Journal of Geodynamics 96 (2016) 131–145

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A review of the plate convergence history of the East Anatolia-Transcaucasus region during the Variscan: Insights from the Georgian basement and its connection to the Eastern Pontides

Y. Rolland a,∗, M. Hässig a, D. Bosch b, M.J.M. Meijers c, M. Sosson a, O. Bruguier b, Sh. Adamia d, N. Sadradze e a Université de Nice Sophia-Antipolis, CNRS IRD, Observatoire de la Côte d’Azur, Géoazur UMR 7329, bat. 1, 250 rue Albert Einstein, Sophia-Antipolis, 06560 Valbonne, France b Géosciences Montpellier, UMR 5243—CC 60, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier cedex 5, France c Dept. of Earth Sciences, University of Minnesota, 291 Shepherd Labs, 100 Union Street SE, Minneapolis, MN 55455, USA d Institute of Geophysics, 1 M. Alexidze Str., 0193 Tbilisi, Georgia e Geological Institute, 1/9 M. Alexidze Str., 0193 Tbilisi, Georgia article info abstract

Article history: This article summarizes the geodynamic evolution of the Variscan to Mesozoic Tethyan subduction his- Received 5 February 2015 tory, based on a review of geochronological data from Eastern Anatolia and the Lesser Caucasus, and new Received in revised form 22 February 2016 isotopic ages for the Georgian crystalline basements. The geological history of the basements of Georgia Accepted 8 March 2016 (Transcaucasus) and NE Turkey (eastern Pontides) appears to be similar and provides evidence for a Available online 11 March 2016 continuously active continental margin above a north-dipping subduction since at least the Lower Juras- sic. New La-ICPMS U-Pb ages from the Georgian basement provide further evidence for the derivation Keywords: of the Transcaucasus and its western continuation (the eastern Pontides) from Gondwana. A migma- Subduction ± Magmatism tized granodiorite provides preserved magmatic zircon cores with an age of 474 3 Ma, while the age of ± U-Pb dating migmatization is constrained by its 343 2 Ma metamorphic rims. Metamorphism is synchronous with Variscan widespread I-type granites that were emplaced at 335 ± 8 Ma in the neighbouring Dzirula massif, and Tethys closure in the eastern Pontides. These U-Pb ages are in close agreement with recently obtained Ar/Ar ages from Rheic closure biotites and muscovites from metamorphic schists and U-Pb ages ranging from 340 to 330 Ma in the Georgian basement. The narrow range of ages suggests that the Variscan LP-HT metamorphic event in the eastern Pontides and Georgia was of short duration and likely related to mantle-derived intrusives. Furthermore, we suggest that (1) rifting of the Pontides-Transcaucasus block (PTB) from Gondwana at 450–350 Ma could have been driven by roll-back of the south-dipping Rheic slab, (2) that the main metamorphic and coeval magmatic events are related to the accretion of the PTB to the Eurasian margin at c. 350 Ma, while the source of magmatism is ascribed to slab detachment of the south-dipping slab at 340 Ma and that (3) three subduction zones may have been contemporaneously active in the Tethyan domain during the Jurassic: (i) the Lesser Caucasus South Armenian Block (SAB) shares a similar Gond- wana afﬁnity, but bears younger ages for its MP-MT metamorphic evolution and calc-alkaline magmatism bracketed from 160 to 123 Ma; (ii) north-dipping subduction below the PTB from c. 210 Ma to 150 Ma; (iii) northward intra-oceanic subduction bracketed from 180 to 90 Ma between the SAB and the PTB. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction

The crystalline basements of the NE Anatolia − Caucasus region are largely unaffected by Africa-Arabia-Anatolia collision. Their rel- ative pristine condition allows us to study the tectonic history of ∗ Corresponding author. these Gondwana-derived tectonic blocks that were dislocated in E-mail address: [email protected] (Y. Rolland). the Early Paleozoic, until their accretion to the Eurasian margin http://dx.doi.org/10.1016/j.jog.2016.03.003 0264-3707/© 2016 Elsevier Ltd. All rights reserved. 132 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 from the Late Paleozoic to Cenozoic. The main questions posed in 900–1000 Ma and 500–650 Ma, which suggests a NE Africa this paper concern (1) what is the origin of the metamorphic base- Gondwana origin (Ustaömer et al., 2012). In Georgia, the ments currently exposed in the Transcaucasus, Pontides and Lesser protolith of crystalline basements is formed by calc-alkaline Caucasus (Georgia, NE Turkey and Armenia), (2) what are the lateral plutons, which ages are bracketed between 750 and 400 Ma, correlations between these three distinct geographic and political with large uncertainties (Sm-Nd, Rb-Sr and K-Ar on whole- zones, and (3) what was their position with respect to the Gond- rock, Shengelia and Okrostsvaridze, 1998; Okrostsvaridze et al., wanan and Eurasian margins in Late Paleozoic to Mid-Mesozoic 2002; Zakariadze et al., 2007) and ∼540 Ma by U-Pb on zir- times? These questions still arise due to lack of accurate geochrono- con (Mayringer et al., 2011). In the SAB, protolith ages of logical data, in Georgia especially, of reliable paleomagnetic data ∼610 ± 36 Ma were obtained using the Rb-Sr isochron method and as a result of the scarcity of crystalline basements outcrops, (Baghdasarian and Ghukasian, 1983), but these are considered which are covered by thick sequences of Cenozoic volcanic rocks. unreliable. In addition, there is no review at hand that compiles the ages that (2) Variscan (345–310 Ma) high Temperature (HT) magmatism and were recently obtained in the study region. metamorphism occurred in the NE Turkish Pontides (Topuz The Caucasus and Transcaucasus basements (Fig. 1A) have et al., 2007; Dokuz, 2011) as well as in Trans-Caucasian South undergone numerous thermal events, resulting from their for- Georgia (Mayringer et al., 2011; Shengelia et al., 2012). mation in the Neoproterozoic, their dislocation from Gondwana (3) In the Lesser Caucasus and Pontides, the Transcaucasus and (Fig. 1B) and subsequent accretion to the Eurasian margins in Paleo- Sakarya basements are cross-cut by widespread magmatic zoic to Mesozoic times. The highly deformed Istanbul˙ and the suites related to northward subduction of the Tethys ocean Sakarya Zone in the Turkish Pontides display varying lithologies in the Jurassic (200–150 Ma) and in the late Early Cretaceous of different ages. The occurrence of numerous superposed tectonic (120–110 Ma, Adamia, 1984; Yılmaz et al., 2000; Ustaömer events from Proterozoic to Cenozoic times therefore renders the et al., 2012; Shengelia et al., 2012; Meijers et al., 2010c; Okay interpretation of geochronological data difficult to address, result- et al., 2014). In contrast, the Lesser Caucasus basement of ing in various spatio-temporal models of their accretion to Eurasia the SAB is largely overprinted by 160–123 Ma medium Pres- (Okay and Tüysüz, 1999; Göncüoglu˘ et al., 2000; Ustaömer et al., sure − medium Temperature (MP-MT) metamorphism and 2011, 2012, 2013; Aysal et al., 2012; Moritz et al., 2015). subduction-related magmatism (U-Pb on zircon and Ar–Ar on Here, we present a synthesis of recently acquired, well- biotite and muscovite, Hässig et al., 2015a,b). The age of this constrained, geochronological data obtained from NE Anatolian, MP-MT metamorphic and magmatic event thus partly overlaps Armenian and Georgian metamorphic and magmatic basement with Jurassic magmatism in the Pontides and Transcauca- rocks, supplemented by new U-Pb ages from the Georgian Tran- sus. Contemporaneously, the Sevan-Akera ophiolite formed scaucasus basements. The combination of results leads us to in a back-arc environment between the SAB and Transcau- propose correlations of basements between the aforementioned casus (Galoyan et al., 2009; Rolland et al., 2009b). Ophiolite geographic areas, as well as lateral correlations to W Turkey and formation occurred in the Middle to Late Jurassic, which is the Balkans. Furthermore, we interpret the geochronological data based on 178–155 Ma Ar/Ar ages (on amphibole) for gabbros with respect to main basement structures and other magmatic and within the ophiolite (Galoyan et al., 2009; Rolland et al., 2010; metamorphic evidences in terms of subduction polarity and oro- Hässig et al., 2013a) and biostratigraphic ages from radiolaria genic events since the Early Paleozoic. (Danelian et al., 2007, 2008, 2010, 2012, 2014; Asatryan et al., 2010, 2012). The Middle to Late Jurassic ages are similar to those obtained by Ç elik et al. (2011) and Topuz et al. (2013a,b) 2. General overview of Eastern Anatolia and Transcaucasus along the western continuation of the Sevan-Akera suture (i.e. crystalline basements the Izmir-Ankara-Erzincan suture), which suggests that the ophiolites that are exposed along the Sevan-Akera and Izmir- The study area covers the Eurasian crystalline basements of the Ankara-Erzincan suture form part of the same ophiolitic belt. Pontides, Lesser Caucasus and Transcaucasus domains in Eastern We suggest that the Ar/Ar ages from the gabbro reflect the ini- Turkey, South Georgia and Armenia (Fig. 1A; Fig. 2). Further south, tial oceanic crust emplacement age, rather than the obduction the Eurasian basement is separated by the Sevan-Akera suture age, which would explain why they are similar to oceanic crust zone (Adamia et al., 1981, 1990a,b, 2011a,b; Dercourt et al., 1986; ages such as zircon U-Pb ages (see Topuz et al., 2013a,b). The Zonenshain and Le Pichon, 1987; Galoyan et al., 2009; Rolland foliation in the gabbros is most likely related to intra-oceanic et al., 2009a,b, 2010; Sosson et al., 2010) from the Daralagöz or ductile deformation (‘flaser-gabbros’, Mevel et al., 1978), and the South Armenian Block (SAB) (Zonenshain and Le Pichon, 1987). might be mistaken for a true metamorphic foliation resulting We will only refer to the term of SAB. The SAB is a Gondwana- from obduction. Blue amphibole-bearing greenschists, garnet derived terrane that was accreted to the Eurasian margin during the amphibolite and eclogites from Refaiye (Izmir-Ankara-Erzincan Late Mesozoic to Early Cenozoic (Rolland et al., 2012; Hässig et al., suture) have been dated with U-Pb on rutile and Ar–Ar on 2015a,b, 2016a,b,c; Meijers et al., 2015a). The origin of the Eurasian phengite by Topuz et al. (2013a) at 172–176 Ma. The age of basement of Georgia is still unclear and may be derived from Lau- the blueschists and eclogites, as well as their tectonic posi- russia, as well as from Gondwana (e.g., Kröner and Romer, 2013; tion, suggest a similar intra-oceanic setting for their formation and references therein). Recently published data provide evidence between the Taurides and the Pontides, as for the gabbros from for the following succession of events in the crystalline basements the Sevan-Akera ophiolite. (see for syntheses: Sosson et al., 2010; Ustaömer and Robertson, (4) The intra-oceanic ophiolite that formed from ∼178 to 155 Ma 2010; Ustaömer et al., 2012; Mayringer et al., 2011; Adamia et al., between the SAB and the Transcaucasus was obducted onto the 2011a,b; Topuz et al., 2007; Dokuz et al., 2011; Rolland et al., 2012; SAB at c. 90 Ma (Sosson et al., 2010; Hässig et al., 2013a,b; Hässig Moritz et al., 2015): et al., 2015b; Hässig et al., 2016a,b,c, this issue a-b; Topuz et al., 2013b). Obduction preceded the accretion of the SAB–Taurides- (1) Neoproterozoic to Lower Cambrian ages for the magmatic Anatolides to the Pontides Transcaucasus block (PTB) in the Late calc-alkaline protoliths of the Pontides, the SAB and the Tran- Mesozoic to Early Cenozoic (Adamia et al., 2011a,b; Rolland scaucasus in South Georgia. In NE Turkey, detrital zircon et al., 2012; Ustaömer et al., 2012). ages from two meta-sedimentary units yield populations of Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 133

Fig. 1. A, General geological map of the Anatolia − Caucasus region, from Sosson et al. (2010), modified. Insert location of Fig. 2 is shown. B, The location of Pontides-Caucasus in the context of Variscan orogen, after Kröner and Romer (2013), modified. The reconstruction of Pangea is shown at 250 Ma. The orogeny encompasses an area of c. 2500 by 2000 km. Paleo-equator after Roscher et al. (2011). Active plate margin of the Paleotethys is after Stampfli and Borel (2002) and Rolland et al. (2011). Red circles: positions of the proposed rotation axes describing the opening of the Paleotethys (PT) and Neotethys Ocean (NT) at 380 Ma and 300 Ma, respectively. Abbreviations: NAC: North American Craton; EEC: East European Craton; WAC: West African Craton; A: Avalonia; FMC: French Massif Central; IZ: Istanbul Zone; CAR: Carpathians; Cau: Caucasus; GAL: Galicia; MBM: Moldanubian − Bohemian Massif; : Pontides Transcaucasus; T-A-SAB: Taurides-Anatolides-South Armenian Block. TAR: Tarim (cf, Loury et al., 2016). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 134 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

Fig. 2. Sketch geological map of Lesser Caucasus Eastern Pontides − Armenia and Georgian Transcaucasus, with a synthesis of corresponding geochronological data. Outline geological map of the eastern Pontides in Turkey showing the main tectonic units of the region. Turkish part is modiﬁed from the 1:500 000 geological map of Turkey (MTA, 2002); the Georgian-Armenian zone of the Caucasus is after Sosson et al. (2010). Locations of studied samples are also shown. Details on bibliographic sources of geochronological data is displayed in Fig. 7.

3. In situ U-Pb zircon dating of the South Georgian Basemen nitsky et al., 1990), Sm-Nd ‘error-chron’ rock population ages of 607 ± 78 Ma (Zakariadze et al., 1998, 2007), and Rb-Sr whole- 3.1. Geological context and sampling rock ages of 686 ± 54 Ma and 532 ± 63 Ma (Okrostsvaridze et al., 2002). Basement formation ages at 556 ± 14 Ma and 543 ± 16 Ma for The geological context of the samples from the Georgian Dzirula have been obtained from zoned zircons within a granodi- basement that were analysed and described in this paper is orite using in-situ U-Pb dating (Mayringer et al., 2011). 221 ± 2Ma fully developed in a companion paper, which we refer to for a to 335 ± 11 Ma ages from a gabbro most likely reflect a meta- more detailed description (Rolland et al., 2011). We also refer to morphic event (Shengelia et al., 2012). Consequently, the Sm-Nd Zakariadze et al. (2007), Adamia (2004) and Adamia et al. (2011a,b) age range seems overestimated. In order to evaluate the age of for the definition of the discussed units. The geological setting of emplacement of the older magmatic protoliths, complementing the Transcaucasus Massif is briefly summarized below. the Mayringer et al. (2011) U-Pb age by other dating techniques The Transcaucasus Massif is situated between the Greater and/or new ages is desirable. Further, the Gray Granite Complex Caucasus in the North and the Lesser Caucasus to the South is cross-cut by the Middle-Late Carboniferous Microcline Granite (Figs. 1 and 2) and comprises a number of crystalline massifs. Complex (Zakariadze et al., 2007), which was dated at 340 Ma by The crystalline massifs (or salients, Figs. 2 and 3A and B) are in-situ U-Pb dating on zircon (Mayringer et al., 2011). The high- Dzirula, Khrami and Loki. All three massifs are overlain by a K ‘I type’ granites can be correlated to similar magmatic rocks non-metamorphic volcano-sedimentary cover of Upper Paleozoic from the Pontides (Dokuz, 2011), which suggests that the whole to Cenozoic age (Adamia, 1984; Adamia and Shavishvili, 1979; region underwent a phase of mixed mantle-crustal magmatism. Adamia et al., 1981, 1987, 1990a,b, 2010, 2011a,b; Zakariadze The Georgian basement of Dzirula exhibits low pressure-high tem- et al., 1998, 2007; Gamkrelidze and Shengelia, 1999; Gamkrelidze perature (LP-HT) regional metamorphism dated at 340–330 Ma et al., 1981, 1999). Unconformities can be found within the Middle in gneisses and micaschists, using the U-Pb on zircon method Carboniferous − lower Upper Jurassic and the Paleocene–Eocene (Mayringer et al., 2011) and at 290 ± 2 Ma by carrying out Ar/Ar sequences, which correspond to major phases of arc-type volcan- dating on biotite (Rolland et al., 2011). The latter Ar/Ar dates are ism (Adamia et al., 1981). The possible westward continuation of likely cooling ages that were recorded after the thermal peak. The the Transcaucasian Massif stretches to the Sakarya Zone in NW Carboniferous metamorphic episode in Dzirula can likely be cor- Turkey (e.g., Okay and Sahintürk, 1997; Topuz et al., 2004a,b, 2007, related to a similar event that affected the Pontides at ∼330 Ma 2010), while its eastward continuation into Iran is still a mat- (Ar/Ar ages on biotite and muscovite; Topuz et al., 2004a, 2007). ter of debate (Kalvoda and Bábek, 2010). The Neoproterozoic − The metamorphic event in the Transcaucasus and Pontides was Early Paleozoic Gray Granite Complex (Zakariadze et al., 1998)or short-lived, of less than 20 Ma, and was followed by numerous Tonalite-Granodiorite complex (Mayringer et al., 2011) makes up similarly short-lived thermal events (and corresponding resettings most of the Dzirula massif. Previously published age constraints of isotopic systems) that occurred from Early Permian to Early for Tonalite-Granodiorite complex vary widely and yield large Cretaceous times. Resetting of the K-Ar chronometer occurred in uncertainties, and include U-Pb zircon ages of 491 ± 93 Ma (Bar- the Permian (305–275 Ma), the Late Triassic (209 ± 10 Ma), the Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 135

Fig. 3. Geological maps of studied Khrami and Dzirula Georgian crystalline basements, with location of samples dated by U-Pb on zircon. A, Khrami after Mayringer et al. (2011), modiﬁed in Rolland et al. (2011); B, Dzirula after Adamia (2004). 136 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

Fig. 4. Field photographs and corresponding microphotographs of lithologies from rocks of the Georgian Transcaucasus basement dated by U-Pb in this study. (A–B) Khrami Salient migmatite. Metatexite texture of gneiss sample Geo 07–16 is displayed on picture B. The picture shows a pristine magmatic texture comprised of plagioclase (Pl) and biotite (Bt) + quartz (Qtz), that is reacting into symplectite coronas (Symp) to form muscovite (Ms) + Qtz. (C–D) Dzirula Salient granite. Granite sample Geo 07–21 from Dzirula massif is shown on picture D. The magmatic texture is well preserved, with unaltered plagioclase, K-feldspar (Kfs) and biotite, and slightly undulosed quartz.

Lower-Middle Jurassic (183–166 Ma) and the Middle Cretaceous 3.3. Results (115 ± 3Ma;Rolland et al., 2011). 3.3.1. Khrami migmatite Sample Geo07-16 was collected from the Khrami crystalline 3.2. Analytical techniques massif, and was taken from migmatites reworking a grano-dioritic protolith (Figs. 3 A and 4 A ). The migmatite’s most refractory part, Two samples were processed by crushing, magnetic separa- formed by melting of a pristine granodiorite, mainly constitutes tion and heavy liquid separation following conventional techniques centimeter-scale plagioclases and biotites, surrounded by sym- (Bosch et al., 1996). Zircon grains from the nonmagnetic fractions plectites of quartz-albite and muscovite neocrysts (Fig. 4B). Zircon were hand-picked and mounted in epoxy resin along with chips grains have a euhedral to subhedral shape, and show core to rim of the G91500 zircon standard (Wiedenbeck et al., 1995). Details zoning (see Fig. 5). Plotted on the concordia diagram (Fig. 6a), they of the analytical procedure are described in Neves et al. (2006) and yield a bimodal distribution of concordant analyses. All analysed Dhuime et al. (2007). The polished epoxy plugs were analysed using zircon cores yield concordant results. The obtained data there- a Lambda Physik CompEx 102 excimer laser (AETE Plateform, Uni- fore represent a well-preserved protolith age with a 238U-206Pb versity of Montpellier, France) generating 15 ns duration pulses of weighted mean age of 474 ± 3 Ma (MSWD = 0.4; n = 7; Table 1). radiation at a wavelength of 193 nm. Laser spot sizes were of 50 ␮m We interpret the core zircon age as a representative magmatic for the largest grains and of 26 ␮m for most others. Samples were emplacement age of the granodiorite. The rim analyses cluster on a ablated under helium in a 15 cm3, circular-shaped cell, using an concordant age of 343 ± 2 Ma (MSWD = 0.9; n = 4). Three data points energy density of 15 Jcm−2 at a frequency of 4 Hz. For analyses, the plot in between these two age groups and likely reﬂect an inter- laser was coupled to an Element XR sector ﬁeld ICP-MS. Analyte sig- mediate component between the rim and core ages. We did not nal was acquired during 45 s and the blank was measured before include the three intermediate data points in the weighted means each sample during 15 s. All isotopes (202Hg, 204Pb + Hg, 206Pb, of the rim, not the core. 207Pb, 208Pb, 238U and 232Th) were measured in pulse counting The age derived from the rim of the zircons is interpreted as mode using 15 points per peak and a 20% mass window result- the age of metamorphism as it falls within error of published Ar/Ar ing in three measured points for each mass station. Unknowns ages from Variscan metamorphic and related magmatic rocks that were bracketed by measurements of the G91500 standard, which were dated in the Georgian basement units (see following Section were used to calculate a mass bias factor (Pb/Pb ratio) and the 5.2). We therefore attribute the rim-derived age of 343 ± 2Mato inter-element fractionation (U-Pb ratio). The calculated bias fac- the main stage of migmatization related to LP-HT metamorphism. tors and their associated errors were then added in quadrature to The 182 Ma Ar/Ar age (on amphibole) obtained on a neighbouring individual errors measured on each unknown following the pro- sample by Rolland et al. (2011) is attributed to a later lower- cedure described in Horstwood et al. (2003). The decay constants temperature event, which did not reset the U-Pb system in the and present day 238U-235U value given by Steiger and Jager (1977) Variscan migmatites. were used and ages were calculated using the Isoplot/Ex program of Ludwig (2002). Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 137 (1s) ± (1s) 207Pb/206Pb ± 206Pb/238U (1s) Rho Apparent Ages (Ma) Err R8% Err 7/6% Conc. (%) ± (1s) 206Pb/238U ± (1s) 207Pb/235U ± Sample Pb* (ppm) Th (ppm) U (ppm) Th/U 208 Pb/206GEO721 Pb 207Pb/206Pb #1#2#3 24#4 13#5 31#6 15#7 154 21#8 82 21#9 166 17 424#10 97 49#11 165 238 32 548#12 211 0.36 19#13 0.121 127 21 283 0.35 384#14 312 0.30 24 0.110 395#15 0.091 38 43 0.34 93 323#16 0.43 28 0.108 152 948 0.0532#17 0.136 0.53 27 189#18 0.156 0.39 17 648 0.0534 303 370 0.0534#19 0.114 0.33 50 363 136 0.0006#20 0.101 41 423 0.0533 0.06 124 0.0532#21 0.25 14 782 0.0006 0.019 150 0.42 0.0532 0.0005#22 0.075 0.3943 17 529 0.144 409 0.45 0.0535#23 19 512 0.0005 0.3892 0.156 287 0.39 0.0533 0.0006#24 0.4017 28 314 0.113 102 0.26 0.0068 0.0005#25 19 913 0.0534 0.0537 0.3992 0.074 109 0.24 0.0534 0.0005 0.3893 0.0062 31 753 0.0532 0.071GEO716 156 0.48 0.0051 0.0528 0.0006 0.3687 27 258 0.0532 0.0545 0.146#1 166 0.45 0.3841 0.0007 0.0051 313 0.0007 0.0528 0.129#2 108 0.38 0.0052 0.77 0.0544 0.0007 0.3800 355 0.0532 0.0530 0.0005 0.113 337.5#3 0.0006 233 0.40 0.0042 0.0004 73 533 0.72 0.0530 0.0503 0.0007 0.3971 0.121#4 205 0.35 0.0045 0.64 0.3855 331.9 63 360 0.0532 0.0521 0.0004 0.105 0.4042#5 342.2 0.0005 0.44 0.0045 0.0003 60 555 0.72 0.0529 0.0517 0.0006 0.135 0.3974#6 0.31 4.4 0.50 341.3 0.0002 0.0065 54 479 0.0531 0.0006 0.092 0.3948#7 333.1 0.30 83 0.0055 0.43 0.0539 0.0003 3.7 91 0.0058 337.4 0.0528 0.0524 0.0006 0.093 0.3957#8 316.3 0.42 315 2.7 0.53 0.0551 0.0003 104 0.0068 0.0529 0.0006 0.123 0.3951 327.4#9 0.43 68 346.5 0.47 0.0541 3.1 29 0.0047 347.6 0.0530 0.0005 0.140 0.3778#10 325.0 0.0006 291 2.1 1371 0.0543 0.0004 65 0.0068 0.66 821 0.0531 0.0007 0.3867#11 742 0.0006 1.5 339.6 24.8 0.47 0.0539 338.4 189 65 0.0052 338.8 0.70 0.0532 0.0008 0.3899#12 329.3 0.06 0.0006 2.0 50 1186 1.3 0.0541 345.5 24.6 0.0053 336.4 693 0.66 0.0531 0.0005 0.3947#13 0.019 211 0.38 0.0005 1.8 58 21.9 0.0516 339.9 0.0044 348.7 1132 1.1 0.74 0.0531 0.0005 0.3885#14 0.114 404 0.06 0.0007 47 2069 0.8 0.0530 340.7 3.5 20.1 1.1 0.0051 341.7 0.78 0.0005 0.3777#15 0.018 86 0.42 0.0004 2.2 39 25.8 0.0532 338.5 256 0.66 0.0061 3.4 361 0.9 0.52 0.0005 0.3842 0.130 1.1 0.0004 42 347.1 0.09 23.2 0.7 0.0542 339.8 0.193 713 1.0 0.0069 3.7 344.1 829 0.56 0.0007 0.0537 0.3861 0.0003 0.040 86 22.3 100.0 339.3 0.5 0.0532 324.1 309 0.0050 2.9 0.43 0.0565 0.3941 0.59 0.0004 0.9 1286 23.5 338.5 721 0.6 0.0517 333.2 158 1.1 95.8 0.0048 4.4 0.64 0.0537 0.3926 0.167 0.49 0.0005 98.5 318.4 674 0.6 0.0525 334.4 165 27.5 1.0 0.0055 2.3 0.55 0.0562 0.0005 0.148 0.07 0.0005 28.2 338.9 566 0.0526 0.0564 340.1 255 0.35 1.0 100.5 0.0047 2.5 23.1 1.1 0.56 0.0005 0.0531 0.019 0.0004 98.3 326.7 514 0.7 0.0539 334.3 0.132 1.06 1.0 0.0058 1.6 29.2 0.65 1.0 0.0005 0.4259 0.0005 94.0 335.2 872 0.0536 324.9 0.299 0.55 2.7 18.0 0.69 0.0563 1.1 0.0005 0.5931 1.2 0.0006 93.9 323.4 1703 0.0005 330.0 0.177 0.31 1.3 2.8 24.3 0.76 0.0565 0.9 0.0013 0.4014 0.0004 1.0 95.1 333.6 330.5 0.097 0.19 3.2 0.0061 25.4 0.61 0.0534 1.3 0.5870 0.0004 0.15 1.3 322.2 0.0559 0.0575 338.3 0.060 0.5696 97.5 2.7 0.0068 26.1 0.54 0.7 0.0007 0.074 0.4013 0.8 95.7 326.0 0.0558 0.0761 336.6 2.8 0.0044 23.5 101.8 0.8 0.0005 1.1 328.8 0.0558 0.0542 3.5 0.0069 22.4 100.4 0.5 0.0005 0.5975 0.0007 1.1 0.0064 331.0 0.0560 0.0758 0.0006 2.4 29.1 107.0 0.0101 0.80 0.8 0.0732 0.5946 0.0006 1.2 338.5 0.0530 0.0006 0.0548 360.2 2.6 32.9 99.9 0.63 0.8 0.0531 0.4043 0.0003 1.0 331.2 0.0005 0.5341 472.7 0.0091 22.5 104.0 0.59 1.0 0.0005 1.0 333.6 0.0769 0.0005 0.5887 340.1 0.0005 0.0091 20.5 96.7 0.60 0.9 1.3 0.0002 0.61 0.0763 0.0005 0.5885 470.7 0.0049 4.0 20.9 103.0 0.9 0.17 0.0016 455.4 1.5 0.0064 0.0550 0.5912 343.7 3.3 21.5 100.2 1.1 0.0692 0.0006 1.0 0.0073 360.3 0.3980 2.1 28.0 105.6 0.52 0.7 0.0766 0.4008 0.0010 0.9 0.0085 473.3 477.7 3.2 102.6 0.84 0.8 0.0765 0.0004 0.9 0.0088 3.0 360.3 474.2 0.0003 98.8 1.5 0.60 0.0766 1.0 0.0106 460.1 0.35 344.9 0.0005 99.7 19.3 0.0128 469.6 0.0545 431.6 1.2 0.49 335.1 0.0548 0.0008 3.6 97.6 19.7 1.2 475.6 0.75 0.0009 5.9 102.1 19.8 0.7 475.4 465.6 0.81 0.0014 2.5 100.9 20.8 0.6 475.6 0.0004 0.9 1.8 471.6 19.6 0.94 55.1 0.7 0.30 341.9 0.9 2.8 343.7 0.7 343.8 450.1 0.4 0.9 5.0 28.6 100.0 442.7 0.9 5.5 18.3 0.9 99.9 443.2 0.8 8.3 2.5 21.9 94.4 2.4 452.4 1.3 24.9 102.3 328.8 0.7 1.3 23.9 97.0 331.8 0.4 102.6 0.8 21.1 0.6 1.0 19.4 1.1 1.1 102.6 20.2 1.2 1.1 100.6 67.7 2.5 1.0 100.3 0.7 95.9 0.9 107.4 0.9 3.2 107.3 105.1 104.0 103.6 Table 1 Summary of U-Pb results from Georgian Crystalline basement samples. 138 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

Fig. 5. Zircon EBSD images of Khrami and Dzirula crystalline basement rocks. Geo 07–16 migmatite gneiss shows a bimodal age distribution ascribed to metamorphic overgrowth of ∼340 Ma zircon over a pristine zoned magmatic core of ∼475 Ma age. Geo 07–21 granite displays a normal magmatic zoning with ages spread between 337 and 348 Ma.

3.3.2. Dzirula granite the vergence of tectonic motions and the polarity of subduction Sample Geo07-21 is an undeformed I-type biotite-bearing zones for each complex. Recent studies that were carried out in granite from the Microcline Granite Complex that intruded the several countries, including (Eastern) Turkey, Georgia and Armenia, Georgian crystalline basement (the Grey Granite Complex) dur- improved our understanding of the tectonic history of this complex ing the Variscan event (Figs. 3B, 4B). Zircon grains have euhedral region. In the following discussion we propose a reconstruction of shapes, and no core-rim zoning has been observed (see Fig. 5). the evolution of the Eurasian margin based on a review of ages from Reported on the concordia diagram (Fig. 6), the plot yields an uni- the literature. modal distribution of concordant analyses. Central parts of the analysed grains are concordant to sub-concordant and thus reflect 4.1. Origin of Lesser and Trans-Caucasus basements and their the crystallization age of the granite with an upper intercept age of pre-Variscan evolution 335 ± 8 Ma (MSWD = 0.1; n = 25; Table 1). The rim analyses cluster towards slightly younger ages (315–325 Ma), which may reflect the A geochronological compilation of the Eastern Pontides − Tran- duration of magmatic cooling in a HT-LP metamorphic climax (see scaucasus − SAB basements is shown in Fig. 7. There is general following Section 4.2). consensus on the Panafrican affinity of the pre-Variscan portion of ± We attribute the age of 335 8 Ma to the main stage of magma- the Transcaucasus basements of the Pontides (Okay and Nikishin, tism that occurred during the Variscan orogenic event. A younger 2015 and references therein). The oldest inherited ages that are pre- ± biotite Ar/Ar age of 289.7 1.5 Ma was obtained from the same served in the Transcaucasian basements suggest that they form all sample (Rolland et al., 2011). The difference between both ages parts of an E-W striking continental block, comprising the Pontides reflects most likely the time taken for the sample to cool down ◦ from South Georgia to the central and western parts of N-Turkey below the 300 C closure temperature of biotite. (Sakarya, Istanbul Zone), as well as the Balkans in the Paleozoic (e.g., Stampfli and Borel, 2002; Okay et al., 2008; Bozkurt et al., 4. Discussion 2008; Robertson et al., 1996, 2004; Robertson, 2012). The Tran- scaucasus basement units record Late Neoproterozoic-Cambrian In order to propose lateral correlations between the different and Variscan tectono-thermal events (Adamia et al., 2011a; Somin complexes that constitute the North-East Anatolian and Transcau- 2011; Zakariadze et al., 2007). The obtained age ranges, and corre- casian basements, we must resolve the timing of orogenic events, sponding errors from the Sm-Nd, Rb-Sr and K-Ar isotopic systems Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 139

PTB Block SAB Events in Eastern Fig. 8 Pontides South Georgia Armenia Ar/Ar (6)

50 Sole garnet Ar/Ar (12) amphibolites Collision greenschists Obduction 100 Ar/Ar (4) 150 Ar/Ar (6) 5 Ar/Ar & U/Pb (8) Ar/Ar (7)

200 Ar/Ar (4) (9,10,11,12) U/Pb (5) 250 4 Punctual thermal events Punctual (S of Pontides) subduction below BPT Arc-related magmatism Blueschists intra-oceanic subduction Ar/Ar (4)

? Arc magmatism &N-dipping 300 SAB magmatism& Metamorphism

Back-arc intraoceanic 3 Izmir-AnkaraErzincan Suture blueschists S-dipping subduction below SAB spreading N of SAB 350 Time (Ma) Time Ar/Ar (4) Ar/Ar (3) Accretion & I-type granites

I-type granites 2 Metamorphism 400 Metamorphism Slab detachment N-dipping intra-oceanic subduction Nof SAB U/Pb ((2), this study)

450 n o i t m c 1 s i u t d

500 a b U/Pb (this study) u m s g

a g y n i m 550 n

e p c r g p i U/Pb (5) ArcA magmatism o d r - O S-dippingS subduction

U/Pb (2) n n Rb/Sr (13) Basement inherited ages y 650 a Basement inherited ages a c n c i i e r r f f g Sm/Nd (1) a a o r n n a O a Orogeny Basement inherited ages Panafrican Orogeny Panafrican P 750 Panafrican P

Fig. 7. Compilation of geochronological results for the Eastern Pontides- Transcaucasus-SAB basements, and proposed interpretative geological events. Reference numbers refer to: (1) Zakariadze et al. (1998); (2) Mayringer et al. (2011) and Shengelia et al. (2012); (3) Topuz et al. (2007); (4) Rolland et al. (2011); (5) Fig. 6. Tera–Wasserburg Concordia diagrams for zircon grains from rocks of the Ustaömer et al. (2012) and Okay et al. (2014); (6) Rolland et al. (2009a); (7) Hässig Georgian Transcaucasus basement. (A) Khrami salient Geo 07–16 migmatite. (B) et al. (2015a,b); (8) Topuz et al. (2013a,b); (9) Galoyan et al. (2009); (10) Rolland et al. Dzirula Geo 07–21 granite. Error crosses are ±1␴ and ages are given at the 95% (2010); (11) Hässig et al. (2013a); (12) Hässig et al. (in review); (13) Baghdasarian conﬁdence limits. All ages have been anchored to a common Pb composition at and Ghukasian (1983). PTB: Pontides-Transcaucasus block. 540 Ma given by the model of Stacey and Kramers (1975). patterns, a similar setting and correlation has previously been should not be taken into account. After their formation, the dated proposed by Ustaömer et al. (2012), which gives weight to the rocks underwent a Variscan thermal event and resided in the hang- hypothesis of the PTB to be a single and coherent continental block. ing wall of a subduction zone from the Jurassic to Cretaceous. The similar timing and type of magmatism of the tectonic event Additionally, the rocks of the Tonalite Granodiorite complex are that was recorded along the northern margin of Gondwana and in often extensively hydrated. The signiﬁcance of the published ages the Transcaucasus-Pontides basements suggests that the Pontides- is therefore questionable. Therefore, only the U-Pb ages should be Transcaucasus constituted an elongated continental tectonic block regarded as true ‘formation ages’ for these lithologies. Here we that rifted away from the NE margin of Gondwana between 450 show these rocks to be in agreement with the lower bound of and 350 Ma (Fig. 8; e.g. Adamia et al., 2011a,b). the 750–400 Ma age range, in our sample Geo07-16 (474 ± 3 Ma), in the same way as Mayringer et al. (2011) U-Pb (zircon) ages of 4.2. Variscan evolution 556 ± 14 Ma and 543 ± 16 Ma ages. These younger (Paleozoic and not Proterozoic) ages suggest that the Early Paleozoic magmatic Carboniferous magmatic and metamorphic rocks of Variscan phase started at 540 Ma or earlier, and lasted until at least 474 Ma. age are well exposed in the Sakarya basement of central and east- The 540–474 Ma age range for arc magmatism and juvenile crust ern Pontides (Okay and S¸ ahinturk,¨ 1997; Topuz et al., 2004a,b, formation matches very well the history of NE African Gondwana 2007; Topuz and Altherr, 2004; Dokuz, 2011; Dokuz et al., 2011; (e.g., Okay et al., 2008; Nance, 2010; Kröner and Romer, 2013; Ustaömer et al., 2012; Fig. 7). The Variscan HT metamorphics and and references therein). It is well-known that during this period, peridotites are cross-cut by granitoids (Topuz et al., 2007, 2009; the northern margin of Gondwana underwent a major magmatic Dokuz et al., 2011). Based on Ar/Ar dating of high-T metamorphic arc event above a southward-dipping subduction zone (Fig. 1B; rocks, peak metamorphism is thought to have occurred at ∼ 330 Ma, Kröner and Romer, 2013). On the basis of U-Pb ages obtained from with exhumation following at ∼310 Ma (Topuz et al., 2004a,b; detrital zircons from NE Pontides paragneisses and their compari- Topuz and Altherr, 2004). In Georgia, U-Pb dating on zircon from son with other Gondwana-derived U-Pb ages from detrital zircon granodiorites from the Dzirula metamorphic basement gave ages 140 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

South North Pontides Northern margin of Gondwana (Georgia)

Eurasia Gondwana Lower Ordovician arc + 1 + + + + + + + + + + + + + + c. 474 Ma + + + + + + + + + + + + + + + + + + + + + + inherited zircon poplations 0.5-0.65 and 0.9-1.1 Ga S-dipping subduction Juvenile crust formed at c. 474 Ma

Pontides (PTB block) Northern margin of Gondwana (S Georgia) Back-arc extension Gondwana Rheic Ocean + + + + + + + + + + + + + + + + + + + + + + + + + 2 + + + + + + + + + ++ + + + + + + 450-350 Ma S-dipping subduction

Drift PTB collision - block accretion Gondwana Future break-up Paleotethys Eurasian margin (N Georgia) + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 3 + + + + + + + + + + + + + + + + c. 350-280 Ma Mantellic melts, Regional HT Slab detachment metamorphism asthenosphere

break-up at 210 Ma Eurasian margin Gondwana Paleotethys PTB (N Georgia) + + + + + + + + + + + + + + + + + + + + + + 4 + + + + + + + + + + + + + + + + + + + + + + + + + + + c. 280-200 Ma Future break-up

N-dipping subduction

Back-arcBack-arce extensionxtension Back-arcBack-arce extensionxtension Late CCretaceous,retaceous, opening of black sea Taurides-anatolides-SABTaurides-anatolides-SAB Intra-oceanicIntra-oceanic Back-arcBack-arc eextensionxtension EurasianEurasian marginmargin GGondwanaondwana LLowerower JuJurassicrassic arcarc SouthSouth NeotethysNeotethys PTBPTB ((NN Georgia)Georgia) PaleotethysPaleotethys 175-155175-155 MMaa LowerLower JuJurassicrassic aarcrc + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + NorthNorth NeotethysNeotethys + + + + + + + + + + + + CCAA mamagmatism,gmatism, + + 5 ReRegionalgionalM MP-HTP-HT metamorphism, c. 200-90 MaMa 16160-1200-120 MMaa N-dippingN-dipping subdsubductionuction

Fig. 8. Proposed geodynamic evolution of the Eastern Pontides-Transcaucasus-SAB domain from the Early Paleozoic to the Late Mesozoic times. PTB: Pontides-Transcaucasus block. that cluster around 330 Ma (Mayringer et al., 2011). The 330 Ma Rheic Ocean was continuous from the Early Ordovician to the Early age in the Dzirula basement correlates with our age of 335 ± 8Ma Carboniferous and not only confined to the Devonian. In contrast (Geo07-21), pointing to a short-lived episode of magmatism. to Dokuz’s model a southward subduction seems more appropri- The cause of the Variscan metamorphic and magmatic events in ate as should have been below the northern margin of Gondwana; the PTB continental domain is under debate. Most authors argue there is no apparent reason for a polarity shift of subduction. Roll- that the metamorphic and magmatic events occurred along the back of this south-dipping slab could have led to northward drift southern margin of Eurasia, i.e. as a result of ongoing Paleotethys of the PTB block with respect to Gondwana (Fig. 8). Following this subduction below Eurasia (Adamia et al., 1995; Adamia et al., 1977, model, the 330–340 Ma Variscan event recorded in the PTB would 1981, 2011a,b; Robertson and Dixon, 1984; Robertson et al., 2004; correspond to its final accretion to the Eurasian margin at c. 350 Dercourt et al., 1986, 1993; Ricou, 1994; Stampfli et al., 2001; Ma, as Barrovian metamorphism generally develops some 10 Ma Stampfli and Borel, 2002; Stampfli and Kozur, 2004; Nikishin et al., after initial collision time (e.g., Guillot et al., 1999). This Variscan 2011; Rolland et al., 2011). Many authors suggest that southward suture could actually lie in the front of the Great Caucasus, where subduction of the Rheic slab below Gondwana led to rifting along HP rocks (including eclogites) mark a Carboniferous suture zone its margin, and subsequent opening of the Paleotethys ocean in the (Perchuk and Philippot, 1997; Philippot et al., 2001; Somin, 1991) Early Devonian (S¸ engör and Yılmaz, 1981; S¸ engör, 1984; S¸ engör The significance of the accretion of the PTB block to the Eurasian et al., 1984; Göncüoglu˘ et al., 2000; Xypolias et al., 2006; Topuz margin at ca. 350 Ma as (i) arc-related event, (ii) significant colli- et al., 2009; Romano et al., 2004; Zulauf et al., 2007; von Raumer sional event, or (iii) short-lived accretionary episode, is a matter of and Stampfli, 2008; Nance, 2010 Robertson and Ustaömer, 2009a,b, debate. 2012; Robertson, 2012). In contrast, Dokuz et al. (2011) propose (i) Development of HT metamorphism within an arc system that Early Devonian rifting resulted from northward subduction of was proposed by Rolland et al. (2011). This idea is mainly based the Rheic Ocean below Laurussia, which consequently led to the for- on the numerous thermal events occurring in the following Perm- mation of the Paleotethys ocean. In Fig. 8 a simplified model from ian to Cretaceous periods, as revealed by Ar/Ar data. The nature Dokuz et al. (2011) is shown, where southward subduction of the of LP-HT metamorphism and combined magmatism would fit an Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 141

Andean-type model (Rolland et al., 2011). However, the time range (1) After the Carboniferous, the crystalline basement of PTB region of metamorphism from combined U-Pb on zircon and Ar/Ar on mica underwent episodic short-lived thermal/magmatic events from ages appears to be extremely short, which is in disagreement with a the Early Permian to the Late Lower Cretaceous (Rolland long-lived HT context that would be implied by such Andean-type et al., 2011). There are Permo-Triassic accretionary complexes model. More data would however be necessary for this discussion. to the north of the IAE suture, suggesting that there was In contrast, (ii) a significant collisional event is suggested in the also northward subduction below the Eurasian margin dur- Pontides (Topuz et al., 2007) and in the Pelagonian zone further ing the Permo-Triassic time (e.g., Okay and Göncüoglu,˘ 2004; west (Kotopouli et al., 2000; Pe-Piper and Piper, 2002). This event Topuz et al., 2004a, 2014). However the transition from the broadly coincides with the long-lived Hercynian/Variscan colli- Permo-Triassic accretionary complexes to Early Jurassic supra- sional episode in Western Europe (350–300 Ma; e.g., Corsini and subduction-zone ophiolites and accretionary complexes is Rolland, 2009). However, the Pontides-Transcaucasus underwent unconstrained. So it still unclear if there has been a continuous a more short-lived thermal episode than the Western European subduction below the Eurasian margin during the whole Perm- Variscan belt. In the Pontides, the ages obtained by both U/Pb and ian to Jurassic times (as suggested by Rolland et al., 2011) or not. Ar/Ar datings of metamorphism (∼340 ± 5 Ma) and magmatism Numerous granitic intrusions were emplaced in the Transcau- (330–290 Ma) are very close (Nzegge et al., 2006; Topuz et al., 2010; casus during the Lower-Middle Jurassic (Adamia et al., 2010 Dokuz, 2011; Kaygusuz et al., 2012; Ustaömer et al., 2012, 2013). and references therein) and can be correlated to thermal reset This is even more the case in Georgia, where there is a seemingly of amphibole and micas in the basement at 183–166 Ma. Sim- perfect coincidence of both ages (Mayringer et al., 2011; this study: ilar Lower Jurassic ages were obtained by Dokuz et al. (2010) Fig. 7). The magmatism is unlikely the consequence of thermal and Ustaömer et al. (2012) in the Eastern Pontides for cross- relaxation of the crust following collision. The short time interval cutting subduction-derived granitic bodies using both U-Pb of metamorphism and magmatism does not fit the models for the on zircon and Ar/Ar on mica methods, ranging from 190 to production of syn-collisional granites in for example the Himalayan 150 Ma, confirmed by other datings in central Pontides (Okay (e.g., Guillot et al., 1999) or Hercynian West and Central European et al., 2014) and Crimea (Meijers et al., 2010c). Two models (e.g., Ledru et al., 2001) chains. The models suggest that a period have been proposed for this magmatic episode, invoking exten- of at least 20 Ma is required for the production of syn-collisional sion in an intra/back-arc position over either south-dipping granites. In contrast to such collisional settings, as pointed out by subduction on northern side of PTB (Dokuz et al., 2010) or north- Mayringer et al. (2011), the within-error age coincidence of mag- dipping subduction on south side of PTB (e.g., Okay et al., 2014; matism and metamorphism suggests the former as being the cause Robertson and Ustaömer, 2009a,b; Ustaömer et al., 2012, and of the latter, in Georgia at least. (iii) An alternative hypothesis for references therein; Fig. 8). The south-dipping subduction model this event would be a short-lived subduction-accretion episode contradicts the fact that paleomagnetic data show that Pon- (e.g., Robertson and Ustaömer, 2009a,b; Fig. 8). Following Dokuz tides lie at ∼41◦ N in the Lower Jurassic (Channell et al., 1996), (2011), the contemporaneous production of I-type granites and HT and should already form part of the Eurasian margin at that metamorphism at c. 340–330 Ma could be related to oceanic slab time. North-dipping flat slab subduction is suggested by con- detachment closely following the accretion at c. 350 Ma. Further, comitant Lower Jurassic arc volcanism in Crimea (Meijers et al., the LP-HT metamorphic conditions of metamorphism featured by 2010c). Further, opening of the Black Sea as a back-arc basin is andalusite-bearing schists in the Georgian basement contradicts suggested to have occurred as a result of slab roll-back above the idea that the PTB block might have been significantly thick- a north-dipping subduction in the Cretaceous (Adamia et al., ened by this event. In addition, the long time span between the 1977; Gamkrelidze, 1986; Zonenshain and Le Pichon, 1986; U-Pb zircon age (335 ± 8 Ma) and the Ar/Ar biotite age (290 ± 2Ma) Nikishin et al., 2011). Opening of the Black Sea might have been on the same granite sample Geo07-21 suggests that the amount of localized along the former Variscan suture north of the PTB, exhumation between the two thermal events −or the two steps of therefore reactivating the suture zone (Fig. 8). cooling- (700 ◦C and 300 ◦C) was relatively moderate. This is there- (2) North-dipping intra-oceanic subduction between the SAB and fore in contradiction with significant exhumation of the PTB block the PTB blocks (Fig. 8) is evidenced along the Izmir-Ankara- at ∼310 Ma, as is the case in Western Europe (Oliot et al., 2015). Erzincan suture (Galoyan et al., 2009; Rolland et al., 2010; However, the orogeny may not have been cylindrical, symmetri- Topuz et al., 2013a,b, 2014), i.e. in the (ophiolitic) suture zone cal, along the PTB belt and there may have been a gradient in the between the Taurides and Pontides. Further, the Sevan-Akera amount of collision from East to West, especially towards Western ophiolite was obducted onto the SAB in Coniacian to Santo- Europe (Matte, 2001). In the Balkans, new La-ICPMS on zircon dates nian times, as evidenced by nannofossil ages in the frontal part show significant magmatism represented by syntectonic granites of the obduction (Sosson et al., 2010). This top-to-the-south at 301.9 ± 1.1 Ma and post-tectonic/post-metamorphic granites at obduction implies de facto a northward-dipping intra-oceanic 293.5 ± 1.7 Ma (Machev et al., 2015), which argues for a similar subduction zone. tectonic setting as in the Georgian region. (3) In contrast to the PTB, paleomagnetic data from the SAB show that it was positioned on the northern edge the African margin in the Lower Jurassic (Bazhenov et al., 1996; Torsvik et al., 2012), about ∼3500 km to the south of its present position in the 4.3. Permian to Late Cretaceous evolution Lower Jurassic. The earliest age for the initiation of northward drift of the SAB is therefore Lower Jurassic. In the SAB crys- From the Permian to the Late Cretaceous, numerous thermal talline basement, the metamorphism is marked by Barrovian events occurred in the Lesser and Transcaucasus ranges. Timing, (MP-MT) conditions with top-to-the-north ductile motions at position and polarity of subduction zones in this tectonic domain c. 160 Ma, followed by HT-LP metamorphism, partial melting at remain a subject of debate in recent literature. For a complete 140–150 Ma and cooling at 123 Ma (Hässig et al., 2015a). Both review of the literature in this period of time, we refer to Hässig the kinematics and position of magmatic intrusions suggest a et al. (2013b, 2015b; this issue-a; and references therein), Robert- south-dipping subduction below SAB during this period of time. son et al. (2012, 2013; and references therein). The main facts are (4) The final closure of the Northern Neotethys branch and accre- kept in the frame of this paper, for a matter of comparison between tion of the SAB (and correlated Tauride-Anatolide Block) to NE Anatolia and Georgia the Eurasian margin is witnessed by Cretaceous-Eocene fly- 142 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

sch basin (Rustamov, 2005; Sosson et al., 2010; Rolland et al., Adamia, Sh., Lordkipanidze, M., Kvantaliani, I., Kutelia, Z., 1990a. Geology of the 2011). Further, paleomagnetic data show that at ∼84 Ma, the Caucasus: A Guide of Field Meeting of the Working Group 5.1. Paleogeography and Tectonics of the Paleozoic Fold Areas and Their Platform Frame. paleolatitude of SAB is less than 1000 km from the margin Geotraverse 10 (Caucasus) Tbilisi, September 1–6, 1990. Al. Djanelidze of PTB (Meijers et al., 2015a). Laterally, Late Cretaceous or Geological Institute of the Academy of Sciences of GSSR, 39 p. Paleocene oroclinal bending occurs in the Central Pontides as Adamia, Sh., Lordkipanidze, M., Beridze, M., Kotetishvili, E., 1990. Paleogeography − of the Ukrainian Carpathians, the Crimea, and the Caucasus. Evolution of the a result of Pontides Central Anatolian Crystalline Complex northern margin of Tethys. International Geological Correlation Program: collision (Meijers et al., 2010b, 2015b; Lefebvre et al., 2013). Project 198, Memoires de la Société Géologique de France, Paris, Nouvelle Série Simultaneous trigger of subduction on the Southern side of the no. 154 (III), Ocassional Publications ESRI, New series 3, 123–145. Taurides-Anatolides occurred at 74–71 Ma, featured by Bitlis Adamia, Sh., Alania, V., Chabukiani, A., Chichua, G., Enukidze, O., Sadradze, N., 2010. Evolution of the Late Cenozoic Basins of Georgia (SW Caucasus): A Review, blueschists, calc-alkaline magmatism and back-arc opening 340. Geological Society, London, pp. 239–259, http://dx.doi.org/10.1144/ (Oberhänsli et al., 2010; Rolland et al., 2012; Ç etinkaplan et al., SP340.11, Special Publications. 2014). Adamia, Sh., Alania, V., Chabukiani, A., Kutelia, Z., Sadraze, N., 2011a. Great Caucasus (Cavcasioni): a longlived North Tethyan Back-Arc Basin. Turk. J. Earth Sci. 20, 489–544. In conclusion, three subduction zones may have been active Adamia, Sh., Zakariadze, G., Chkhotua, T., Sadraze, N., Tsereteli, N., Chabukiani, A., Gventsadze, A., 2011b. Geology of the Caucasus: a review. Turk. J. Earth Sci. 20, simultaneously in the Early Jurassic across the tectonic domain cur- 611–628. rently represented by the Lesser Caucasus and Transcaucasus: (1) Adamia, Sh., 1984. Prealpine basement of the Caucasus—composition, structure, to the north, the north-dipping subduction below the PTB that had and formation. In: Otkhmezuri, Z.V. (Ed.), Tectonika I Metallogenia Kavkaza, already accreted to Eurasia, (2) a north-dipping intra-oceanic sub- 86. Metsniereba, Tbilisi, pp. 3–104. Adamia, Sh., 2004. Geological Map of Georgia, Scale 1:500 000. M. Nodia Institute duction zone between the PTB active margin and the SAB and (3) a of Geophysics, Tbilisi http://ig-geophysics.ge/sakartvelo.html. south-dipping subduction below the SAB (Fig. 8). Asatryan, G., Danelian, T., Sosson, M., Sahakyan, L., Person, A., Avagyan, A., et Galoyan, G., 2010. Radiolarian ages for the sedimentary cover of sevan ophiolite (Armenia, lesser Caucasus). Ofioliti 35, 91–101. 5. Conclusion Asatryan, G., Danelian, T., Sahakyan, L., Galoyan, G., Seyler, M., Sosson, M., Avagyan, A., Hubert, B.L.M., Ventalon, S., 2012. Radiolarian biostratigraphic constraints for latest Jurassic-earliest Cretaceous submarine volcanic activity in the From the preservation of similar Early Paleozoic ages, the vari- Tethyan oceanic realm of the Sevan ophiolite (Armenia). Bull. Soc. Géol. France ous Lesser Caucasus and Transcaucasus basements appear to share 183, 319–330. a similar origin from NE African Gondwana. The new U-Pb age of Aysal, N., Ustaomer, T., Ongen, S., Keskin, M., Köksal, S., Peytcheva, I., Fanning, M., ± 2012. Origin of the Early-Middle Devonian magmatism in the Sakarya Zone, 474 3 Ma obtained in this study in the zircon cores of migmatites NW Turkey: geochronology, geochemistry and isotope systematics. J. Asian derived from a granodiorite, in complement with published data, Earth Sci. 45, 201–222. argues for an Andean active margin setting on the NE boundary of Baghdasarian, G.P., Ghukasian, R.Kh., 1983. The age of Bdjni migmatite-granitic massif (By the Rb-Sr Isochrone radiometric data and geological ideas. Izvestia Gondwana. Drift of the Balkan-PTB Block could have been driven NAS of Armenian SSR. Nauki o Zemle 6, 15–29 (in Russian). by slab roll-back of the southward subducting Rheic Ocean. Accre- Bazhenov, M., Burtman, V.S., Levashova, N.M., 1996. Lower and Middle Jurassic tion to the Eurasian margin may have occurred during a short paleomagnetic results from the south Lesser Caucasus and the evolution of the Mesozoic Tethys ocean. Earth Planet. Sci. Lett. 141, 79–89. subduction-accretion event at 350–330 Ma. The age of the resulting Bosch, D., Bruguier, O., Pidgeon, R.T., 1996. The evolution of an Archaean regional thermal event is 350–330 Ma, featured by migmatiza- metamorphic belt: a conventional and SHRIMP U-Pb study of accessory tion dated in this study at 343 ± 2 Ma followed by magmatism at minerals from the Jimperding Metamorphic Belt, Yilgarn Craton, Western ∼ Australia. J. Geol. 104, 695–711. 335–330 Ma (Ar/Ar on biotite and muscovite, and U/Pb on zir- Bozkurt, E., Francisco Pereira, M., Strachan, R., Quesada, C., 2008. Evolution of the con). Coincidence of metamorphism and I-type magmatism (dated Rheic Ocean. Tectonophysics 461, 1–8. at 335 ± 8 Ma in this paper) suggests slab detachment shortly after Ç elik, Ö.F., Marzoli, A., Marschik, R., Chiaradia, M., Neubauer, F., Öz, I., 2011. ˙ the accretion event. The onset of north-dipping subduction below Early–Middle Jurassic intra-oceanic subduction in the Izmir-Ankara-Erzincan Ocean, Northern Turkey. Tectonophysics 509, 120–134. the PTB in the Triassic at c. 210 Ma is shown by the onset of a new Ç etinkaplan, M., Pourteau, A., Candan, O., Koralay, O.E., Oberhänsli, R., Okay, A.I., thermal episode culminating at c. 180–150 Ma. The thermal episode et al., 2014. P–T–t evolution of eclogite/blueschist facies metamorphism in resulted in the production of numerous calc-alkaline granitic intru- Alanya Massif: time and space relations with HP event in Bitlis Massif. Turk. Int. J. Earth Sci., 1–35, http://dx.doi.org/10.1007/s00531-014-1092-8. sions in both NE Anatolia and Transcaucasus basements. Channell, J.E.T., Tuys¨ uz,¨ O., Bektas¸¸, O., S¸ engör, A.M.C., 1996. Jurassic-Cretaceous paleomagnetism and paleogeography of the Pontides (Turkey). Tectonics 15, 201–212. Acknowledgements Corsini, M., Rolland, Y., 2009. Late evolution of the southern European Variscan belt: exhumation of the lower crust in a context of oblique convergence. C.R. This work benefited from DARIUS grants. The authors warmly Geosci. 341, 214–223. Danelian, T., Galoyan, G., Rolland, Y., Sosson, M., 2007. Palaeontological thank the support of DARIUS sponsors, and the coordination (Radiolarian) late jurassic age constraint for the stepanavan ophiolite (Lesser and support of E. Barrier and M.F. Brunet. In addition, thorough Caucasus, Armenia). Proceedings of the 11th International Congress, Athens, reviews undertaken by G. Topuz and two anonymous reviewers, May 2007 Bulletin of the Geological Society of Greece 40, 31–38. Danelian, T., Asatryan, G., Sosson, M., Person, A., Sahakyan, L., Galoyan, G., 2008. and detailed editorial comments of P. Agard, have significantly Discovery of two distinct Middle Jurassic Radiolarian assemblages in the helped enhancing this article. sedimentary cover of the Vedi ophiolite (Lesser Caucasus, Armenia). C.R. Palevol 7, 324–334. Danelian, T., Asatryan, G., Sahakyan, L., Galoyan, G.H., Sosson, M., Avagyan, A., References 2010. New and revised Radiolarian biochronology for the sedimentary cover of ophiolites in the Lesser Caucasus (Armenia). In: Sosson, M., Kaymakci, N., Adamia, Sh., Shavishvili, I.D., 1979. Model of tectonic evolution of the Earth crust of Stephenson, R.A., Bergerat, F., Starostenko, V. (Eds.), Sedimentary Basin the Caucasus and adjacent territory. Geotectonica 1, 77–84. Tectonics from the Black Sea and Caucasus to the Arabian Platform, 340. Adamia, Sh., Lordkipandize, M.B., Zakariadze, G.S., 1977. Evolution of an active Geological Society, London, pp. 383–391, Special Publications. continental margin as exemplified by the alpine history of the Caucasus. Danelian, T., Asatryan, G., Galoyan, G., Sosson, M., Sahakyan, L., Caridoit, M., Tectonophysics 40, 183–199. Avagyan, A., 2012. Geological history of ophiolites in the Lesser Caucasus and Adamia, Sh., Chkhotua, T., Kekelia, M., Lordkipanidze, M., et al., 1981. Tectonics of correlation with the Izmir-Ankara-Erzincan suture zone: insights from the Caucasus and adjoining regions: implications for the evolution of the radiolarian biochronology. Bull. Soc. Géol. France 183, 331–342. Tethys ocean. J. Struct. Geol. 3, 437–447. Danelian, T., Zambetakis-Lekkas, A., Galoyan, G., Sosson, M., Asatryan, G., Hubert, Adamia, Sh., Belov, A.A., Kekelia, M.A., Shavishvili, I.D., 1987. Paleozoic tectonic B., Grigoryan, A., 2014. Reconstructing Upper Cretaceous (Cenomanian) development of the caucasus and Turkey (Geotraverse C). In: Flugel, H.W., paleoenvironments in Armenia based on Radiolaria and benthic Foraminifera; Sassi, F.P., Grecula, P. (Eds.), Pre-Variscan and Variscan Events in the implications for the geodynamic evolution of the Tethyan realm in the Lesser Alpine–Mediterranean Mountain Belts: Mineralia Slovaca—Monography. Alfa, Caucasus. Palaeogeogr. Palaeoclimatol. Palaeoecol. 413, 123–132. Bratislava, pp. 23–50. Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 143

Dercourt, J., Zonenshain, L.P., Ricou, L.-E., Kazmin, V.G., Le Pichon, X., Knipper, A.L., Kröner, A., Romer, R.L., 2013. Two plates—many subduction zones: the variscan Grandjacquet, C., Sbortshikov, I.M., Geyssant, J., Lepvrier, C., Pechersky, D.H., orogeny reconsidered. Gondwana Res. 24, 298–329. Boulin, J., Sibuet, J.-C., Savostin, L.A., Sorokhtin, O., Westphal, M., Bazhenov Ledru, P., Courrioux, G., Dallain, C., Lardeaux, J.M., Montel, J.M., Vanderhaeghe, O., Lauer, J.P., Biju-Duval, B., 1986. Geological evolution of the Tethys belt from the Vitel, G., 2001. The Velay dome (French Massif Central): melt generation and Atlantic to the Pamirs since the Lias. Tectonophysics 123, 241–315. granite emplacement during orogenic evolution. Tectonophysics 342, 207–237. Dercourt, J., Ricou, L.E., Vrielynck, B., 1993. Atlas of Tethys Palaeoenvironmental Lefebvre, C., Meijers, M.J.M., Kaymakci, N., Peynircioglu, A., Langereis, C.G., van Maps. Gauthier-Villars, Paris, 307 p. Hinsbergen, D.J.J., 2013. Reconstructing the geometry of central Anatolia Dhuime, B., Bosch, D., Bruguier, O., Caby, R., Pourtales, S., 2007. Age, provenance during the late Cretaceous: large-scale Cenozoic rotations and deformation and post-deposition metamorphic overprint of detrital zircons from the between the Pontides and Taurides. Earth Planet. Sci. Lett. 366, 83–98, http:// Nathorst Land group (NE Greenland)—a LA-ICP-MS and SIMS study. dx.doi.org/10.1016/j.epsl.2013.01.003. Precambrian Res. 155, 24–26. Loury, C., Rolland, Y., Cenki-Tok, B., Lanari, P., Guillot, S., 2016. Late Paleozoic Dokuz, A., 2011. A slab detachment and delamination model for the generation of evolution of the South Tien Shan: insights from P-T estimates and allanite Carboniferous high-potassium I-type magmatism in the Eastern Pontides, NE geochronology on retrogressed eclogites (Chatkal Range, Kyrgyzstan). J. Turkey: köse composite pluton. Gondwana Res. 19, 926–944. Geody., http://dx.doi.org/10.1016/j.jog.2015.06.005. Dokuz, A., Karslı, O., Chen, B., Uysal, I.,˙ 2010. Sources and petrogenesis of Jurassic Ludwig, K.R., 2002. Isoplot/Ex Version 2.4. A Geochronological Toolkit for Microsoft granitoids in the Yusufeli area, Northeastern Turkey: implications for pre- and Excel. Berkeley Geochronological Center, Berkeley, Special Publication 56 p. post collisional lithospheric thinning of the eastern Pontides. Tectonophysics Machev, P., Ganev, V., Klain, L., 2015. New LA–ICP–MS U–Pb zircon dating for 480, 259–279. strandja granitoids 1 (SE Bulgaria): evidence for two-Stage late variscan Dokuz, A., Uysal, I.,˙ Kaliwoda, M., Karslı, O., Ottley, C.J., Kandemir, R., 2011. Early magmatism in the internal balkanides. Turk. J. Earth Sci. 24, 230–248, http:// abyssal- and late SSZ-type vestiges of the Rheic oceanic mantle in the Variscan dx.doi.org/10.3906/yer-1407-21. basement of the Sakarya Zone, NE Turkey: implications for the sense of Mayringer, F., Treloar, P.J., Gerdes, A., Finger, F., Shengelaia, D., 2011. New age data subduction and opening of the Paleotethys. Lithos 127, 176–191. from the Dzirula massif, Georgia: implications for the evolution of the Galoyan, G., Rolland, Y., Sosson, M., Corsini, M., Billo, S., Verati, C., Melkonyan, R., Caucasian Variscides. Am. J. Sci. 311, 404–441, http://dx.doi.org/10.2475/05. 2009. Geology, geochemistry and Ar/Ar dating of Sevan ophiolites (Lesser 2011.02. Caucasus, Armenia): evidence for Jurassic Back-arc opening and hot spot event Matte, P., 2001. The Variscan collage and orogeny (480–290 Ma) and the tectonic between the South Armenian Block and Eurasia. J. Asian Earth Sci. 34, 135–153. definition of the Armorica microplate: a review. Terra Nova 13, 117–121. Gamkrelidze, I.P., 1986. Geodynamic evolution of the Caucasus and adjacent areas Meijers, M.J.M., Kaymakci, N., Van Hinsbergen, D.J.J., Langereis, C.G., Stephenson, in alpine time. Tectonophysics 127, 261–277. R.A., Hippolyte, J.-C., 2010b. Late Cretaceous to paleocene oroclinal bending in Gamkrelidze, I.P., Dumbadze, G.D., Kekeliya, M.A., et al., 1981. Ophiolites of the the Central Pontides (Turkey). Tectonics 29, http://dx.doi.org/10.1029/ Dzirula massif and the problem of the Paleotethys on the Caucasus. 2009TC002620 (TC4016). Geotektonika 5, 23–33. Meijers, M.J.M., Vrouwe, B., van Hinsbergen, D.J.J., Kuiper, K.F., Wijbrans, J., Davies, Gamkrelidze, I.P., Shengelia, D.M., Shvelidze, IuU., Vashakidze, G.T., 1999. The new G.R., Stephenson, R.A., Kaymakcı, N., Matenco, L., Saintot, A., 2010c. Jurassic arc data about geological structure of the Lokhi crystalline massif and Gorastskali volcanism on Crimea (Ukraine): implications for the paleo-subduction zone metaophiolites. Proceedings of Geological Institute of Academy of Sciences configuration of the Black Sea region. Lithos 119, 412–426. Georgia New Series 114, 82–108. Meijers, M.J.M., Smith, B., Kirscher, U., Mensink, M., Sosson, M., Rolland, Y., Göncüoglu,˘ M.C., Turhan, N., S¸ enturk,¨ K., Özcan, A., Uysal, S¸ ., Yalınız, M.K., 2000. A Grigoryan, A., Sahakyan, L., Avagyan, A., Langereis, C., Müller, C., 2015a. A geotraverse across NW Turkey: tectonic units of the Central Sakarya region paleolatitude reconstruction of the South Armenian Block (Lesser Caucasus) and their tectonic evolution. In: Bozkurt, E., Winchester, J.A., Piper, J.A.D. (Eds.), for the Late Cretaceous: constraints on the Tethyan realm. Tectonophysics Tectonics and Magmatism in Turkey and Surrounding Area, 173. Geological 644–645, 197–219. Society, London, pp. 139–161, Special Publications. Meijers, M.J., Smith, B., Pastor-Galán, D., Degenaar, R., Sadradze, N., Adamia, S., Guillot, S., Cosca, M., Allemand, P., Le fort, P., 1999. Contrasting metamorphic and Sahakyan, L., Avagyan, A., Sosson, M., Rolland, Y., Langereis, C.G., Müller, C., geochronologic evolution along the Himalayan belt. Geol. Soc. Am. Spec. Paper 2015b. Progressive Orocline Formation in the Eastern Pontides–Lesser 328, 117–128. Caucasus, 428. Geological Society, London, Special Publications SP428-8. Hässig, M., Rolland, Y., Sosson, M., Galoyan, G., Müller, C., Avagyan, A., Sahakyan, L., Mevel, C., Caby, R., Kienast, J.R., 1978. Amphibolite facies conditions in the oceanic 2013a. New structural and petrological data on the Amasia ophiolites (NW crust: example of amphibolitized flaser-gabbro and amphibolites from the Sevan–Akera suture zone, Lesser Caucasus): insights for a large-scale Chenaillet ophiolite massif (Hautes Alpes, France). Earth Planet. Sci. Lett. 39, obduction in Armenia and NE Turkey. Tectonophysics 588, 135–153. 98–108. Hässig, M., Rolland, Y., Sosson, M., Galoyan, G., Sahakyan, L., Topuz, G., Ç elik, O.F., Moritz, R., Rezeau, H., Ovtcharova, M., et al., 2015. Long-lived, stationary Avagyan, A., Muller,¨ C., 2013b. Linking the NE Anatolian and Lesser Caucasus magmatism and pulsed porphyry systems during Tethyan subduction to ophiolites: evidence for large-scale obduction of oceanic crust and implications post-collision evolution in the southernmost Lesser Caucasus, Armenia and for the formation of the Lesser Caucasus-Pontides Arc. Geodinamica Acta 26, Nakhitchevan. Gondwana Res., http://dx.doi.org/10.1016/j.gr.2015.10.009. 311–330, http://dx.doi.org/10.1080/09853111.2013.877236. MTA, 2002. 1:500,000-Scale Map of Turkey. MTA, Ankara. Hässig, M., Rolland, Y., Sahakyan, L., Sosson, M., Galoyan, G., Avagyan, A., Bosch, D., Nance, R.D., 2010. The Rheic Ocean: palaeozoic evolution from Gondwana and Müller, C., 2015a. Multi-stage metamorphism in the South Armenian Block Laurussia to Pangaea—introduction. Gondwana Res. 17, 189–192, http://dx.doi. during the Late Jurassic to Early Cretaceous: tectonics over south-dipping org/10.1016/j.gr.2009.12.001. subduction of Paleotethys. J. Asian Earth Sci. 102, 4–23, http://dx.doi.org/10. Neves, S.P., Bruguier, O., Vauchez, A., Bosch, D., da Silva, J.M.R., Mariano, G., 2006. 1016/j.jseaes.2014.07.018. Timing of crust formation, deposition of supracrustal sequences, and Hässig, M., Rolland, Y., Sosson, M., 2015b. From Sea-floor Spreading to Obduction: Transamazonian and Brasiliano metamorphism in the East Pernambuco belt Jurassic-Cretaceous Evolution of the Northern Branch of the Neotethys to (Borborema Province, NE Brazil): implications for western Gondwana Obduction Initiation: History of the Northern Branch of Neotethys in the assembly. Precambrian Res. 149, 197–216. North-eastern Anatolian and Lesser Caucasus Regions, 428. Geological Society, Nikishin, A.M., Ziegler, P.A., Bolotov, S.N., Fokin, P., 2011. Late Palaeozoic to London, Special Publications (SP428.10). Cenozoic evolution of the Black Sea-Southern Eastern Europe region: a view Hässig, M., Rolland, Y., Duretz, T., Sosson, M., 2016a. Obduction triggered by from the Russian platform. Turk. J. Earth Sci. 20, 571–634. regional heating during plate reorganization. Terra Nova 28 (1), 76–82, http:// Nzegge, O.M., Satır, M., Sıebel, W., Taubald, H., 2006. Geochemical and isotopic dx.doi.org/10.1111/ter.12193. constraints on the genesis of the Late Paleozoic Deliktas¸ and Sivrikaya granites Hässig, M., Duretz, T., Rolland, Y., Sosson, M., 2016b. Obduction of old oceanic from the Kastamonu granitoid belt (Central Pontides, Turkey). Neues Jahrbuch lithosphere due to due to reheating and plate reorganization: insights from für Mineralogie Abhandlungen 183, 27–40. numerical modelling and the NE Anatolia—Lesser Caucasus case example. J. Oberhänsli, R., Candan, O., Bousquet, R., Rimmele, G., Okay, A., Goff, J., 2010. Alpine Geodyn., http://dx.doi.org/10.1016/j.jog.2015.07.006. High Pressure Evolution of the Eastern Bitlis Complex, Se Turkey, 340 (1. Hässig, M., Rolland, Y., Sosson, M., Avagyan, A., 2016c. Lithological nature of the Geological Society, London, pp. 461–483, Special Publications. subduction channel: Insights from the Karabakh suture zone (Lesser Caucasus) Okay, A.I., Sahintürk, Ö., 1997. Geology of the Eastern Pontides. In: Robinson, A.G. and general comparisons. J. Geodyn., http://dx.doi.org/10.1016/j.jog.2015.07. (Ed.), Regional and Petroleum Geology of the Black Sea and Surrounding 006. Region, 68. AAPG Memoir, pp. 291–311. Horstwood, M.S.A., Parrish, R.R., Nowell, G.M., Noble, S.R., 2003. Accessory mineral Okay, A.I., Tüysüz, O., 1999. Tethyan sutures of northern Turkey. In: Mascle, A., U-Th-Pb geochronology by laser-ablation plasma-ionisation multi-collector Jolivet, L. (Eds.), The Mediterranean Basin: Tertiary Extension Within the mass spectrometry (LA-PIMMS). J. Anal. At. Spectrom. 18, 837–846. Alpine Orogen, 156. Geological Society, London, pp. 475–515. Kalvoda, J., Bábek, O., 2010. The margins of laurussia in central and southeast Okay, A.I., Göncüoglu,˘ M.C., 2004. The Karakaya complex: a review of data and europe and southwest asia. Gondwana Res. 17, 526–545, http://dx.doi.org/10. concepts. Turk. J. Earth Sci. 13, 77–95. 1016/j.gr.2009.09.012. Okay, A.I., Bozkurt, E., Satir, M., Yigitbas, E., Crowley, Q.G., Shang, C.K., 2008. Kaygusuz, A., Arslan, M., Siebel, W., Sipahi, F., Ilbeyli,˙ N., 2012. Geochronological Defining the southern margin of Avalonia in the Pontides: geochronological evidence and tectonic significance of Carboniferous magmatism in the data from the Late Proterozoic and Ordovician granitoids from NW Turkey. southwest Trabzon area, eastern Pontides, Turkey. Int. Geol. Rev., 1776–1800. Tectonophysics 461, 252–264, http://dx.doi.org/10.1016/j.tecto.2008.02.004. Kotopouli, C.N., Pe-Piper, G., Piper, D.W.J., 2000. Petrology and evolution of the Okay, A.I., Sunal, G., Tüysüz, O., Sherlock, S., Keskin, M., Kylander-Clark, A.R.C., Hercynian Pieria Granitoid Complex (Thessaly, Greece): palaeogeographic and 2014. Low-pressure–high-temperature metamorphism during extension in a geodynamic implications. Lithos 50, 137–152. Jurassic magmatic arc, Central Pontides, Turkey. J. Metamorph. Geol. 32, 49–69, http://dx.doi.org/10.1111/jmg.12058. 144 Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145

Okay, A.I., Nikishin, A.M., 2015. Tectonic evolution of the southern margin of Somin, M.L., 2011. Pre-Jurassic basement of the Greater Caucasus: brief overview. Laurasia in the Black Sea region. Int. Geol. Rev. 57, 1051–1076, http://dx.doi. Turk J. Earth Sci 20, 545–610. org/10.1080/00206814.2015.1010609. S¸ engör, A.M.C., Yılmaz, Y., Sungurlu, O., 1984. Tectonics of the Mediterranean Okrostsvaridze, A., Clarke, D., Reynolds, P., 2002. Sm-Nd, Rb-Sr and K-Ar isotope Cimmerides: nature and evolution of the western termination of system and geochemistry and geochronology of the pre-Alpine granitoides of Palaeo-Tethys. In: Dixon, J.E., Robertson, A.H.F. (Eds.), The Geological Evolution the Dzirula salient of the Caucasian median massif (in Russ). Proceedings of of the Eastern Mediterranean, 17. Special Publications, Geological Society, Geological Institute of Georgian Academy of Sciences New Series 117, 173–186. London, pp. 77–112. Oliot, E., Melleton, J., Schneider, J., Corsini, M., Gardien, V., Rolland, Y., 2015. Shengelia, D., Okrostsvaridze, A., 1998. New data on the structure of the Dzirula Variscan crustal thickening in the Maures–Tanneron massif (South Variscan salient of pre-Alpine basement of Georgian Block. Dokl. Russ. Acad. Sci. 6, belt: France): new in situ monazite U-Th-Pb chemical dating of high-grade 801–803 (in Russian). rocks. Bull. Soc. Geol. France 186, 145–169. Shengelia, D., Shubitidze, L., Chung, S.-L., Chiu, H.-Y., Treloar, P., 2012. New data on Pe-Piper, G., Piper, D.W.J., 2002. The igneous rocks of Greece. The anatomy of an the formation and age of Orthoclase Gabbro of the Dzirula Crystalline Massif orogen. Beitrage Zur Regionalen Geologie Der Erde, 30. Gebruder¨ Borntaeger, (Georgia). Bull. Georgian Acad. Sci. 6, 75–82. Berlin/Stuttgart. Sosson, M., Rolland, Y., Danelian, T., Muller, C., Melkonyan, R., Adamia, S., Kangarli, Perchuk, A., Philippot, P., 1997. Rapid cooling and exhumation of eclogitic rocks T., Avagyan, A., Galoyan, G., 2010. Subductions, Obduction and Collision in the from the Great Caucasus, Russia. J. Metamorphic Geol. 15, 299–310. Lesser Caucasus (Armenia Azerbaijan, Georgia), New Insights, 340. Special Philippot, P., Blichert-Toft, J., Perchuk, A., Costa, S., Gerasimov, V., 2001. Lu–Hf and Publications, Geological Society, London, pp. 329–352. Ar–Ar chronometry supports extreme rate of subduction zone metamorphism Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotope evolution deduced from geospeedometry. Tectonophysics 342, 23–38. by a two-stage model. Earth Planet. Sci. Lett 26, 207–221. Ricou, L.E., 1994. Tethys reconstructed: plates, continental fragments and their Stampfli et al., 2001. Palaeotectonic and palaeogeographic evolution of the western boundaries since 260 Ma from Central America to South-Eastern Asia. Tethys and PeriTethyan domain (IGCP Project 369). Episodes 24, 222–228. Geodinamica Acta 7, 169–218. Stampfli, G.M., Borel, G.D., 2002. A plate tectonic model for the Paleozoic and Robertson, A.H.F., 2012. Late Palaeozoic–Cenozoic tectonic development of Greece Mesozoic constrained by dynamic plate boundaries and restored synthetic and Albania in the context of alternative reconstructions of Tethys in the oceanic isochrones. Earth Planet. Sci. Lett. 196, 17–33. Eastern Mediterranean region. Int. Geol. Rev. 54, 373–454. Stampfli, G., Kozur, H.W., 2004. Europe from Variscan to Alpine cycles. In: Gee, Robertson, A.H.F., Dixon, J.E., 1984. Introduction: Aspects of the Geological D.G., Stepherson, R. (Eds.), European Lithosphere Dynamics, 32. Memoirs, Evolution of the Eastern Mediterranean, 17. Special Publications, Geological Geological Society, London, pp. 57–82. Society of London, pp. 1–74. Steiger, R.H., Jager, E., 1977. Subcommission on geochronology—convention on use Robertson, A.H.F., Dixon, J.E., Brown, S., Collins, A., Morris, A., Pickett, E., Sharp, I., of decay constants on geochronology and cosmochronology. Earth Planet. Sci. Ustaömer, T., 1996. Alternative Tectonic Models for the Late Palaeozoic-Early Lett 36, 359–362. Tertiary Development of Tethys in the Eastern Mediterranean Region, 105. Topuz, G., Altherr, R., 2004. Pervasive rehydration of granulites during Geological Society Special Publication, pp. 239–263. exhumation—example from the Pulur complex Eastern Pontides, Turkey. Robertson, A.H.F., Ustaömer, T., Pickett, E., Collins, A.S., Andrew, T., Dixon, J.E., Mineral. Petrol. 81, 165–185. 2004. Testing models of Late Palaeozoic-Early Mesozoic oprogeny in Western Topuz, G., Altherr, R., Satır, M., Schwarz, W.H., 2004a. Low-grade metamorphic Turkey: support for an evolving open-Tethyan model. J. Geol. Soc. London 161, rocks from the Pulur complex, NE Turkey: implications for the pre-Liassic 501–511. evolution of the Eastern Pontides. Int. J. Earth Sci. 93, 72–91. Robertson, A.H.F., Ustaömer, T., 2009a. Formation of the upper Palaeozoic Konya Topuz, G., Altherr, R., Kalt, A., Satır, M., Werner, O., Schwartz, W.H., 2004b. Complex and comparable units in southern Turkey subduction–accretion Aluminous granulites from the Pulur Complex, NE Turkey: a case of partial processes: implications for the tectonic development of Tethys in the Eastern melting, efficient melt extraction and crystallisation. Lithos 72, 183–207. Mediterranean region. Tectonophysics 473, 113–148. Topuz, G., Altherr, R., Schwarz, W.H., Dokuz, A., Meyer, H.P., 2007. Variscan Robertson, A.H.F., Ustaömer, T., 2009b. Upper Palaeozoic subduction/accretion amphibolite-facies rocks from the Kurtoglu˘ metamorphic complex processes in the closure of Palaeotethys: evidence from the Chios Melange (E (Gum¨ us¨ ¸ hane area, Eastern Pontides, Turkey). Int. J. Earth Sci. 96, 861–873. Greece), the Karaburun Melange (W Turkey) and the Teke Dere Unit (SW Topuz, G., Altherr, R., Schwarz, W., Zack, T., Sunal, G., 2009. Middle Devonian Turkey). Sediment. Geol. 220, 29–59. blueschist metamorphism in the eastern Pontides, NE Turkey: vestiges of the Robertson, A.H.F., Ustaomer, T., 2012. Testing alternative tectono-stratigraphic Rheic Ocean? In: 2nd International Symposium on the Geology of the Black Sea interpretations of the Late Palaeozoic-Early Mesozoic Karakaya Complex in Region, Abstracts, 5–9 October, Ankara, Turkey, pp. 203–204. NW Turkey: support for an accretionary origin related to northward Topuz, G., Altherr, R., Siebel, W., Schwartz, W.H., Zack, T., Hasözbek, A., Barth, B., subduction of Palaeotethys. Turk. J. Earth Sci. 21, 961–1027. Satır, M., S¸ en, C., 2010. Carboniferous high-potassium I-type granitoid Robertson, A., Parlak, O., Ustaömer, T., Taslı, K., Inan,˙ N., Dumitrica, P., Karaoglan,˘ F., magmatism in the Eastern Pontides: the Gumus¸ hane pluton (NE Turkey). 2013. Subduction, ophiolite genesis and collision history of Tethys adjacent to Lithos 116, 92–110. the Eurasian continental margin: new evidence from the Eastern Pontides, Topuz, G., Göç mengil, G., Rolland, Y., Ç elik, Ö.F., Zack, T., Schmitt, A.K., 2013a. Turkey. Geodinamica Acta 26, 230–293. Jurassic accretionary complex and ophiolite from Northeast Turkey: no Rolland, Y., Billo, S., Corsini, M., Sosson, M., Galoyan, G., 2009a. Blueschists of the evidence for the Cimmerian continent. Geology 41, 255–258. Amassia-Stepanavan Suture Zone (Armenia): linking Tethys subduction Topuz, G., Ç elık, Ö.F., S¸ engör, A.M.C., Altintas¸,I.E.,˙ Zack, T., Rolland, Y., Barth, M., history from E-Turkey to W-Iran. Int. J. Earth Sci. (Geologische Rundschau) 98, 2013b. Jurassic ophiolite formation and emplacement as backstop to a 533–550. subduction-accretion complex in northeast Turkey, the Refahıye ophiolite, and Rolland, Y., Galoyan, Gh., Bosch, D., Sosson, M., Corsini, M., Fornari, M., Vérati, C., relation to the Balkan ophiolites. Am. J. Sci. 313, 1054–1087. 2009b. Jurassic Back-arc and hot-spot related series in the Armenian Topuz, G., Okay, A.I., Altherr, R., Schwarz, W.H., Sunal, G., Altinkaynak, L., 2014. ophiolites—implications for the obduction process. Lithos 112, 163–187. Triassic warm subduction in northeast Turkey: evidence from the Agvanis Rolland, Y., Galoyan, G., Sosson, M., Melkonian, R., Avagyan, A., 2010. The Armenian metamorphic rocks. Isl. Arc 23, 181–205. Ophiolites: Insights for Jurassic Back-arc Formation, Lower Cretaceous Torsvik, T.H., Van der Voo, R., Preeden, U., Mac Niocaill, C., Steinberger, B., Hot-spot Magmatism, and Upper Cretaceous Obduction over the South Doubrovine, P.V., van Hinsbergen, D.J.J., Domeier, M., Gaina, C., Tohver, E., Armenian Block, 340. Special Publication, Geological Society of London, pp. Meert, J.G., McCausland, P.J.A., Robin, L., Cocks, M., 2012. Phanerozoic polar 353–382. wander, palaeogeography and dynamics. Earth Sci. Rev. 114, 325–368. Rolland, Y., Sosson, M., Adamia, Sh., Sadradze, N., 2011. Prolonged Variscan to Ustaömer, T., Robertson, A.H.F., 2010. Late Palaeozoic–Early Cenozoic Tectonic Alpine history of an active Eurasian margin (Georgia, Armenia) revealed by Development of the Eastern Pontides (Artvin area): Turkey: Stages of Closure Ar/Ar dating. Gondwana Res. 20, 798–815. of Tethys Along the Southern Margin of Eurasia, 340. Special Publications, Rolland, Y., Perincek, D., Kaymakci, N., Sosson, M., Barrier, E., Avagyan, A., 2012. Geological Society, London, pp. 281–327. Evidence for ∼80–75 Ma subduction jump during Anatolide-Tauride-Armenian Ustaömer, P.A., Ustaömer, T., Gerdes, A., Zulauf, G., 2011. Detrital zircon ages from block accretion and ∼48 Ma Arabia-Eurasia collision in Lesser Caucasus-East Ordovician quartzites of the Istanbul˙ exotic terrane (NW Turkey): evidence for Anatolia. J. Geodyn. 56–57, 76–85, http://dx.doi.org/10.1016/j.jog.2011.08.006. Amazonian affinity. Int. J. Earth Sci. 100, 23–41. Romano, S.S., Dörr, W., Zulauf, G., 2004. Significant Pb loss of Cadomian zircons due Ustaömer, P.A., Ustaömer, T., Robertson, A.H.F., 2012. Ion Probe U-Pb dating of the to Alpine subduction of pre-Alpine basement of eastern Crete (Greece). Int. J. Central Sakarya basement: a peri-Gondwana terrane intruded by late Lower Earth Sci. 93, 844–859. Carboniferous subduction/collision related granitic rocks. Turk. J. Earth Sci., Roscher, M., Stordal, F., Svensen, H., 2011. The effect of global warming and global 905–932 (Black Sea Special Issue 21). cooling on the distribution of the latest Permian climate zones. Palaeogeogr. Ustaömer, T., Robertson, A.H.F., Ustaömer, P.A., Gerdes, A., Peytcheva, I., 2013. Palaeoclimatol. Palaeoecol. 309, 186–200. Constraints on Variscan and Cimmerian Magmatism and Metamorphism in the Rustamov, M., 2005. South Caspian Basin—Geodynamic Events and Processes. Pontides (Yusufeli-Artvin area), NE Turkey from U-Pb Dating and Granite Institute of Geology, NASA-press, Baki, 345 p. (in Russian). Geochemistry, 372. Special Publications, Geological Society, London, pp. 49–74. S¸ engör, A.M.C., 1984. The Cimmeride Orogenic system and the tectonics of Eurasia. von Raumer, J.F., Stampfli, G.M., 2008. The birth of the Rheic Ocean—Early Geol. Soc. Am. Spec. Paper 195, pp. 82. Palaeozoic subsidence patterns and subsequent tectonic plate scenarios. S¸ engör, A.M.C., Yılmaz, Y., 1981. Tethyan evolution of Turkey: a plate tectonic Tectonophysics 461, 9–20. approach. Tectonophysics 75, 181–241. Wiedenbeck, M., Allé, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., von Quadt, A., Somin, M.L., 1991. Geological characteristics of the metamorphic complexes of the Roddick, J.C., Spiegel, W., 1995. Three natural zircon standards for U-Th-Pb Great Caucasus. In: Korikovsky, S.P. (Ed.), The Petrology of Metamorphic Lu-Hf, trace element and REE analyses. Geostan. Newsl. 19, 1–23. Complexes of the Great Caucasus. Nauka, Moscow, pp. 8–43. Y. Rolland et al. / Journal of Geodynamics 96 (2016) 131–145 145

Xypolias, P., Dörr, W., Zulauf, G., 2006. Late Carboniferous plutonism within the Zakariadze, G.S., Dilek, Y., Adamia, S.A., Adamia, Sh.A., Oberhaensli, R.E., Karpenko, pre-Alpine basement of the External Hellenides (Kithira, Greece): evidence S.F., Bazylev, B.A., Solov’eva, N., 2007. Geochemistry and geochronology of the from U-Pb zircon dating. J. Geol. Soc. London 163, 539–547. Neoproterozoic Pan-African Trans-caucasian Massif (Republic of Georgia) and Yılmaz, A., Adamia, S., Chabukiani, A., Chkhotua, T., Erdogan, K., Tuzcu, S., implications for island arc evolution of the late Precambrian Arabian–Nubian Karabiyikoglu, M.F., 2000. Structural Correlation of the Southern Shield. Gondwana Res. 11, 92–108. Transcaucasus (Georgia) Eeastern Pontides (Turkey), 173. Special Publication, Zonenshain, L.P., Le Pichon, X., 1986. Deep basins of the Black Sea and Caspian Sea Geological Society, London, pp. 171–182. as remnants of Mesozoic back-arc basins. Tectonophysics 123, 181–211. Zakariadze, G.S., Karpenko, S.F., Bazylev, B.A., Adamia, Sh.A., Oberhaensli, R.E., Zulauf, G., Romano, S.S., Dörr, W., Fiala, J., 2007. Crete and Minoan Terranes: Age et al., 1998. Petrology, geochemistry, and Sm–Nd age of the pre-late Hercynian Constraints from U-Pb Dating of Detrital Zircons, 423. Special Publication, paleooceanic complex of the Dzirula salient, Trans-caucasian massif. Petrology Geological Society of America, pp. 401–411. 6, 388–408 (Translated from Petrologiya, 1998, v. 6, No. 4, 422–444).