The Eastern Pontides orogenic belt in the Black Sea region of Turkey offers a critical window to plate kinematics and subduction polarity during the closure of the Paleotethys. Here we provide a brief synthesis on rec...The Eastern Pontides orogenic belt in the Black Sea region of Turkey offers a critical window to plate kinematics and subduction polarity during the closure of the Paleotethys. Here we provide a brief synthesis on recent information from this belt. We infer a southward subduction for the origin of the Eastern Pontides orogenic belt and its associated late Mesozoic--Cenozoic magmatism based on clear spatial and temporal variations in Late Cretaceous and Cenozoic arc magmatism, together with the exis- tence of a prominent south-dipping reverse fault system along the entire southern coast of the Black Sea. Our model is at variance with some recent proposals favoring a northward subduction polarity, and illus- trates the importance of arc magmatism in evaluating the geodynamic milieu associated with convergent margin orocesses.展开更多
A series of Cretaceous plutons is present in the eastern Pontides of northeastern Turkey. The Turnag61 intrusion is the least studied and, thus, the least understood plutons in the orogen. This intrusion consists of h...A series of Cretaceous plutons is present in the eastern Pontides of northeastern Turkey. The Turnag61 intrusion is the least studied and, thus, the least understood plutons in the orogen. This intrusion consists of hornblende-biotite granodiorites emplaced at 78 Ma based on LA-ICP-MS U-Pb zircon dating. It is of sub- alkaline affinity, belongs to the medium- to high-K calc-alkaline series, and displays features typical of I- type granites. The rocks of the intrusion are enriched in large-ion lithophile elements and light rare earth- elements with negative Eu anomalies （EuJEu＊ = 0.69-0.82）, but are deficient in high-field-strength elements. They have a small range of （87Sr/S6Sr）i （0.7060 0.7063）, ENd （-2.6 to 3.1）, and 6180 （＋8.1 to ＋9.1） values. Their Pb isotopic ratios are 206pb/204pb = 18.63-18.65, ＇207Tpb/204pb = 15.62-15.63, and 208pb/204pb 38.53-38.55. The fractionation of plagioclase, hornblende, and Fe-Ti oxides had key functions in the evolution of the Turnag61 intrusion. The crystallization temperatures of the melts ranged from 758 to 885 ℃ as determined by zircon and apatite saturation thermometry. All these characteristics, combined with the low values of K20/Na20 and （Na20 ＋ K20）/（FeOt ＋ MgO ＋ TiO2）, as well as the high values of （CaO ＋ FeOt ＋ MgO ＋ TiO2）, suggest an origin by dehydration melting from a metabasaltic lower crustal source.展开更多
The Eastern Pontides orogenic belt(EPOB)represents a significant segment of the AlpineHimalayan orogenic belt that evolved from the Paleozoic to Cenozoic periods.Here we report new zircon U-Pb ages,together with Lu-Hf...The Eastern Pontides orogenic belt(EPOB)represents a significant segment of the AlpineHimalayan orogenic belt that evolved from the Paleozoic to Cenozoic periods.Here we report new zircon U-Pb ages,together with Lu-Hf isotopes,and whole-rock geochemical and Sr-Nd isotopic analyses of plutonic rocks from EPOB,northeastern Turkey.Our aim is to interpret magmatic evolution in which the granitoids formed.Zircon U-Pb dating of six samples yielded crystallization ages of~134,~82,~39 Ma,respectively.They show a wide range of87Sr/86Sr((i))(0.7039–0.7109),andεNd(t)values varying from-9 to+4.6,yielding model ages(TDM)from 520 to 1623 Ma,suggesting a heterogeneous magma source.Dated zircons show exlusively positiveεHf(t)values(+12.4 to+1.4),yielding model ages(TDM)from 352 to 1059 Ma,implying that they are most likely derived from a juvenile lower crust rather than the mature continental crust.In this study,we suggested that the northward subduction of the Neo-Tethyan oceanic slab began from the Early Cretaceous and resulted in the Late Cretaceous magmatism.Moreover,the Middle Eocene magmatism in the EPOB was related to the collision of the Anatolide Taurid Platform(ATP)with the Pontides.展开更多
The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine-Himalayan belt. The late Mesozoic-Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on th...The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine-Himalayan belt. The late Mesozoic-Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on the nature of the transition from the adakitic to non-adakitic magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved. The adakitic lithologies comprise porphyries and hyaloclastites. The porphyries are represented by biotite-rich andesites, hornblende-rich andesite and dacite. The hayaloclastites represent the final stage of adakitic activity and they were generated by eruption/intrusion of adakitic andesitic magma into soft carbonate mud. The non-adakitic lithologies include basaltic-andesitic volcanic and associated pyroclastic rocks. Both rock groups are cutting by basaltic dikes representing the final stage of the Cenozoic magmatism in the study area. We report zircon U-Pb ages of 48.71 ± 0.74 Ma for the adakitic rocks, and 44.68 ± 0.84 Ma for the non-adakitic type, suggesting that there is no significant time gap during the transition from adakitic to non-adakitic magmatism. We evaluate the origin, magma processes and tectonic setting of the magmatism in the southern part of the eastern Pontides orogenic belt. Our results have important bearing on the late Mesozoic-Cenozoic geodynamic evolution of the eastern Mediter- ranean region.展开更多
The Meso-Cenozoic geodynamic evolution of northern Türkiye remains a subject of debate primarily due to a lack of systematic geological,geochemical,geochronological,and geophysical investigations.This paper prese...The Meso-Cenozoic geodynamic evolution of northern Türkiye remains a subject of debate primarily due to a lack of systematic geological,geochemical,geochronological,and geophysical investigations.This paper presents comprehensive geochronological and geochemical data on the Late Triassic andesite porphyry,andesite breccia and quartz diorite porphyry,and the Middle Jurassic diabase,and amphibole-poor and amphibole-rich andesite porphyry fromÇevrepınar Igneous Complex(Gümüşhane)in the southern part of the Eastern Pontides Orogenic Belt(EPOB),a well-preserved continental arc in the Alpine-Himalayan orogen.Zircon U-Pb geochronology indicates crystallization ages of∼208-202 Ma(Rhaetian)for the Late Triassic rocks and∼175-172 Ma(Aalenian)for the Middle Jurassic rocks.Whole-rock geochemical and Sr-Nd-Pb isotopic data,and zirconεHf(t)data indicate that both the Late Triassic and the Middle Jurassic rocks originated by low-degree melting of a spinel lherzolite lithospheric mantle source modified by subduction-related fluids and/or melts.Based on the new and published data,we suggest that the Late Triassic to Middle Jurassic arc magmatism in EPOB occurred as a result of southward subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana-Land.Late Triassic to Jurassic arc magmatism and basin evolution occurred synchronously in the northern and southern peripheries of the present-day Eastern Black Sea Basin,indicating divergent double subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana and southern margin of Laurasia during the Early Mesozoic.展开更多
The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s)and to understand how its western and eastern branches were connected.One of the lesser known branches of the Mesozoic oc...The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s)and to understand how its western and eastern branches were connected.One of the lesser known branches of the Mesozoic ocean(s)is preserved in the northern ophiolite suture zone exposed in Turkey,namely,the Intra-Pontide suture zone.It is located between the Sakarya terrane and the Eurasian margin(i.e.,Istanbul-Zonguldak terrane)and consists of several metamorphic and non-metamorphic units containing ophiolites produced in supra-subduction settings from the Late Triassic to the Early Cretaceous.Ophiolites preserved in the metamorphic units recorded pervasive deformations and peak metamorphic conditions ranging from blueschist to eclogite facies.In the nonmetamorphic units,the complete oceanic crust sequence is preserved in tectonic units or as olistoliths in sedimentary melanges.Geochemical,structural,metamorphic and geochronological investigations performed on ophiolite-bearing units allowed the formulation of a new geodynamic model of the entire"life"of the IntraPontide oceanic basin(s).The reconstruction starts with the opening of the Intra-Pontide oceanic basins during the Late Triassic between the Sakarya and Istanbul-Zonguldak continental microplates and ends with its closure caused by two different subductions events that occurred during the upper Early Jurassic and Middle Jurassic.The continental collision between the Sakarya continental microplate and the Eurasian margin developed from the upper Early Cretaceous to the Palaeocene.The presented reconstruction is an alternative model to explain the complex and articulate geodynamic evolution that characterizes the southern margin of Eurasia during the Mesozoic era.展开更多
Most of the massive sulfide deposits (VMS) occurring from Precambrian to Cenozoic throughout the world has been subsequently metamorphosed at various grades. Thus, all the original textures have been either completely...Most of the massive sulfide deposits (VMS) occurring from Precambrian to Cenozoic throughout the world has been subsequently metamorphosed at various grades. Thus, all the original textures have been either completely destroyed or strongly modified. However, there are a very few examples, rather younger deposits such as late Cretaceous Turkish VMS deposits and Miocene Kuroko deposits of Japan in which representative and original ore textures are preserved. The Turkish massive sulfide deposits are mainly Cu-Zn-Pb-type and entirely hosted by Late Cretaceous felsic volcanic rocks within a paleoarc geotectonic setting.展开更多
The Pontide belt in northern Turkey includes three major tectonic terranes,the Strandja Massif（Sj M）,and the Istanbul（ISZ）and Sakarya Zones（SZ）(Fig.1).We present new age and geochemical data from ophiolites and ...The Pontide belt in northern Turkey includes three major tectonic terranes,the Strandja Massif（Sj M）,and the Istanbul（ISZ）and Sakarya Zones（SZ）(Fig.1).We present new age and geochemical data from ophiolites and ophiolitic mélanges within the Sakarya Zone and show that these mafic–ultramafic rocks are the remnants of Tethyan oceanic lithosphere formed in different tectonic settings.The main ophiolite occurrences investigated in this study along the Karakaya Suture（KS）are associated with the latest Triassic Cimmeride orogeny,and in the Küre–Yusufeli ophiolite belt are part of the Alpide orogeny.The Karakaya Suture Zone ophiolites in northern west Turkey are comprised mainly of the Denizgoren（?anakkale）ophiolite,Bo?azk?y（Bursa）,Geyve（Sakarya）,Almac?k（Düzce）and?ele（Bolu）metaophiolites.The Denizg?ren ophiolite largely contains upper mantle peridotites,which are equivalents of the Permo–Triassic Lesvos peridotites and mélange units farther SW in the northern Aegean Sea.The Bo?azk?y ophiolite includes serpentinite and metagabbro,and the Almac?k and Geyve ophiolites display an almost complete Penrose–type sequence consisting of serpentinizeduppermantleperidotites,cumulate ultramafic–mafic rocks,isotropic gabbros,dolerite and plagiogranite dikes,and extrusive rocks.U–Pb zircon dating of plagiogranite dikes from?ele has revealed an igneous age of 260 Ma,and 255,235,227 Ma from Almac?k（Bozkurt et al.,2012a,b）.Consistent with the previouslypublished Permo–Triassic age,we obtained a 268.4±6.3 Ma U–Pb zircon age from a plagiogranite dike within the Almacik ophiolite to the west.This KS ophiolite belt containing the?ele,Almac?k,Geyve ophiolites within the SZ extends westward into the Armutlu Peninsula and then into the Biga Peninsula（i.e.Denizg?ren ophiolite）and most likely connects with the remnants of the Triassic Meliata–Meliac ocean basin（Stampfli and Borel,2002）in the Balkan Peninsula.The KS ophiolites also continue eastward within the Pontide Belt into the Elekda?ophiolite（eastern Kastamonu）and then to the Refahiye ophiolite in NE Anatolia.Triassic granites in the SZ represent a magmatic arc that formed as a result of the northward subduction of the Izmir–Ankara–Erzincan oceanic lithosphere existing during the late Paleozoic through Cretaceous（Sarifakioglu et al.,2014）beneath the Pontides.We obtained a U–Pb zircon age of 231±2 Ma from a metagranitic intrusion into the Variscan basement of the SZ in the Kastamonu region of the central Pontides.This metagranite is enriched in LILE（Rb:63 ppm;Ba:65 ppm;Sr:200 ppm）and depleted in HFSE（Y:12.58 ppm;Yb:1.26 ppm;Ti O2:0.2 wt.%;Nb:7.6 ppm;Hf:3.9 ppm）,characterizing it as subduction–related calc-alkaline pluton.Lead（3.9 ppm）,U（1.6 ppm）and Ce（59 ppm）contents are interpreted as evidence for contamination by continental crust.The Küre basin to the north opened during the late Triassic to Liassic,following a backarc rifting episode in the central Pontides.Metabasic dike intrusions in the Devrekani metamorphic massif represent the first magmatic stage of this backarc rifting event.Whole-rock 40Ar-39Ar dating ofthe metabasic dikes has yielded cooling ages of 160.5±1.2 Ma. We infer that this age was reset due to thermal heating during the emplacement of the Middle Jurassic granitoids as the Küre oceanic basin was closing. The Küre ophiolite contains upper mantle peridotites and oceanic crustal rocks composed mainly of pillow–massive–breccia basalts, dacitic and rhyolitic lavas–tuffs, diabase dyke swarms, massive gabbros and a limited extent mafic cumulates. We obtained 182.6±1.9 Ma as a whole-rock 40Ar-39 Ar age from a pillow basalt and a U–Pb zircon age of 171±1 Ma from the granitic intrusion cross-cutting the peridotites. The easternmost representatives of the Küre ophiolite occur in the Yusufeli（Artvin） area in the eastern part of the Pontide belt. Here, oceanic crustal rocks are tectonically related to metamorphic rocks of the Variscan basement of the SZ. The ophiolitic crustal rocks contain isotropic gabbro and mafic and felsic dikes. Serpentinized upper mantle peridotites are scarce. Pillow lava basalts are overlain by a thick metasandstone–metashale association with locally foliated meta–lava and some manganiferous chert and mudstone interlayers. We obtained a U–Pb zircon age of 172.5±1.4 Ma from the granitic intrusion cross-cutting the Yusufeli ophiolite and of 181.9±0.9 Ma from a felsic dike（plagiogranite） in the Yusufeli ophiolite. The Middle Jurassic granites are related to the closure of the Küre-Yusufeli marginal ocean basin. The Küre and Yusufeli ophiolites have been previously interpreted as the remnants of the Paleotethys or the Intra-Pontide Ocean. However, we posit that these ophiolites represent amarginal, short-lived（;0 Ma） ocean basin, which opened during the late Triassic through Liassic, and then closed in Dogger. This oceanic lithosphere is similar to the Evros ophiolite in the northeastern Greece in terms of its ages and geochemical characteristics.展开更多
基金The Scientific and Technological Research Council of Turkey(TUBITAK-Grant 108Y309)
文摘The Eastern Pontides orogenic belt in the Black Sea region of Turkey offers a critical window to plate kinematics and subduction polarity during the closure of the Paleotethys. Here we provide a brief synthesis on recent information from this belt. We infer a southward subduction for the origin of the Eastern Pontides orogenic belt and its associated late Mesozoic--Cenozoic magmatism based on clear spatial and temporal variations in Late Cretaceous and Cenozoic arc magmatism, together with the exis- tence of a prominent south-dipping reverse fault system along the entire southern coast of the Black Sea. Our model is at variance with some recent proposals favoring a northward subduction polarity, and illus- trates the importance of arc magmatism in evaluating the geodynamic milieu associated with convergent margin orocesses.
基金the grant No.109Y052 from the Turkish Research Foundation(TBITAK)
文摘A series of Cretaceous plutons is present in the eastern Pontides of northeastern Turkey. The Turnag61 intrusion is the least studied and, thus, the least understood plutons in the orogen. This intrusion consists of hornblende-biotite granodiorites emplaced at 78 Ma based on LA-ICP-MS U-Pb zircon dating. It is of sub- alkaline affinity, belongs to the medium- to high-K calc-alkaline series, and displays features typical of I- type granites. The rocks of the intrusion are enriched in large-ion lithophile elements and light rare earth- elements with negative Eu anomalies （EuJEu＊ = 0.69-0.82）, but are deficient in high-field-strength elements. They have a small range of （87Sr/S6Sr）i （0.7060 0.7063）, ENd （-2.6 to 3.1）, and 6180 （＋8.1 to ＋9.1） values. Their Pb isotopic ratios are 206pb/204pb = 18.63-18.65, ＇207Tpb/204pb = 15.62-15.63, and 208pb/204pb 38.53-38.55. The fractionation of plagioclase, hornblende, and Fe-Ti oxides had key functions in the evolution of the Turnag61 intrusion. The crystallization temperatures of the melts ranged from 758 to 885 ℃ as determined by zircon and apatite saturation thermometry. All these characteristics, combined with the low values of K20/Na20 and （Na20 ＋ K20）/（FeOt ＋ MgO ＋ TiO2）, as well as the high values of （CaO ＋ FeOt ＋ MgO ＋ TiO2）, suggest an origin by dehydration melting from a metabasaltic lower crustal source.
基金supported by the Scientific and Technical Research Council of Turkey International Research Fellowship Programme(Nos.TüB?TAK 2214-A,1059B141800146)supported by OYP research foundation。
文摘The Eastern Pontides orogenic belt(EPOB)represents a significant segment of the AlpineHimalayan orogenic belt that evolved from the Paleozoic to Cenozoic periods.Here we report new zircon U-Pb ages,together with Lu-Hf isotopes,and whole-rock geochemical and Sr-Nd isotopic analyses of plutonic rocks from EPOB,northeastern Turkey.Our aim is to interpret magmatic evolution in which the granitoids formed.Zircon U-Pb dating of six samples yielded crystallization ages of~134,~82,~39 Ma,respectively.They show a wide range of87Sr/86Sr((i))(0.7039–0.7109),andεNd(t)values varying from-9 to+4.6,yielding model ages(TDM)from 520 to 1623 Ma,suggesting a heterogeneous magma source.Dated zircons show exlusively positiveεHf(t)values(+12.4 to+1.4),yielding model ages(TDM)from 352 to 1059 Ma,implying that they are most likely derived from a juvenile lower crust rather than the mature continental crust.In this study,we suggested that the northward subduction of the Neo-Tethyan oceanic slab began from the Early Cretaceous and resulted in the Late Cretaceous magmatism.Moreover,the Middle Eocene magmatism in the EPOB was related to the collision of the Anatolide Taurid Platform(ATP)with the Pontides.
基金supported by the Scientific and Technological Research Council of Turkey(TBITAK,Grant No.108Y309)
文摘The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine-Himalayan belt. The late Mesozoic-Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on the nature of the transition from the adakitic to non-adakitic magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved. The adakitic lithologies comprise porphyries and hyaloclastites. The porphyries are represented by biotite-rich andesites, hornblende-rich andesite and dacite. The hayaloclastites represent the final stage of adakitic activity and they were generated by eruption/intrusion of adakitic andesitic magma into soft carbonate mud. The non-adakitic lithologies include basaltic-andesitic volcanic and associated pyroclastic rocks. Both rock groups are cutting by basaltic dikes representing the final stage of the Cenozoic magmatism in the study area. We report zircon U-Pb ages of 48.71 ± 0.74 Ma for the adakitic rocks, and 44.68 ± 0.84 Ma for the non-adakitic type, suggesting that there is no significant time gap during the transition from adakitic to non-adakitic magmatism. We evaluate the origin, magma processes and tectonic setting of the magmatism in the southern part of the eastern Pontides orogenic belt. Our results have important bearing on the late Mesozoic-Cenozoic geodynamic evolution of the eastern Mediter- ranean region.
基金supported by Karadeniz Technical University Research Foundation(FBA-2017-7286 and FBA-2023-10635)National Natural Science Foundation of China(42103038)Open Research Project from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR201815).
文摘The Meso-Cenozoic geodynamic evolution of northern Türkiye remains a subject of debate primarily due to a lack of systematic geological,geochemical,geochronological,and geophysical investigations.This paper presents comprehensive geochronological and geochemical data on the Late Triassic andesite porphyry,andesite breccia and quartz diorite porphyry,and the Middle Jurassic diabase,and amphibole-poor and amphibole-rich andesite porphyry fromÇevrepınar Igneous Complex(Gümüşhane)in the southern part of the Eastern Pontides Orogenic Belt(EPOB),a well-preserved continental arc in the Alpine-Himalayan orogen.Zircon U-Pb geochronology indicates crystallization ages of∼208-202 Ma(Rhaetian)for the Late Triassic rocks and∼175-172 Ma(Aalenian)for the Middle Jurassic rocks.Whole-rock geochemical and Sr-Nd-Pb isotopic data,and zirconεHf(t)data indicate that both the Late Triassic and the Middle Jurassic rocks originated by low-degree melting of a spinel lherzolite lithospheric mantle source modified by subduction-related fluids and/or melts.Based on the new and published data,we suggest that the Late Triassic to Middle Jurassic arc magmatism in EPOB occurred as a result of southward subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana-Land.Late Triassic to Jurassic arc magmatism and basin evolution occurred synchronously in the northern and southern peripheries of the present-day Eastern Black Sea Basin,indicating divergent double subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana and southern margin of Laurasia during the Early Mesozoic.
基金supported by the Darius Project,PRIN 2008 and PRIN 2010-11 projects (resp.M.Marroni) and PRA 2018 from Universita di Pisa
文摘The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s)and to understand how its western and eastern branches were connected.One of the lesser known branches of the Mesozoic ocean(s)is preserved in the northern ophiolite suture zone exposed in Turkey,namely,the Intra-Pontide suture zone.It is located between the Sakarya terrane and the Eurasian margin(i.e.,Istanbul-Zonguldak terrane)and consists of several metamorphic and non-metamorphic units containing ophiolites produced in supra-subduction settings from the Late Triassic to the Early Cretaceous.Ophiolites preserved in the metamorphic units recorded pervasive deformations and peak metamorphic conditions ranging from blueschist to eclogite facies.In the nonmetamorphic units,the complete oceanic crust sequence is preserved in tectonic units or as olistoliths in sedimentary melanges.Geochemical,structural,metamorphic and geochronological investigations performed on ophiolite-bearing units allowed the formulation of a new geodynamic model of the entire"life"of the IntraPontide oceanic basin(s).The reconstruction starts with the opening of the Intra-Pontide oceanic basins during the Late Triassic between the Sakarya and Istanbul-Zonguldak continental microplates and ends with its closure caused by two different subductions events that occurred during the upper Early Jurassic and Middle Jurassic.The continental collision between the Sakarya continental microplate and the Eurasian margin developed from the upper Early Cretaceous to the Palaeocene.The presented reconstruction is an alternative model to explain the complex and articulate geodynamic evolution that characterizes the southern margin of Eurasia during the Mesozoic era.
文摘Most of the massive sulfide deposits (VMS) occurring from Precambrian to Cenozoic throughout the world has been subsequently metamorphosed at various grades. Thus, all the original textures have been either completely destroyed or strongly modified. However, there are a very few examples, rather younger deposits such as late Cretaceous Turkish VMS deposits and Miocene Kuroko deposits of Japan in which representative and original ore textures are preserved. The Turkish massive sulfide deposits are mainly Cu-Zn-Pb-type and entirely hosted by Late Cretaceous felsic volcanic rocks within a paleoarc geotectonic setting.
基金supported by a grant from the General Directorate of Mineral Research and Exploration of Turkey (MTA, Ankara project no: 2009.30.14.09.4+1 种基金 2010.30.14.08.32011.30.14.08.3)
文摘The Pontide belt in northern Turkey includes three major tectonic terranes,the Strandja Massif（Sj M）,and the Istanbul（ISZ）and Sakarya Zones（SZ）(Fig.1).We present new age and geochemical data from ophiolites and ophiolitic mélanges within the Sakarya Zone and show that these mafic–ultramafic rocks are the remnants of Tethyan oceanic lithosphere formed in different tectonic settings.The main ophiolite occurrences investigated in this study along the Karakaya Suture（KS）are associated with the latest Triassic Cimmeride orogeny,and in the Küre–Yusufeli ophiolite belt are part of the Alpide orogeny.The Karakaya Suture Zone ophiolites in northern west Turkey are comprised mainly of the Denizgoren（?anakkale）ophiolite,Bo?azk?y（Bursa）,Geyve（Sakarya）,Almac?k（Düzce）and?ele（Bolu）metaophiolites.The Denizg?ren ophiolite largely contains upper mantle peridotites,which are equivalents of the Permo–Triassic Lesvos peridotites and mélange units farther SW in the northern Aegean Sea.The Bo?azk?y ophiolite includes serpentinite and metagabbro,and the Almac?k and Geyve ophiolites display an almost complete Penrose–type sequence consisting of serpentinizeduppermantleperidotites,cumulate ultramafic–mafic rocks,isotropic gabbros,dolerite and plagiogranite dikes,and extrusive rocks.U–Pb zircon dating of plagiogranite dikes from?ele has revealed an igneous age of 260 Ma,and 255,235,227 Ma from Almac?k（Bozkurt et al.,2012a,b）.Consistent with the previouslypublished Permo–Triassic age,we obtained a 268.4±6.3 Ma U–Pb zircon age from a plagiogranite dike within the Almacik ophiolite to the west.This KS ophiolite belt containing the?ele,Almac?k,Geyve ophiolites within the SZ extends westward into the Armutlu Peninsula and then into the Biga Peninsula（i.e.Denizg?ren ophiolite）and most likely connects with the remnants of the Triassic Meliata–Meliac ocean basin（Stampfli and Borel,2002）in the Balkan Peninsula.The KS ophiolites also continue eastward within the Pontide Belt into the Elekda?ophiolite（eastern Kastamonu）and then to the Refahiye ophiolite in NE Anatolia.Triassic granites in the SZ represent a magmatic arc that formed as a result of the northward subduction of the Izmir–Ankara–Erzincan oceanic lithosphere existing during the late Paleozoic through Cretaceous（Sarifakioglu et al.,2014）beneath the Pontides.We obtained a U–Pb zircon age of 231±2 Ma from a metagranitic intrusion into the Variscan basement of the SZ in the Kastamonu region of the central Pontides.This metagranite is enriched in LILE（Rb:63 ppm;Ba:65 ppm;Sr:200 ppm）and depleted in HFSE（Y:12.58 ppm;Yb:1.26 ppm;Ti O2:0.2 wt.%;Nb:7.6 ppm;Hf:3.9 ppm）,characterizing it as subduction–related calc-alkaline pluton.Lead（3.9 ppm）,U（1.6 ppm）and Ce（59 ppm）contents are interpreted as evidence for contamination by continental crust.The Küre basin to the north opened during the late Triassic to Liassic,following a backarc rifting episode in the central Pontides.Metabasic dike intrusions in the Devrekani metamorphic massif represent the first magmatic stage of this backarc rifting event.Whole-rock 40Ar-39Ar dating ofthe metabasic dikes has yielded cooling ages of 160.5±1.2 Ma. We infer that this age was reset due to thermal heating during the emplacement of the Middle Jurassic granitoids as the Küre oceanic basin was closing. The Küre ophiolite contains upper mantle peridotites and oceanic crustal rocks composed mainly of pillow–massive–breccia basalts, dacitic and rhyolitic lavas–tuffs, diabase dyke swarms, massive gabbros and a limited extent mafic cumulates. We obtained 182.6±1.9 Ma as a whole-rock 40Ar-39 Ar age from a pillow basalt and a U–Pb zircon age of 171±1 Ma from the granitic intrusion cross-cutting the peridotites. The easternmost representatives of the Küre ophiolite occur in the Yusufeli（Artvin） area in the eastern part of the Pontide belt. Here, oceanic crustal rocks are tectonically related to metamorphic rocks of the Variscan basement of the SZ. The ophiolitic crustal rocks contain isotropic gabbro and mafic and felsic dikes. Serpentinized upper mantle peridotites are scarce. Pillow lava basalts are overlain by a thick metasandstone–metashale association with locally foliated meta–lava and some manganiferous chert and mudstone interlayers. We obtained a U–Pb zircon age of 172.5±1.4 Ma from the granitic intrusion cross-cutting the Yusufeli ophiolite and of 181.9±0.9 Ma from a felsic dike（plagiogranite） in the Yusufeli ophiolite. The Middle Jurassic granites are related to the closure of the Küre-Yusufeli marginal ocean basin. The Küre and Yusufeli ophiolites have been previously interpreted as the remnants of the Paleotethys or the Intra-Pontide Ocean. However, we posit that these ophiolites represent amarginal, short-lived（;0 Ma） ocean basin, which opened during the late Triassic through Liassic, and then closed in Dogger. This oceanic lithosphere is similar to the Evros ophiolite in the northeastern Greece in terms of its ages and geochemical characteristics.
