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The Rheic Ocean is the most significant Paleozoic ocean that detached peri-Gondwana terranes from the northern Gondwana margin throughout the closure of the Iapetus Ocean. The suture of the Rheic Ocean spreads from Mexico to the Middle East, and the timing of its final closure is well-documented by the rocks formed in the Variscan-Alleghanian-Ouachita orogeny which led to the formation of the supercontinent Pangaea. However, as robust paleomagnetic and quantitative data are mostly lacking, the onset and evolution of the subduction of the Rheic Ocean are highly speculative, and they require further confirmation. Recently, the well-preserved metagranitoids along the western Sakarya Zone (SZ) in Anatolia have been identified, and they provide new data that improve our knowledge on the evolution of the Early Paleozoic Rheic Ocean along the northern Gondwana. Here, we present new geochronological, in situ zircon Hf isotope, and whole-rock geochemical analyses of these metagranitoids from the western SZ to enhance our understanding of the subduction processes of the Rheic Ocean. IA-ICP-MS zircon U-Pb dating demonstrated that the Boziiyuk and Borcak metagranitoids from the western SZ were emplaced during the Silurian to Early Devonian (431 +/- 2.7 to 403 +/- 3.5 Ma). The both granitoids have medium- to high-K. calc-alkaline magmatic character, and exhibit peraluminous to slightly metaluminous geochemical signature. They show a typical arc pattern in terms of trace elements and have a uniform, moderate negative epsilon(Hf) (t) of -3.2 to -9.7, with Mesoproterozoic Hf depleted mantle model ages (T-DM1 = 12 to 1.4 Ga). The geochemical and isotopic characteristics are not consistent with those of depleted mantle melts and melts derived from the crustal rocks in an intracontinental environment. Instead, the parental magma is likely generated from the partial melting of a homogeneous and enriched mantle wedge source. We propose that the Silurian to Early Devonian arc-related magmatism is associated with a northward subduction episode of the Rheic Oceanic lithosphere beneath the peri-Gondwana terranes. Hence, we consider that the opening of Paleotethys Ocean formed in a back-arc basin of subduction in Andean style to the north rather than a continental rift to the south in response to south-directed and short-lived supra-subduction zone (SSZ)-type subduction during the Silurian to Early Devonian. (C) 2020 Elsevier B.V. All rights reserved.

Upper Jurassic-lower Cretaceous carbonates (Berdiga Fm.) are widely exposed in the NE Turkey. An integrated study of sedimentological and geochemical analysis was carried out on the lower Cretaceous carbonates of Berdiga Fm. in Trabzon area in order to reveal the paleoenvironmental and paleoclimatological conditions of northern Tethyan Ocean. Three microfacies types were identified corresponding to inner to slope environments. Inner platform environment developed during the Hauterivian-Aptian interval. End of the Aptian, syn-sedimentary extensional tectonic regime might probably have caused the progressive deepening of the environment, so the inner platform environment evolved into an outer platform and then into slope during the late Aptian-Albian time. Additionally, delta O-18 stable isotope values of the belemnites of studied section indicate that paleotemperature ranged between 25 and 26 degrees C during AptianAlbian interval. Therefore warm Cretaceous climate conditions were recorded in the Eastern Pontides.

Late Carboniferous to early Permian granitoid rocks represent a volumetrically minor component of the Eastern Pontide lithosphere, but they preserve useful information about the region's tectonomagmatic history. The Casurluk and Camlik plutons primarily consist of gabbro, gabbroic diorite, diorite, monzogabbro, monzodiorite and monzonite, which intrude early to middle Carboniferous granitic basement rocks in the region. In this study, we use in situ zircon U-Pb ages and Lu-Hf isotopic values, whole-rock Sr-Nd isotopic values, and mineral chemistry and geochemistry of these plutons to determine petrogenesis and crustal evolution; we also discuss geodynamic implications. LA-ICP-MS zircon U-Pb dating of magmatic zircons from the rocks suggests that the plutons were emplaced during the late Carboniferous to early Permian (302 Ma). The metaluminous and I-type intrusive rocks belong to the high-K calc-alkaline series. In addition, they are relatively enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs); they are depleted in heavy rare earth elements (HREEs) and high field strength elements (HFSEs), such as Nb and Ti. All of the samples have homogeneous initial I-Sr values (0.70675 to 0.70792) and low epsilon(Nd) (t) values (-5.1 to -3.3). Zircons from the rocks of both plutons have uniform negative to slightly positive epsilon(Hf) (t) values (-3.5 to 1.4) and old Hf two-stage model ages (1323 to 1548 Ma), implying that they have the same source, as well as suggesting the involvement of old enriched litho spheric mantle materials during their magma genesis. These results, combined with the epsilon(Hf) (t) values and two stage model ages, demonstrate that the primary magmas were derived from partial melting of old lithospheric mantle material metasomatized by subduction-related fluids. Considering other regional geological data from the Sakarya Zone where these plutons formed, we conclude that late Carboniferous to early Permian magmatism in the area involved the partial melting of a phlogopite- and spinel-bearing lherzolite under an extensional regime in a subduction-related setting. Such an extension event would have caused hot asthenospheric upwelling and was likely triggered by back-arc rifting during subduction of the Paleo-Tethyan oceanic slab. Thus, the magmas are likely subduction-related products, implying that southward subduction of Paleo-Tethys oceanic lithosphere in the region began during the late Carboniferous to early Permian. (C) 2016 Elsevier B.V. All rights reserved.

We report on the structure, geochemistry, Re-Os isotopes and relative abundances of highly siderophile elements (HSEs) of the Paleozoic peridotite-basalt occurrences in the Eastern Pontide belt of northeastern Turkey. These peridotites and the associated basaltic rocks are the remnants of the Rheic oceanic lithosphere, incorporated into the Eurasian continental margin during the Variscan (Hercynian) orogeny. The peridotites display a complex record of multiple magmatic, metasomatic and metamorphic events in different tectonic settings during the evolution of the Rheic upper mantle. The Beycam harzburgite (BH) contains low Al2O3 (0.51-1.88 anhydrous wt.%) and high MgO (4135-4234 wt.%) contents, and its bulk-rock trace element compositions are less than 10% of the primitive upper mantle (PUM) values. The platinum, Pd and Re contents of the Beycam harzburgite are highly depleted, whereas its Os, It, and Ru contents are slightly enriched relative to the PUM values. Its Pd and Re contents that are higher than those of the fertile Pulur Iherzolite (PL) to the south and the absence of an isochronous relationship between its Os-187/Os-188 and Re-187/Os-188 show that the trace element distribution and the isotope ratios of the Beycam harzburgite were significantly modified after the first melt-extraction episode. The first melt extraction occurred beneath the Rheic mid-ocean ridge spreading center, whereas the second melt extraction occurred in a mantle wedge above a Rheic subduction zone. The primary magmatic phases of the Pulur lherzolite show the geochemical characteristics typical for fertile lherzolite, formed in the early stages of oceanic lithosphere generation subsequent to the continental break up. The Pulur Iherzolite also contains a secondary magmatic phase in the form of networks of dinopyroxene veins and channels, which are interpreted as an evidence for solid state melt-rock reactions between the Iherzolite and a percolating basaltic melt above a subduction zone. This dinopyroxene addition resulted in the formation of variable concentrations of Al2O3 (2.47-433 wt.%) and MgO (29.76-40.10 wt.%) in the lherzolite. The rhenium, Pd and Pt concentrations of the Pulur lherzolite are depleted relative to the PUM values, whereas the Os, Ir and Ru concentrations are in the range of the PUM values as commonly observed in peridotites with a melt depletion history. The high suprachondritic Os-187/Os-188 is however, inconsistent with a simple melt depletion history, and can be explained by the addition of radiogenic Os-bearing sulfide phases into the lherzolite as a result of melt-rock reactions. Basaltic rocks with an island arc tholeiitic composition from the Beycam area represent the partial melting product of the moderately depleted Beycam harzburgite and the basaltic parental melt from which the dinopyroxene precipitated. The covariation between the Re-187/Os-188 and Os-187/Os-188 of these basaltic rocks defines an isochron age of 377 +/- 8 Ma (late Devonian). The combined structural, geochemical and isotope data indicate a prolonged history of multiple episodes of melt extraction-depletion, and melt-rock interaction and fertilization of the mantle lithosphere of the Rheic Ocean. (C) 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

SARI, Bilal/0000-0002-2389-2772; KANDEMIR, RAIF/0000-0002-0344-9159 WOS: 000346592200003 The upper Campanian (Cretaceous) of the Hacimehmet area (south of the city of Trabzon; Eastern Pontides) is mainly composed of calciclastic turbidites. the basinal unit of the 119 m thick succession includes thin red pelagic limestone interlayers and conglomerates dominated by volcanic clasts. the overlying upper slope and lower slope units of the sequence consist of an alternation of allochthonous calcarenite/calcirudite beds and pelagic marls and mudstones. Calcarenite/calcirudite beds dominate the upper slope unit of the succession and are composed of transported material, including benthic foraminifers, red algae, bryozoan, crinoid and rudist fragments, inoceramid bivalve prisms and neritic and pelagic carbonate lithoclasts. the occurrence of Helicorbitoides boluensis (Sirel) extracted from the calcarenite/calcirudite beds indicates a Campanian age. Identifiable rudists such as Joufia reticulata Boehm, Bournonia cf. anatolica Ozer, Biradiolites cf. bulgaricus Pamouktchiev and ?Biradiolites sp. from the upper slope unit of the succession indicate a late Campanian-Maastrichtian age. the planktonic foraminifers within the red pelagic limestone beds, marls and mudstones throughout the succession consist mainly of Campanian-Maastrichtian forms and suggest mainly basinal depositional conditions. the presence of Radotruncana cf. calcarata (Cushman) accompanied by Globotruncanita elevata (Brotzen) in the basinal unit of the succession indicates an early late Campanian age for the lower part of the succession. Inoceramid bivalves have been collected from the upper part of the succession. the fauna is dominated by 'Inoceramus' tenuilineatus Hall and Meek, 1854 and Cataceramus haldemensis (Giers, 1964); other taxa recognised are: 'Inoceramus' algeriensis Heinz, 1932, Platyceramus vanuxemi (Meek and Hayden, 1860), 'Inoceramus' cf. nebrascensis Owen, 1852, Cataceramus aff. barabini (Morton, 1834), Cataceramus gandjaensis (Aliev, 1956), and 'Inoceramus' sp.; the assemblage indicates the 'Inoceramus' tenuilineatus Zone; corresponding to the middle-late Campanian boundary interval. the uppermost part of the succession is characterized by the presence of the trace fossils Scolicia strozzii and Scolicia isp., indicating a mixed Skolithos-Cruziana ichnofacies. This ichnofacies suggests a well-oxygenated environment. TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [106Y144] We would like to thank the journal referees, M. Ziya Kirmaci, from the Karadeniz Technical University in Trabzon, Turkey, and an anonymous one, and the editor, Chris J. Wood, Mineahead, for various comments, which helped us to improve the final version of this paper. This study was financially supported by TUBITAK Grant no: 106Y144, which is acknowledged.

WOS: 000282474000001, We present elemental and Sr-Nd-Pb isotopic data for the magmatic suite (similar to 79 Ma) of the Harsit pluton, from the Eastern Pontides (NE Turkey), with the aim of determining its magma source and geodynamic evolution. The pluton comprises granite, granodiorite, tonalite and minor diorite (SiO(2) = 59.43-76.95 wt%), with only minor gabbroic diorite mafic microgranular enclaves in composition (SiO(2) = 54.95-56.32 wt%), and exhibits low Mg# (, Scientific and Technological Research Council of Turkey (TUBITAK) [107Y177, 108Y200], This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) with grants # 107Y177 and 108Y200. The authors are also grateful to Durmus Boztug and Hakan Coban for their critical and constructive comments. Ahmet D. Sen and Murat Ketenci are thanked for their enthusiastic assistances during fieldwork.

WOS: 000274378300008, Early Cenozoic (48-50 Ma) adakitic volcanic rocks from the Eastern Pontides NE Turkey consist of calc-alkaline and high-K calc-alkaline andesite and dacite, with SiO(2) contents ranging from 56 01 to 65 44 wt.%.. This is the first time that Early Eocene volcanism and adakites have been reported from the region. The rocks are composed of plagioclase, amphibole, quartz, and Mg-rich biotite. They have high and low-Mg# values ranging from 55 to 62 and 13 to 42. respectively. High-Mg# rocks have higher Ni and Co contents than low-Mg# samples. The rocks exhibit enrichments in large ion lithophile elements including the light rare earth elements, depletions in Nb, Ta and Ti and have high La/Yb and Sr/Y ratios. Their relative high I(Sr) (0.70474-0.70640) and low epsilon(Nd) (50 Ma) values (-2.3 to 0.8) are inconsistent with an origin as partial melts of a subducted oceanic slab. Combined major- and trace element and Sr-Nd isotope data suggest that the adakitic magmas are related to the unique tectonic setting of this region, where a transition from a collision to an extension stage has created thickening and delamination of the Pontide mafic lower crust at 50 Ma The. high-Mg adakitic magmas resulted from partial melting of the delaminated eclogitic mafic lower crust that sank into the relatively hot subcrustal mantle, and its subsequent interaction with the mantle peridotite during upward transport, leaving garnet as the residual phase, elevates the MgO content and Mg# of the magmas, whereas low-Mg# magmas formed by the melting of newly exposed lower crustal rocks caused by asthenospheric upwelling, which supplies heat flux to the lower crust. The data also suggest that the mafic lower continental crust beneath the region was thickened between the Late Cretaceous and the Late Paleocene and delaminated during Late Paleocene to Early Eocene time, which coincides with the initial stage of crustal thinning caused by crustal extensional events in the Eastern Pontides and rules out the possibility of an extensional regime before similar to 50 Ma in the region during the Late Mesozoic to Early Cenozoic. (C) 2009 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [107Y177], Financial support of this work was provided by the Scientific and Technological Research Council of Turkey (TUBITAK) with grant# 107Y177. We thank Bin Chen for the Sr-Nd isotopic analyses and Ahmet D. Sen and Murat Ketenci for their assistance with the fieldwork. Special thanks are due to Murat Erduran for his useful comments on an early version of this manuscript. We thank the editor, Professor Nelson Eby, and Pat Castillo and an anonymous reviewer for their constructive reviews.