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• Mersin peridotites show significantly depleted nature. • Peridotites indicate metasomatic interaction with boninitic melts. • Chromitites derived from boninitic melts. • Composition of laurite inclusions indicate low fS 2 conditions. • Subduction initiation formed island arc tholeiites and boninites. The Mersin ophiolite of the Central Taurides in southern Turkey represents an incomplete section of ocean lithosphere consisting from bottom to top of chromitite-bearing mantle peridotites, cumulate dunites, clinopyroxenites, and gabbros with rare pillow lavas covered by bathypelagic sedimentary rocks. The tectonized peridotites are harzburgites with minor dunites. They are strongly melt-depleted peridotites, comprising chromian spinel (Cr-spinel) with medium to high Cr-numbers (Cr#) [100 × Cr/(Cr + Al) = 48–82] and low Al 2 O 3 concentrations (0.05–2.2 wt%). They display concave chondrite-normalized rare earth element (REE) patterns, which we interpret as evidence for their refertilization by boninitic melts in a mantle wedge. Geochemical evidence suggests that the parental magmas of the high-Cr podiform chromitites (Cr# Sp = 71–83) were of boninitic composition. The chromitites host a platinum-group mineral (PGM) assemblage of laurite [Ru# = 64.0–90.7] and Os-Ir alloys, indicating crystallization within a range of low f S 2 conditions (log f S 2 ∼ −2 to −1.3) and a T max of ∼1200 °C. Mineral compositions and geochemical data of the basalts show tholeiitic to alkali compositions. The tholeiites show mildly light REE depleted patterns and high Th/Yb and La/Nb ratios indicate the presence of a sediment component, implying a subduction-related origin. Petrogenetic modeling indicates that the tholeiitic basalts resulted from 20% melting of a spinel-bearing asthenospheric mantle. The initial ε Nd values of 7.2 and 4.9 for two tholeiite samples indicate depleted asthenosphere and more enriched mantle sources probably due to the input of older sediment. A comparison with the data of other ophiolite complexes from southern Turkey suggests subduction-overprinted mantle sources as seen in immature island arcs. The trace element patterns of the alkali basalts are similar to OIB implying an origin unrelated to that of the ophiolite assemblage. The composition of the OIB can be modeled by mixing of magmas from low-degree (1–2%) melting of garnet-bearing lherzolite (GLS) with melt fractions from a spinel-bearing lherzolite (SLS) at variable proportions (GLS/SLS = 7/10–1/10). We propose the following tectono-magmatic model for the petrogenetic evolution of the Mersin ophiolite: i) oceanic ridge spreading generated MORB type magmas (not observed in our sample collection), (ii) melting of deep mantle sources beneath MORB type crust generated OIB-like basalts in Neo-Tethyan oceanic basin, (iii) subduction initiation and formation of an infant forearc basin formed island arc tholeiites and boninites. [ABSTRACT FROM AUTHOR]

The fossil record of slipper lobsters (Scyllaridae) is very poor, even though the earliest species of the modern slipper lobsters (Neoscyllaridae) are known from the Early Cretaceous. Among the clades ('subfamilies') of slipper lobsters, perhaps the most remarkable is Ibacinae (currently monogeneric), which contains species with a very wide carapace (cephalothoracic shield) and very deep incisions. Fossil species assigned to Ibacinae were reported from the Oligocene and Pleistocene. However, a recent reappraisal of Scyllaridae phylogeny revealed that the genus to which these two fossil occurrences belong is not closely allied to Ibacinae. Therefore, Ibacinae was left with no known fossil record until the present study. The present study describes a new species, which can be confidently assigned to Ibacinae (closely allied to Ibacus), from the Ypresian (early Eocene) of the Ghazij Formation in Shaisuro, Dera Ghazi Khan District, Pakistan. This new species, Ibacus? mazariorum sp. nov., corresponds to the oldest recorded occurrence of Ibacinae. The Ghazij Formation was deposited on the north-western margin of the India-Pakistan plate during a critical period, shortly before the collision between the India-Pakistan plate and Asia. Consequently, it is possible that Ibacus and closely allied species may have remained in the same biogeographical area since the Eocene. Considering the extant and fossil distribution of Ibacinae, additional fossil discoveries may be found in existing collections and fossiliferous outcrops from the Neotethys, Indian and Pacific oceans. http://zoobank.org/urn:lsid:zoobank.org:pub:84F54514-AA21-4A9D-91CA-BDCACBA5F4F8 [ABSTRACT FROM AUTHOR]

The formation of the Jurassic Xiongcun porphyry copper deposit, within the Gangdese magmatic belt of southern Tibet, took place coincident with subduction of the Neotethyan oceanic lithosphere. Although the Yeba Formation (coeval and co-magmatic intrusions and volcanic rocks) in the eastern Gangdese magmatic belt formed at the same time as the Xiongcun deposit, the Yeba Formation is devoid of subduction-related porphyry Cu deposits. Here, we report detrital zircon U-Pb ages for sedimentary rocks of the Yeba and Bima Formations along with a summary of all published whole-rock geochemical data and zircon epsilon Hf isotopes for the volcanic rocks in the Yeba Formation. We use these data to re-evaluate the petrogenesis, magmatic source, and tectonic setting of the volcanic rocks. Detrital zircon ages from the sedimentary rocks reveal that the volcanic rocks of the Yeba and Bima Formations are the main source for their sedimentary interlayers. In addition, the Yeba sedimentary layers contain inherited zircons sourced from older country rocks whereas the Bima Formation is devoid of ancient zircons. Geochemically, the Yeba volcanic rocks resemble a bimodal volcanic suite. Geochemical data reveal that the Yeba volcanic rocks formed in a continental arc setting, while the mafic ones were derived from the partial melting of the mantle wedge above the subducting slab rather than from the melting of the descending oceanic slab. In addition, the mafic ensemble formed in a back-arc setting, indicative of subduction-related extension in the Lhasa terrane. In contrast, the felsic ensemble may originate from the melting of basaltic lower crust. Thus, the magma source and tectonic setting for the Yeba Formation are distinct from typical subduction-related Cu-hosted porphyry and volcanic rocks in a compressional setting. [ABSTRACT FROM AUTHOR]

Abstract The Southeast Anatolian Orogenic Belt (SEAOB) exposes abundant intra-oceanic arc-system rocks. This system consists of ophiolites and arc-type volcanic and intrusive rocks (e.g., granitoids). The volcanics and plutonics have geochemical characteristics similar to modern intra-oceanic arc-system rocks. The petrogenesis of the granitoids and associated volcanic rocks has been widely related to the subduction of the southern branch of the Neotethyan beneath the Anatolian microplate. We report the first detailed SHRIMP zircon U–Pb chronology and a major and trace element geochemical study of the intra-oceanic arc magmatics (i.e. Elazığ magmatics) that out-crop extensivley in the Elazığ-Malatya region and the Eastern part of the SEAOB. The volcanics, which show a low K-tholeiite and calc-alkaline affinity, have LA-ICPMS zircon U–Pb ages of 84–82 Ma. The plutonics, which show low K- tholeiite, calc-alkaline, and shoshonite affinity, have LA-ICPMS zircon U-Pb ages of 84–72 Ma. SHRIMP zircon U–Pb dating reveals that the volcanics and plutonics were formed in the Late Cretaceous. The geochemical and geochronological features indicate that the Elazığ magmatics formed in three stages. The first- and second-stage intrusives’ geochemical characteristics indicate that these rocks are derived from an enriched lithospheric mantle source by a partial melting of the metasomatized mantle in a subduction setting, and the late-stage plutonics are shoshonitics formed in a collisional zone environment. Highlights • We present a study of the volcanic and plutonic rocks of the Elazig magmatics wich are widesprea in the Southeast Anatolian Orogenic Belt. • They are characterized by significant geochemical variation over time. • New Zircon U-Pb dating of volcanics and plutonics yield late Cretaceous ages (between 84 and 72 Ma). [ABSTRACT FROM AUTHOR]

Carboniferous-to-Triassic sediments and volcanics of the External Hellenides were deposited in different environments of the Paleotethys realm: a back-arc setting along the active margin of Eurasia (Tyros Unit), and a passive margin setting along northern Gondwana/Cimmeria (Phyllite-Quartzite Unit s.str.). The volcanosedimentary records and the age spectra of detrital zircons of both units suggest that their different settings persisted until the Anisian, as long as the Paleotethys was open, but approximated in Ladinian times, when both units collided and the Paleotethys was closed. We present provenance data of post-collisional sediments, a Norian quartzite of the Tyros Unit (Toplou Beds) and a Norian (meta)conglomerate of the Phyllite-Quartzite Unit s.str. (Mana Beds). The type of clastic grains and the ages of detrital zircons indicate a similar source of both units dominated by (1) Cryogenian and Tonian/Stenian basement, (2) low-grade Cadomian basement, and (3) Ladinian/Carnian magmatic rocks. The Carnian zircons in the Norian Tyros Unit (223 ± 7 Ma) and in the Norian Phyllite-Quartzite Unit s.str. (223 ± 5 Ma) are strong evidence that the basins of both units were situated close together. Subsequent to Ladinian collision, the Carnian-to-Norian strata of both units were deposited in adjacent interrelated shallow-marine-to-lacustrine basins, the deposits of which are characterized by black shales, reddish bauxite-type pisolites, and badly sorted sandstones/conglomerates supplied from nearby pre-Ordovician East Gondwana-derived basement. The Variscan basement towards the north was largely drowned in Upper Triassic times as is indicated by only few Variscan-aged zircons in the Carnian/Norian Tyros rocks. [ABSTRACT FROM AUTHOR]

Abstract We integrated our new data with a review of published work on the Indo-Myanmar Orogenic Belt (IMOB) of the eastern Neotethys in Myanmar, western Yunnan (China) and Naga Hills (India), in order to better understand subduction-accretion processes of the Neotethys Ocean in SE Asia, and interactive relationships between the Gondwana and Laurasia supercontinents. From east to west, the IMOB is divided into three geographic units, the Shan-Thai Plateau, Myanmar Central Basin and Indo-Burma Range; the Mogok Metamorphic and Slate Belt is within the Shan-Thai Plateau. The Shan-Thai Plateau and eastern Myanmar Central Basin contain Paleozoic sedimentary successions, low-grade to amphibolitic facies metamorphic rocks, and the Luxi ultramafic and Myitkyina-Mogok ultramafic-diorite belts. Unmetamorphosed and metamorphosed sediments have similar detrital zircon age peaks of 1000 Ma, and 700 Ma or 500 Ma, and they are separated by the Luxi ultramafic belt, whose ε Nd (0) and 87Sr/86Sr (i) values are similar to surrounding granite, diorite and migmatite and the γOs = −4.8 ~ −8.8 is indicative of old sub-continental lithospheric mantle, rather than an oceanic suture zone. These data and relations suggest that these regions belong to the Cimmerian continental sliver, derived from the Gondwana supercontinent. The Myitkyina-Mogok ultramafic-diorite belt, located along the eastern margin of the Myanmar Central Basin that was associated with the continental sliver, contains peridotite, andesite, hornblende gabbro, diorite, granodiorite and plagiogranite, all with arc geochemical signatures and ages of 177–166 Ma. The source region of some of these igneous rocks contains a component of EM1, which is close to low 87Sr/86Sr (i) ratio of a migmatite in the Cimmerian continental sliver as shown by Sr Nd isotopes values, suggesting this belt developed as a Jurassic continental margin arc. The Mogok Metamorphic and Slate Belt contains granodiorite, diorite, tonalite, granite and migmatite extending from the Gongshan, Tengchong and Luxi areas in western Yunnan (China) to Mandalay, Kalaw, Padatchaung and Moulmein in Myanmar. These rocks have arc geochemical character and yield ages of 185–170 Ma, 128–112 Ma, 91 Ma and 75–45 Ma, suggesting development of four episodes of arc magmatism. Along the central axis of the Myanmar Central Basin there are magmatic arc-related 106–94 Ma diorite, granodiorite and tonalite, as well as Eocene and Neogene-Present (38–0 Ma) andesite, dacite, trachyte and rhyolite. Accretion took place along the central axis of the Myanmar Central Basin towards the Indo-Burma Range, and westward to the present trench axis on the margin of the Indian Ocean, as shown by westward younging of accretionary complexes and trench-slope basins. A Jurassic accretionary complex, located in the Hpakan area in the north of the Myanmar Central Basin, contains 189–147 Ma high-pressure metamorphic rocks such as jadeitite, garnet-mica schist and glaucophane schist. In the eastern belt of the Indo-Burma Range Early Cretaceous (119–115 Ma) accretionary complexes consist of upper plate Triassic unmetamorphosed and low-grade metamorphic sediments, and lower plate amphibolites, high-pressure metamorphic rocks and Jurassic-Early Cretaceous oceanic plate stratigraphy containing MORB- and OIB-type basalts and thin-bedded radiolarian cherts. Late Early Cretaceous (~100 Ma) and Late Cretaceous to Middle Eocene (75–45 Ma) trench-slope basin deposits, containing abundant fossil plants and shallow-water sedimentary structures, cover most of the Indo-Burma Range, where sediments rest with an angular unconformity on older accretionary complexes. The presence of earlier magmatic arcs, accretionary complexes and trench-slope basins suggests that the present trench on the margin of the Indian Ocean has evolved by continuous eastward subduction since the Jurassic. The magmatic arc axis migrated eastward (landward) during some time periods (Jurassic to Early Cretaceous, and Late Cretaceous to Middle Eocene) and westward (seaward) migration during others (Early Cretaceous to late Early Cretaceous, and Middle Eocene to Present), during continuous east-dipping subduction. Highlights • Indo-Myanmar Orogenic Belt develop multiple alternating forearc- and backarc-ward migration of magmatism • The long-lived subduction-accretion of Neotethys Ocean in SE Asia began in the Jurassic • Magmatic arcs and accretionary complexes occur at the eastern and western portion of the IMOB, respectively [ABSTRACT FROM AUTHOR]

This paper investigates the structure of the northern margin of the Ararat depression in a study area in SE Armenia. The depression is a Cenozoic intermontane basin located to the south of the Lesser Caucasus. The purpose is to improve understanding of the basin's structure and origin within a regional tectonic framework which has been dominated since the Late Cretaceous by the closure of Neotethys and the Arabia‐Eurasia collision. We suggest that the depression is not a graben controlled by normal faults; rather, based on detailed observations, structures in the study area are interpreted as oblique‐slip reverse and thrust faults activated in post Oligocene‐Miocene times. These compressional faults resulted in the formation of asymmetric fold structures including the Lanjanist and Urts anticlines which are well expressed in the surface relief to the north of the Ararat depression. In general the structural pattern is complicated by secondary normal faults which resulted in superimposed gravitational slope processes and erosion. Major structures in the study area originated in a compressional setting associated with the closure of Neotethys since the latest Cretaceous. Post‐collisional strike‐slip faulting was linked to convergence of the Arabian and Eurasian plate margins. Pliocene and Quaternary structures, some still active, show evidence of structural inheritance. The Armenian portion of the Ararat depression contains obduction‐related nappes, anticlines and thrust faults which have potential as structural traps for hydrocarbons. These should be investigated in detail using advanced geophysical methods including 2D and 3D seismic analyses. [ABSTRACT FROM AUTHOR]

We integrate stratigraphic, petrographic and geochemical analysis of subsurface data (wells) together with field surveys to study the sedimentation of a marginal Miocene sub-basin of the Southeastern Anatolian Foreland Basin (SEAFB; SE Turkey). This sub-basin, located in the Batman-Siirt region, is characterized by the existence of evaporites (carbonates, sulphates and chlorides) and alluvial detritus which were divided in the following five lithostratigraphic members, from older to younger: Lower and Upper Yapılar; and Lower, Middle and Upper Sulha. These members deposited in an epicontinental mudflat during the Early Miocene. Both the bromine content and the sulphur and oxygen isotope composition (δ 34 S V-CDT and δ 18 O V-SMOW ) of halite and sulphates samples, respectively, also suggest a marine origin of the precipitation brines. However, influence of geothermal fluids and dissolution-and-re-precipitation of evaporites from uplifted areas in these brines, such as the Early Miocene members and/or Triassic units, is interpreted. Comparing and integrating our results with data documented in previous works, it is here recognized that the depositional model of the studied sub-basin differs from that which explain the coeval sedimentation of units situated in the western part of the SEAFB. Moreover, our model shows some depositional and paleoenvironmental similarities with Miocene evaporites located in the Mesopotamian Foreland Basin. This work provides valuable insights on the Middle Miocene Salinity Crisis which is related to the evolution of the Neotethys closure. [ABSTRACT FROM AUTHOR]

This study concentrates on the petrological and geochemical investigation of mafic rocks embedded within the voluminous Triassic June Complex of the central Sanandaj-Sirjan zone (Iran), which are crucial to reconstruct the geodynamics of the Neotethyan passive margin. The Triassic mafic rocks are alkaline to sub-alkaline basalts, containing 43.36-49.09 wt% SiO2, 5.19-20.61 wt% MgO and 0.66-4.59 wt% total alkalis. Based on MgO concentrations, the mafic rocks fall into two groups: cumulates (Mg# = 51.61-58.94) and isotropic basaltic liquids (Mg# = 24.54-42.66). In all samples, the chondrite-normalized REE patterns show enrichment of light REEs with variable (La/Yb)N ratios ranging from 2.48 to 9.00, which confirm their amalgamated OIB-like and E-MORB-like signatures. Enrichment in large-ion lithophile elements and depletion in high field strength elements (HFSE) relative to the primitive mantle further support this interpretation. No samples point to crustal contamination, all having undergone fractionation of olivine + clinopyroxene + plagioclase. Nevertheless, elemental data suggest that the substantial variations in (La/Sm)PM and Zr/Nb ratios can be explained by variable degrees of partial melting rather than fractional crystallization from a common parental magma. The high (Nb/Yb)PM ratio in the alkaline mafic rocks points to the mixing of magmas from enriched and depleted mantle sources. Abundant OIB alkaline basalts and rare E-MORB appear to be linked to the drifting stage on the northern passive margin of the Neotethys Ocean. [ABSTRACT FROM AUTHOR]

Ostracod association from the Upper Triassic ( Tropites dilleri zone of the Carnian stage) of the sedimentary succession (Mufara Formation) exposed along the east side of Monte Scalpello (Catenanuova, central eastern Sicily) has been studied for the first time. The specimens, silicified, are rare but well preserved and often consist of complete carapaces. They belong to eight families: Healdiidae, Cavellinidae, Bairdiidae, Acratiidae, Bythocyprididae, Pontocyprididae, Judahellidae, Glorianellidae. Twenty-three taxa have been listed; the family Bairdiidae is the most represented among all the others with fifteen species. Four species are new: Bairdia scaliae n. sp., Acratia maugerii n. sp., “ Anchistrocheles” gemmellaroi n. sp. and Judahella? montanarii n. sp. Other species are left in open nomenclature because of the lack of specimens. [ABSTRACT FROM AUTHOR]

The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275-375, 375-500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed. [ABSTRACT FROM AUTHOR]

The Urumieh plutonic complex, in the northernmost part of Sanandaj-Sirjan zone (SSZ) of Iran, consists of ten basic-acidic units which formed in response to subduction and continental collision of the SSZ with the Arabian plate to the south during Mid-Late Cretaceous times. Geochemically, the plutonic unit is divided into three distinct groups: I-type, S-type and A-type that mainly belong to calc-alkalic series. The I-type intrusions, especially mafic members, are enriched in LREE and LILE and possibly formed from metasomatized mantle wedge during the subduction of the Neo-Tethys oceanic crust beneath the SSZ. The felsic I-type rocks are depleted in Ba, Sr, Nb, Ta, Ti and Eu, but enriched in Rb, Th, K, Ce, U and La. These data suggest that they formed in deep crustal levels via partial melting of crustal sources by injection of hot mantle magmas. The S-type rocks are characterized by low Na 2 O (<3.02 wt%), high LILE, relatively high values of molar Al 2 O 3 /(MgO+FeO) and K 2 O/Na 2 O ratios combined with low CaO/(MgO+FeO*) ratios. These features show that the S-type granites originated from partial melting of a metapelitic to metagreywacke source. The A-type alkali feldspar granites formed through the slab break off after the continental collision in northwestern Iran by decompression melting of crustal protolith. The author's new model implies that collision between Arabian margin and north SSZ initiated in the Late Cretaceous and completed until Late Paleocene. In contrast, in the southeast, subduction was active during this period of time, but collision presumably occurred during the Middle to Late Miocene. [ABSTRACT FROM AUTHOR]

The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during Eocene. Mafic and ultramafic units are exposed along the northern part of the CIM in the Sabzevar area. The geology and field relation of Sabzevar ophiolite indicate northward subduction of the Sabzevar basin. The average whole rock chemistry of mafic (gabbros) and ultramafic samples (lherzolite, harzburgite and dunite) is characterized by a range of MgO of 11.16–31.88, CaO 5.22–11.53 and Al2O3 2.77–14.57, respectively. Low LREE/HREE ratio of ultramafic samples is accompanied by enrichment of large ion lithophile elements (LILE) such as Sr, Pb and K. Mafic samples show two distinct groups with low and high LREE/HREE ratios. The spider diagram of mafic samples indicates enrichment in Sr, Pb and K and depletion in REE. Petrological and geochemical evidence and field relations show that the mafic rocks formed in a supra-subduction zone setting. Petrological studies reveal the role of fractional crystallization and assimilation effect by released fluids during subduction related generation of the Sabzevar mafic rocks. We suggest that the studied mafic rocks likely represent the basement of an initial island arc, which was generated in a supra-subduction zone setting within the Neotethys branch of the Sabzevar Ocean at the north of CIM. Copper, gold and chromite mineralizations are studied in relation to island arc setting and supra-subduction environment. Similarities in lithology, ophiolite age and mineralization between Sabzevar ophiolite and Bardaskan-Torbat Heydariyeh ophiolites testify for their separation due to rotation (or faulting) of the Central Iranian Micro-continent. [ABSTRACT FROM AUTHOR]

Orbitolinids with simple embryo and a reduced exoskeletal complexity are reported for the first time from upper Berriasian and upper Valanginian strata of the eastern part of the Getic Carbonate Platform system (Southern Carpathians, Romania). Most of the described taxa belong to the genera Cribellopsis Arnaud-Vanneau and Orbitolinopsis Henson. Other taxa are treated in open nomenclature due to the scarcity of available material and/or poor preservation. Some of them are already well known from the Berriasian of eastern Serbia, and some species have been occasionally found in other places along the northern margin of the Neotethys. The upper Berriasian and upper Valanginian occurrences of dictyoconids in the Southern Carpathians widen the paleogeographic distribution of the earliest record of this group of larger benthic foraminifera. [ABSTRACT FROM AUTHOR]

The Matruh Basin is located in the northwestern part of the Western Desert of Egypt. Being part of the structurally complex northeast African margin, the basin underwent multiple phases of Mesozoic-Cenozoic deformation. Detailed structural analysis of the subsurface structures of this basin, using high-quality 3D seismic and well datasets, has identified two main fault sets: 1) Jurassic- Early Cretaceous (Barremian) NNE-striking normal faults; and 2) Late Cretaceous NW-striking normal faults. The older NNE-striking normal faults were later inverted due to Late Cretaceous compression forming fault-propagation folds (inversion anticlines) in their upper tips. This positive inversion initiated with the "Santonian Event" and continued into the Early Cenozoic. The NW-striking normal faults were not inverted due to their unfavorable orientations. Most inversion structures in the greater Western Desert trend E-W or ENE-WSW and reflect the reactivation of similarly oriented pre-existing normal faults. The NNE orientation of the old, major extensional structures in the Matruh Basin and the resulting control on the later inversion fabric reflects a very different fault architecture. This has dramatically impacted sedimentation patterns and potential hydrocarbon accumulations. The Matruh Basin illustrates the complexities that can be present along the North African Neotethyan margin and underlines the necessity to avoid regional generalizations where gaps in data may be present. [Display omitted] • Matruh Basin underwent multiple phases of Mesozoic-Cenozoic deformation. • Detailed subsurface structural analysis identified two main fault sets. • The basin witnessed positive inversion during the Santonian-Early Cenozoic time. • The NNE-striking normal faults were inverted forming fault-propagation folds. • The NW-striking normal faults were not inverted due to their unfavorable orientations. [ABSTRACT FROM AUTHOR]

The Sistan Suture Zone, eastern Iran, includes blocks and lenses of eclogite-, blueschist- and/or epidote amphibolite-facies rocks that provide an excellent opportunity to examine the exhumation history of oceanic HP/LT rocks and their retrograde derivatives. Zr-in-rutile thermometry of eclogites corroborates previous interpretations suggesting metamorphic temperatures of ca. 550–600 °C during the HP stage in the Sistan area. Flat HREE distribution patterns and Ti-in-zircon temperatures of ca. 500–600 °C document that zircon in eclogite is of metamorphic origin. REE patterns of zircon from felsic meta-igneous rocks do not allow to distinguish between a magmatic or metamorphic origin, but relatively low temperatures indicated by Ti-in-zircon thermometry (ca. 500–600 °C) and the close similarity of zircon (U–Pb) and white mica (Rb–Sr, Ar–Ar) ages favor a metamorphic zircon origin. Previously published isotopic ages of the felsic rocks cannot unambiguously be linked to the eclogite- and/or blueschist-facies P–T conditions due to the absence of unequivocal mineralogical and petrological evidence. Instead, these rocks may record contemporaneous metamorphic processes that took place at a different depth within the subduction complex, or may indicate active ridge subduction and/or melt formation in the subduction zone at relatively low pressures. Biotite-based internal Rb–Sr isochrons of newly dated epidote amphibolite and biotite-albite gneisses indicate ages of ca. 74–80 Ma, either dating fluid-infiltration-induced formation of biotite during relatively fast uplift, or the time of final passage through the effective biotite closure temperature. Rb–Sr ages of phengite from both an epidote amphibolite and a biotite-albite gneiss yield ages that correspond to the HP/LT stage. This outcome, combined with textural evidence for derivation from eclogitic precursors documents that white mica ages of some strongly overprinted Sistan rocks are compromised by inheritance and do not record later exhumation. [ABSTRACT FROM AUTHOR]

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The Gangdese magmatic belt is located in the southern margin of the Lhasa terrane, south Tibet. Here zircon U-Pb ages and Hf isotopic data, as well as whole-rock geochemistry and Sr-Nd isotopes on andesites from the Bima Formation with a view to evaluating the history of the Gangdese magmatism and the evolution of the Neotethys Ocean. Zircon U-Pb dating yields an age of ca 170 Ma from six samples, representing the eruptive time of these volcanic rocks. Zircon Hf isotopes show highly positive ε Hf(t) values of +13 to +16 with a mean of +15.2. Whole-rock geochemical and Sr-Nd isotopic results suggest that the magma source of these andesites was controlled by partial melting of a depleted mantle source with addition of continental-derived sediments, similar to those in the southern arcs of the Lesser Antilles arc belt. In combination with published data, the volcanic rocks of the Bima Formation are proposed to have been generated in an intra-oceanic arc system, closely associated with northward subduction of the Neotethyan oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The Urumieh-Dokhtar magmatic belt of Central Iran runs parallel to the Zagros orogenic belt and has been resulted from Neotethys ocean subduction underneath Eurasia. The Bahr Aseman volcanic-plutonic complex (BAC), covering an area ~ 2000 km 2 in the Kerman magmatic belt (KMB) in the southern section of the Urumieh-Dokhtar belt, has long been considered as the earliest manifestation of extensive Cenozoic arc magmatism in KMB. The nature and timing of the magmatism, however, is poorly constrained. An area ~ 1000 km 2 , in BAC and adjacent Razak volcaniclastic complex and Jebal Barez-type granitoids, was mapped and sampled for geochemistry and geochronology. Andesite and basaltic andesite are the main volcanic components in the study area; plutonic bodies vary from tonalite to quartz diorite, granodiorite and biotite-granite. The rocks in BAC display dominantly normal calc-alkaline character. On spider diagrams, the rocks are characterized by enrichments in LILE relative to HFSE and enrichments in LREE relative to HREE. These features suggest a subduction related setting for the BAC. La N /Yb N ratios for the intrusive and volcanic rocks range from 1.41 to 5.16 and 1.01 to 6.42, respectively. These values are lower than those for other known granitoids in KMB, namely the abyssal, dominantly Oligocene Jebal Barez-type (La N /Yb N = 1.66–9.98), and the shallow, dominantly late Miocene Kuh Panj-type (La N /Yb N = 12.97–36.04) granitoids. This suggests a less evolved magma source for the BAC igneous rocks. In Y vs. Nb and Th/Yb vs. La/Yb discrimination diagrams, an island-arc setting is defined for the BAC rocks. The rocks further plot in primitive island-arc domain in Nb vs. Rb/Zr and Y/Nb vs. TiO 2 diagrams. The BAC volcanic and plutonic rocks yielded zircon U–Pb ages of 78.1 to 82.7 Ma and 77.5 to 80.8 Ma, respectively. Zircon U–Pb dating of volcanic rocks and granitoids from the adjacent Razak complex and the Jebal Barez-type granitoids indicated 48.2 Ma and 26.1 Ma ages, respectively, consistent with earlier works on similar rocks elsewhere in KMB. The new data allow a revision of the chronostratigraphy/tectonic history of KMB. In Late Cretaceous, a back arc rift developed extending from Nain to Baft (NB back arc) to the northeast of the Sanandaj-Sirjan magmatic arc. Along with shrinking of the Neotethys Ocean, the dip angle of the subducting slab decreased during the Late Cretaceous, and arc magmatism moved from the Sanandaj-Sirjan zone landward. Meanwhile, Bahr Aseman volcanic-plutonic complex formed as an island-arc in NB back arc rift. Later with arc shift, due to shallowing of subducted slab, magmatism moved toward continent leading to extensive volcanism in Kerman magmatic arc during Eocene and Oligocene, represented by volcanic-sedimentary Razak and Hezar Complexes, respectively. [ABSTRACT FROM AUTHOR]

Major, trace and rare earth element (REE) abundances along with Nd isotopic ratios are measured in serpentinized peridotite samples from the Manipur Ophiolite Complex (MOC), Indo-Myanmar range (IMR). An attempt is made to resolve the conundrum caused by apparently contradictory petrogenetic models and tectonic settings reported in literature. Nd isotope ratios, reported for the first time, range from − 7.6 to + 10.4 in epsilon units in the whole-rock samples of serpentinized harzburgite and lherzolite. Variation of La/Yb with ε Ndt is consistent with the progressive addition of a subduction derived fluid to a depleted mantle source. Literature data from the mafic extrusive, intrusive and ultramafic rocks together with new data generated during this study can be explained by a two stage petrogenetic model. Non-modal dynamic melting in the mantle-wedge subsequent to the mixing of fluids derived from the subducted slab explains the observed range of elemental abundances in the MOC mafic and ultramafic rocks. This model also explains the observed variability of Nb and Th in the mafic rocks without invoking different sources for the different types of rocks. Taking into account field, petrographic and geochemical evidences, we propose, that MOC comprises a buoyant fore-arc-mantle-wedge system along with the subducted slab that was obducted during the terminal stage of subduction of the Neotethys below the Burmese plate. [ABSTRACT FROM AUTHOR]

The Indo-Burma Range (IBR) of Myanmar, the eastern extension of the Yarlung-Tsangpo Neotethyan belt of Tibet in China, contains mélanges with serpentinite, greenschist facies basalt, chert, sericite schist, silty slate and unmetamorphosed Triassic sandstone, mudstone and siltstone interbedded with chert in the east, and farther north high-pressure blueschist and eclogite blocks in the Naga Hills mélange. Our detailed mapping of the Mindat and Magwe sections in the middle IBR revealed a major ~18 km antiformal isocline in a mélange in which greenschist facies rocks in the core decrease in grade eastwards and westwards symmetrically 'outwards' to lower grade sericite schist and silty slate, and at the margins to unmetamorphosed sediments, and these metamorphic rocks are structurally repeated in small-scale imbricated thrust stacks. In the Mindat section the lower western boundary of the isoclinal mélange is a thrust on which the metamorphic rocks have been transported over unmetamorphosed sediments of the Triassic Pane Chaung Group, and the upper eastern boundary is a normal fault. These relations demonstrate that the IBR metamorphic rocks were exhumed by wedge extrusion in a subduction-generated accretionary complex. Along strike to the north in the Naga Hills is a comparable isoclinal mélange in which central eclogite lenses are succeeded 'outwards' by layers of glaucophane schist and glaucophanite, and to lower grade greenschist facies sericite schist and slate towards the margins. In the Natchaung area (from west to east) unmetamorphosed Triassic sediments overlie quartzites, sericite schists, actinolite schists and meta-volcanic amphibolites derived from MORB-type basalt, which are in fault contact with peridotite. Olivine in the peridotite has undulatory extinction suggesting deformation at 600-700 °C, similar to the peak temperature of the amphibolite; these relations suggest generation in a metamorphic sole. The amphibolites have U/Pb zircon ages of 119 ± 3 Ma and 115 Ma, which are close to the zircon ages of nearby calc-alkaline granite and diorite, which belong to an active continental margin arc that extends along the western side of the Shan-Thai block. The IBR accretionary complex and the active continental margin arc were generated during Early Cretaceous (115-128 Ma) subduction of the Neotethys Ocean. [ABSTRACT FROM AUTHOR]

Marine clastic rocks occurring in the Walash and Naopurdan Groups in the Hasanbag and Qalander areas, Kurdistan region, Iraqi Zagros Suture Zone, are lithic arenites with high proportions of volcanic rock fragments. Geochemical classification of the Eocene Walash and Oligocene Naopurdan clastic rocks indicates that they were mainly derived from associated sub-alkaline basalt and andesitic basalt in back-arc and island arc tectonic settings. Major and trace element geochemical data reveal that the Naopurdan samples are chemically less mature than the Walash samples and both were subjected to moderate weathering. The seaway in the southern Neotethys Ocean was shallow during both Eocene and Oligocene permitting mixing of sediment from the volcanic arcs with sediment derived from the Arabian continental margin. The Walash and Naopurdan clastic rocks enhance an earlier tectonic model of the Zagros Suture Zone with their deposition occurring during the Eocene Walash calc-alkaline back-arc magmatism and Early Oligocene Naopurdan island arc magmatism in the final stages of intra-oceanic subduction before the Miocene closure and obduction of the Neotethys basin. [ABSTRACT FROM AUTHOR]

We have carried out a several-year-long study of the Amanos Mountains, on the basis of which we present new sedimentary and structural evidence, which we combine with existing data, to produce the first comprehensive synthesis in the regional geological setting. The ca. N-Strending Amanos Mountains are located at the northwesternmost edge of the Arabian plate, near the intersection of the African and Eurasian plates. Mixed siliciclastic-carbonate sediments accumulated on the north-Gondwana margin during the Palaeozoic. Triassic rift-related sedimentation was followed by platform carbonate deposition during Jurassic-Cretaceous. Late Cretaceous was characterised by platform collapse and southward emplacement of melanges and a supra-subduction zone ophiolite. Latest Cretaceous transgressive shallow-water carbonates gave way to deeper-water deposits during Palaeocene-Eocene. Eocene southward compression, reflecting initial collision, resulted in open folding, reverse faulting and duplexing. Fluvial, lagoonal and shallow-marine carbonates accumulated during Late Oligocene(?)-Early Miocene, associated with basaltic magmatism. Intensifying collision during Mid-Miocene initiated a foreland basin that then infilled with deep-water siliciclastic gravity flows. Late Miocene-Early Pliocene compression created mountain-sized folds and thrusts, verging E in the north but SE in the south. The resulting surface uplift triggered deposition of huge alluvial outwash fans in the west. Smaller alluvial fans formed along both mountain flanks during the Pleistocene after major surface uplift ended. Pliocene-Pleistocene alluvium was tilted towards the mountain front in the west. Strike-slip/transtension along the East Anatolian Transform Fault and localised sub-horizontal Quaternary basaltic volcanism in the region reflect regional transtension during Late Pliocene-Pleistocene (<4 Ma). [ABSTRACT FROM AUTHOR]

Miocene planktonic foraminifers occur in shale intercalated with thinly bedded siltstone and sandstone of the Surma Group in the foothills of the Naga Schuppen Belt of the Indo-Myanmar Range. Fourteen species from eleven genera are the first clearly imaged middle Miocene foraminifers recorded from the Surma Group in the Naga Hills. This new M5-M6 assemblage from the upper unit of the Bhuban Formation correlates to the uppermost Burdigalian to Langhian (16–14 Ma). Biostratigraphy, paleoenvironment and paleogeography of the assemblage are all significant. They provide a basis for widespread regional and global correlation constraining the timing of elimination of the final remnants of the Neotethyan seaway between India and eastern Eurasia. Results indicate that, unlike the western and Tibetan Himalayas where similar seaways disappeared before the Miocene, a shallow marine embayment that connected to the Indian Ocean endured in eastern parts of the India-Eurasia collision zone until the Middle Miocene. • The studied planktonic foraminiferal assemblage indicates M5-M6 zone (16–14 Ma). • Results indicate fluctuating sea-level changes in the Naga Hills from Eocene through Miocene. • This study provides the timing of the latest closure of the Neo-Tethys sea in the region. • This work is in contrast with many of the regions of Western and Tibet Himalaya. • It is also correlated with gobal eustatic level changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Sabzevar Oceanic Basin (SOB) represents a classic Wilson Cycle, operating in 130 Ma. • The SOB's life time was concurrent with the Neotethys initial subduction to collision. • The Sabzevar records a progressive Spatio-temporal evolution from south to north. • Paleogeographic reassessing indicates an independent extensional basin for the SOB. The issue about the Sabzevar Oceanic Basin (SOB) lifetime and its paleogeographic position, as a branch of the NeoTethyan oceanic system in Northeast Iran, has long been debated. In the present work, we carried out a full reconstruction of the evolutionary geologic history of the SOB using detailed geological evidence to build a schematic descriptive model. The model describes the historical development of the SOB spanning from the Late Triassic up to Neogene; including continental rifting leading to the opening and development of an oceanic basin, magmatism and metamorphism resulting from subductional events, and finally collision to post-collisional magmatic episodes. The evidence testifies that the SOB formed as an intra-​continental independent basin over the Central Iran Cadomian basement during Late Triassic-Early Jurassic times as a result of extensional movements following the subduction initiation of the Iranian sector of the NeoTethys in the Zagros orogenic belt and closed in the Paleocene after NeoTethyan early continental collision. Magmatic activity in the SOB represents a progressive spatio-temporal evolution from south to north at various time intervals during different tectonic processes with having distinct ranges of magma series including rift-related alkaline, subduction-related tholeiitic to calc-alkaline arc magmas, and post-collisional high-K to shoshonitic magmas respectively. This review indicates that the SOB experienced a classic Wilson Cycle, operating over a period of approximately 130 million years (185–55 Ma). [ABSTRACT FROM AUTHOR]

Ammonoids are key fossil indexes for Triassic biochronology, as all Triassic stages and substages were initially defined on ammonoid faunas. In recent decades, the temporal resolution of ammonoid biostratigraphical scales for the Early Triassic has been greatly improved. However, many uncertainties in zones correlation and superpositions remain, mainly due to sampling heterogeneities, preservation biases, and faunal endemicity. In this work, we present the first comprehensive Early Triassic ammonoid zonation from South Tibet, China, a previously poorly investigated region. Ammonoids were sampled from the Kangshare Formation at four sections (Selong, Paizi, Qubu and Xialong), representing a total of 140 species, ranging from the Griesbachian to the Smithian. These new robust data allow the construction of a high-resolution biostratigraphy using the Unitary Association (UA) method. A total of 22 Unitary Association zones (UAZs) were recognized, including two UAZs for the Griesbachian, nine for the Dienerian, and 11 for the Smithian. Then, we integrated data from neighboring basins, i.e., Spiti (India) and the Salt Range (Pakistan), and the new data from South Tibet to construct synthetic, laterally reproducible Dienerian-Smithian ammonoid UAZs, which include 12 UAZs for the Dienerian and 16 UAZs for the Smithian. Based on the newly obtained data and high-resolution biostratigraphic scales, we revised global correlations known for the ammonoid biostratigraphy in the Griesbachian, Dienerian and Smithian. Finally, the high-resolution ammonoid zones are generally in agreement with conodont zones in defining stage/substage boundaries. They also provide a robust and accurate time calibration for Early Triassic carbon isotope trends and temperature changes. [ABSTRACT FROM AUTHOR]

The Cretaceous Gharuchah-Sofla intrusion is a composite batholith consisting of a variety of mafic to felsic rocks in the northwestern Sanandaj-Sirjan zone, Iran. Both its age and the relationship between various rock types in the intrusion are unknown. To address these issues, we conducted a detailed age, petrologic, and geochemical study of the intrusion, their country rocks, and mafic microgranular enclaves (MMEs) hosted therein. Plutonic rocks from the main mass of the intrusion, dated at ∼110 Ma by in-situ zircon U Pb method, are dominated by gabbroic, dioritic, and quartz dioritic with subordinate granodioritic rocks. Magmatic rocks occurring mostly along margins of the intrusion have Late Ediacaran zircon U Pb ages (∼560 Ma). Both the Early Cretaceous and the Ediacaran magmatic rocks are sub-alkaline; the former has I-type affinity whereas the latter has S-type affinity with a tendency towards I-type. Both sets of rocks are characterized by continental crust-like trace element patterns showing negative anomalies in Nb, Ta, Sr, P, Eu, and Ti of variable intensity. Early Cretaceous gabbroic rocks exhibit unfractionated rare-earth element patterns (La/Yb = 1.9–3.0) and negative Zr Hf anomalies. In contrast, other rocks of the Early Cretaceous and Ediacaran magmatic rocks show fractionated rare-earth element patterns (La/Yb = 11.0–16.8) along with the lack of such anomalies. MMEs, which occur within Early Cretaceous plutonic rocks, have major and trace element compositions similar to the gabbroic rocks. Contrasting Nd isotopic ranges are present between the Early Cretaceous plutonic rocks and the MMEs (ɛNd = +2.0 to +4.1) and the Ediacaran magmatic rocks (ɛNd = −5.8 to −0.4). Based on the geochemical and isotopic data obtained, we suggest that (i) the Ediacaran magmatic rocks formed by melting of Cadomian basement rocks below the blocking temperature of U Pb exchange between zircon and melt, (ii) the MMEs represent frozen melts (i.e., calc-alkaline basalts) that formed the gabbroic rocks in the Early Cretaceous instruction, and (iii) fractional crystallization with slightly concomitant assimilation of Cadomian basement rocks was a key process forming intermediate and silicic rocks of the intrusion. The ∼110 Ma Gharuchah-Sofla intrusion was likely associated with a continental margin arc related to the subduction of the Neotethys, providing solid evidence that this segment of the arc was built directly on the Cadomian basement. [Display omitted] • The main mass of the Gharuchah-Sofla intrusion formed during the Early Cretaceous • The intrusion formed during the subduction of Neotethys beneath the Central Iran Plate. • The intrusion was emplaced into Ediacaran magmatic rocks, which might be part of the Cadomian basement of Iran. • The main factor for lithological and geochemical diversity is fractional crystallization. [ABSTRACT FROM AUTHOR]

In NE Iraq, the eastern edge of the Arabian plate is overlain by arc rock allochthons whose genesis and tectonic emplacement were related to the consumption and closure of the Neotethys Ocean. This paper demonstrates the occurrence of unrelated Paleogene arc rocks in two adjacent allochthons. The Bulfat Igneous Complex at Wadi Rashid (NE Iraq) is an intrusion within the Upper Allochthon Albian–Cenomanian Gimo–Qandil sequence suprasubduction zone assemblage. A thrust separates this allochthon from the underlying Lower Allochthon of the Eocene-Oligocene Walash–Naopurdan volcanic-sedimentary arc rocks. The Bulfat Igneous Complex at Wadi Rashid consists of gabbro and granitic composite intrusions in which components mingle down to a small scale. Textural relationships in the Bulfat Igneous Complex rocks indicate emplacement at high crustal levels with rapid cooling, which is consistent with amphibole geobarometry indicating crystallisation pressures between ~ 250 and 300 Mpa. Ti-rich igneous pargasite and Ti-rich igneous Fe-biotite from gabbroic and granitic components yielded 40 Ar/ 39 Ar ages of 39.23 ± 0.21 and 38.87 ± 0.24 Ma respectively. These ages agree within analytical error and suggest coeval emplacement and rapid cooling of mafic and felsic magmas in the Eocene, in an event that was distinct and much younger than the host Albian–Cenomanian rocks. This igneous event was unrelated to formation of Cenozoic rocks in the underlying, tectonically separate, lower allochthon. The trace element signatures of the Wadi Rashi volcanic rocks show volcanic-arc characteristics for the granites and the gabbroic rocks resemble E type MORB. The presence of Eocene arc-related rocks in two allochthons suggests complexity in Paleogene subduction systems, with possibly two subduction zones operating at that time. [ABSTRACT FROM AUTHOR]

Guleman ofiyolitine ait gabro ve plajiyogranitlerin petrografik ve jeokimyasal özellikleri belirlenmiş olup, gabroların dalma-batma zonu üstündeki bazik kökenli kayaçlar olabileceği, gabroların içerisinde yer alan plajiyoklazca zengin lökokratik kayaçların (plajiyogranit) ise; magma odasındaki, bazik bir magmanın fraksiyonel kristalleşmesi ile oluşan ayrımlaşma ürünü olduğu sonucuna varılmıştır.

[Display omitted] • New zircon U-Pb age and Hf isotope data from bauxite deposits in Adria and Sardinia, Italy. • Bauxite deposits in Sardinia show a parental affinity of Variscan metasedimentary basement. • Bauxite deposits in Adria were mainly supplied from coeval volcanic materials. • Diversity of provenances in bauxite deposits may cause differences in geochemical composition. Bauxite deposits in Italy mainly distribute in Sardinia and Adria regions within Cretaceous carbonate sequences. Parental affinity of Italian bauxite deposits has long been a controversial problem. At least four potential sources have been proposed: (1) Cretaceous debris and autochthonous marlstones; (2) alluvial sheets from the weathered Variscan basement; (3) weathering materials from North Africa and (4) Cretaceous bimodal volcanism in the Dinaric and Carpatho-Balkan orogenic belts. In this study, a total of 374 detrital zircon U-Pb ages and 86 Hf isotope values have been acquired from Cretaceous bauxites of Sardinia and Adria regions. Combining with the published geochemical data, provenances of Cretaceous bauxite deposits in Sardinia and Adria regions have been discussed. In bauxite deposits of Sardinia, dominant Early Paleozoic aged zircon grains (main age peaks at 291 – 295 Ma, 454 – 465 Ma, and 582 – 639 Ma) and their various Hf isotope compositions (εHf(t) = +9.61 to −5.66) indicate a parental affinity of Variscan metasedimentary basement. As a contrast, bauxite deposits in Adria show abundant Jurassic – Cretaceous (93 – 178 Ma) zircon grains with negative εHf(t) values (-13.75 to −4.61), demonstrating significant supply from coeval volcanic materials. Cretaceous bauxite samples from Sardinia and Adria shed light on paleogeographic restoration and tectonic evolution of Alpine Tethys. Began in Early Cretaceous, Sardinia was affected by uplift due to the subduction between Ligurian oceanic crust and the Iberia plate. The Mesozoic carbonate sequence were eroded and the underlying Variscan basement was exposed in the area from Sardinia to the Massif Meridional, provided weathering materials for bauxitization. Late Cretaceous witnessed the further NNE-trending subduction of the Adria Plate to the West Vardar oceanic plate, where calcalkaline igneous rocks and volcanic ashes from Dinarides supplied windborne weathering materials to carbonate platforms in Adria. Particularly, provenance difference between the bauxite of central-southern Apennine and Sardinian reveals that the hosting carbonate sequence in Apennine was not located on the Sardinia shelf before the Cenozoic tectonism in the south Mediterranean realm. Diversity of provenances in bauxite deposits from Sardinia and Adria may cause differences in geochemical composition and further influence qualities of bauxite ore in two regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Late Triassic volcanic-sedimentary rocks in the Yidun Terrane were deposited at 219–216 Ma. • N-S, E-W, and NW-SE folds are ascribed to closure of Paleo- and NeoTethys and subsequent intracontinental deformation. • Five stages of Cenozoic faulting are determined and their paleostress inversions are ascribed to the India-Asia collision. • The Yidun Terrane was a foreland basin rather than a trench-arc-basin system during the Late Triassic. • Late Triassic to Quaternary tectonic evolution history of the Yidun Terrane is reconstructed. Although polyphase deformation is reported in the Late Triassic volcano-sedimentary rocks in the Yidun Terrane at the eastern Qinghai-Tibet Plateau, deformation events, formation ages and tectonic implications are still hotly debated. Based on the 1: 50, 000-scale regional geological survey, structural analysis, paleostress inversion and zircon U-Pb geochronology were carried out on the Late Triassic volcano-sedimentary rocks in the Yidun Terrane. U-Pb ages of youngest detrital zircons from meta-sandstone of the Lamaya Formation (220 Ma for sample D2000 and 225 Ma for sample D2023), welded tuff (219.4 ± 1.2 Ma) and quartz monzogranite (216.7 ± 0.5 Ma) indicate that the Late Triassic volcano-sedimentary rocks were deposited during 219–216 Ma. These volcano-sedimentary rocks were deposited in a foreland basin caused by the closure of the Jinshajiang Ocean. Structural analysis shows that three generations of folds with different orientations and five stages of Cenozoic faulting occurred in the Late Triassic volcano-sedimentary rocks. These three generations of folds consist of Late Triassic N-S-trending tight folds, Early-Middle Paleogene E-W-striking open folds and Late Neogene NW-SE-trending drag folds. The stress inversion of the fault-slip data reveals that Late Paleogene strike-slip regime, Early Miocene NE-SW extensional regime, Late Miocene strike-slip regime, Pliocene N-S extensional regime and Quaternary E-W extensional regime subjected to the Yidun Terrane. Combining these with previously published data, we ascribe the N-S-trending tight folds to the Late Triassic final closure of Paleo-Tethys Ocean, whereas the E-W-striking open folds to the closure of the NeoTethys Ocean and subsequent India-Asia collision. The NW-SE-trending drag folds and the five stages of faulting regimes were possibly related to the intracontinental stresses originating of India-Asia collision. [ABSTRACT FROM AUTHOR]

The early Paleogene "greenhouse" is the warmest geological period of the Cenozoic and a suitable source to unlock crucial information for better understanding how ecosystems such as coral reefs reacted to a climate much warmer than the present. Herein, we analyse in detail the rich museum coral collections from Friuli region (NE Italy) focusing only on the so-called reef corals, mostly colonial, and on those localities for which the age constraints are well-defined. We grouped the localities into four time-intervals within the Ypresian-Lutetian and thus within EECO (Early Eocene Climatic Optimum) and post-EECO phase, in order to assess the main changes in the following traits: 1) richness and relative abundance at the generic and species level; 2) relative abundance of growth forms; 3) colony size. By systematic revision we recognized a total of 37 genera and 103 species. During the EECO interval (late Ypresian or Cuisian), the diversity at both genus and species level was relatively low (21 genera, 37 species). An abrupt increase is then recorded in the post-EECO 1 interval (latest Ypresian), whereas a peak is reached in the earliest Lutetian (post-EECO 2) (35 genera, 90 species). These results undoubtedly show that a coral hotspot occurred in the region during the late Ypresian-early Lutetian time and highlight that corals of Friuli reacted positively immediately after the warming event of the EECO. This coral hotspot was the most diverse at global scale during the Ypresian and formed in a deltaic depositional setting, most probably in mesophotic conditions as suggested by the dominant growth forms, where rapid sediment accumulation, enhanced nutrient delivery and stressful climatic conditions reduced frame-building capacity. We finally document that corals were resilient to climate stressors and recovered before reefs which, in contrast, required much more time to achieve their buildup potential. • We document the oldest coral hotspot ever reported after the K-Pg extinction. • The central Neotethys was the centre of coral diversity during the Early Eocene. • Reef corals reacted positively after the Early Eocene Climatic Optimum (EECO). • Reef coral diversity recovers earlier than coral reef building after the EECO. • The mesophotic deltaic environment was a suitable refuge during and after the EECO. [ABSTRACT FROM AUTHOR]

The Ghorveh-Dehgolan plutons of the northern Sanandaj-Sirjan Zone, Zagros Orogen, comprise seven composite intrusive bodies that were generated during northeastward subduction of Neotethys beneath the Iranian sector of the Eurasian plate. Zircon U-Pb SHRIMP dating reveals that the magmatic activity spanned from ~160 to ~140Ma. It started with intrusion of arc-related calc-alkaline mafic to intermediate rocks closely followed by felsic I-type granitoids. This magmatism was post-dated by felsic alkaline A-type granites. In addition to compositional changes over time, the plutons forming the arc young towards the southwest: the north Ghorveh batholith (161±4Ma) and Shanevareh (160±2Ma); Qalaylan (159±3Ma); then central Ghorveh, Galali and Saranjianeh (151±0.2Ma to 148±1Ma); and, lastly, the south Ghorveh batholith (147±3Ma) and Bolbanabad-Havarpan (144±1Ma). Whatever the process driving the changes, be it arc- or ridge-collision with the subducting system, slab roll-back, slab breakoff, subduction initiation transference, etc., the progression from I-type to A-type magmatism appears to mark a significant change from a collisional to an extensional setting in the region in the Late Jurassic. Geochemical and isotopic characteristics of the Ghorveh-Dehgolan plutons indicate that Arabian-Nubian-like crust was an important component of the magmatic sources.

Kinematic reconstruction of modern ocean basins shows that since Pangea breakup a vast area in the Neotethyan realm was lost to subduction. Here we develop a first-order methodology to reconstruct the kinematic history of the lost plates of the Neotethys, using records of subducted plates accreted to (former) overriding plates, combined with the kinematic analysis of overriding plate extension and shortening. In Cretaceous-Paleogene times, most of Anatolia formed a separate tectonic plate-here termed 'Anadolu Plate'-that floored part of the Neotethyan oceanic realm, separated from Eurasia and Africa by subduction zones. We study the sedimentary and structural history of the Ulukışla basin (Turkey); overlying relics of this plate to reconstruct the tectonic history of the oceanic plate and its surrounding trenches, relative to Africa and Eurasia. Our results show that Upper Cretaceous-Oligocene sediments were deposited on the newly dated suprasubduction zone ophiolites (~92 Ma), which are underlain by mélanges, metamorphosed and nonmetamorphosed oceanic and continental rocks derived from the African Plate. The Ulukışla basin underwent latest Cretaceous-Paleocene N-S and E-W extension until ~56 Ma. Following a short period of tectonic quiescence, Eo-Oligocene N-S contraction formed the folded structure of the Bolkar Mountains, as well as subordinate contractional structures within the basin. We conceptually explain the transition from extension, to quiescence, to shortening as slowdown of the Anadolu Plate relative to the northward advancing Africa-Anadolu trench resulting from collision of continental rocks accreted to Anadolu with Eurasia, until the gradual demise of the Anadolu-Eurasia subduction zone. [ABSTRACT FROM AUTHOR]

Different models have been proposed for the formation and tectonic evolution of the South China Sea (SCS), including extrusion of the Indochina Peninsula, backarc extension, two-stage opening, proto-SCS dragging, extension induced by a mantle plume, and integrated models that combine diverse factors. Among these, the extrusion model has gained the most attention. Based on simplified physical experiments, this model proposes that collision between the Indian and Eurasian Plates resulted in extrusion of the Indochina Peninsula, which in turn led to opening of the SCS. The extrusion of the Indochina Peninsula, however, should have led to preferential opening in the west side of the SCS, which is contrary to observations. Extensional models propose that the SCS was a backarc basin, rifted off the South China Block. Most of the backarc extension models, however, are not compatible with observations in terms of either age or subduction direction. The two-stage extension model is based on extensional basins surrounding the SCS. Recent dating results indeed show two-stage opening in the SCS, but the Southwest Subbasin of the SCS is much younger, which contradicts the two-stage extension model. Here we propose a refined backarc extension model. There was a wide Neotethys Ocean between the Australian and Eurasian Plates before the Indian-Eurasian collision. The ocean floor started to subduct northward at ~125 Ma, causing backarc extension along the southern margin of the Eurasian Plate and the formation of the proto-SCS. The Neotethys subduction regime changed due to ridge subduction in the Late Cretaceous, resulting in fold-belts, uplifting, erosion, and widespread unconformities. It may also have led to the subduction of the proto-SCS. Flat subduction of the ridge may have reached further north and resulted in another backarc extension that formed the SCS. The rollback of the flat subducting slab might have occurred ~90 Ma ago; the second backarc extension may have initiated between 50 and 45 Ma. The opening of the Southwest Subbasin is roughly simultaneous with a ridge jump in the East Subbasin, which implies major tectonic changes in the surrounding regions, likely related to major changes in the extrusion of the Indochina Peninsula. [ABSTRACT FROM AUTHOR]

The Kata–Rash arc fragment is an allochthonous thrust-bound body situated near Penjween, 100 km northeast of Sulymannia city, Kurdistan Region, within the Iraqi portion of the Zagros suture zone. It forms part of the suprasubduction zone ‘Upper Allochthon’ terranes (designated as the Gimo–Qandil Group), which is dominated by calc-alkaline andesite and basaltic–andesite, rhyodacite to rhyolite, crosscut by granitic, granodioritic, and dioritic dykes. Previously, rocks of the Kata–Rash arc fragment were interpreted as a part of the Eocene Walash volcanic group. However, SHRIMP zircon U–Pb dates on them of 108.1 ± 2.9 Ma (Harbar volcanic rocks) and 107.7 ± 1.9 Ma (Aulan intrusion) indicate an Albian–Cenomanian age, which is interpreted as the time of igneous crystallisation. The Aulan intrusion zircons have initial ε Hf values of + 8.6 ± 0.2. On a Nb/Yb–Th/Yb diagram, all Kata–Rash samples fall within the compositional field of arc-related rocks, i.e. above the mid-ocean-ridge basalt (MORB)—ocean island basalt (OIB) mantle array. Primitive-mantle-normalised trace-element patterns for the Kata–Rash samples show enrichment in the large ion lithophile elements and depletion in the high-field-strength elements supporting their subduction-related character. Low Ba/La coupled with low La/Yb and Hf/Hf* < 1 for the Aulan sample with initial ε Hf of + 8.6 ± 0.2 is interpreted as the magma dominated by contributions from fluid fluxing of the mantle wedge and lesser contributions of low temperature melt from subducted slab sediment, in an oceanic setting. This mechanism can explain the sub-DM initial ε Hf value, without the need to invoke melting of significantly older (continental) crust in an Andean setting. We interpret the Kata–Rash igneous rocks as a fragment of the Late Cretaceous suprasubduction zone system (named here the Kata–Rash arc) that most likely developed within the Neotethys Ocean rather than at a continental margin. Subsequently during the latest Cretaceous to Paleocene, the arc was accreted to the northern margin of the Arabian plate. The results indicate a > 3000 km continuity of Cretaceous arc activity (Oman to Cyprus), that consumed Neotethyian oceanic crust between Eurasia and the Gondwanan fragment Arabia. [ABSTRACT FROM AUTHOR]

A new, marine osteichthyan (bony fish) fauna from the Early Triassic of northern India is presented. The material was collected in situ at localities within Pin Valley (Lahaul and Spiti District, Himachal Pradesh, India) and is dated as middle-late Dienerian (one specimen possibly earliest Smithian). The new ichthyofauna includes a lower jaw of the predatory basal ray-finned fish Saurichthys, a nearly complete specimen of a parasemionotid neopterygian (cf. Watsonulus cf. eugnathoides), as well as further articulated and disarticulated remains (Actinopterygii indet., Actinistia indet.), and thus comprises the most complete Triassic fish fossils known from the Indian subcontinent. Saurichthys is known from many Triassic localities and reached a global distribution rapidly after the Late Permian mass extinction event. Parasemionotidae, a species-rich family restricted to the Early Triassic, also achieved widespread distribution during this epoch. Comparison of the Spiti material with other parasemionotid species reveals similarities with Watsonulus eugnathoides from Madagascar. However, taxonomic ambiguities within Parasemionotidae prevent a specific attribution of the Spiti specimen. The new material also includes an isolated actinistian urohyal exhibiting morphology distinct from any previously described urohyal. Marine Dienerian black shale deposited on continental shelves are common not only in the Himalayas but also in other geographic regions. Anoxic depositional settings provide ideal preservational conditions for vertebrate fossils, suggesting that additional ichthyofaunas could still be discovered in marine Dienerian strata of other localities. The study of Early Triassic fish assemblages, including the presented one, is fundamental for our understanding of the great osteichthyan diversification after the Late Permian mass extinction event. [ABSTRACT FROM AUTHOR]

The Ankara Mélange is a complex formed by imbricated slices of limestone block mélanges (Karakaya and Hisarlıkaya Formations), Neotethyan ophiolites (Eldivan, Ahlat and Edige ophiolites), post-ophiolitic cover units (Mart and Kavak formations) and Tectonic Mélange Unit (Hisarköy Formation or Dereköy Mélange). The Karakaya and Hisarlıkaya formations are roughly similar and consist mainly of limestone block mélange. Nevertheless, they represent some important geological differences indicating different geological evolution. Consequently, the Karakaya and Hisarlıkaya formations are interpreted as Eurasian and Gondwanian marginal units formed by fragmentation of the Gondwanian carbonate platform during the continental rifting of the Neotethys in the Middle Triassic time. During the latest Triassic, Neotethyan lithosphere began to subduct beneath the Eurasian continent and caused intense deformation of the marginal units. The Eldivan, Ahlat and Edige ophiolites represent different fragments of the Neotethyan oceanic lithosphere emplaced onto the Gondwanian margin during the Albian-Aptian, middle Turonian and middle Campanian, respectively. The Eldivan Ophiolite is a NE-SW trending and a nearly complete assemblage composed, from bottom to top, of a volcanic-sedimentary unit, a metamorphic unit, peridotite tectonites, cumulates and sheeted dykes. The Eldivan Ophiolite is unconformably covered by Cenomanian-Lower Turonian sedimentary unit. The Eldivan Ophiolite is overthrust by the Ahlat Ophiolite in the north and Edige Ophiolite in the west. The Ahlat ophiolite is an east-west oriented assemblage comprised of volcanic-sedimentary unit, metamorphic unit, peridotite tectonites and cumulates. The Edige Ophiolite consists of a volcanic-sedimentary unit, peridotite tectonites, dunite, wherlite, pyroxenite and gabbro cumulates. The Tectonic Mélange Unit is a chaotic formation of various blocks derived from ophiolites, from the Karakaya and Hisarlıkaya formations and from post-ophiolitic sedimentary units. It was formed during the collision between Anatolian Promontory and Eurasian Continent in the middle Campanian time. [ABSTRACT FROM AUTHOR]

The subduction polarity of Tethyan oceanic lithosphere during Jurassic is a controversial topic in relation to the geodynamic evolution of the Alpine–Himalayan system. We present new geological, geochemical and zircon U–Pb data from four different regions of the Eastern Pontides Orogenic Belt, a key area of the Alpine–Himalayan system. We discuss the origin of the magmatism and also the existence of an ocean in the eastern Mediterranean region during the Jurassic period. Jurassic intrusions, predominantly gabbro, tonalite and minor diorite, are well exposed in the southern and axial zones of the orogenic belt. Thermobarometry indicates that high-pressure (6–10 kb) crystallization of these intrusions occurred at temperatures of 1183–1250 °C. Zircon U–Pb dating from 10 samples show ages between 195 and 165 Ma, indicating that magmatism occurred between Sinemurian and Callovian time. We characterize the intrusions from electron microprobe, zircon geochronology, and whole rock and Sr, Nd, and Pb isotopes. Our data show that the studied intrusions are broadly tholeiitic, except for two calc-alkaline bodies, and formed in an arc-related setting with minimal involvement of older crust or sediment. The most widely accepted model proposes that the ultramafic–mafic rocks exposed between the Pontide arc and the Tauride belt are remnants of a Jurassic Penrose-type and/or suprasubduction zone ophiolite. However, new zircon U–Pb age data from mafic lithologies cutting the Kop ultramafic massif do not support this model and clearly indicate that the ultramafic lithologies are Paleozoic or older in age and are not remnants of a Jurassic ocean that known as ‘’Northern Branch of Neotehtys”. [ABSTRACT FROM AUTHOR]

The Eldivan ophiolite along the Izmir–Ankara–Erzincan suture zone in north-central Anatolia represents a remnant of the Neotethyan oceanic lithosphere. Its upper mantle peridotites include three lithologically and compositionally distinct units: clinopyroxene (cpx)–harzburgite and lherzolite (Group-1), depleted harzburgite (Group-2), and dunite (Group-3). Relics of primary olivine and pyroxene occur in the less refractory harzburgites, and fresh chromian spinel (Cr-spinel) is ubiquitous in all peridotites. The Eldivan peridotites reflect a petrogenetic history evolving from relatively fertile (lherzolite and cpx–harzburgite) toward more depleted (dunite) compositions through time, as indicated by (i) a progressive decrease in the modal cpx distribution, (ii) a progressive increase in the Cr#s [Cr / (Cr + Al)] of Cr-spinel (0.15–0.78), and (iii) an increased depletion in the whole-rock abundances of some magmaphile major oxides (Al 2 O 3 , CaO, SiO 2 and TiO 2 ) and incompatible trace elements (Zn, Sc, V and Y). The primitive mantle-normalized REE patterns of the Group-1 and some of the Group-2 peridotites display LREE depletions. Higher Yb N and lower Sm N /Yb N ratios of these rocks are compatible with their formation after relatively low degrees (9–25%) of open-system dynamic melting (OSDM) of a Depleted Mid-ocean ridge Mantle (DMM) source, which was then fluxed with small volumes of oceanic mantle-derived melt [fluxing ratio (β): 0.7–1.2%]. Accessory Cr-spinel compositions (Cr# = 015–0.53) of these rocks are consistent with their origin as residual peridotites beneath a mid-ocean ridge axis. Part of the Group-2 harzburgites exhibit lower Yb N and higher Sm N /Yb N ratios, LREE-enriched REE patterns, and higher Cr-spinel Cr#s ranging between 0.54 and 0.61. Trace element compositions of these peridotites can be modeled by approximately 15% OSDM of a previously 17% depleted DMM, which was then fluxed (β: 0.4%) with subduction-influenced melt. The Group-3 dunite samples contain Cr-spinel with elevated Cr#s (0.73–0.78) and low-TiO 2 contents (< 0.13 wt.%), implying higher degrees of melting (21–24%) of an already depleted DMM that was triggered by infiltration of low-Ti boninite melt with fluxing rates of 0.4–4.0%. The existence of interstitial, idiomorphic Cr-spinel (high Cr# and low Ti) in the Group-3 dunites is consistent with this interpretation. The occurrence of both MOR- and SSZ-type peridotites in the Eldivan ophiolite suggests that its heterogeneous upper mantle was produced as a result of different partial melting and melt–rock reaction processes in different tectonic settings within the Neotethyan realm. [ABSTRACT FROM AUTHOR]

The Sanandaj-Sirjan zone of Iran is a northwest trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. The zone contains the most extensive, best preserved record of key events in the formation and evolution of the Neotethys, from its birth in Late Paleozoic time through its demise during the mid-Tertiary collision of Arabia with Eurasia. The record includes rifting of continental fragments off of the northern margin of Gondwanaland, formation of facing passive continental margins, initiation of subduction along the northern margin, and progressive development of a continental magmatic arc. The latter two of these events are critical phases of the Wilson Cycle that, elsewhere in the world, are poorly preserved in the geologic record because of superimposed events. Our new synthesis reaffirms the similarity between this zone and various terranes to the north in Central Iran. Late Paleozoic rifting, preserved as A-type granites and accelerated subsidence, was followed by a phase of pronounced subsidence and shallow marine sedimentation in Permian through Triassic time, marking the formation and evolution of passive margins on both sides of the suture. Subduction and arc magmatism began in latest Triassic/Early Jurassic time, culminating at ~170 Ma. The extinction of arc magmatism in this zone, and its shift northeastward to form the subparallel Urumieh-Dokhtar arc, occurred diachronously along strike, in Late Cretaceous or Paleogene time. Post-Cretaceous uplift transformed the zone from a primarily marine borderland into a marine archipelago that persisted until mid-Tertiary time. [ABSTRACT FROM AUTHOR]

In contrast to the present hyper-arid inland basin surrounded by the high mountains of Central Asia, the western Tarim Basin was once connected with the Tajik Basin at least in the late Eocene, when an epicontinental sea extended from the western Tarim Basin to Europe. Western Tarim is a key site for studying the retreat of seawater, which was likely caused by the northward indentation of the Pamir arc and facilitated by the climatic cooling and eustatic sea level change in the Cenozoic. Here we present a new magnetostratigraphic record from the Tarim Basin that provides evidence of diachronous seawater retreat from its southwestern margin. We studied about 1360 m of well-exposed Eocene–Oligocene strata at Keliyang in the folded foreland of the West Kunlun orogen. Until now, the age of the strata has only been minimally constrained by the presence of late mid-Eocene marine fossils. Our biostratigraphic and magnetostratigraphic results demonstrate that the age of the sedimentary sequence ranges from ∼46 Ma to ∼26 Ma (mid-Eocene to late-Oligocene) and the seawater retreat at Keliyang took place at ∼40 Ma. Considering the stepwise northward indentation and uplift of the Pamir orogen, together with the other previous results, we propose that seawater retreat from the southwestern margin of the Tarim Basin was diachronous in the late Eocene ranging from 47 Ma to 40 Ma. The regional indentation, uplift and erosion of the Pamir orogen played the dominant and important role in controlling the seawater retreat from the southwestern margin of the Tarim Basin. [ABSTRACT FROM AUTHOR]

This study focuses on the palaeoclimatic evolution and relative sea-level fluctuations of the northern branch of NeoTethys during the late Campanian–early Danian. The studied succession (İsmailler Section) is located in the Mudurnu–Göynük Basin, NW Turkey and dominated by apparently continuous pelagic muddy deposits. Stable isotopic and elemental compositions of the mudrocks are investigated in order to evaluate the palaeoceanographic conditions as well as broad tectonic reconstruction of the basin. The mudrock geochemistry suggests a tectonic reorganization during late Campanian as reflected by a distinct shift from felsic to mafic sediment provenance. In the İsmailler Section, five δ 13 C events are identified; four or which are well correlatable with major events in other records around the world, such as the late Campanian Event (LCE), Campanian–Maastrictian Boundary (CMB) and the late Maastrichtian Event (LME). The relative sea-level variations in the basin typically match both short- and long-term global sea-level fluctuations. The remaining globally uncorrelatable δ 13 C event does coincide with tectonic uplift and the abrupt negative δ 13 C shift, and is inferred to be the result of regional factors. The dominance of worldwide events in the records of the relatively restricted ocean branch reflects the strength of global factors. [ABSTRACT FROM AUTHOR]