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The Lesser Caucasus, situated between Asia and Europe, has long been recognised as a key region for the study of human evolution in terms of the timing and routes of dispersal, as well as, ecological adaptations. In particular, scholars have argued whether stable environments persisted in the region throughout the last glaciation, serving as a refugium for temperate biota, likely attracting human settlement and use. Here, we present the results of a multidisciplinary study of Karin Tak Cave, which contains sediments that accumulated between 48,000 and 24,000 cal yr BP. We examined biostratigraphic changes at the site by looking at the composition of fauna, which we hypothesise to be naturally accumulated, in different stratigraphic phases using traditional zooarchaeological approaches combined with collagen fingerprinting (ZooMS, Zooarchaeology by Mass Spectrometry). To gain further insights into regional palaeoenvironmental conditions, we also applied stable carbon and oxygen isotope analyses to faunal tooth enamel. The obtained results suggest that the onset of the last glaciation did not cause dramatic changes in regional environments, indicating that the Lesser Caucasus was a climatically and ecologically stable region despite significant global climatic changes during this period. • Karin Tak is a Lesser Caucasus palaeontological site that preserves records of the 48,000-24,000-year-old local environment. • Morphological identifications of fossil material combined with ZooMS reveal a rich faunal composition at the site. • Stable carbon and oxygen isotopic analyses indicate a mosaic of forests, shrublands, and grasslands in the Late Pleistocene. • Stable environmental settings persisted in the southeastern Lesser Caucasus throughout late MIS 3 and early MIS 2 [ABSTRACT FROM AUTHOR]

[Display omitted] • In the Talesh Massif, we document an Eocene high-K volcanic flare-up. • A trachytic ignimbrite layer is dated at 43.17 ± 0.40 Ma. • Melting of previously metasomatized lithospheric mantle source has occurred. • Geodynamic scenario is south-dipping subduction and asthenospheric upwelling. • Efficient magma transfer occurred along strike-slip faults related to a step fault. The geodynamic significance of Cenozoic magmatism of the Central Tethyan orogenic belt linking the tectonic zones of Iran, South Armenian Block (Lesser Caucasus) and Turkey remains a subject of debate. This study is focused on the thick geological succession of high potassic magmatic rocks erupted in Talysh Massif, NW Iran. We report a comprehensive geochemical study that demonstrates that this succession is comprised of shoshonitic mostly basaltic and some rhyolitic pyroclastic rocks emplaced during an Eocene magmatic flare-up. Forsterite rich olivine (Fo 70–93), combined to high-Mg clinopyroxene (Mg# 0.6–0.8) and high-Ti calcic amphibole (magnesiohastingsite) are the dominant mafic minerals in these rocks. Mafic lavas are enriched in LILE and depleted in HFSE, with high Th/Yb, Ba/Th and Nb/Zr ratios, suggestive of an enriched mantle source following Tethys subduction history. Interlayered felsic lavas allowed to date the series by U-Pb on zircon at 43.17 ± 0.40 Ma, with one relict core displaying an inherited age of 580 Ma. eHf i CHUR of Eocene zircons range from 1.7 to −0.9 (with corresponding T DM ages around 1.0 Ga). The latter, along with the detection of a Neoproterozoic zircon xenocryst, indicates a crustal contamination by a Neoproterozoic (and older) lower crust. These data are in agreement with the partial melting of a subduction-modified subcontinental mantle. This magmatic flare-up could have been triggered by an Asthenosphere upwelling related to the onset of south-dipping subduction in the Transcaucasus region and transcrustal strike-slip faults with a more significant crustal contamination than in the Lesser Caucasus region. [ABSTRACT FROM AUTHOR]

Apatite fission-track analysis and thermochronologic statistical modeling of Precambrian–Oligocene plutonic and metamorphic rocks from the Lesser Caucasus resolve two discrete cooling episodes. Cooling occurred during incremental crustal shortening due to obduction and continental accretion along the margins of the northern branch of the Neotethys. (1) The thermochronometric record of a Late Cretaceous (Turonian–Maastrichtian) cooling/exhumation event, coeval to widespread ophiolite obduction, is still present only in a relatively small area of the upper plate of the Amasia-Sevan-Akera (ASA) suture zone, i.e. the suture marking the final closure of the northern Neotethys during the Paleogene. Such area has not been affected by significant later exhumation. (2) Rapid cooling/exhumation occurred in the Early-Middle Miocene in both the lower and upper plates of the ASA suture zone, obscuring previous thermochronologic signatures over most of the study area. Miocene contractional reactivation of the ASA suture zone occurred contemporaneously with the main phase of shortening and exhumation along the Bitlis suture zone marking the closure of the southern branch of the Neotethys and the ensuing Arabia-Eurasia collision. Miocene collisional stress from the Bitlis suture zone was transmitted northward across the Anatolian hinterland, which was left relatively undeformed, and focused along preexisting structural discontinuities such as the eastern Pontides and the ASA suture zone. Image 1 • Collisional stress was transmitted from the Bitlis suture to the Lesser Caucasus. • In the Lesser Caucasus rapid exhumation occurred in the Early-Middle Miocene. • Earlier Late Cretaceous exhumation was related to widespread ophiolite obduction. [ABSTRACT FROM AUTHOR]

In this study, we explore the Late Pleistocene (LP) vertebrate faunal diversity in south-eastern Lesser Caucasus based on morphological and genetic identification of fossil bones from Karin Tak cave. For the first time in this under-studied region, we used a bulk bone metabarcoding genetic approach to complement traditional morphology-based taxonomic identifications that are hampered by highly fragmented fossil bones. Excellent ancient DNA (aDNA) preservation allowed for a successful species identification of many bone remains and improved paleoenvironmental interpretations for the region. The aDNA identification of fossil bones revealed a high diversity of animal taxa inhabiting the region between ca. > 42,000 and 25,683–24,803 calibrated years before present (cal. BP). • Insights into Late Pleistocene faunal diversity in the Lesser Caucasus. • Assessment of prehistoric fauna of the region based on bulk bone metabarcoding. • The MIS 3–MIS 2 transition did not cause a dramatic change in the faunal composition. • Karin Tak provides possibility for molecular reconstruction of palaeoenvironment. [ABSTRACT FROM AUTHOR]

The present-day configuration of the Lesser Caucasus and Eastern Pontides regions has been shaped by multiple episodes of arc magmatism, opening and closure of oceanic domains, obductions and collisions from the Paleozoic (∼350–310 Ma) to Cenozoic (∼50–20 Ma). This fascinating magmatic and tectonic evolution along these two adjacent regions was also associated with an exceptional metal endowment in the form of polymetallic deposits, volcanogenic massive sulfide deposits, porphyry Cu-Mo deposits and epithermal Cu-Au deposits in the Mesozoic and Cenozoic. Several decades of research have significantly improved our understanding of these two regions, yet conflicting models exist for the tectono-magmatic evolution of this orogenic belt. Here we present new zircon Hf isotopic data (n = 575) for magmatic rocks formed in the Lesser Caucasus at Kapan (136–16 Ma, 51 Ma), Gedabek (138–158 Ma), Tsaghkuniats (530 Ma, 320 Ma, 136–153 Ma), Alaverdi (146–164 Ma) and Bolnisi (82–85 Ma, 52 Ma) districts, and in the Eastern Pontides at Elbeyli (74 Ma), Emeksen (78–79 Ma), Güzelyayla (80 Ma) and Ulutas-Ispir (128–129 Ma) districts. The new results are combined with a comprehensive compilation of igneous ages (n = 4560), zircon Hf isotopic compositions (n = 1466), bulk rock major and trace element (n = 1304–1647) and Sr and Nd isotopic compositions (n = 1079) for magmatic rocks formed along the Eastern Pontides and the Lesser Caucasus. These complementary datasets highlight three well-defined cycles of arc magmatism during the Mesozoic and Cenozoic between the two regions, which is characterized by comparable temporal and geochemical trends in the Middle Jurassic-Early Cretaceous and the Late Cretaceous cycles, whereas these trends are no longer similar in the Eocene-Miocene cycle. The new data also reveal that Carboniferous basement rocks in the Tsaghkuniats area have overlapping ages and zircon Hf data with Carboniferous basement in the northernmost Lesser Caucasus and Eastern Pontides. This may suggest the presence of a composite basement in the Lesser Caucacus made of southern Eurasian margin slivers rifted prior to Early Mesozoic and Gondwana-derived South Armenian block accreted to the southern Eurasian margin during the Late Mesozoic-Early Cenozoic. This regional synthesis of the geochemistry of arc magmatism across the Lesser Caucasus and Eastern Pontides over time offers new additional petrological constraints and allows to support our model for the geodynamic evolution of the region. Building on this regional geodynamic framework, the spatial and temporal distribution of ore deposits provides important pieces of information regarding key factors, such as long-lived arc magmatism and switch of tectonic stress regime, controlling arc magma fertility, which ultimately offers new perspectives for exploration opportunities in the middle section of the Tethyan metallogenic belt. [ABSTRACT FROM AUTHOR]

Abstract River management is generally thought to have started at 5500 cal. BC within the development of eastern Neolithic societies. In the Lesser Caucasus, evidence of early river management has been discovered around the famous Neolithic sites of Shulaveri, Gadachrili Gora, and Imiris Gora in Georgia. Here we report a preliminary data set indicating that river management was set up at 5900 cal. BC leading to the flooding, destruction, and local abandonment of the hydraulic infrastructures of the Gadachrili village between 5750 and 5430 cal. BC. The hydraulic infrastructures were developed during a more humid period encompassing the 8200 cal. BP (6200 cal. BC) climatic event, probably to optimize agricultural yield. It potentially led to the first prehistoric engineering accident for which there is evidence, which may have been followed by the reorganisation of the occupation and/or to architectural modifications. Highlights • In the Lesser Caucasus, some evidences of Early Neolithic river management have been discovered. • We report a preliminary data set indicating that the river management was made 5900 cal. BC ago and led to Neolithic village flooding, destruction and local abandonment of the hydraulic infrastructures between 5750 and 5430 cal. BC. • We carried out isotopic analyzes on the seeds in order to characterize or not the occurrence of irrigation. • We highlight the possibility of a development in the Caucasus of the oldest known water management practices. • We also present an original focus on the potential effects of torrential palaeo-floods in Neolithic water management structures and riparian habitats. [ABSTRACT FROM AUTHOR]

This study investigates distribution of natural and technogenic radionuclides in rock samples in the southern part of the Mtskheta-Mtianeti region, located in the so-called Transcaucasian intermountain area (II) and in the Lesser Caucasus fold system (III). Several geotectonic units are identified here: the eastern immersion zone or Georgian Block (II 3 ), the molassic subzone of Kartli (II 3 1 ), the central (axial) subzone (III 1 3 ), and the southern subzone (III 1 4 ) of the Adjara-Trialeti folded zone (III 1 ). The radioactivity of rocks in this region has not been investigated. Twenty samples of rocks of various types, including sedimentary and metamorphic, were investigated with the gamma-spectroscopic method. Up to 21 naturally occurring radionuclides and one technogenic radionuclide were identified in samples. Average activity concentration of Th-232 family radionuclides varied from 4.5 to 67.0 Bq/kg, U-238 family: from 4.5 to 93.5 Bq/kg, and U-235 family: from 0.22 to 4.3 Bq/kg. The highest activity concentration was observed for K-40 (maximal value of 746 Bq/kg). Activity of technogenic radionuclide Cs-137 varied from 0.12 to 6.3 Bq/kg. There are some marked features in radionuclide distribution depending, in particular, on rock type, tectonic zone, and age. Some radionuclide activity ratios have been considered: U-238/U-235, U-238/Th-232, Ra-226/U-238, and Pb-210/Ra-226. These ratios allowed estimation of the system's condition (closed or opened) and information about the character of relevant geochemical processes. Comparison was carried out with existing data in the literature. [ABSTRACT FROM AUTHOR]

Mountain regions such as the Lesser Caucasus are a focus of ongoing environmental changes. To understand their future evolution, information about their former geomorphic and environmental dynamics is required. The former fluvial dynamics derived from fluvial sediment archives can offer such insights. However, the fluvial dynamics of the Lesser Caucasus since the Eemian interglacial have not been systematically investigated so far. Thus, we have studied late Pleistocene and Holocene sediments of several rivers originating from the central Lesser Caucasus. The studied rivers show a mostly coherent record of fluvial dynamics: Minor aggradation occurred during early Marine Isotope Stage (MIS) 5, incision during late MIS 5 or early MIS 4, intensive silty aggradation at least during late MIS 3, incision during early MIS 2, coarse-grained aggradation probably during some millenia until ca. 19 ka, and aggradation ca. 14-13 ka. Following incision around the Pleistocene/Holocene transition, aggradation resumed around 6.0, 3.4 – 2.0 and 0.5 – 0.15 cal. ka BP. Generally, periods of aggradation, incision and stability could be linked with regional climatic or anthropogenic influences on regional landscape stability and water availability. The fluvial dynamics of the central Lesser Caucasus mostly differed even between neighbouring regions, and only in cases of significant hemispheric climatic fluctuations as around 20 ka, during the Pleistocene/Holocene transition or the Little Ice Age, were similar over-regional fluvial patterns observed. This demonstrates the individual character of river systems especially in mountain regions such as the southern Caucasus with strong geoecological gradients. Thus, to understand the former landscape dynamics of mountain landscapes, investigations of fluvial sediment archives on a regional to sub-regional scale are necessary. [ABSTRACT FROM AUTHOR]

Three magmatic series of substantially different ages and compositions were successively emplaced to form the composite Meghri–Ordubab pluton (MOP) in the southernmost Lesser Caucasus. The protracted incremental assembly during 30 Myr, from Middle Eocene to Early Miocene, renders this location particularly suitable to characterize the petrogenetic evolution of Cenozoic magmatism during the final stage of the Neotethyan subduction. Based on whole-rock geochemistry, two main transitions tightly constrained in time are recognized. The first transition from Middle Eocene medium-K calc-alkaline to Late Eocene–Middle Oligocene shoshonitic magmatism corresponds to a marked increase in LREE and MREE and more juvenile 87 Sr/ 86 Sr and 143 Nd/ 144 Nd ratios. The second transition to Late Oligocene–Early Miocene high-K calc-alkaline “adakite-like” magmatism is coeval with a marked increase in Mg#, and Ni and Cr contents together with a depletion in MREE and HREE. Although the three differentiation series are derived from lower to mid-crustal hydrous magma fractionation, temporal variations of the magmatic source conditions are required to explain the contrasting chemistry of the parental magmas over time. Medium-K calc-alkaline parental magmas were generated by high degree of partial melting (~ 15%) of a garnet lherzolite. The shoshonitic and adakitic magmatic series represent magmas produced by low degree (1–5%) of partial melting of a garnet lherzolite, but a higher amount of residual garnet is required to reproduce the "adakite-like" signature. The timing of the two main geochemical transitions in the MOP is correlated with a progressive evolution from a compressional to an extensional stress regime linked to (1) the final stage of the Neotethyan subduction followed by the Arabia–Eurasia continental collision during the Eocene–Oligocene, and (2) the transition toward post-collisional magmatism, combined with a switch toward transcurrent tectonics during the Late Oligocene–Early Miocene. [ABSTRACT FROM AUTHOR]

Evidence of widespread alpine glaciations during the Late Pleistocene in mid-latitudes has long attracted attention of researchers. However, there were no studies that contain absolute ages in the Lesser Caucasus despite the fact that it is one of the major glaciated regions in Eurasia. Here, we present first cosmogenic 36 Cl surface exposure ages from the Karçal Mountains (41.24° N, 42.06° E, 3431 m a.s.l., above sea level) which is located in the most western part of the Lesser Caucasus in the northeastern Anatolia. In the Karçal Mountains, there are numerous valleys that have experienced significant glaciations since Late Pleistocene. We have investigated one of the largest valleys, the east-facing Karçal Valley, that hosts even a small (2926 m a.s.l.) recent glacier located at above 3000 m a.s.l. Fossil and recent rock glaciers along with lateral and recessional moraines exist in the valley. We conducted the study in two stages. First, we mapped the geomorphological units in the Karçal Valley in detail based on our field works and aerial photography. Later, we collected 10 rock samples from the fossil rock glacier and recessional moraines for cosmogenic 36 Cl surface exposure dating. The results outline a glacial chronology that is typical of the Last Glacial Maximum. Although the maximum extent and timing of the glaciation is not exactly known as lateral and terminal moraines were not suitable for sampling, recessional moraines indicate that the Karçal Valley palaeoglacier deglaciation started at least 19.9 ± 1.2 ka ago. Fossil rock glacier samples were dated to 15.7 ± 1.3 ka. These quantitative results are first in the Lesser Caucasus and compatible with previous ages obtained from other valleys in the nearby Eastern Black Sea region, Anatolian and some of the European Mountains. [ABSTRACT FROM AUTHOR]

Recent archaeological studies in the Lori Depression of Armenia (Lesser Caucasus) revealed a series of multilevel Early Paleolithic (Acheulian) sites belonging to the Early-Middle Pleistocene stage of occupation of the Caucasus. In the uppermost layers of these sites, the paleosols and sediments contain carbonate features (CFs) whereas the lower layers are absolutely free from carbonates. The aim of this work is to examine the role of detected CFs as an indicator for reconstructions of the Early-Middle Pleistocene paleoenvironments, to determine the source, time and conditions of carbonates' accumulation in initially non-calcareous and high-degree weathered humid paleosols. Three sections were studied: Kurtan I, points 1–2 and Muradovo. There are different forms of CFs represented by the calcified root cells in the layer 1, the hard nodules in the layer 2 and the laminae-like carbonates in the layer 3 of the sites studied. All the CFs are of the aqueous (hydrogenic) origin. The CFs of the uppermost layers 1 and 2 in the Kurtan I, point 2 were accumulated in the Holocene lake. The calcified root cells were formed on the swamp shore whereas the hard nodules on the lake bottom under stagnant water. The laminae-like carbonates in the layer 3 were accumulated in the Kurtan I and Muradovo sections due to strong erosion cycle(s) in the Late Pleistocene interglacial period(s) that led to the limestone scour in the region by ground and surface water. They reflect the earliest stage of the allochthonous carbonate accumulation in the area dated by radiocarbon method to approximately 20 ka cal BP. Therefore, all the CFs cannot be regarded as indicative of Early and Middle Pleistocene environmental changes, as they appeared in the uppermost layers of the studied sections much later than the time of formation for the surrounding groundmass. [ABSTRACT FROM AUTHOR]

The composite Meghri–Ordubad and Bargushat plutons of the Zangezur–Ordubad region in the southernmost Lesser Caucasus consist of successive Eocene to Pliocene magmatic pulses, and host two stages of porphyry Cu–Mo deposits. New high-precision TIMS U–Pb zircon ages confirm the magmatic sequence recognized by previous Rb–Sr isochron and whole-rock K–Ar dating. A 44.03 ± 0.02 Ma-old granite and a 48.99 ± 0.07 Ma-old granodiorite belong to an initial Eocene magmatic pulse, which is coeval with the first stage of porphyry Cu–Mo formation at Agarak, Hanqasar, Aygedzor and Dastakert. A subsequent Oligocene magmatic pulse was constrained by U–Pb zircon ages at 31.82 ± 0.02 Ma and 33.49 ± 0.02 Ma for a monzonite and a gabbro, and a late Miocene porphyritic granodioritic and granitic pulse yielded ages between 22.46 ± 0.02 Ma and 22.22 ± 0.01 Ma, respectively. The Oligo-Miocene magmatic evolution broadly coincides with the second porphyry-Cu–Mo ore deposit stage, including the major Kadjaran deposit at 26–27 Ma. Primitive mantle-normalized spider diagrams with negative Nb, Ta and Ti anomalies support a subduction-like nature for all Cenozoic magmatic rocks. Eocene magmatic rocks have a normal arc, calc-alkaline to high-K calc-alkaline composition, early Oligocene magmatic rocks a high-K calc-alkaline to shoshonitic composition, and late Oligocene to Mio-Pliocene rocks are adakitic and have a calc-alkaline to high-K calc-alkaline composition. Radiogenic isotopes reveal a mantle-dominated magmatic source, with the mantle component becoming more predominant during the Neogene. Trace element ratio and concentration patterns (Dy/Yb, Sr/Y, La/Yb, Eu/Eu*, Y contents) correlate with the age of the magmatic rocks. They reveal combined amphibole and plagioclase fractionation during the Eocene and the early Oligocene, and amphibole fractionation in the absence of plagioclase during the late Oligocene and the Mio-Pliocene, consistent with Eocene to Pliocene progressive thickening of the crust or increasing pressure of magma differentiation. Characteristic trace element and isotope systematics (Ba vs. Nb/Y, Th/Yb vs. Ba/La, 206 Pb/ 204 Pb vs. Th/Nb, Th/Nb vs. δ 18 O, REE) indicate that Eocene magmatism was dominated by fluid-mobile components, whereas Oligocene and Mio-Pliocene magmatism was dominated by a depleted mantle, compositionally modified by subducted sediments. A two-stage magmatic and metallogenic evolution is proposed for the Zangezur–Ordubad region. Eocene normal arc, calc-alkaline to high-K calc-alkaline magmatism was coeval with extensive Eocene magmatism in Iran attributed to Neotethys subduction. Eocene subduction resulted in the emplacement of small tonnage porphyry Cu–Mo deposits. Subsequent Oligocene and Miocene high-K calc-alkaline and shoshonitic to adakitic magmatism, and the second porphyry Cu–Mo deposit stage coincided with Arabia–Eurasia collision to post-collision tectonics. Magmatism and ore formation are linked to asthenospheric upwelling along translithospheric, transpressional regional faults between the Gondwana-derived South Armenian block and the Eurasian margin, resulting in decompression melting of lithospheric mantle, metasomatised by sediment components added to the mantle during the previous Eocene subduction event. [ABSTRACT FROM AUTHOR]

We report 28 successful Thellier type absolute geomagnetic paleointensity determinations from a Pleistocene lava sequence composed of 39 successive flows in the Djavakheti Highland (Lesser Caucasus, Georgia). Additionally, multispecimen technique provided the estimation of geomagnetic field strength for 12 independent cooling units. Paleointensity studies were performed using both Thellier type double heating and multispecimen techniques. Samples selection was mainly based on uni-vectorial remanent magnetization, thermal stability and domain size of the samples. Flow-mean Thellier paleointensity values range from 16.3 ± 5.2 to 71.0 ± 0.3 μT, while intensities obtained using multispecimen approach vary from17.2 ± 2.3 to 69.3 ± 7.9 μT. One of the flows is located near a possible discontinuity in the sequence and yields a rather low Thellier absolute intensity (16.3 ± 5.2) suggesting a transitional regime and the onset of the Matuyama-Olduvai polarity transition, which does not appear on the directional record. Multispecimen paleointensities from the same flow, however, yield higher, close to present day values which makes untenable the hypothesis of occurrence of transitional field. Thus the whole sequence was emplaced in a short time between the Olduvai chron and 1.73 ± 0.03 Ma, as suggested by available radiometric and paleomagnetic data ( Caccavari et al., 2014 ). [ABSTRACT FROM AUTHOR]

The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an obduction over ∼200 km of oceanic lithosphere of Middle Jurassic age (c. 175–165 Ma) along an entire tectonic boundary (>1000 km) at around 90 Ma. The obduction process is characterized by four first order geological constraints: (1) Ophiolites represent remnants of a single ophiolite nappe currently of only a few kilometres thick and 200 km long. The oceanic crust was old (∼80 Ma) at the time of its obduction. (2) The presence of OIB-type magmatism emplaced up to 10 Ma prior to obduction preserved on top of the ophiolites is indicative of mantle upwelling processes (hotspot). (3) The leading edge of the Taurides-Anatolides, represented by the South Armenian Block, did not experience pressures exceeding 0.8 GPa nor temperatures greater than ∼300 °C during underthrusting below the obducting oceanic lithosphere. (4) An oceanic domain of a maximum 1000 km (from north to south) remained between Taurides-Anatolides and Pontides-Southern Eurasian Margin after the obduction. We employ two-dimensional thermo-mechanical numerical modelling in order to investigate obduction dynamics of a re-heated oceanic lithosphere. Our results suggest that thermal rejuvenation (i.e. reheating) of the oceanic domain, tectonic compression, and the structure of the passive margin are essential ingredients for enabling obduction. Afterwards, extension induced by far-field plate kinematics (subduction below Southern Eurasian Margin), facilitates the thinning of the ophiolite, the transport of the ophiolite on the continental domain, and the exhumation of continental basement through the ophiolite. The combined action of thermal rejuvenation and compression are ascribed to a major change in tectonic motions occurring at 110–90 Ma, which led to simultaneous obductions in the Oman (Arabia) and NALC regions. [ABSTRACT FROM AUTHOR]

A sediment core has been retrieved from Vanevan peat (south-eastern shore of Lake Sevan, Armenia), which is today disconnected from Lake Sevan thanks to an artificial shallowing of the lake. Based on 5 radiocarbon dates, Vanevan record covers the Mid Holocene (from ca. 7800 to ca. 5100 cal. BP). The Late Holocene is today absent in the peat stratigraphy due to modern peat exploitation by surface mining. This study focuses on a multi-proxy approach including pollen, charcoals, and pollen-inferred climate reconstruction. An open-land, steppic vegetation is recorded up to ca. 7700 cal. BP, followed by a more forested landscape during the Mid Holocene (up to ca. 5700 cal. BP), and ending again with an open-land vegetation (to the end of record, 5100 cal. BP). This vegetation dynamics responds to general climate changes documented in the Near East. Whether human activities are documented since ca. 7500 cal. BP (Late Neolithic) in Vanevan, they remain marginal and probably did not affect the area. Early Holocene dry climate, which caused the steppic environment to be widespread through the Near East, is strongly related to low late spring precipitation (P May–Jun = 180 mm). Mid Holocene forested landscape and increasing lake-level seem related to late spring precipitation (+28%), which is the main change in estimated climate parameters. This has to be linked with reinforcement of the Westerlies and less active Siberian High, which are inversely involved in the following, dry phase starting at ca. 5700 cal. BP. [ABSTRACT FROM AUTHOR]

The Daghkesemen Au-bearing polymetallic vein-type deposit, which is the most important ore deposit of the Kazakh graben located in the northwestern part of the Lesser Caucasus, is hosted by calc-alkaline volcanic rocks (andesite, dacite, basaltic trachyandesite, trachyandesite, rhyodacite and their pyroclastics), subvolcanic rocks (andesite porphyry, dolerite, albitophyre/rhyodacite porphyry), and volcanic breccias. The mineralization is commonly observed as gold-bearing quartz-sphalerite-galena-chalcopyrite veins. The Daghkesemen Au-bearing polymetallic deposit, mostly observed in the propylitic alteration, is commonly composed of primarily sphalerite, galena, chalcopyrite, pyrite, native gold, bornite and magnetite, and secondarily digenite, cerussite, covellite, chalcocite, malachite, azurite, hematite, jarosite, and anglesite. The Daghkesemen Au-bearing polymetallic deposit mostly comprises Zn, Pb, Cu, Au, Ag, Fe and Cd. Homogenization temperatures (Th) of the fluid inclusions in sphalerite and quartz range from 200.1 °C to 281.2 °C and 266.4–266.7 °C, respectively. The low salinities for the fluid inclusions in sphalerite and quartz show a range of 0.7–6.6 wt % NaCl equivalent and 2.7 to 3.1 wt % NaCl equivalent, respectively. Eutectic temperatures measured in the fluid inclusions vary between −27.4 and −18.2 °C, indicating H 2 O–NaCl–KCl system. The δ34S H2S values (−0.8 to −4.4‰) of sulfides (chalcopyrite, sphalerite, galena and pyrite) suggest a magmatic-hydrothermal origin for sulfur. The calculated sulfur isotopic geothermometer is value of 190 °C for sphalerite-chalcopyrite pair. The geochemical, mineralogical, sulfur isotopic and fluid inclusion data of the Daghkesemen Au-bearing polymetallic deposit suggest an intermediate sulfidation epithermal deposit associated with volcanic rocks. • The Daghkesemen deposit is hosted by calc-alkaline volcanic rocks in the porphyry-epithermal ore field of Azerbaijan • associated with dominantly propylitic alteration and primarily composed of Zn, Pb, Cu, Fe, Au, Ag, Cd. • The calculated sulfur isotopic geothermometer (190 °C) consistent with microthermometric data (200–281 °C). • The ore-forming fluid was derived from a primarily magmatic source mixed with meteoric fluids. • Corresponds to an intermediate-sulfidation epithermal system. [ABSTRACT FROM AUTHOR]

The geologic evolution of the South Armenian Block (SAB) in the Mesozoic is reconstructed from a structural, metamorphic, and geochronologic study including U–Pb and 40 Ar/ 39 Ar dating. The South Armenian Block Crystalline Basement (SABCB) outcrops solely in a narrow tectonic window, NW of Yerevan. The study of this zone provides key and unprecedented information concerning closing of the Northern Neotethys oceanic domain north of the Taurides-Anatolides platform from the Middle Jurassic to the Early Cretaceous. The basement comprises of presumed Proterozoic orthogneiss overlain by metamorphosed pelites as well as intrusions of granodiorite and leucogranite during the Late Jurassic and Early Cretaceous. Structural, geochronological and petrological observations show a multiphased evolution of the northern margin of the SAB during the Late Jurassic and Early Cretaceous. A south-dipping subduction under the East Anatolian Platform-South Armenian Block (EAP-SAB) is proposed in order to suit recent findings pertaining emplacement of relatively hot subduction related granodiorite as well as the metamorphic evolution of the crystalline basement in the Lesser Caucasus area. The metamorphism is interpreted as evidencing: (1) M1 Barrovian MP–MT conditions (staurolite–kyanite) at c. 157–160 Ma and intrusion of dioritic magmas at c. 150–156 Ma, (2) near-adiabatic decompression is featured by partial melting and production of leucogranites at c. 153 Ma, followed by M2 HT–LP conditions (andalusite–K-feldspar). A phase of shearing and recrystallization is ascribed to doming at c. 130–150 Ma and cooling at 400 °C by c. 123 Ma (M3). Structural observations show (1) top to the north shearing during M1 and (2) radial extension during M2. The extensional event ends by emplacement of a thick detrital series along radial S, E and W-dipping normal faults. Further, the crystalline basement is unconformably covered by Upper Cretaceous-Paleocene series dated by nannofossils, evolving from Maastrichtian marly sandstones to Paleocene limestones. [ABSTRACT FROM AUTHOR]

The continental South Armenian Block – part of the Anatolide–Tauride South Armenian microplate – of Gondwana origin rifted from the African margin after the Triassic and collided with the Eurasian margin after the Late Cretaceous. During the Late Cretaceous, two northward dipping subduction zones were simultaneously active in the northern Neo-Tethys between the South Armenian Block in the south and the Eurasian margin in the north: oceanic subduction took place below the continental Eurasian margin and intra-oceanic subduction resulted in ophiolite obduction onto the South Armenian Block in the Late Cretaceous. The paleolatitude position of the South Armenian Block before its collision with Eurasia within paleogeographic reconstructions is poorly determined and limited to one study. This earlier study places the South Armenian Block at the African margin in the Early Jurassic. To reconstruct the paleolatitude history of the South Armenian Block, we sampled Upper Devonian–Permian and Cretaceous sedimentary rocks in Armenia. The sampled Paleozoic rocks have likely been remagnetized. Results from two out of three sites sampled in Upper Cretaceous strata pass fold tests and probably all three carry a primary paleomagnetic signal. The sampled sedimentary rocks were potentially affected by inclination shallowing. Therefore, two sites that consist of a large number of samples (> 100) were corrected for inclination shallowing using the elongation/inclination method. These are the first paleomagnetic data that quantify the South Armenian Block's position in the Tethys ocean between post-Triassic rifting from the African margin and post-Cretaceous collision with Eurasia. A locality sampled in Lower Campanian Eurasian margin sedimentary rocks and corrected for inclination shallowing, confirms that the corresponding paleolatitude falls on the Eurasian paleolatitude curve. The north–south distance between the South Armenian Block and the Eurasian margin just after Coniacian–Santonian ophiolite obduction was at most 1000 km. [ABSTRACT FROM AUTHOR]

The polymetallic Cu–Au–Ag–Zn±Pb, Cu–Au and Cu deposits in the Kapan, Alaverdi and Mehmana mining districts of Armenia and the Nagorno–Karabakh region form part of the Tethyan belt. They are hosted by Middle Jurassic rocks of the Lesser Caucasus paleo-island arc, which can be divided into the Kapan Zone and the Somkheto–Karabakh Island Arc. Mineralization in Middle Jurassic rocks of this paleo-island arc domain formed during the first of three recognized Mesozoic to Cenozoic metallogenic epochs. The Middle Jurassic to Early Cretaceous metallogenic epoch comprises porphyry Cu, skarn and epithermal deposits related to Late Jurassic and Early Cretaceous intrusions. The second and third metallogenic epochs of the Lesser Caucasus are represented by Late Cretaceous volcanogenic massive sulfide (VMS) deposits with transitional features towards epithermal mineralization and by Eocene to Miocene world-class porphyry Mo–Cu and epithermal precious metal deposits, respectively. The ore deposits in the Kapan, Alaverdi and Mehmana mining districts are poorly understood and previous researchers named them as copper–pyrite, Cu–Au or polymetallic deposits. Different genetic origins were proposed for their formation, including VMS and porphyry-related scenarios. The ore deposits in the Kapan, Alaverdi and Mehmana mining districts are characterized by diverse mineralization styles, which include polymetallic veins, massive stratiform replacement ore bodies at lithological contacts, and stockwork style mineralization. Sericitic, argillic and advanced argillic alteration assemblages are widespread in the deposits which have intermediate to high-sulfidation state mineral parageneses that consist of tennantite–tetrahedrite plus chalcopyrite and enargite–luzonite–colusite, respectively. The ore deposits are spatially associated with differentiated calc-alkaline intrusions and pebble dykes are widespread. Published δ 34S values for sulfides and sulfates are in agreement with a magmatic source for the bulk sulfur whereas published δ 34S values of sulfate minerals partly overlap with the isotopic composition of contemporaneous seawater. Published mineralization ages demonstrate discrete ore forming pulses from Middle Jurassic to the Late Jurassic–Early Cretaceous boundary, indicating time gaps of 5 to 20m.y. in between the partly subaqueous deposition of the host rocks and the epigenetic mineralization. Most of the described characteristics indicate an intrusion-related origin for the ore deposits in Middle Jurassic rocks of the Lesser Caucasus, whereas a hybrid VMS–epithermal–porphyry scenario might apply for deposits with both VMS- and intrusion-related features. The volcanic Middle Jurassic host rocks for mineralization and Middle to Late Jurassic intrusive rocks from the Somkheto–Karabakh Island Arc and the Kapan Zone show typical subduction-related calc-alkaline signature. They are enriched in LILE such as K, Rb and Ba and show negative anomalies in HFSE such as Nb and Ta. The ubiquitous presence of amphibole in Middle Jurassic volcanic rocks reflects magmas with high water contents. Flat REE patterns ([La/Yb]N =0.89–1.23) indicate a depleted mantle source, and concave-upward (listric-shaped) MREE–HREE patterns ([Dy/Yb]N =0.75–1.21) suggest melting from a shallow mantle reservoir. Similar trace element patterns of Middle Jurassic rocks from the Somkheto–Karabakh Island Arc and the Kapan Zone indicate that these two tectonic units form part of one discontinuous segmented arc. Similar petrogenetic and ore-forming processes operated along its axis and Middle Jurassic volcanic and volcanosedimentary rocks constitute the preferential host for polymetallic Cu–Au–Ag–Zn±Pb, Cu–Au and Cu mineralization, both in the Somkheto–Karabakh Island Arc and the Kapan Zone. [ABSTRACT FROM AUTHOR]

The Kapan Zone in southern Armenia is a Middle Jurassic to Upper Cretaceous island-arc domain at the southern margin of Eurasia that collided with the Gondwana-derived South-Armenian Block in the Upper Cretaceous–Paleocene. Igneous rocks of Middle Jurassic to Quaternary age record the geodynamic evolution of the Kapan Zone, whose tectonic setting changed from an active arc environment, related to the northeastwards subduction of the Neotethys, to a post-collisional setting. U–Pb zircon ages of intrusive rocks from the Kapan Zone confirm the division of the stratigraphic column into the Middle Jurassic, Upper Jurassic–Lower Cretaceous and Paleogene magmatic complexes. Middle Jurassic tonalite was sampled from pebble dykes and dated at 165.6±1.4Ma, voluminous plutons intruded in the Kapan Zone between 137.7±1.6Ma and 131.5±2.1Ma within a time span of less than 10Ma and Paleogene gabbro was dated at 50.82±0.51Ma. Volcanic rocks in the Kapan Zone range from basaltic to rhyolitic composition with andesite being the most common rock type. Intrusive and volcanic rocks from the three magmatic complexes and Quaternary basanite have subduction-related signatures. They are enriched in fluid-mobile LILE such as K, Rb and Ba and are depleted in HFSE such as Zr, Nb and Ta, which suggest their derivation from a metasomatized mantle source as old crustal material is virtually absent in the Kapan Zone. The subduction-related signature is conserved in post-collisional rocks from the Paleogene magmatic complex and the Quaternary basanite, indicating their origin from a mantle source which was metasomatized during preceding subduction. REE patterns from igneous rocks of the Kapan Zone are characterized by increased slope in younger rocks. Flat patterns in Middle Jurassic rocks indicate melting from a depleted mantle reservoir whereas REE patterns with increased slope in rocks from the Upper Jurassic–Lower Cretaceous magmatic complex, the Paleogene magmatic complex and the Quaternary basanite suggest either smaller amounts of partial melting and/or input of less depleted mantle material in the source region. The initial isotopic signature of rocks from the Kapan Zone supports melting of a primitive mantle source with limited contribution of assimilated crustal material. The more crustal isotopic signature of rocks from the Middle Jurassic and Paleogene magmatic complexes relative to rocks from the Upper Jurassic–Lower Cretaceous magmatic complex indicates subduction of continent-derived sedimentary material and interaction with old basement units at depth. Reported coeval subduction-related Middle Jurassic to Cretaceous intrusive and volcanic rocks from the Sanandaj–Sirjan Zone in Iran are in good agreement with our results from the Kapan Zone in southern Armenia. This suggests a continuation of the magmatic arc of the Lesser Caucasus to the southwest of the Kapan Zone, indicating continuous arc magmatic activity along the Eastern Pontides, the Lesser Caucasus and the Sanandaj–Sirjan Zone. [ABSTRACT FROM AUTHOR]

Abstract: The ophiolites of Amasia in the northwestern part of the Sevan–Akera suture zone (Lesser Caucasus, NW Armenia) correspond to a well-preserved example of a major obduction of oceanic lithosphere over the South Armenian continental block. Our mapping evidenced a series of (1) un-metamorphosed gabbroic oceanic crust, (2) serpentinites and a greenschist grade tectonic melange composed of deformed pillow-basalts, radiolarites and cherts, and (3) a basal slice of garnet amphibolites bearing similar compositional features as the ophiolite. These units are sliced and deformed by post-Eocene thrusting related to the shortening of the suture zone after the collision of the South Armenian Block with Eurasia. 40Ar/39Ar dating on gabbro amphiboles yielded ages of 169.0±4.6 to 175.8±3.9Ma. This age and geochemical composition of ophiolite rocks are similar to those of other ophiolite outcrops in Armenia and NE Turkey. Structural and geochemical analyses undertaken on the garnet amphibolites suggest it to represent the obducted ophiolite metamorphic sole. All these data are in agreement with the presence of a unique ophiolite nappe at the scale of NE Turkey–Armenia originating from a Jurassic intra-oceanic back-arc basin, obducted onto the Armenian–Taurides–Anatolides microblocks in the early Late Cretaceous (c. 90Ma). [Copyright &y& Elsevier]

Abstract: Orogens formed by a combination of subduction and accretion are featured by a short-lived collisional history. They preserve crustal geometries acquired prior to the collisional event. These geometries comprise obducted oceanic crust sequences that may propagate somewhat far away from the suture zone, preserved accretionary prism and subduction channel at the interplate boundary. The cessation of deformation is ascribed to rapid jump of the subduction zone at the passive margin rim of the opposite side of the accreted block. Geological investigation and 40Ar/39Ar dating on the main tectonic boundaries of the Anatolide–Tauride–Armenian (ATA) block in Eastern Turkey, Armenia and Georgia provide temporal constraints of subduction and accretion on both sides of this small continental block, and final collisional history of Eurasian and Arabian plates. On the northern side, 40Ar/39Ar ages give insights for the subduction and collage from the Middle to Upper Cretaceous (95–80Ma). To the south, younger magmatic and metamorphic ages exhibit subduction of Neotethys and accretion of the Bitlis–Pütürge block during the Upper Cretaceous (74–71Ma). These data are interpreted as a subduction jump from the northern to the southern boundary of the ATA continental block at 80–75Ma. Similar back-arc type geochemistry of obducted ophiolites in the two subduction–accretion domains point to a similar intra-oceanic evolution prior to accretion, featured by slab steepening and roll-back as for the current Mediterranean domain. Final closure of Neotethys and initiation of collision with Arabian Plate occurred in the Middle-Upper Eocene as featured by the development of a Himalayan-type thrust sheet exhuming amphibolite facies rocks in its hanging-wall at c. 48Ma. [Copyright &y& Elsevier]

Abstract: Variscan to Alpine magmatic activity on the North Tethys active Eurasian margin in the Caucasus region is revealed by 40Ar/39Ar ages from rocks sampled in the Georgian Crystalline basement and exotic blocs in the Armenian foreland basin. These ages provide insights into the long duration of magmatic activity and related metamorphic history of the margin, with: (1) a phase of transpression with little crustal thickening during the Variscan cycle, evidenced by HT-LP metamorphism at 329–337Ma; (2) a phase of intense bimodal magmatism at the end of the Variscan cycle, between 303 and 269Ma, which is interpreted as an ongoing active margin during this period; (3) further evolution of the active margin evidenced by migmatites formed at ca. 183Ma in a transpressive setting; (4) paroxysmal arc plutonic activity during the Jurassic (although the active magmatic arc was located farther south than the studied crystalline basements) with metamorphic rocks of the Eurasian basement sampled in the Armenian foreland basin dated at 166Ma; (5) rapid cooling suggested by similar within-error ages of amphibole and muscovite sampled from the same exotic block in the Armenian fore-arc basin, ascribed to rapid exhumation related to extensional tectonics in the arc; and finally (6) cessation of ‘Andean’-type magmatic arc history in the Upper Cretaceous. Remnants of magmatic activity in the Early Cretaceous are found in the Georgian crystalline basement at c. 114Ma, which is ascribed to flat slab subduction of relatively hot oceanic crust. This event corresponds to the emplacement of an oceanic seamount above the N Armenian ophiolite at 117Ma. The activity of a hot spot between the active Eurasian margin and the South Armenian Block is thought to have heated and thickened the Neo-Tethys oceanic crust. Finally, the South Eurasian margin was uplifted and transported over this hot oceanic crust, resulting in the cessation of subduction and the erosion of the southern edge of the margin in Upper Cretaceous times. Emplacement of Eocene volcanics stitches all main collisional structures. [Copyright &y& Elsevier]

Abstract: The identification of a large OIB-type volcanic sequence on top of an obducted nappe in the Lesser Caucaus of Armenia helps us explain the obduction processes in the Caucasus region that are related to dramatic change in the global tectonics of the Tethyan region in the late Lower Cretaceous. The ophiolitic nappe preserves three distinct magmatic series, obducted in a single tectonic slice over the South Armenian Block during the Coniacian–Santonian (88–83 Ma), the same time as the Oman ophiolite. Similar geological, petrological, geochemical and age features for various Armenian ophiolitic massifs (Sevan, Stepanavan, and Vedi) argue for the presence of a single large obducted ophiolite unit. The ophiolite, shows evidence for a slow-spreading oceanic environment in Lower to Middle Jurassic. Serpentinites, gabbros and plagiogranites were exhumed by normal faults, and covered by radiolarites. Few pillow-lava flows have infilled the rift grabens. The ophiolite lavas have hybrid geochemical composition intermediate between Arc and MORB signatures: (La/Yb) N =0.6–0.9; (Nb/Th) N =0.17–0.57; (143Nd/144Nd) i =0.51273–0.51291; (87Sr/86Sr) i =0.70370–0.70565; (207Pb/204Pb) i =15.4587–15.5411; (208Pb/204Pb) i =37.4053–38.2336; (206Pb/204Pb) i =17.9195–18.4594. These compositions suggest they were probably formed in a back-arc basin by melting of a shallow asthenosphere source contaminated by a deeper mantle source modified by subducted slab-derived products. 87Sr/86Sr ratios and petrological evidence show that these lavas have been intensely altered by mid-oceanic hydrothermalism as well as by serpentinites, which are interpreted as exhumed mantle peridotites. The gabbros have almost the same geochemical composition as related pillow-lavas: (La/Yb) N =0.2–2.3; (Nb/Th) N =0.1–2.8; (143Nd/144Nd) i =0.51264–0.51276; (87Sr/86Sr) i =0.70386–0.70557; (207Pb/204Pb) i =15.4888–15.5391; (208Pb/204Pb) i =37.2729–37.8713; (206Pb/204Pb) i =17.6296–17.9683. Plagiogranites show major and trace element features similar to other Neo-Tethyan plagiogranites (La/Yb) N =1.10–7.92; (Nb/Th) N =0.10–0.94; but display a less radiogenic Nd isotopic composition than basalts [(143Nd/144Nd) i =0.51263] and more radiogenic (87Sr/86Sr) i ratios. This oceanic crust sequence is covered by variable thicknesses of unaltered pillowed OIB alkaline lavas emplaced in marine conditions. 40Ar/39Ar dating of a single-grain amphibole phenocryst provides a Lower Cretaceous age of 117.3±0.9 Ma, which confirms a distinct formation age of the OIB lavas. The geochemical composition of these alkaline lavas is similar to plateau-lavas [(La/Yb) N =6–14; (Nb/Th) N =0.23–0.76; (143Nd/144Nd) i =0.51262–0.51271; (87Sr/86Sr) i =0.70338–0.70551; (207Pb/204Pb) i =15.5439–15.6158; (208Pb/204Pb) i =38.3724–39.3623; (206Pb/204Pb) i =18.4024–19.6744]. They have significantly more radiogenic lead isotopic compositions than ophiolitic rocks, and fit the geochemical compositions of hot-spot derived lavas mixed with various proportions of oceanic mantle. In addition, this oceanic+plateau sequence is covered by Upper Cretaceous calc-alkaline lavas: (La/Yb) N =2.07–2.31; (Nb/Th) N =0.08–0.15; (144Nd/143Nd) i =0.51271–0.51282; (87Sr/86Sr) i =0.70452–0.70478), which were likely formed in a supra-subduction zone environment. During the late Lower to early Upper Cretaceous period, hot-spot related magmatism related to plateau events may have led to significant crustal thickening in various zones of the Middle-eastern Neotethys. These processes have likely hindered subduction of some of the hot and thickened oceanic crust segments, and allowed them to be obducted over small continental blocks such as the South Armenian Block. [Copyright &y& Elsevier]

The South Armenian Block (SAB) belongs to the Lesser Caucasus, and it is located where the Central Tethyan belt bends from an EW orientation in Turkey to the NW-oriented Iranian tectonic zones. Magmatism in these belts is the result of convergence, collision and post-collision evolution of the Arabian plate with the Eurasian margin. An exhaustive study including whole-rock major, trace element, and radiogenic isotope (Sr, Nd, Pb) data, and zircon Hf isotopes, and U-Pb dating has been conducted in three areas of the SAB, including Tejsar, Amulsar and Bargushat. Combined with previous data, this study reconstructs the Cenozoic magmatic and geodynamic evolution of the Turkish-Lesser Caucasian-Iranian magmatic belt, with a particular focus on the SAB. The Cenozoic intrusions in the SAB are dominantly K-rich and characterized by an enrichment in LILE and depletion in Nb, Ta and Ti. They were emplaced in Tejsar and Bargushat between 43.0 and 37.7 Ma, in Amulsar between 35.9 and 32.1 Ma, predating or being contemporaneous with a 37.8 to 28.1 Ma shoshonitic pulse recorded in the southernmost SAB at the Meghri-Ordubad pluton. This K-rich magmatism is characterized by a juvenile mantle dominated composition, evidenced by εHf(i) zircon values higher than 8.1 and εNd(i) whole-rock values higher than 3.1. Modelling of the Nd and Sr isotope data shows that the mid-Eocene to early Oligocene K-rich magmatism of the SAB is the result of low degree partial melting of a metasomatized mantle source (SCLM), mixing with an upwelling asthenospheric mantle. Mid-Eocene-early Oligocene K-rich magmatism in the SAB and NW Iran coincided with a magmatic lull in Turkey at 40–20 Ma. While frontal Arabia-Turkish plate collision totally shut off magmatism, ongoing coeval magmatism in the SAB and NW-Iran is explained by strike-slip fault tectonics during oblique convergence of the Arabian plate along the Iranian and SAB segment. The dominant juvenile mantle signature of the Cenozoic SAB magmatism contrasts with more crustal-enriched sources in the adjacent NW Iranian and eastern Turkish Cenozoic magmatic rocks, revealing a mantle anomaly underneath the SAB. Our study concludes that the compressive to tranpressive tectonic regime in the SAB during Arabia-Eurasia collision resulted in delamination of a metasomatized SCLM, which interacted with a juvenile asthenospheric mantle upwelling underneath the SAB. Low degree partial melting of this mixed mantle reservoir resulted in the formation of the mid-Eocene to Oligocene K-rich magmatic rocks in the SAB. [ABSTRACT FROM AUTHOR]

Abstract: In the Lesser Caucausus the Sevan-Akera ophiolites of N Armenia have lithological features of a slow-spreading oceanic lithosphere: serpentinites are frequently exposed and hydrothermalized at sea-floor level, plutonic rocks and dykes are rare. A complete differentiation trend is observed from mafic norites evolving to diorites and plagiogranites. Normal faults have exposed some of the deep magmatic rocks at sea-floor level. Geochemically, two distinct lava flow series have been distinguished: (1) a contaminated Mid-Oceanic Ridge Basalt (MORB) series evolving from gabbros to plagiogranites and from basalts to basaltic andesites, exhibiting slight calc-alkaline features (enrichments in Large Ion Lithophile Elements (LILE); negative anomalies in Nb–Ta and Ti relative to N-MORB); (2) an alkaline series evolving from basanites to trachy-andesites (on anhydrous basis). 40Ar/39Ar age on amphibole-bearing gabbros evidence a Middle Jurassic age (165.3±1.7Ma,2σ) for oceanic crust formation. Structural data, including geological cross-sections and logs of the ophiolite along the northern part of Sevan Lake allow discussing the geodynamic evolution of that segment of the Amassia-Sevan-Akera ophiolitic suture zone. [Copyright &y& Elsevier]

The post-collisional Syunik and Vardenis volcanic highlands, located in the southern Lesser Caucasus mountains (part of the Arabia-Eurasia collision zone) are host to over 200 monogenetic volcanoes, as well as 2 large Quaternary polygenetic volcanoes in the Syunik highland. The latter are overlain by lavas from the monogenetic volcanoes, suggesting there was a transition in the style of volcanic activity from large-volume central vent eruptions to dispersed small-volume eruptions. 12 new high quality 40Ar/39Ar ages are presented here, with 11 ages calculated by step-heating experiments on groundmass separates, and the final age obtained from total fusions of a population of sanidines. All the ages were younger than 1.5 Ma, except for one ignimbrite deposit whose sanidines gave an age of 6 Ma. While the bulk of the exposed products of post-collisional volcanism relate to Pleistocene activity, it is clear there has been active volcanism in the region since at least the late Miocene. All ages for monogenetic volcanoes in the Syunik highland are younger than 1 Ma, but to the north in Vardenis there is geochronological evidence of monogenetic volcanism at 1.4 and 1.3 Ma. An age of 1.3 Ma is determined for a lava flow from one of the polygenetic volcanoes- Tskhouk, and when combined with other ages helps constrain the timing of the polygenetic to monogenetic transition to around 1 Ma. The new ages illustrate a degree of spatio-temporal coupling in the formation of new vents, which could be related to pull-apart basins focussing ascending magmas. This coupling means that future eruptions are particularly likely to occur close to the sites of the most recent Holocene activity. The polygenetic to monogenetic transition is argued to be the result of a decreasing magma supply based on: (i) volume estimates for Holocene eruptions and for all monogenetic volcanoes and their lava flows in Syunik; and (ii) the volcanic stratigraphy of the Lesser Caucasus region which shows late Pliocene- early Pleistocene continental flood basalts being succeeded by a few large andesite-dacite volcanoes and then the most recent deposits consisting of small-volume scoria cones. The Syunik highland has the highest density of monogenetic centres in the Lesser Caucasus, which is taken to indicate this region has the highest magma flux, and was therefore the last location to transition to monogenetic volcanism, which is why the transition is most clearly seen there. There is no evidence from Sr-Nd-B isotope measurements for the exhaustion of fusible slab components in the mantle source, showing that an inherited slab signature can survive for millions of years after the end of subduction. Although volcanism in the Lesser Caucasus is currently waning, a future pulse of activity is possible. • Volcanism in Syunik (S. Armenia) has transitioned from polygenetic to monogenetic. • New 40Ar/39Ar ages constrain the timing of this transition to around 1 Ma. • Polygenetic to monogenetic transition due to waning post-collisional magma supply. • No evidence for exhaustion of mantle source meaning future eruptions are likely. [ABSTRACT FROM AUTHOR]

The 350 km-long Adjara-Trialeti fold-and-thrust belt of southwestern Georgia is the result of the structural inversion of a continental back-arc basin developed in the Paleogene on the upper (Eurasian) plate of the northward subducting northern branch of the Neotethys. Low-temperature thermochronological data [fission-track and (U-Th)/He analyses on apatite] from sedimentary and plutonic rocks provide robust constraints on the tectonic evolution of the Adjara-Trialeti orogenic belt. Fission-track central ages range from the Middle Eocene to the Middle Miocene (46–15 Ma); helium ages are clustered in the Late Miocene-Pliocene (10–3 Ma). Time-temperature paths obtained integrating thermochronologic, stratigraphic, and radiometric data show that the volcanosedimentary basin fill of the Adjara-Trialeti back-arc basin underwent progressive burial heating prior to final cooling/exhumation in the late Middle Miocene-Pliocene. These new data show that the Adjara-Trialeti back-arc basin was inverted and developed as a fold-and-thrust belt starting at 14–10 Ma, in tune with widespread Middle-to-Late Miocene shortening and exhumation across wide areas of the Middle East, from the eastern Pontides of NE Turkey to the Lesser Caucasus in northern Armenia and NW Azerbaijan, and the Talysh and Alborz ranges in northern Iran. Such a supraregional tectonism is interpreted as a far-field effect of the Arabia-Eurasia collision along the Bitlis suture ca. 400 km to the south of the study area. [Display omitted] • The Adjara-Trialeti back-arc was structurally inverted from the late Middle Miocene. • Basin inversion occurred in response to Arabia-Eurasia far-field collisional stress. • The Khrami N-vergent basement thrust is due to Paleocene Sevan-Akera deformation. [ABSTRACT FROM AUTHOR]

• The Gedabek deposit is an intrusion-related gold-silver-copper deposit. • The Gedabek mineralization is closely related to advanced argillic alteration. • Ore-forming fluids are of low-intermediate temperature and low salinity. • Ore-forming fluids are primarily derived from a magmatic source with a contribution of meteoric waters. • The Au-Ag-Cu deposit is a high sulfidation deposit associated with late stage porphyry system. The Gedabek Au-Ag-Cu deposit located in the western part of Azerbaijan is hosted by quartz porphyry which is situated at contact between Middle Jurassic andesitic tuff and Late Jurassic-Early Cretaceous Gedabek intrusive rocks consisting of granodiorite, diorite and gabbro. Geochemical investigations for the Gedabek intrusive rocks indicate that these are calc-alkaline, and probably developed pre-collisional regime. The Gedabek Au-Ag-Cu deposit, mainly observed in the advanced argillic alteration, is composed of native gold, electrum, hessite, petzite, chalcopyrite, sphalerite, galena, molybdenite, pyrite, arsenopyrite, fahlore, enargite, bornite, hematite, barite, jarosite, adularia, covellite, chalcocite, malachite and azurite. The Gedabek Au-Ag-Cu deposit predominantly comprises Au, Ag, Cu, Zn, Pb, Fe, As, and S for the ore-bearing samples. Homogenization temperatures and salinities of fluid inclusions (FIs) trapped in quartz and sphalerite range from 134 to 371 °C and 227 to 410 °C; 3.4 to 15.2 wt% NaCl equivalent and 4.0–12.0 wt% NaCl equivalent, respectively. The δ34S H2S values (2.0–5.9‰) of sulfides (chalcopyrite, pyrite and sphalerite) from the Gedabek Au-Ag-Cu deposit indicate a magmatic origin for the ore-forming fluids. The geological, mineralogical, geochemical, isotopic, and microthermometric data for the Gedabek Au-Ag-Cu deposit suggest a high sulfidation epithermal deposit associated with porphyry system. [ABSTRACT FROM AUTHOR]

The Bolnisi district is a distinct tectonic zone of the Lesser Caucasus, which is considered to represent the eastern extremity of the Turkish Eastern Pontides. Late Cretaceous, low-K, calc-alkaline to high-K rhyolite of the Mashavera and Gasandami Suites is the predominant rock type of the district, and is accompanied by subsidiary dacite, and rare high-alumina basalt and trachyandesite of the Tandzia Suite. The Mashavera and Gasandami rhyolite and dacite have yielded U-Pb LA-ICP-MS and TIMS zircon ages between 87.14 ± 0.16 and 81.64 ± 0.94 Ma, which are in line with the Coniacan-Santonian ages of radiolarian fauna of the Mashavera Suite. The felsic rocks of the Mashavera and Gasandami Suites were deposited during a ~6.6 m.y.-long silicic magmatic flare-up event, which together with the Tandzia Suite mafic rocks, documents Late Cretaceous bimodal magmatism in an extensional tectonic setting. Trace element data indicate that high Y-Zr, low- to high-silica rhyolite and dacite, and low Y-Zr high-silica rhyolite have been erupted, respectively, from coeval deep and shallow crustal reservoirs. The rocks of the bimodal magmatic event are overlain by high-K volcanic rocks of the Campanian Shorsholeti Suite, which have been erupted during slab roll-back and steepening, from magmas produced by deep melting of a metasomatised mantle. Eocene postcollisional felsic intrusions crosscut the Late Cretaceous rock. The Coniacian to early Campanian bimodal magmatism, and the subsequent high-K magmatism of the Bolnisi district are contemporaneous and share geochemical characteristics with the Late Cretaceous magmatism of the Eastern Pontides. It documents the existence of a Late Cretaceous regional silicic magmatic province, and subsequent high-K magmatism during slab steepening. This regional magmatic evolution coincided with the opening of the Black Sea and the Adjara-Trialeti basins. This evolution was coeval with the wanning stages of northern Neotethyan subduction, after a ~40 m.y.-long magmatic lull along the southern Eurasian convergent margin. Early Eocene adakite-like magmatism affected both the Bolnisi district and the Eastern Pontides, demonstrating a common postcollisional magmatic evolution. Image 1 • Late Cretaceous subduction-related silicic magmatic flare-up, north Lesser Caucasus. • Bimodal magmatism in Lesser Caucasus-Eastern Pontides coeval with Black Sea opening. • High-K magmatism and slab steepening during final northern Neotethys subduction. • Early Eocene postcollisional adakite-like magmatism of the northern Lesser Caucasus. [ABSTRACT FROM AUTHOR]