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Despite significant progress in Arctic geological studies, a number of principal questions concerning the Paleozoic collisional events remain unanswered. Therefore, the Taimyr Peninsula, representing the only outcropped high Arctic region where magmatic complexes, formed by Hercynian collision between the Siberian Craton and the Kara Block, are well exposed, is crucially important. In this paper we report new geochemical and geochronological data for intrusions in the poorly studied northeastern part of the Taimyr Peninsula. The obtained results in combination with published data show that supra-subduction magmatism at the southern active margin of the Kara Block continued from ca. 345 to 285 Ma (Early Carboniferous to Early Permian), and was followed by a post-collisional magmatic pulse that affected the whole Taimyr across terrane boundaries at ca. 280 Ma in the Early Permian. After cessation of the post-collisional magmatism at ca. 265 Ma, the Taimyr experienced extension, and voluminous magmatic series associated with a Siberian mantle plume were formed between 251 and 228 Ma during the Triassic. The studied post-collisional and plume-related intrusions of the Northeastern Taimyr are generally classified as evolved high-K I-type granites with adakitic affinity. The latter is a regional feature because the majority of the analyzed plume-related granitoids are geochemically similar to high potassium continental adakites. It is suggested that the adakitic geochemical characteristics of the plume-related granitoids resulted from melting of hydrated mafic lower crustal protoliths and were controlled by the source lithology. Comparison of the new results with data available for adjacent areas allows for correlation of terranes on a regional scale and sheds light on the evolution of the Arctic continental margins in general. In the Early–Middle Paleozoic, the Kara Block was part of a continental terrane that formed at the northern edge of Baltica as a result of Neoproterozoic Timanian orogeny. In the Early Carboniferous, the southern margin of Kara turned into an active margin, while its inferred continuation in the eastern Uralian margin of Baltica remained a passive margin until the Early Permian. This discrepancy can be explained by dextral displacement of Kara relative to Baltica that took place in the Early Carboniferous and was later accommodated by the formation of the Taimyr collisional belt in the course of the Early Permian collision between Kara and Siberia. After collision, the Taimyr was incorporated into the northern Eurasian margin as an uplifted block that experienced surface erosion and supplied clastic material in surrounding basins. [ABSTRACT FROM AUTHOR]

Geologically, the Arctic is one of the least explored regions of Earth. Its significance, in terms of indigenous populations, resource extraction, tourism, shipping and a rapidly changing climate, is increasing. The Arctic offers geological diversity encompassing onshore and offshore environments, include active subduction zones in Alaska, deep sedimentary basins on the Siberian and Barents Sea shelves, widespread ancient Arctic volcanism and magmatism, the world's slowest spreading mid-ocean ridge (Gakkel Ridge in the Eurasia Basin), as well as world-class examples of extensional and compressional basins exposed onshore Svalbard. Obtaining data is logistically, economically and environmentally expensive in the high Arctic, but the township of Longyearbyen at 78° N represents a relatively easily accessible gateway to Arctic geology. The year-round settlement on Spitsbergen, the main island of the Svalbard archipelago is home to The University Centre in Svalbard (UNIS). Reached by a year-round airport with regular connections to mainland Norway, Svalbard provides a foundation from which to teach and explore Arctic geology via the classroom, the laboratory, and the field. In this contribution, we present a new graduate course (Masters and PhD level) on Arctic Tectonics and Volcanism that we have established and taught annually at UNIS since 2018. We outline the course itself, before presenting student perspectives based on both an anonymous questionnaire (n = 27) and in-depth perceptions of four selected students. The course, with an intake of up to 20 MSc and PhD international students, is held over a 6-week period, typically in Spring or Autumn. The course comprises modules on field and polar safety, Svalbard/Barents Sea geology, wider Arctic geology, plate tectonics, mantle dynamics, geo- and thermochronology, and geochemistry of igneous systems. All modules include individual and group-based exercises in addition to introductory lectures. A field component, which in some years included an overnight expedition, provides an opportunity to appreciate Arctic geology and gather own field observations and data. Digital outcrop models and photospheres viewed with state-of-the-art visualization in the classroom facilitate efficient fieldwork through pre-fieldwork preparation and post-field work quantitative analyses. The course assessment is centered on an individual research project that is presented orally and in a short and impactful Geology journal-style article. Apart from the course at UNIS we have jointly initiated several one-off research and education-based events at partner institutions, and briefly outline these. [ABSTRACT FROM AUTHOR]

Provenance study plays an important role in paleogeographic and tectonic reconstructions. Detrital zircons are commonly used to identify sediment provenance; however, a wide range of detrital zircon ages in clastic rock often represent a fingerprint of reworked older terrigenous successions rather than ages of magmatism and metamorphism in the provenance area. This study focuses on the provenance of detrital rutile grains in the Triassic–Jurassic sandstones from Franz Josef Land and shows the importance of multiproxy approaches for provenance studies. Trace element data demonstrate that most rutile grains were sourced from metapelitic rocks, with a subordinate population having a metamafic origin. The Zr-in-rutile thermometer and U-Pb geochronology suggest that detrital rutile grains were predominantly derived from rocks that underwent amphibolite facies metamorphism during the Paleozoic era, with a predominance of the Carboniferous–Permian ages. Therefore, we suggest that the provenance area for the studied sandstones on Franz Josef Land has a similar geological history to the Taimyr region and Severnaya Zemlya archipelago. We propose that this crustal domain extends across the Kara Sea and forms the basement to the north and east of FJL, representing a proximal provenance for the studied Mesozoic terrigenous rocks. This domain experienced both Middle–Late Ordovician and Carboniferous–Permian metamorphism. The comparison of U-Pb dating and the geochemistry of rutile, U-Th/He, and U-Pb dating of zircons showed that detrital rutiles are the powerful toll in provenance restoration and can give additional constrains when a provenance area locates within collisional-convergent settings. [ABSTRACT FROM AUTHOR]

The Arctic sedimentary basins are still poorly studied in comparison with other regions. The lack of deep wells across the eastern Russian Arctic has resulted in numerous contrasting geodynamic models for the geological evolution and age of sedimentary successions within this frontier region, where a modern mid-ocean ridge breaks through the continental crust in the Laptev Sea. The only onshore evidence of rifting processes is a number of small graben-like depressions exposed on the New Siberian Islands and along the Laptev Sea coast. We present U-Pb detrital zircon provenance and palynology study results of the Cenozoic sedimentary rocks filling graben-like depressions across western Kotel'nyi Island. Palynological data indicate that these sedimentary rocks are Early Eocene to Pleistocene in age. Based on U-Pb detrital zircon dating, Early Eocene and Late Oligocene clastic sediments were sourced from underlying deformed Palaeozoic rocks as well as by reworking of Upper Mesozoic rocks outcropping elsewhere on Kotel'nyi Island, which bear Siberian signature. Plio-Pleistocene clastic sediments were not derived from the erosion of deformed Palaeozoic rocks, suggesting the cessation of active uplift by this time and the development of a regional peneplain. Therefore, by extrapolating our onshore observations to the neighbouring offshore, we propose that graben structures imaged by seismic profiles along the eastern flank of the Laptev Rift System are likely to host Eocene and Oligocene sediments. Thus, it implies the Cenozoic extension led to formation of grabens on- and offshore in the eastern portion of Laptev Sea as early as Eocene. Further studies are necessary to evaluate the age of graben-related basins in the central and western part of the Laptev Sea. [ABSTRACT FROM AUTHOR]

Study of the Mesozoic succession of Franz Josef Land (FJL) has shed new insights on the stratigraphy and geological history of the neighboring portion of the Arctic. Based on the composition of pebbles and cobbles from Lower Jurassic conglomerates, we suggest that the pre‐Mesozoic stratigraphy of the NE Barents Sea comprises Cambrian metasandstones intruded by Late Paleozoic granites and overlain by Carboniferous–Permian sedimentary deposits. U‐Pb and ZHe ages of detrital zircons from Uppermost Triassic–Lower Cretaceous strata of FJL reveal Precambrian to Early Mesozoic grains. The most abundant Late Paleozoic detrital zircon population suggests the existence of the same in age magmatic events in the provenance area. ZHe ages show Late Triassic (ca. 225 Ma) exhumation of the provenance area. Moreover, the youngest grains of detrital zircons are Middle‐Late Triassic in age pointing that significant uplift of provenance coincides with magmatic activity. Based on these data, we suggest that the provenance area for Triassic–Lower Cretaceous strata of FJL was characterized by a similar geological composition, as well as magmatic and tectonic history, to the Taimyr fold‐and‐thrust belt and Kara terrane. A comparison of detrital zircon data from coeval strata elsewhere in the Arctic realm suggests that this eastern provenance area was actively sourcing sediments right across the Barents Sea Basin, and possibly as far as the Sverdrup basin, during the Latest Triassic–Jurassic. The period of Late Triassic uplift represented a significant tectonic event across the north‐eastern Barents Sea, and likely initiated an increase in sediment supply and a reorganization of pre‐existing sediment transport pathways. Key Points: Pre‐Mesozoic rocks of NE Barents Sea are Cambrian metasediments intruded by Late Paleozoic granites and overlain by Upper Paleozoic depositsTriassic–Lower Cretaceous strata of Franz Josef Land were sourced from a proximal provenance area uplifted in the Late TriassicTwo major shifts in sedimentary transport pathway occurred in Barents Sea and Sverdrup basins in Late Triassic and Late Jurassic [ABSTRACT FROM AUTHOR]

Small depressions across the north-eastern part of October Revolution Island (Severnaya Zemlya archipelago, Kara terrane) are filled with continental terrigenous rocks, dated as Upper Carboniferous–Lower Permian in age based on palynological data. These rocks overlie Ordovician volcaniclastic rocks above a prominent angular unconformity. U-Pb dating of detrital zircons from the Late Carboniferous–Lower Permian rocks reveals that most grains are Ordovician in age, ranging between 475–455 Ma. A subordinate population of Silurian detrital zircons is also present, contributing up to 15% of the dated population, while Precambrian grains mainly yield Neo-Mesoproterozoic ages and do not form prominent peaks. The combined U-Pb and (U-Th)/He ages indicate that most zircon (U-Th)/He ages were reset and average at ca. 317 Ma, suggesting ~6–7 km of Late Carboniferous uplift within the provenance area. This provenance area, mainly comprising Ordovician magmatic and volcanic rocks, was located close to the study area based on the coarse-grained nature of Late Carboniferous–Lower Permian rocks of north-eastern October Revolution Island. Therefore, we propose that Late Paleozoic tectonism significantly affected both the southern margin of the Kara terrane, as previously supposed, and also its north-eastern part. We propose that the Late Paleozoic Uralian suture zone continued to the north-eastern October Revolution Island and was responsible for the significant tectonic uplift of the studied region. This suture zone is now hidden beneath the younger Arctic basins. [ABSTRACT FROM AUTHOR]

This study presents new whole rock major and trace element, Sr-Nd isotopic, petrographic, and geochronologic data for seven latest Permian (Changhsingian)-Late Triassic (Carnian) granitoid intrusions of the northwestern and northeastern Taimyr Peninsula in the Russian High Arctic. U-Pb zircon ages, obtained using secondary ion mass spectrometry (SIMS), sensitive high-resolution ion microprobe (SHRIMP), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), define the crystallization age of the Taimyr intrusions studied as ranging from ca. 253 Ma to 228 Ma, which suggests two magmatic pulses of latest Permian-Early Triassic and Middle-Late Triassic age. Ar-Ar dating of biotite and amphibole indicate rapid cooling of the intrusions studied, but Ar-Ar ages of several samples were reset by secondary heating and hydrothermal activity induced by the Middle-Late Triassic magmatic pulse. Petrographic data distinguish two groups of granites: syenite-monzonites and granites-granodiorites. Sr-Nd isotopic data, obtained from the same intrusions, show a variation of initial (87Sr/86Sr)i ratios between 0.70377 and 0.70607, and εNd(t) values range between -6.9 and 1.2. We propose that the geochemical and isotopic compositions of the Late Permian-Triassic Taimyr granites record the existence of a magma mush zone that was generated by the two pulses of Siberian Traps large igneous province (LIP) magmatism. [ABSTRACT FROM AUTHOR]

We report new results of a comprehensive study into Carboniferous – Early Permian granite magmatism of the northern Taimyr Peninsula, Russia (southern part of the Kara Terrane). U-Pb zircon ages (SHRIMP and LA–ICP–MS) represent the crystallization ages of these intrusions and range from ca. 344.5 to 288.4 Ma, defining the onset of granite magmatism during the Early Carboniferous (Visean; ca. 344 Ma) and its termination in the Early Permian (Artinskian; ca. 288 Ma). Ar-Ar dating of micas and amphiboles indicates that Late Palaeozoic tectonic activity in northern Taimyr ceased during the Middle Permian (Roadian; ca. 272 Ma). Rb/Sr and Sm/Nd isotopic data from the same intrusions, show initial (87Sr/86Sr)i ratios of between 0.70288 and 0.71027, with εNd(t) values range between −3.3 and +3.1. The combined geochemical and isotopic compositions of the granites describe an affinity to peraluminous I-type granites, probably formed in an Andean-type active continental margin setting. Our new geochemical, isotopic, and geochronological data indicate the existence of a long-lived (ca. 56 Myr) Andean-type active continental margin along the southern edge of the Kara Terrane during the Late Palaeozoic. Furthermore, our study reveals a causal relationship between Late Palaeozoic magmatism across northern Taimyr and closure of the Uralian Ocean. [ABSTRACT FROM AUTHOR]

Glendonites represent pseudomorphs after calcium carbonate hexahydrate (ikaite) and can be used as indicators of past cold climates, because ikaite only naturally occurs in cold environments (<7°C) in the modern. The results of a multi‐proxy study of 11 glendonite and host concretion samples from Palaeogene (Gennoishi Formation) and Neogene (Bora and Vengeri formations) sediments from Sakhalin Island, Russian Far East are reported here. Petrographic, cathodoluminescence, powder X‐ray diffraction and scanning electron microscope analyses reveal that glendonites are composed of several successive mineralogical phases: low‐magnesium ikaite‐derived calcite, high‐magnesium acicular cement (calcite and dolomite) and blocky calcite or authigenic quartz filling the remaining pore space. Host concretions comprise sandy limestones cemented by high‐magnesium calcite. The δ13C and δ18O values for host concretions and enclosed glendonites are very similar, with δ13C ranging from –20.3 to +1.9‰ Vienna Pee‐Dee Belemnite and δ18O ranging from –3.4 to +3.4‰ Vienna Pee‐Dee Belemnite. Such isotopic values suggest that seawater was the main source of oxygen, while dissolved inorganic carbon and decaying organic matter were the main carbon sources for ikaite growth, concretion and glendonite cementation. The 87Sr/86Sr values within the glendonites and host concretions are significantly lower compared with coeval Palaeogene–Neogene marine carbonates, suggesting an influence of continental runoff on their isotopic composition. Post Archean Australian Shale normalized rare earth element patterns display negative Ce anomalies and positive Eu anomalies, with a depletion in light rare earth elements or bulge in middle rare earth elements. Such spectra of rare earth elements indicate that ikaite growth and replacement occurred very close to the aerobic–anaerobic boundary, with pore waters derived from trapped seawater and/or ikaite dehydration. Since Mg/Ca ratios and alkalinity increase with depth below the sediment–water interface, subsequent mineral phases show enrichment in Mg, while the lack of diagenetic alteration by basinal fluids enabled preservation of the primary isotopic and geochemical characteristics of ikaite within the recrystallized pseudomorph. [ABSTRACT FROM AUTHOR]

This database of Phanerozoic occurrences and isotopic characteristics of metastable cold-water calcium carbonate hexahydrate (ikaite; CaCO 3 ⚫6H 2 O) and their associated carbonate pseudomorphs (glendonites) has been compiled from academic publications, explanatory notes, and reports. Our database including more than 700 occurrences reveals that glendonites characterize cold-water environments, although their distribution is highly irregular in space and time. A significant body of evidence suggests that glendonite occurrences are restricted mainly to cold-water settings; however they do not occur during every glaciation or cooling event of the Phanerozoic. While Quaternary glendonites and ikaites have been described from all major ocean basins, older occurrences have a patchy distribution, which may suggest poor preservation potential of both carbonate concretions and older sediments. The data file described in this paper is available on Zenodo at 10.5281/zenodo.4386335 (Rogov et al., 2020). [ABSTRACT FROM AUTHOR]

This database of Phanerozoic occurrences and isotopic characteristics of metastable cold-water calcium carbonate hexahydrate (ikaite; CaCO3·6H2O) and their associated carbonate pseudomorphs (glendonites) has been compiled from academic publications and open-access reports. Our database including 690 occurrences reveals that glendonites characterize cold-water environments, although their distribution is highly irregular in space and time. A significant body of evidence suggests that glendonite occurrences are restricted mainly to cold-water settings, however they do not occur during every glaciation or cooling event of the Phanerozoic. While Quaternary glendonites and ikaites have been described from all major ocean basins, older occurrences have a patchy distribution, which may suggest poor preservation potential of both carbonate concretions and older sediments. The data file described in this paper is available on Zenodo at https://doi.org/10.5281/zenodo.3991964 (Rogov et al., 2020). [ABSTRACT FROM AUTHOR]

U-Pb and Lu-Hf isotope analyses of detrital zircons collected from metasedimentary rocks from the southern part of Kara Terrane (northern Taimyr and Severnaya Zemlya archipelago) provide vital information about the paleogeographic and tectonic evolution of the Russian High Arctic. The detrital zircon signatures of the seven dated samples are very similar, suggesting a common provenance for the clastic detritus. The majority of the dated grains belong to the late Neoproterozoic to Cambrian ages, which suggests the maximum depositional age of the enclosing sedimentary units to be Cambrian. The "Hf(t) values indicate that juvenile magma mixed with evolved continental crust and the zircons crystallized within a continental magmatic arc setting. Our data strongly suggest that the main provenance for the studied clastics was located within the Timanian Orogen. A review of the available detrital zircon ages from late Neoproterozoic to Cambrian strata across the wider Arctic strongly suggests that Kara Terrane, Novaya Zemlya, Seward Peninsula (Arctic Alaska), Alexander Terrane, De Long Islands, and Scandinavian Caledonides all formed a single tectonic domain during the Cambrian age, with clastics predominantly sourced from the Timanian Orogen. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of Late Ordovician (Sandbian) granitic rocks from the southeastern part of October Revolution Island in the Severnaya Zemlya archipelago (Kara Terrane). U-Th-Pb zircon ionmicroprobe data and Ar-Ar biotite dating from two samples allow us to determine a crystallisation age for the intrusions at c. 457 Ma. Based on their geochemical and isotopic composition, the granites can be defined as I-type, suggesting island-arc magmatism development within Kara Terrane in the Late Ordovician. This arc magmatism may be correlated with the Mid-Late Ordovician early stage of the Caledonian Orogeny. The obtained data support a tectonic model proposing that the Kara Terrane represented a marginal part of Baltica during the Early to Middle Palaeozoic. [ABSTRACT FROM AUTHOR]

U–Pb dating of detrital zircons collected from the Middle–Upper Palaeozoic strata of the Prikolyma terrane (Verkhoyansk–Kolyma orogen) provide the first insight into provenance areas and the Middle–Late Palaeozoic geological history of the Russian Far East. Detrital zircon ages from the Lower–Middle Devonian sandstones group around 395–405 M (Emsian–Eifelian) which correlate well to trachyte of the Uvyazka zone and the Kedon Complex of the North Okhotsk active continental margin located on the Omolon terrane. Precambrian-aged zircons group around 1740–2080 and 2460–2800 Ma, respectively, suggesting possible sources within metamorphic rocks of the basement of the Omolon terrane or the Siberian Craton. The majority of the zircons from the Lower and Upper Carboniferous sandstones group around 333–375 Ma, suggesting that the principle source of the clastics were volcanic rocks and comagmatic felsic intrusions of the Kedon Complex of the North Okhotsk active continental margin. Our new data allow us to evaluate and revise the available palaeotectonic reconstructions of northeast Asia for the Devonian and Carboniferous. [ABSTRACT FROM AUTHOR]

We present the results of an optical microscopy, cathodoluminoscopy and isotopic study on nine glendonite concretions (calcite pseudomorphs replacing metastable hexahydrate ikaite) from Lower-Middle Jurassic sediments of Northeast Russia (Anabar Bay and Lena River region). Glendonite concretions are mainly found within Late Pliensbachian, Toarcian, Aalenian, Bajocian and Lower Bathonian clastic sediments, correlating to episodes of global climatic cooling as determined by independent paleoclimate proxy data. Stable carbon and oxygen isotopic values of glendonite concretions suggest that the primary source of carbon was derived from diagenetically altered organic matter, and the source of oxygen was from seawater. The secondary diagenetic cement is characterized by a significantly lighter δ18O and significantly heavier δ13C signature than the isotopic characteristics of the bulk rock glendonite concretion. This secondary diagenetic cement is thought to have precipitated rapidly during burial diagenesis and since it occupies a significant volume of the glendonite concretion, it has the potential to significantly influence the isotopic composition of bulk rock glendonites. [ABSTRACT FROM AUTHOR]

Combined U–Pb detrital zircon dating of 21 samples, along with whole-rock chemical composition and Sm–Nd isotopic studies of 39 samples of Triassic and Jurassic rocks from Franz Josef Land and wells in the southern part of the Russian (eastern) Barents Sea, were analyzed for a reconnaissance provenance study. The similarity of detrital zircon age distributions was statistically assessed using the Kolmogorov–Smirnov (K–S) test and points to a common source area for the clastic material of Triassic to Middle Jurassic age. Uralian-age detrital zircons predominate in all samples, with a comparably smaller portion of Caledonian- and Timanian-age detrital zircons. The number of Palaeoproterozoic and Archean grains is very small and becomes significant only in a few Jurassic samples. εNd(t) values gradually decrease from −1.5 to +2.5 in Lower Triassic rocks, to −2.0 to −8.2 in Jurassic rocks, suggesting an increasing influence of ancient metamorphic basement erosion in the younger Jurassic rocks. High Co/Th ratios, suggesting the erosion of mafic rocks, were mainly recorded in Lower Triassic rocks, whereas increasing Th/Sc ratios, suggesting the erosion of felsic rocks, were recorded only in some uppermost Triassic and Jurassic rocks. We identify the Urals and, in addition during the Triassic, the basement of the West Siberian Basin as the main provenance for the studied clastic rocks. By contrast, only a small volume of fine-grained clastic detritus was derived from basement erosion of the East European Craton, which was characterized by a subdued relief during this time. [ABSTRACT FROM AUTHOR]

Abstract Tectonic evolution of the New Siberian Islands (NSI) has been revealed based on detailed structural investigations and a (U-Th)/He low-temperature thermochronologic study of detrital zircons (ZHe) and apatite (AHe). Our study supports models claiming a non–Siberian affinity of the NSI and furthermore suggests that the study area formed a part of the Arctic-Alaska-Chukotka microcontinent. Seven stages of deformation have been revealed. The earliest stage (Stage 1) involved contractional deformation with transport directions towards the W-to WSW and occurred during the Late Cambrian across the De Long Islands. The next episode of deformation (Stage 2) has been revealed based on the low-temperature thermochronology (ca. 378–414 Ma, ZHe) and structural data. A pre-Frasnian angular unconformity formed as a result of Stage 2 deformation on Kotel'nyi Island, which involved contractional deformation with S-to SW transport directions (modern coordinates) in the mid-Paleozoic. In the latest Early Cretaceous–Late Cretaceous, three deformation stages were initiated by collision between the western part of the Arctic-Alaska-Chukotka microcontinent and Siberia, forming the South Anyui suture zone and overlapping orogenic belt. Stage 3 was characterized by the formation of major NW-trending folds, thrusts, and both transfer dextral and sinistral strike-slip faults with a reverse component. During Stage 4, the Arctic Alaska-Chukotka microcontinent moved westward. On Bolshoy Lyakhovsky Island, sinistral strike-slip faults were formed, whilst E-W compression took place across the Anjou islands. In Stage 5, the Arctic Alaska-Chukotka microcontinent shifted southward, forming a series of N-S-trending dextral strike-slip faults. The ZHe and AHe ages (ca. 93–125 Ma) suggest that these deformation events were associated with significant uplift in the western part of the NSI (Kotel'nyi and Bel'kovsky islands), whilst the eastern part (De Long Islands) was marginally affected by these events without significant uplift. The Cenozoic extension event (Stage 6) corresponds to the opening of the Eurasian Basin. This stage is manifested by the cooling episode (ca. 53 Ma, Early Eocene, AHe) established in the eastern part of the NSI (Jeannette Island). The origins of the late Cenozoic contractional deformations described from the Cenozoic deposits of the Anjou Islands (Stage 7) are unclear, but were possibly caused by movements along the Eurasian and North-American lithospheric plates. [ABSTRACT FROM AUTHOR]

U–Pb and Lu–Hf isotope analyses of detrital zircons collected from the Devonian–Permian strata of Kotel’ny Island (New Siberian Islands, Eastern Russian Arctic) provide vital information about provenance areas and history of the poorly studied Paleozoic basement of the Laptev and East Siberian shelves. Based on detrital zircon signatures, our study reveals that the studied succession can be divided into two distinct groups: Devonian–Lower Carboniferous and uppermost Carboniferous–Permian. U–Pb and Lu–Hf isotope signatures of detrital zircons from the Devonian–Lower Carboniferous deposits correspond to well-known Precambrian–Early Paleozoic magmatic and metamorphic events within the northern part of Baltica, indicative of a peri-Baltican affinity of the New Siberian Islands during this time. A lack of zircon ages close to the depositional age of the formation, along with a mature composition of the sandstones, suggest that the Devonian–Lower Carboniferous succession formed as a result of extensive sediment reworking from a distal provenance. By contrast, uppermost Carboniferous–Permian sandstones have an immature composition, with numerous young detrital zircons close to the age of sedimentation and Hf signatures typical of a continental arc environment. We therefore suggest that the provenance for these younger deposits was located within a coeval orogeny and based on previous studies, we conclude that these deposits were sourced from the north-western part of the Uralian Orogen. [ABSTRACT FROM AUTHOR]

Combined (U-Th)/He and U-Pb detrital zircon geochronological data are reported from Ordovician to Devonian strata of the Severnaya Zemlya archipelago to address the paleogeography of the Kara Terrane in the Russian High Arctic. (U-Th)/He ages from all six samples analyzed were not reset after sediment deposition, indicating that detrital zircons carry information on the exhumation history in the source region of the clastic material. In Ordovician-Silurian strata, (U-Th)/He ages range from 583.8 ± 46.7 to 429.0 ± 34.3 Ma. These ages nicely coincide with significant regional exhumation during the Caledonian and Timanian orogenies. In addition, combined U-Pb and (U-Th)/He dating show that within the source region, zircons that were crystalized during the Timanian Orogeny (U-Pb ages 680–560 Ma) were likely exhumed during younger Caledonian events ((U-Th)/He ages of 455–495 Ma), suggesting potential overlap of these orogens within the source region. In Devonian strata, detrital zircon (U-Th)/He ages range from 517.2 ± 41.38 to 332.9 ± 26.6 Ma, with a peak age of ca. 375 Ma. This 375 Ma event may be correlated with either the Ellesmerian Orogeny or the terminal Solundian/Svalbardian stages of the Caledonian Orogeny. [ABSTRACT FROM AUTHOR]

An acanthodian assemblage is reported for the first time from the Silurian-Devonian boundary beds of Novaya Zemlya Archipelago, Russia. The acanthodian scales and rare other vertebrate microremains were in a sample collected from the Reliktovoe Formation of the western coast of Inostantzev Bay, North Island. The assemblage includes Gomphonchus mediocostatus, Gomphonchoporus hoppei taxa previously described from the Pridoli - Lochkovian of Laurussia, and Taimyrolepis composita occurred in the Lochkovian of Siberia. Gomphonchus mediocostatus and Gomphonchoporus hoppei are widely distributed in the Baltica palaeogeographic province, and Taimyrolepis is known from the Siberia province, indicating connection between those provinces. [ABSTRACT FROM AUTHOR]

Here we present the first description and images of foraminiferal fauna from the carbonate cobbles and pebbles of Early Jurassic polymictic conglomerates from Graham Bell Island, in the easternmost part of the Franz Joseph Land archipelago. The composition of the conglomerates suggests a proximal provenance area. The identified foraminiferal genera and species suggest a Serpukhovian-Late Carboniferous age for the primary carbonates from which the conglomerate clasts were derived, and which can be correlated with coeval carbonate strata of Svalbard, the Volga-Urals and the Pechora region. Combined with previous studies, our new data lead us to assert that a shallow-marine carbonate platform occupied the entire Barents shelf, including its northeasternmost part, during Carboniferous-Early(?) Permian time. This study improves our understanding of the composition and age of pre-Mesozoic successions of Franz Joseph Land and surrounding parts of the Barents Sea. [ABSTRACT FROM AUTHOR]

Identifying the cratonic affinity of Neoproterozoic crust that surrounds the northern margin of the Siberian Craton (SC) is critical for determining its tectonic evolution and placing the Craton in Neoproterozoic supercontinental reconstructions. Integration of new U–Pb–Hf detrital zircon data with regional geological constraints indicates that distinct Neoproterozoic arc-related magmatic belts can be identified within the Taimyr orogen. Sedimentary rocks derived from 970 to 800 Ma arc-related suites reveal abundant Archean and Paleoproterozoic detritus, characteristic of the SC. The 720–600 Ma arc-related zircon population from the younger Cambrian sedimentary rocks is also complemented by an exotic juvenile Mesoproterozoic zircon population and erosional products of older arc-related suites. Nonetheless, numerous evidences imply that both arcs broadly reworked Siberian basement components. We suggest that the early Neoproterozoic (ca. 970–800 Ma) arc system of the Taimyr orogen evolved on the active margin of the SC and probably extended along the periphery of Rodinia into Valhalla orogen of NE Laurentia. We also suggest the late Neoproterozoic (750–550 Ma) arc system could have been part of the Timanian orogen, which linked Siberia and Baltica at the Precambrian/Phanerozoic transition. [ABSTRACT FROM AUTHOR]

The Arctic basins attract broad international interest because of the region's potentially significant undiscovered hydrocarbon resources. The Russian High Arctic is mostly represented by broad shelves, with a few wells drilled only in its western part (Kara and Barents shelves). This contribution provides an overview of the geological setting, stratigraphy, paleogeography, and tectono-sedimentary evolution of the middle–late Paleozoic basins of the Eastern Russian Arctic, including: Severnaya Zemlya, the New Siberian Islands, northern Siberia, the Taimyr and Chukotka peninsulas, and Wrangel Island. Reconstructing the geological evolution of the Eastern Russian Arctic during the middle–late Paleozoic is very difficult because the region was overprinted by a number of late Paleozoic to early Mesozoic tectonic events. [ABSTRACT FROM AUTHOR]

Permian strata of northern Siberia contain a rich record of the late Paleozoic history of Siberia and surrounding fold and thrust belts (FTB). More than 850 uranium–lead (U–Pb) detrital zircon ages collected from the Permian strata provide vital information about sediment source areas and history of the sedimentary basins. The detrital zircon populations obtained from the Permian clastics of northern Siberia are characterized by large percentages of late Paleozoic and early Paleozoic zircons, whose ages can be correlated with magmatic events known from the Ural-Mongolian Orogen. Our data suggest that Permian clastics of northern Siberia were mainly sourced from orogens developed along the western and southwestern margins of the Siberian Craton (in present-day coordinates), with an additional sediment contribution from the reworked sedimentary cover and basement of Siberia. The contribution from Siberian sources is distinguished in the Precambrian part of the detrital zircon populations by wide distribution of ca. 1700–2000 Ma and 2500–2750 Ma zircons with an almost total lack of zircons ranging in age from 800 to 1700 Ma. We propose that a major fluvial system, which we here term the “Paleo-Khatanga”, was the main sediment transport pathway along the western and northern margins of Siberia during the Permian. From a regional overview of detrital zircon populations in Permian deposits across the Arctic realm, we propose that the New Siberian Islands, Alexander and Farewell terranes were sourced from the western framework of the Ural-Mongolian Orogen and were located along the northern margin of Baltica during the late Paleozoic. The Arctic–Alaska–Chukotka Terrane on the other hand does not have Uralian signatures in the detrital zircon populations of the Permian sediments, and can be reconstructed adjacent to the northern margin of Laurentia. Our new data presented here help to better define the enigma of Arctic paleogeography during the Paleozoic. [ABSTRACT FROM AUTHOR]

The vast Laptev and East Siberian shelves in the eastern Russian Arctic, largely covered by a shallow sea and buried beneath sea ice for 9 months of the year, remain one of the least studied parts of continental crust of the Earth and represent a big unknown when performing pre-Cenozoic reconstructions of the Arctic. The De Long Islands provide an important window into the geology of this area and are a key for understanding the Early Paleozoic history of the Amerasian Arctic. Four of them (Jeannette, Henrietta, Bennett and Zhokhov islands) were studied using structural data, petrographic and geochemical analyses and U–Pb zircon age dating to offer the following new constraints for the Early Paleozoic paleogeography of the Arctic realm. The basement beneath the De Long Islands is of Late Neoproterozoic to earliest Cambrian age, about 670–535 Ma. In the Early Paleozoic, the De Long Islands were located along the broad Timanian margin of Baltica, with a clastic sediment provenance from the Timanian, Grenville–Sveconorwegian, and Baltic Shield domains. The Cambro-Ordovician volcaniclastic successions on Jeannette and Henrietta islands formed part of a continental volcanic arc with a corresponding back-arc basin located to the south (in present co-ordinates). On the continent-ward side of the back-arc basin, shallow marine shelf clastic and carbonate rocks were deposited, which are exposed today on Bennett Island in the south-west of the archipelago (in modern coordinates). The De Long Islands together with other continental blocks, such as Severnaya Zemlya, Arctic Alaska–Chukotka, and the Alexander Terrane, formed the contiguous active continental margin of Baltica during the Early Paleozoic. Today however, these terranes are spread out over a distance of 5000 km across the Arctic and eastern Pacific margins due to the subsequent opening of a series of Late Paleozoic, Mesozoic and Cenozoic oceanic basins. [ABSTRACT FROM AUTHOR]

An integrated provenance analysis based on sandstone petrography, distribution of REE and trace elements, and U/Pb detrital zircon dating of Carboniferous sedimentary rocks of northern Verkhoyansk Fold and Thrust Belt (FTB) provides new insights into the tectonic evolution of NE Siberia. According to petrographic and geochemical data, Lower Visean sandstones had local provenance that contained mafic magmatic rocks. Wide distribution of ca. 2075 Ma detrital zircons known in the basement of neighboring Olenek and Ust’-Lena uplifts supports local provenance of the Lower Visean sandstones. Starting from Late Visean, clastic sediments have geochemical and petrographic compositions that are characteristic for erosion predominantly felsic rocks in a more remote source region. Detrital zircon age distributions in the Upper Visean – Upper Carboniferous sandstones, point to Taymyr – Severnaya Zemlya FTB and Central Asian Orogenic Belt (CAOB) as the most likely provenances for clastic rocks. However, wide distribution of Neoproterozoic and early Paleozoic detrital zircons that are not typical for synchronous CAOB-derived clastic rocks in the West Verkhoyansk, provide evidence for other than CAOB source area. We infer that the most likely source for Neoproterozoic – early Paleozoic detrital zircons in the Upper Visean – Upper Carboniferous sandstones is the Taimyr-Severnaya Zemlya FTB. The shift to sources from the Taimyr-Severnaya Zemlya FTB suggests an earlier (Late Visean) age for the collision between Kara terrane and Siberia than has been previously assumed (Late Carboniferous – Permian). Our paleogeographic restoration reveals the existence of two major fluvial systems draining eastward across the Siberian Craton during the Carboniferous: the Paleo-Lena in the south and the Paleo-Khatanga in the north. [ABSTRACT FROM AUTHOR]

Detrital zircon U/Pb ages provide new insights into the provenance of Upper Devonian–Permian clastic rocks of Bel’kovsky Island, within the New Siberian Islands archipelago. Based on these new data, we demonstrate that Upper Devonian–Carboniferous turbidites of Bel’kovsky Island were derived from Grenvillian, Sveconorwegian, and Timanian sources similar to those that fed Devonian–Carboniferous deposits of the Severnaya Zemlya archipelago and Wrangel Island and were probably located within Laurentia–Baltica. Detrital zircon ages from the lower Permian deposits of Bel’kovsky Island suggest a drastic change in provenance and show a strong affinity with the Uralian Orogen. Two possible models to interpret this shift in provenance are proposed. The first involves movement of these continental blocks from the continental margin of Laurentia–Baltica towards the Uralian Orogen during the late Carboniferous to Permian, while the second argues for long sediment transport across the Barents shelf. [ABSTRACT FROM AUTHOR]

We present here a detailed study of the Upper Carboniferous–Lower Permian stratigraphy of Bol'shevik Island in the Severnaya Zemlya Archipelago, consisting of the analysis of sedimentary structures and lithostratigraphy, U/Pb detrital zircon dating and structural studies. The preserved sedimentary structures suggest that the studied strata were deposited in a relatively small meandering fluvial system. U/Pb dating of detrital zircons reveals that the Upper Carboniferous–Lower Permian sandstones contain a primary age population ranging from 450 to 570 millions of years, with a predominance of Early–Middle Ordovician zircons. This detrital zircon distribution indicates that the studied formations were derived locally from the erosion of Lower Ordovician deposits of Bol'shevik Island or elsewhere in the archipelago. Our structural studies suggest that Upper Carboniferous–Lower Permian deposits are deformed into a series of west–north-west verging open asymmetric folds, suggesting a west–north-west direction of tectonic transport and that deformation across the island is post-Early Permian in age. [ABSTRACT FROM AUTHOR]

In the Late Devonian-Early Carboniferous the eastern part of Siberia was affected by multi-stage rifting, which led to formation of a Late Paleozoic-Mesozoic passive margin. Four sections of the Lower Visean strata were studied in the northern part of the Kharaulakh Ridge, along the Lena River and Bykov Channel (north-east of Siberia). The studied sedimentary succession comprises two lithologically contrasting units: coarse-grained turbidites and hemipelagic cherts. Deposition occurred in a marine basin bounded by steep slopes, which is a key geomorphological feature facilitating deposition of coarse-grained turbidites. Within the studied sandy turbidites, several different zones of submarine sand-rich fans have been recognized. Integrated sedimentological and petrographical analyses allow us to interpret that the nearby uplifts composed of Proterozoic-Middle Paleozoic rocks were the main provenance areas for the Visean clastic rocks. Those uplifts were formed as a result of the latest stages of rifting in the study region that occurred in the earliest Visean, following termination of much of the tectonic activity during the Tournaisian. A similar rock association has been described previously from the central and southern part of the eastern margin of Siberia suggesting that the rift to drift transition occurred approximately at the same time across East Siberia and is of Early Visean age. [ABSTRACT FROM AUTHOR]

A series of eight related optically active complexes having two or three stereogenic centers, [(μ-H)Os3{μ-OCNH-(R)-CHMePh}(CO)10], 1, and [(μ-H)Os3{μ-OCNH-(R)-CHMePh}(CO)9L] {L=NMe3, 2, and (S)-(−)- or (R)-(+)-NH2CHMePh, 3}, have been prepared and characterized by 1H and 13C NMR, IR, mass-spectral, and [α]D data. As shown by comparison of 1H NMR spectra in the highly informative upfield region, the relative values of δμ-H for corresponding diastereomers depend on a number of stereogenic centers in the molecule, the nature of L (CO or amine) and solvent and most of all on the absolute configuration of the cluster fragment [HOs3(μ-OCN)]. The relative positions of hydride signals in 1H NMR spectra of the diastereomeric pairs 1–3 correlates with the cluster-fragment configuration. The largest value of nonequivalence Δδμ-H (0.36 ppm) was demonstrated by the diastereomers having the opposite cluster-fragment configurations and L=(S)-(−)-NH2CHMePh in CDCl3 solution. [Copyright &y& Elsevier]

We performed U-Pb dating of detrital zircons collected from Middle–Upper Jurassic strata of the Sugoi synclinorium and Cretaceous rocks of the Omsukchan (Balygychan-Sugoi) basin, in order to identify their provenance and correlate Jurassic–Cretaceous sedimentation of the south-eastern Verkhoyansk-Kolyma orogenic belt with various magmatic belts of the north-east Asia active margins. In the Middle–Late Jurassic, the Uda-Murgal magmatic arc represented the main source area of clastics, suggesting that the Sugoi basin is a back-arc basin. A major shift in the provenance signature occurred during the Aptian, when granitoids of the Main (Kolyma) batholith belt, along with volcanic rocks of the Uyandina-Yasachnaya and Uda-Murgal arcs, became the main sources of clastics deposited in the Omsukchan basin. In a final Mesozoic provenance shift, granitoids of the Main (Kolyma) batholith belt, along with volcanic and plutonic rocks of the Uyandina-Yasachnaya and Okhotsk-Chukotka arcs, became the dominant sources for clastics in the Omsukchan basin in the latest Cretaceous. A broader comparison of detrital zircon age distributions in Jurassic–Cretaceous deposits across the south-eastern Verkhoyansk-Kolyma orogen illustrates that the Sugoi and Omsukchan basins did not form along the distal eastern portion of the Verkhoyansk passive margin, but in the Late Mesozoic back-arc basins. [ABSTRACT FROM AUTHOR]

We present new data on the tectonic evolution of north-eastern Siberia using an integrated provenance analysis based on U–Pb detrital zircon dating and sandstone petrography of Devonian sedimentary strata. Our petrographic data suggest that Upper Devonian sandstones of north-eastern Siberia were derived from a local provenance, supported by the widespread distribution of ca. 1900–2000 Ma magmatic events in the basement of the neighboring Ust'-Lena and Olenek uplifts. Devonian detrital zircon age distributions of the Devonian sandstones are similar to ages of Middle Paleozoic magmatic rocks of Yakutsk-Vilyui large igneous province (LIP). Therefore, we suggest that the studied sandstones were derived from proximally-located uplifted blocks composed of Proterozoic–Devonian rocks and Middle–Late Devonian volcanics. Moreover, the abundance of Middle–Late Devonian zircons is suggestive of a wider distribution of coeval magmatism across north-eastern Siberia than previously supposed. We propose that widespread Devonian magmatism associated with the Yakutsk-Vilyui LIP also occurred to the east of our study area and is now buried beneath thick Carboniferous–Jurassic sedimentary rocks of the eastern Siberian passive margin, subsequently deformed into the Late Jurassic–Cretaceous Verkhoyansk fold-and-thrust belt. We also propose that the major pulse of the Yakutsk-Vilyui LIP occurred in north-eastern Siberia during the Middle Devonian at ca. 390 Ma, some 15 million years earlier than within the Vilyui rift basin in eastern Siberia (ca. 375 Ma). [ABSTRACT FROM AUTHOR]

Stellate and plate-like carbonate bodies, traditionally called anthraconites, are found throughout the Baltic-Ladoga Klint in bituminous shale of the Koporye Formation (Tremadocian, Lower Ordovician). Although this time interval is usually considered as a greenhouse, there is some evidence for the existence of at least temporary cold conditions during the Cambrian–Ordovician. However, the origin of anthraconites is still strongly debated. We studied the mineralogical, petrographic, cathodoluminescence, geochemical, and isotopic characteristics of anthraconites from five sections of the Russian part of the Baltic paleobasin. A close similarity between the morphological, petrographic, cathodoluminescence, and isotopic characteristics of the studied anthraconites with those of glendonites allow us to suggest that these bodies formed in a similar paleo-environment and should be considered as pseudomorphs of the mineral ikaite. The oxygen and carbon isotope ratios reveal that ikaite precipitation occurred in low-temperature conditions on the seafloor. The carbon isotopic values reveal influence of inorganic seawater carbon along with organic matter decomposition and/or methane oxidation during ikaite-glendonite transformations. The oxygen isotopic composition significantly changed after deposition due to meteoric diagenesis. We propose that the studied Tremadocian anthraconites formed under a region of upwelling, where cold phosphate-rich deep waters rose to the relatively shallow part of the Baltic paleobasin, providing favorable conditions for ikaite precipitation. Based on our cathodoluminescence study, we suggest that ikaite was transformed to calcite over several stages during diagenesis. Mineralogical studies also reveal that primary calcite was transformed to sulfate (gypsum) or dolomite during late superimposed processes. [ABSTRACT FROM AUTHOR]

The Prikolyma terrane is located in the central part of the Kolyma-Omolon microcontinent, in the east of the Verkhoyansk-Kolyma folded region (VKFR). (U-Th/He) low-temperature thermochronology applied for detrital zircons (ZHe) from variously in age sandstones in the southern part of the terrane. The results obtained are as follows:1. Three samples of Mesoproterozoic (central part of the terrane), Ordovician (?) (western part) and Devonian (eastern part) sandstones yielded very similar ZHe ages of 137+-6.2, 137.3+-5.4, and 137.4+-5.4 Ma, respectively.2. The more southerly sample of sandstone from the Middle Carboniferous rocks metamorphosed to the greenschist facies gave a ZHe age of 104.3+-4.7 Ma.3. The data obtained suggest that in Late Mesozoic time the southern part of the Prikolyma terrane underwent, at least, two stages of tectonic uplift. At the first Valanginian (Early Cretaceous) stage, the thrust sheets made of Precambrian and Lower-Middle Paleozoic rocks overlay Upper Paleozoic deposits as evidenced by the style of tectonic deformations and by metamorphic degree of Middle Carboniferous rocks. The deformation post-dated the emplacement of Late Jurassic granitoids of the Main (Kolyma) belt and the formation of the Uyandina-Yasachnaya magmatic arc as a result of the major pulse of collision between the Kolyma-Omolon superterrane and the eastern margin of the Siberian craton that occurred in the region no earlier than in the Valanginian.4. The second stage of orogenesis and subsequent denudation of the earlier formed thrust sheet package occurred in Albian time (late Early Cretaceous) synchronously with the initiation of the Okhotsk-Chukotka volcanic-plutonic belt and subduction processes along the East Asian active continental margin.5. At the southeastern side of the Prikolyma terrane there are present intensely deformed Upper Cretaceous and/or Lower Cenozoic (?) deposits. Thus, we assume that in the late Late Cretaceous or in the early Cenozoic a final stage of deformation not established from ZHe low-temperature chronometry occurred.Field work was partly conducted following the Research Program of DPMGI (project 0381-2019-0001), isotope-geochemical studies were supported by the Russian Scientific Foundation (project 17-17-01171), and interpretation of the results was made with the support of Russian Foundation for Basic Research (project 19-05-00945). [ABSTRACT FROM AUTHOR]

Sverdrup well is the only well drilled north of the Taimyr Peninsula, in a small island situated in the eastern Kara Sea. It was drilled above the North Siberian Arch (NSA) – which is assumed to be the continuation of Novaya Zemlya-Taimyr fold-and-thrust belt under Kara Sea. NSA divides the South Kara Basin (continuation of Mesozoic West Siberian Basin) and North Kara Basin (presumably part of Baltica continent) and is covered by relatively thin Meso-Cenozoic strata. Sverdrup well penetrated around 1500 m thick clastic Cretaceous and Upper Jurassic succession and reached the NSA basement. Here we present results of U-Pb and U-Th-He detrital zircons (DZ) dating of 8 samples both from sedimentary cover and basement of NSA. Our data shows that the NSA basement is composed of slightly metamorphosed shales of presumably Permian age (based on the youngest cluster of Detrital Zircon). Based on the obtained U-Pb ages of DZ the samples from the Cretaceous-Upper Jurassic succession can be subdivided in two groups. The first group is characterized by numerous Mesoproterozoic zircons ranging in age between 1600-1000 Ma, Neoproterozoic zircons of 700-500 Ma and Carboniferous and Permian grains. The dated sandstones are very immature, mainly lithic with numerous unstable grains pointing on short sediment transport pathways. Moreover, DZ data point that the main source of Upper Jurassic-lowermost Cretaceous clastics locates within neighboring Taimyr peninsula. The second group of samples (Aptian) has a striking difference in DZ age distribution and sedimentary petrography. Dated sandstones are quartz and arkosic arenites. Dated grains form several major peaks at 2700-2500, 1900-2000, 300-250 and 120-150 Ma. Precambrian grains indicate that the Siberian craton basement was a provenance area, whereas Mesozoic zircons likely have their source along the southern margin of Siberia (modern coordinates). Moreover U-Th-He and U-Pb double dating of zircons showed that the main cooling and uplift within provenance of the first group of samples occurred in Permian, whilst for the second group of sample the cooling and uplift is dated as Late Jurassic- Early Cretaceous. The documented variation in U-Pb and U-Th-He characteristics of DZ from the studied succession most likely reflect changes in the river systems that transported clastic sediments from provenance to sedimentary basin. Thus, we propose that big Siberian rivers started to evolve and carry clastic grains from the far located Siberian craton margins to Arctic Ocean since the Aptian time.This research was supported by RCN project- Changes at the Top of the World through Volcanism and Plate Tectonics: A Norwegian-Russian-North American collaboration in Arctic research and education: NOR-R-AM (no. 261729) [ABSTRACT FROM AUTHOR]

The Taimyr Peninsula lies on the northern edge of the Siberia, between the Laptev and KaraSeas. This area is divided into three tectonic domains: Northern, Central and SouthernTaimyr. Northern Taimyr domain represents the southern part of the Kara block. The studiedgranitoid intrusions are located within the Northern Taimyr Zone on the northern andnorthwestern coast of the Taimyr Peninsula. The studied intrusions are mainly represented by muscovite–biotite granites, biotitegranites and biotite–muscovite leucogranites. Less common are hornblende-biotite granitesand medium-grained leucogranites. According to the geochemical data, the granitoids aremagnesian, peraluminous, alkali–calcic and calc–alkalic rocks. They show a negativecorrelation between P2O5 and SiO2 which is akin to I-type granites. The initial 87Sr/86Srratio of granitoids range from 0.70287 to 0.71027, ɛNd(t) varies from -3.4 to 1.8. Thepetrographic, chemical and isotope composition of the studied intrusions is typical for I-typegranites. An Andean-type continental margin is the most probable setting for the studiedgranites. U-Pb zircon age of intrusions varies from 300 to 345 Ma. Ar-Ar micas ages confirm partof the U-Pb zircon ages but for most of the samples Ar-Ar isotopic system was reset in theMiddle Permian. Obtained data indicate that the active margin at the southern edge of the Kara blockstarted to evolve in the Early Carboniferous and existed till the end of Late Carboniferous.This active margin is characterized by multistage evolution reflected in U-Pb zircon andAr-Ar ages. The research was supported by the Russian Science Foundation (project no.17-17-01171). [ABSTRACT FROM AUTHOR]