LITHOSPHERE (Russia)最新文献

{"title":"Typomorphic features of garnet xenocrysts from the crater and diatreme parts of the high diamondiferous V. Grib kimberlite pipe (Arkhangelsk diamondiferous province): application in prospecting and exploration for diamonds in the north of the East European platform","authors":"E. O. Barabash, E. Agasheva","doi":"10.24930/1681-9004-2023-23-4-622-636","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-4-622-636","url":null,"abstract":"Research subject. Morphology of garnet xenocryst grains from the crater and diatreme parts of the highly diamondiferous V. Grib kimberlite pipe of the Arkhangelsk diamondiferous province. Aim. To reconstruct the main stages of endogenous and exogenous morphogenesis of garnet xenocrysts from the crater and diatreme parts of the kimberlite pipe based on a detailed study of their morphological features. To demonstrate the applicability of the data obtained in the interpretation of the morphology of grains of kimberlite indicator minerals from modern alluvial sediments during prospecting and exploration for diamonds in the north of the East European Platform. Materials and methods. A detailed study of the morphology of 655 garnet grains was carried using the methods of optical and electron-scanning microscopy. Garnet grains were selected from the heavy mineral concentrate of crushed rocks, representing the crater (sandstones) and diatreme (kimberlite) parts of the V. Grib pipe. All visually diagnosed garnet grains were handpicked selected from the rocks of the crater part, extracted from the core of one borehole and representing an interval from 70 to 174 m from the surface. For comparison, out of 1100 grains of garnet xenocrysts, selected by random sampling from the concentrate of minerals of the heavy fraction of kimberlite of the diatreme part, 180 garnet grains were selected, representing four-color groups: purple, red, red-orange and orange. Results. The majority of garnets from the crater (96%) and diatreme (89%) parts of the V. Grib kimberlite pipe were shown to exhibit the “primary” magmatic morphology. Nevertheless, the garnet grains with well-developed pyramidal shingle-like (3% in the crater and 11% in the diatreme) and drop-shaped (1% in the crater) reliefs have been identified. These types of garnets were formed under the influence of postmagmatic processes. For the first time, in the deep diatreme part of the pipe (more than 200 m from the surface), composed of dense kimberlite, garnets with a well-developed pyramidal shingle-like relief were found, which had been previously interpreted for the East European Platform only as components of the secondary deposits or the upper horizons of the crater parts of the pipes. Conclusions. Garnets with a well-developed pyramidal shingle-like relief, found in modern alluvial sediments, can be interpreted as from a secondary deposit only if they show signs of mechanical abrasion; the absence of traces of mechanical abrasion on such grains does not allow us to exclude the proximity of the primary source. The presence of drop-shaped relief garnets in the crater of the V. Grib pipe (150-168 m from the surface) also calls into question the unambiguous interpretation of such grains as a sign of secondary deposits: only the maximum degree of chemical abrasion of garnets with the formation of cuboids grains can indicate their redeposited nature. The results confirm the need to improve the method of prospec","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90893361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"U-Pb (LA-ICP-MS) age of detrital zircons from sandstones of the crater part of the V. Grib kimberlite pipe and KL-01 magmatic object, Arkhangelsk diamondiferous province (north of the East European Platform)","authors":"E. Agasheva","doi":"10.24930/1681-9004-2023-23-4-603-621","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-4-603-621","url":null,"abstract":"Research subject. Detrital zircons from sandstones that contain no admixtures of magmatic material, sampled from the crater parts of the highly diamondiferous V. Grib kimberlite pipe and KL-01 magmatic object. Both objects are located in the north of the East European Platform, within the Arkhangelsk diamondiferous province, at a distance of ≈100 km from each other. Aim. To obtain the first data on the composition of the U-Pb isotope system of detrital zircons from sandstones of magmatic objects of the Arkhangelsk diamondiferous province in order to evaluate the ages of their sources and reveal correlations with known tectono-thermal events in the continental crust of the region. Materials and methods. Using the LA-ICP-MS method, data were obtained on the composition of the U-Pb isotopic system of 52 zircon grains from the sandstones of the V. Grib pipe and 143 zircon grains from the KL-01 sandstones. Results. Sources of various ages from Archean to Neoproterozoic were established for the studied zircons. However, the majority zircons have Mesoproterozoic age, namely 63 and 65% of grains from the V. Grib pipe and KL-01 object, respectively. The sandstones of the V. Grib pipe contain a larger amount of Meso- and Neo-Archean zircons (≈15%) and a smaller amount of Paleoproterozoic grains (≈14%) compared to those from the KL-01 object ≈7 and 20%, respectively. The population of zircons with the U-Pb ages of 900-700 Ma is absent in the two objects. The minimum age of zircons from sandstones of the crater of the V. Grib pipe (557 ± ± 9 Ma) and KL-01 object (609 ± 9 Ma) is consistent with that of formation of the Vendian sandstones in the area of the pipes of the Arkhangelsk diamondiferous province. Conclusions. The obtained U-Pb age for the studied detrital zircons generally correlate with the previously identified stages of tectono-thermal events in the continental crust of the northern territories of the East European Platform, with the exception of the Mesoproterozoic period 1.7-1.4 and 1.3-1.0 Ga ago, which corresponds to the predominant part U-Pb age values of the studied zircons.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"141 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85792023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diamond potential of the marginal parts of ancient platforms and associated folded areas","authors":"D. A. Zedgenizov","doi":"10.24930/1681-9004-2023-23-4-471-475","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-4-471-475","url":null,"abstract":"In recent years, more and more information has become available on the subsidence of the oceanic lithosphere into the horizons of the transition zone and the lower mantle of the Earth. Highly metamorphosed rocks are often found in ophiolite complexes of folded areas, which, according to some researchers, can also have significant diamond content. A comprehensive study of all possible sources of information about the formation conditions and evolution of contrasting crustal protoliths opens up new prospects for determining such complex geological processes. These studies are also important in the context of identification of new mineralogical and geochemical markers of diamond-forming processes and, on their basis, determination of the possibility of their practical use in improving methods for predicting, prospecting and evaluating diamond deposits. The current issue of our Journal is devoted to these relevant problems.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76079982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation conditions of andesites of Sulawesi Island (Indonesia)","authors":"N. Dmitrieva, I. Safonova, V. Simonov, A. Kotlyarov, N. Karmanov, I. Nizametdinov","doi":"10.24930/1681-9004-2023-23-3-386-409","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-386-409","url":null,"abstract":"Research subject. Andesitic complexes of the Tondono caldera and Lokon-Empung volcano locate din the northeastern part of the Sulawesi Island (Indonesia).Aim. To determine the petrogenesis conditions of andesites in the northeast Sulawesi Island based on detailed studies of volcanic rocks of the Tondono caldera and Lokon-Empung volcano.Materials and methods. We studied volcanic rock samples collected by I.Yu. Safonova. To determine the petrogenesis conditions of andesites, conventional petrochemical, geochemical and mineralogical methods were used. Melt inclusions were also studied using a MIRA 3 LMU scanning microscope equipped with Aztec Energy XMax 80 system of microanalysis, and a Horiba LabRam HR800 Raman spectroscope. The PT-parameters of crystallization were estimated from the data on the composition of melt inclusions using approaches reported by K.D. Putirka, F. Yavuz and D.K. Yıldırım.Results. The Sulawesi andesites represent tholeiitic and calc-alkaline island-arc magmas. Pyroxenes phenocrysts crystallized from melts that evolved with accumulation of alkalis and silica. Plagioclase phenocrysts crystallized from the felsic magmas, which are characterized by a decreasing role of alkalis. The composition of volcanic glass of the mesostasis suggests participation of felsic melts with a very high content of alkalis. The compositions of minerals and glasses in inclusions and in the mesostasis allowed us to estimate PT-parameters of the petrogenesis of the andesites. The phenocrysts of pyroxene crystallized in two intermediate magma chambers at depths of 27.6–14.6 and 11.3–7.2 km and temperatures ranging from 1150 to 970ºС. The phenocrysts of plagioclase crystallized at 930–910 and 900–890ºС. The microcrystals (laths) of plagioclase in the mesostasis crystallized at lower temperatures of 875–865 and 840–810ºС.Conclusions. The andesites of the Sulawesi Island were derived from tholeiitic to calc-alkaline melts compositionally similar boninites. The compositions of the glasses in melt inclusions and mesostasis showed three types of compositionally different parental magmas, which produced the Sulawesi andesites. The phenocrysts of pyroxenes crystallized from these melts in two magma chambers at depths of 27.6 to 7.2 km and at temperatures of 1150 to 970ºС. The phenocrysts and laths of plagioclase crystallized at lower temperatures of 930 to 810ºС.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88141623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogy and Р-T conditions for the formation of metasomatic rocks of the Voznesenskoye gold deposit (Southern Urals)","authors":"S. E. Znamensky","doi":"10.24930/1681-9004-2023-23-3-430-446","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-430-446","url":null,"abstract":"Research subject. Mineral associations, their chemical composition, and formation conditions of metasomatic rocks of the Voznesenskoye gold deposit located in the area of the Main Ural Fault in the Southern Urals.Methods. The chemical composition of minerals was studied using a Tescan Vega Compact scanning electron microscope equipped with an Oxford Instruments Xplorer 15 energy-dispersive analyzer. The formation P-T parameters were estimated using a chlorite geothermometer and a dolomite-calcite geothermobarometer.Results and conclusions. Two types of metasomatic rocks were identified: 1) propylites, which make up the outer zones of the metasomatic aureole, and 2) beresite-listvenites, common in its inner parts and hosting gold mineralization. The main propylite minerals were amphibole, orthoclase, albite, and ripidolite. Amphibole is represented by two generations, with the early generation comprising magnesian and actinolite hornblende and the late generation comprising actinolite. The crystallization temperature of ripidolite (307–313°С) corresponds to the temperature range of formation of propylites of the albite-actinolite facies. Beresite-listvenites (association: quartz, albite, chlorite, white mica, and carbonate) were formed at a temperature of 255–338°C and a pressure of 0.48–0.72 kbar. Gold ore mineralization was concentrated in the highest temperature zones of the halo of beresite-listvenite alterations. Such temperature conditions existed in dikes and their exocontact zones disturbed by ruptures. Light mica in beresite-listvenites is represented by sericite and phengite, and carbonate is a paragenesis of calcite and dolomite-ankerite. According to the composition and formation period, chlorite is differentiated into early ferruginous ripidolite and late pycnochlorite, depleted in Fe and enriched in Si, which is probably associated with a decrease in temperature during mineral formation and an increase in the activity of sulfide sulfur in the fluid. Along with an increase in the distance from the ore bodies, pycnochlorite exhibits greater contents of Si and lower contents of AlIV. The observed changes in the pycnochlorite composition are related to a decrease in temperature. The research results indicate the formation of the Voznesenskoye deposit under mesothermal conditions.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80356233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-alumina rocks from the Panimba and Mayakon areas (Yenisei Ridge): Composition and industrial perspectives","authors":"A. V. Nekipelova, E. Sokol, S. Kokh, I. Likhanov, P. Khvorov","doi":"10.24930/1681-9004-2023-23-3-447-465","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-447-465","url":null,"abstract":"Research subject. Аndalusite- and kyanite-bearing (13–19 wt % Al2SiO5) rocks of the Teya metamorphic complex (Mayakon and Panimba areas), Yenisei Ridge.Aim. To study the composition and mineral content of high-alumina rocks from the Panimba and Mayakon areas.Materials and methods. Laboratory mineral processing was employed to estimate the mineral content of metamorphic rocks of the Teya complex using a magnetic and gravity separation at the Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences (Novosibirsk). The concentrates were obtained from typical samples of andalusite, kyanite, and andalusite-kyanite metapilites. After crushing and grinding, the rock samples were separated into size fractions <0.06, 0.06 ≤ x < 0.1 and 0.1 ≤ x < 0.25 mm. The concentrates were recovered from size fractions ≥0.06 mm. Phase, bulk rock, and trace element composition of the rock samples, mineral concentrates, and other fractions were analyzed using XRD, XRF, ICP-MS, and SEM.Results. The magnetic product obtained at the first stage of mineral processing using magnetic separation accumalated staurolite, biotite, chlorite, ilmenite, pyrrhotite, and pyrite. At the second stage, light products containing quartz, feldspars, and muscovite were separated from non-magnetic products with CHBr3 using a centrifugal concentrator. At the last stage, using a double-knife separator, the heavy product from the previous beneficiation stage was separated into a “magnetic” raw concentrate (52–92 wt % Al2SiO5) and a “non-magnetic” final (70–97 wt % Al2SiO5) concentrate. The andalusite-kyanite concentrates (up to 97 wt % Al2SiO5) were obtained by the combination of cheapest and simplest methods of magnetic and gravity separation. The concentrates containing andalusite and kyanite with low recovery (0.7–6%) are comparable to the grade of kyanite-bearing ores of Karelia, the Kola Peninsula, and Gansu Province, China.Conclusions. The study shows that high-quality andalusite and/or kyanite concentrates can be recovered from high-alumina metapelites of the Teya metamorphic complex.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75216801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical record of Lake Sabakty: Electrical conductivity and reconstruction of the Lateglacial and Holocene environments in the Southern Urals (Russia) steppe","authors":"A. Maslennikova, D. A. Artemiev, E. Zazovskaia, V. Deryagin, V. O. Gulakov, N. Udachin, P. Aminov, V. Udachin","doi":"10.24930/1681-9004-2023-23-3-410-429","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-410-429","url":null,"abstract":"Research subject. The Lake Sabakty sediments core, as a source of data on the Holocene and Lateglacial environments in the Southern Urals.Aim. To obtain a multiple regression model for quantitative reconstructions of the electrical conductivity of water based on the geochemistry of lake sediments and to reconstruct the Late Glacial and Holocene environments based on the study of the Lake Sabakty geochemical record.Materials and methods. After determination of correlations between the content of chemical elements in lake sediments and hydrochemical parameters of 107 Ural lakes, multiple regression models were obtained. Reconstructions were performed based on the results obtained by accelerator mass spectrometry (AMS 14C), 210Pb activity determination, and an analysis of chemical elements and organic matter contents in the sediment core.Results. Three multiple regression models using the concentrations of Na, Ca, Li, and Sr were obtained for electrical conductivity of water reconstruction. In the cold and dry Lateglacial (>12.0 ka cal BP), Lake Sabakty was a slightly brackish reservoir. During the transition from the Lateglacial to the Holocene (12–11.6 ka cal BP), the Lake Sabakty became more productive. In the Early (11.6–8.2 ka cal BP) and Middle (8.2–4.2 ka cal BP) Holocene, the electrical conductivity of water varied under the action of fluctuations in effective moisture. In the Late Holocene (4.2 ka cal BP – present), the Lake Sabakty became less saline due to an increase in effective moisture.Conclusions. The proposed multiple regression models enable rapid quantitative reconstructions of the electrical conductivity of water, which are particularly relevant for Lateglacial–Early Holocene sediments with a low number of microfossils. The Lake Sabakty geochemical record reflects global and regional climatic fluctuations, being more informative compared to the geochemical records of forest lakes in the Southern Urals. The decrease in the electrical conductivity of water of Lake Sabakty of approximately 7.9 and 4.2 ka cal BP coincides with similar data for several other lakes in the Urals.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82918246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gabbroids of the Bazhenov gabbro-hyperbasite massif (Middle Urals): Material composition and age","authors":"Yu. V. Erokhin, K. Ivanov, V. Smirnov, A. V. Zakharov, A. E. Chugaev","doi":"10.24930/1681-9004-2023-23-3-367-385","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-367-385","url":null,"abstract":"Research subject. Saussurite-amphibole rocks (metagabbroids) of the Bazhenov gabbro-hyperbasite massif (eastern sector of the Middle Urals).Materials and methods. The material composition of metagabbroids and their mineralogy were studied in the analytical laboratories of the Institute of Geological Geology, Ural Branch, Russian Academy of Sciences (Ekaterinburg), Urals State Mining University (Ekaterinburg), Institute of Mineralogy, Ural Branch, Russian Academy of Sciences (Miass), Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (Moscow), and Moscow State University (Moscow). Isotope analyzes of zircon were performed on a SHRIMP-II ion microanalyzer at the Center for Isotope Research of VSEGEI (St.Petersburg).Results. The metagabbroids under study feature the following mineral composition: clinozoisite (zoisite, epidote), magnesian hornblende (pargasite, tremolite), albite, clinochlore, and dolomite. According to petro-geochemistry data, saussurite-amphibole rocks were formed after gabbronorites and olivine gabbro-norites, belonging to the alpine-type formation of gabbro-hyperbasite complexes. U-Pb dating showed the ancient age of zircons from metagabbroids, most of the analyzes are grouped below the concordia line, forming a discordia line, the upper intersection of which with the concordia corresponds to the age of 1992 Ma. Two points on the diagram located below the concordia line, although not falling on the continuation of the discordia line, apparently reflect the influence of intermediate stages of metamorphism, and two points with concordant ages of 256 and 251 Ma record the time of the last tectono-thermal episode.Conclusions. The formation of saussurite-amphibole rocks took place under the conditions of greenschist facies. In local areas of the massif, metamorphism reached the zeolite facies with signs of hydrothermal reworking. The primary gabbroids of the Bazhenov massif were most likely formed under the conditions of a suprasubduction basin. The age of zircons of about 2 Ga obtained by the U-Pb method indicates that the crystallization of the studied zircons occurred in the mantle rocks. It is not yet possible to unambiguously explain the presence of grains of these zircons in the metagabbroids of the Bazhenov massif; several possible explanations have been proposed. Zircons with the youngest age (256 and 251 Ma) were most likely formed as a result of metamorphic transformations under thermal influence from the nearby Aduy granite-leucogranite complex.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85653840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Junction zone structure of the Sarmatia, Volga-Uralia, and Fennoscandia microcontinents as part of the East European Platform basement","authors":"T. N. Kheraskova, Y. Volozh, M. Antipov, V. A. Bykadorov, I. S. Patina, R. B. Saposhnikov","doi":"10.24930/1681-9004-2023-23-3-309-324","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-309-324","url":null,"abstract":"Research subject. The structure of the pre-Paleozoic deposits and different-age Precambrian basement of the East European platform based on geological and geophysical data.Aim. To trace the evolution of the area under study and to study the geodynamics of processes in order to reconstruct the paleostructure of the Baltica continent.Materials and methods. The current state of the consolidated crust was studied using a geological interpretation of seismic profiling data (transects: “EB-1”, “Tatseys”, “Magnit”) and materials of gravity and geomagnetic surveys. The material composition of the basement rock complexes was studied based on drilling data.Results. The Baltica continent forms the basement of the modern East European Platform. After the Sveconorwegian folding about 1000 Ma, Baltica had become part of the Rodinia supercontinent and merged with the North American platform. A passive continental margin with the Riphean-Vendian sedimentary cover was formed on the eastern Baltica edge. The Petrozavodsk-Khopersky orogen, which arose in the place of the Karelian (Early Proterozoic) Petrozavodsk-Khopersky paleoocean, was reconstructed. The submeridional suture was a result of this paleoocean closure. The orogen structure, as well as that of the paleocontinent Baltica, was disturbed and partially destroyed by subsequent tectonic processes, which continue at the present time with modern rifting.Conclusions. The closure of the Petrozavodsko-Khopersky paleoocean led to the formation of the Baltica continent, which included three microcontinents – Sarmatia, Fennoscandia and Volga- Uralia. Baltica became part of the Rodinia supercontinent during the Sveconorwegian orogeny. Volga-Uralia was located on the border with the PaleoPacific and had a Late Riphean sedimentary cover of the Rodinia supercontinent. This margin underwent destruction during a collision with the Timanides. The scale and extent of the reconstructed Petrozavodsk-Khopersky orogen is comparable to Paleozoic orogenic belts, such as Cadomides, Caledonides, Variscides, or Timanides.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"103 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78083289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ostracod zonation of the Givetian-Frasnian boundary interval in the Timan-North Urals Region","authors":"D. B. Sobolev, M. A. Soboleva, I. Evdokimova","doi":"10.24930/1681-9004-2023-23-3-348-366","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-3-348-366","url":null,"abstract":"Research subject. Ostracods and Givetian-Frasnian boundary deposits of the Timan-North Urals Region.Materials and methods. The work was based on the results of studying ostracods from the stratotype sections of the Southern Timan, which are considered referential for regional and global correlations. The analysis of the distribution intervals of the most significant taxa was based on the results of previous studies, both published and archival materials on the Timan-Urals Region. Ostracods were considered in association with conodonts, which is an important criterion for applying a reasonable biostratigraphic subdivision. The use of different-scale regional cyclicity of sedimentation and individual “marking” levels of manifestation of global events were shown.Results. The ostracod distribution in the Givetian-Frasnian boundary interval of the Timan-Northern Urals region was analyzed. The following most significant taxa were identified: Cavellina devoniana, Cavellina uchtensis, Cavellina batalinae, Cavellina chvorostanensis, Nodella faceta, Nodella ex gr. hamata. The correlation of established assemblages with ostracods from the Franco-Belgian basin was shown. The difference consists in the absence of a polyzygid assemblage with Polyzygia beckmanni beckmanni, which was established at the base of the Nismes Formation of Belgium near the historical boundary between the Givetian and Frasnian stages. The determined relationship of biostratigraphic data in combination with the transgressive-regressive sequence of sedimentation shows a more reasonable solution to the problem of the position of the lower boundary of the Frasnian stage of the Upper Devonian in the Timan-Northern Urals Region.Conclusions. An updated version of the scheme of zonal subdivision of the Givetian-Franian boundary interval in the Timan- Northern Urals region has been developed, taking into account the ostracod distribution of the Cavellinidae and Nodellidae families, as well as the discrepancies in the levels of the first appearance of index species and the boundaries of zones in the regional stratigraphic scheme. The correlation of ostracod zones relative to the conodont scale is shown.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85992256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}