A. Shuyskiy, K. Kulikova, Oksana Udoratina, V. Lebedev
The trachytes of the Tsilemsky Kamen of Middle Timan are rocks of the Shoshonitic series. The rocks have a microporphyry structure with a bostonite groundmass. Trachytes contain two varieties of potassium feldspar. The laths of the groundmass are composed of igneous sanidine, and the small grains along the edges of subisometric late quartz segregations are composed of hydrothermal microcline. Dating of trachytes by the K-Ar method gave an age of 365±8 Ma; the intrusion of the alkaline dike occurred in the Late Devonian. These rocks, along with trap basalts, recorded the occurrence of several pulses of plume magmatism on Timan in Devonian time.
{"title":"Late Devonian plume Tsilemsky dyke (Middle Timan): composition and K-Ar age","authors":"A. Shuyskiy, K. Kulikova, Oksana Udoratina, V. Lebedev","doi":"10.19110/geov.2023.12.4","DOIUrl":"https://doi.org/10.19110/geov.2023.12.4","url":null,"abstract":"The trachytes of the Tsilemsky Kamen of Middle Timan are rocks of the Shoshonitic series. The rocks have a microporphyry structure with a bostonite groundmass. Trachytes contain two varieties of potassium feldspar. The laths of the groundmass are composed of igneous sanidine, and the small grains along the edges of subisometric late quartz segregations are composed of hydrothermal microcline. Dating of trachytes by the K-Ar method gave an age of 365±8 Ma; the intrusion of the alkaline dike occurred in the Late Devonian. These rocks, along with trap basalts, recorded the occurrence of several pulses of plume magmatism on Timan in Devonian time.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"47 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140444672","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}
This article shows the role of dynamic non–hydrostatic pressure forces and viscous stresses in asthenosphere of tectonically active transition zones from the continent to the ocean. We have studied zones of active tectonic processes in the lithosphere and the underlying mantle, affecting the lithospheric blocks, the day surface of the Earth and the boundaries of density inhomogeneities. We showed the predominant influence of viscous stresses on the formation of mantle diapers and often associated hydrocarbon deposits. In subduction zones, in which a large-scale descending convective flow descends into the upper mantle as a sinking hard lithospheric block. We studied forces that determine the angle of subduction, depending on the age of the lithosphere, the rate of subduction and the rheological properties of the mantle material. We applied the method of analytical thermodynamic modeling of the tectonic structure of the upper mantle (lithosphere, asthenosphere) in the transition zone from the continent to the ocean. We concluded that the relative role of dynamic pressure forces prevailed in zones characterized by horizontally elongated asthenospheric movements in the mantle, as it happened under extended oceanic lithospheric plates. The novelty of the research is connected with the conclusion that under lithospheric micro-plates and near their boundaries, the roles of dynamic pressure forces and viscous stresses are comparable. In the areas of thermal diapirs associated with subduction zones and often located in transition zones from the continent to the ocean, the role of viscous stresses prevails. Thermal diapirs in subduction zones sometimes lead to the formation of hydrocarbon deposits due to mantle degassing processes.
{"title":"Relative role of dynamic pressure forces and viscous stresses in tectonically active transition zones of the Earth","authors":"S. Gavrilov, A. Kharitonov","doi":"10.19110/geov.2023.12.5","DOIUrl":"https://doi.org/10.19110/geov.2023.12.5","url":null,"abstract":"This article shows the role of dynamic non–hydrostatic pressure forces and viscous stresses in asthenosphere of tectonically active transition zones from the continent to the ocean. We have studied zones of active tectonic processes in the lithosphere and the underlying mantle, affecting the lithospheric blocks, the day surface of the Earth and the boundaries of density inhomogeneities. We showed the predominant influence of viscous stresses on the formation of mantle diapers and often associated hydrocarbon deposits. In subduction zones, in which a large-scale descending convective flow descends into the upper mantle as a sinking hard lithospheric block. We studied forces that determine the angle of subduction, depending on the age of the lithosphere, the rate of subduction and the rheological properties of the mantle material. We applied the method of analytical thermodynamic modeling of the tectonic structure of the upper mantle (lithosphere, asthenosphere) in the transition zone from the continent to the ocean. We concluded that the relative role of dynamic pressure forces prevailed in zones characterized by horizontally elongated asthenospheric movements in the mantle, as it happened under extended oceanic lithospheric plates. The novelty of the research is connected with the conclusion that under lithospheric micro-plates and near their boundaries, the roles of dynamic pressure forces and viscous stresses are comparable. In the areas of thermal diapirs associated with subduction zones and often located in transition zones from the continent to the ocean, the role of viscous stresses prevails. Thermal diapirs in subduction zones sometimes lead to the formation of hydrocarbon deposits due to mantle degassing processes.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"243 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140443429","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}
The object of the study is the carbonate section «Pacha-Lasta» (Ilych river, Northern Urals). The work is based on the study of the composition, structure of rocks and species diversity of the foraminifera contained in them. The rocks are represented by various limestones with numerous remains of foraminifera, brachiopods, corals, echinoderms, frequent calcispheres and rare stromatolites. Based on the presence in the complex of certain foraminifera genera Biseriella, Globivalvulina, various Eostaffella (including E. ikensis tenebrosa) as well as the species Endothyranopsis sphaerica and Asteroarchaediscus baschkiricus, the Venusian age of the deposits is reliably established. Stromatolite formations, which are not characteristic of the same-age deposits of the area, were established at two intervals of the studied section. They are composed of micritized colonies of cyanobacteria, among which Ortonella and Girvanella are identified. These formations belong to the type of skeletal stromatolites, which in the Silurian and Late Devonian had a certain paleogeographic position and fixed the margin of the carbonate platform. For the Ilych River basin, a consistent decrease in relative sea level is assumed after the Early Visean transgression with a change in the conditions of the open sublittoral (Tula and Aleksinsky horizons) to the conditions of insular shallow water (Mikhailovsky and Venevsky horizons). In the latter, stromatolites can sometines occur, which are not characteristic of the Upper Visean deposits of the area.
{"title":"Stromatolites in the Upper Visean sediments of the Pacha-Lasta section (Ilych River, Northern Urals)","authors":"A. Shadrin, R. Ivanova, E. Ponomarenko","doi":"10.19110/geov.2023.12.2","DOIUrl":"https://doi.org/10.19110/geov.2023.12.2","url":null,"abstract":"The object of the study is the carbonate section «Pacha-Lasta» (Ilych river, Northern Urals). The work is based on the study of the composition, structure of rocks and species diversity of the foraminifera contained in them. The rocks are represented by various limestones with numerous remains of foraminifera, brachiopods, corals, echinoderms, frequent calcispheres and rare stromatolites. Based on the presence in the complex of certain foraminifera genera Biseriella, Globivalvulina, various Eostaffella (including E. ikensis tenebrosa) as well as the species Endothyranopsis sphaerica and Asteroarchaediscus baschkiricus, the Venusian age of the deposits is reliably established. Stromatolite formations, which are not characteristic of the same-age deposits of the area, were established at two intervals of the studied section. They are composed of micritized colonies of cyanobacteria, among which Ortonella and Girvanella are identified. These formations belong to the type of skeletal stromatolites, which in the Silurian and Late Devonian had a certain paleogeographic position and fixed the margin of the carbonate platform. For the Ilych River basin, a consistent decrease in relative sea level is assumed after the Early Visean transgression with a change in the conditions of the open sublittoral (Tula and Aleksinsky horizons) to the conditions of insular shallow water (Mikhailovsky and Venevsky horizons). In the latter, stromatolites can sometines occur, which are not characteristic of the Upper Visean deposits of the area.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"149 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140443841","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}
The paper presents the results of macroscopic and microscopic study of Riphean stromatolites of the Pavyuga Formation from a new locality on the left bank of the Vorykva River (Middle Timan). The stromatolites form a stromatolite bioherm. The microstructure of the stromatolite assemblages is characterised by layering of different composition and granularity; traces of organogenic formations of clotted and filamentous type were found in microgranular interlayers. Numerous traces of secondary transformations, such as pyritization, dolomitization on shells, and fenestra formation, were noted. The taxonomic affiliation of the stromatolites to the species Gimnosolen sp. and Inseria djejimi Raab. allows dating to the Late Riphean. A similar association is known from the upper part of the Pavyuga Formation, but the colonies of stromatolites are orientated disorderly in that association, which indicates the environment of the organogenic buildup margins.
{"title":"A new location of stromatolites in the Middle Timan: their morphological and structural features","authors":"E. Antropova","doi":"10.19110/geov.2023.12.3","DOIUrl":"https://doi.org/10.19110/geov.2023.12.3","url":null,"abstract":"The paper presents the results of macroscopic and microscopic study of Riphean stromatolites of the Pavyuga Formation from a new locality on the left bank of the Vorykva River (Middle Timan). The stromatolites form a stromatolite bioherm. The microstructure of the stromatolite assemblages is characterised by layering of different composition and granularity; traces of organogenic formations of clotted and filamentous type were found in microgranular interlayers. Numerous traces of secondary transformations, such as pyritization, dolomitization on shells, and fenestra formation, were noted. The taxonomic affiliation of the stromatolites to the species Gimnosolen sp. and Inseria djejimi Raab. allows dating to the Late Riphean. A similar association is known from the upper part of the Pavyuga Formation, but the colonies of stromatolites are orientated disorderly in that association, which indicates the environment of the organogenic buildup margins.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"13 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140445278","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}
The Upper Pechora basin is part of the northeastrn margin of the European Platform. In the Paleozoic, it was located within the carbonate shelf of the passive continental margin. According to A. I. Eliseev, Visean terrrigenous-carbonate (platamovy type) and Upper Visean-Lower Artinskian carbonate (kaleydovy type) formations occupy the upper part of the final sedimentation cycle of the formations row. According to new data, the history of the geological development of the Upper Pechora basin of the Late Visean-Asselian period has significant differences. Four types can be distinguished in the structure of sediments according to the composition of rocks: siliceous-clay-limestone, limestone, dolomite-limestone, siliceous-limestone. They were formed during three stages respective to the time of formation of three transgressive-regressive cyclites: the Visean-Serpukhovian, Bashkirian-Moscovian, Upper Carboniferous-Lower Permian. The studied deposits are divided into lithological complexes: siliceous-clay-carbonate of open sea (Tulian), siliceous-carbonate of open sea (Aleksinian-Early Mikhailovian, Bashkirian-Early Moscovian, Kasimovian-Midle Gzhelian), carbonate of shallow-shallow (Late Mikhailovian-Protvinian, Moscovian), and also the Late Gzhelian-Asselian shallow-depression (siliceous-limestone, limestone, clay-limestone). Lithological complexes, formed in open-sea conditions, belong to formations from the platamovy type and in shallow-shallow conditions — to formations from the kaleidovy type (by Eliseev, 2008).
上佩乔拉盆地是欧洲地台东北缘的一部分。在古生代，它位于被动大陆边缘的碳酸盐大陆架内。根据阿-伊-埃利塞耶夫（A. I. Eliseev）的说法，维谢安原生碳酸盐岩（platamovy 型）和上维谢安-下阿尔丁斯基碳酸盐岩（kaleydovy 型）地层占据地层行最后沉积周期的上部。根据新的数据，晚维谢安-阿塞尔期上佩乔拉盆地的地质发展史有显著差异。根据岩石成分，沉积物结构可分为四种类型：硅质粘土-石灰岩、石灰岩、白云岩-石灰岩、硅质-石灰岩。这些沉积物形成于三个阶段，分别与三个递降-递降旋回的形成时间有关：维西-塞普霍夫期、巴什基尔-莫斯科期、上石炭纪-下二叠纪。所研究的矿床分为岩性复合体：公海硅质-粘土-碳酸盐岩（图里安期）、公海硅质-碳酸盐岩（阿列克西尼安-早米哈伊洛夫期、巴什基尔-早莫斯科期、卡西莫夫-中格热勒期）、浅层碳酸盐岩（晚米哈伊洛夫期-普罗维尼期、莫斯科期）以及晚格热勒期-阿塞尔期浅层凹陷（硅质-石灰岩、石灰岩、粘土-石灰岩）。在开阔海域条件下形成的岩性复合体属于platamovy型地层，在浅海条件下形成的岩性复合体属于kaleidovy型地层（Eliseev，2008年）。
{"title":"Formations of the Carboniferous-Lower Permian carbonate deposits of the Upper Pechora basin (Northern Urals)","authors":"A. Sandula","doi":"10.19110/geov.2023.12.1","DOIUrl":"https://doi.org/10.19110/geov.2023.12.1","url":null,"abstract":"The Upper Pechora basin is part of the northeastrn margin of the European Platform. In the Paleozoic, it was located within the carbonate shelf of the passive continental margin. According to A. I. Eliseev, Visean terrrigenous-carbonate (platamovy type) and Upper Visean-Lower Artinskian carbonate (kaleydovy type) formations occupy the upper part of the final sedimentation cycle of the formations row. According to new data, the history of the geological development of the Upper Pechora basin of the Late Visean-Asselian period has significant differences. Four types can be distinguished in the structure of sediments according to the composition of rocks: siliceous-clay-limestone, limestone, dolomite-limestone, siliceous-limestone. They were formed during three stages respective to the time of formation of three transgressive-regressive cyclites: the Visean-Serpukhovian, Bashkirian-Moscovian, Upper Carboniferous-Lower Permian. The studied deposits are divided into lithological complexes: siliceous-clay-carbonate of open sea (Tulian), siliceous-carbonate of open sea (Aleksinian-Early Mikhailovian, Bashkirian-Early Moscovian, Kasimovian-Midle Gzhelian), carbonate of shallow-shallow (Late Mikhailovian-Protvinian, Moscovian), and also the Late Gzhelian-Asselian shallow-depression (siliceous-limestone, limestone, clay-limestone). Lithological complexes, formed in open-sea conditions, belong to formations from the platamovy type and in shallow-shallow conditions — to formations from the kaleidovy type (by Eliseev, 2008).","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"72 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140445256","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}
The Bolshezemelskaya tundra is one of the least studied and poorly mapped territories of the European North-East of Russia. The availability of the ArcticDEM digital elevation model with a high spatial resolution allowed conducting a comprehensive joint analysis of digital, geomorphological and geological data. The results of using the ArcticDEM global digital relief model for geological and geomorphological studies of the Seyda River basin (eastern Bolshezemelskaya tundra) in its middle and lower reaches are presented. An irregular triangulation network TIN covering the Seyda River valley was constructed, and the main geomorphometric parameters of the relief were calculated: hypsometric characteristics, surface inclination angles and slope exposures. Based on the obtained morphometric indicators of the relief and the textural and structural characteristics of Quaternary sediments, the following types of relief were identified: accumulative glacial, erosion-accumulative water-glacial and erosion-accumulative alluvial types of relief. A geological and geomorphological diagram of the Seyda River valley was been constructed and the main morphogenetic features of the relief during its formation were identified.
{"title":"Geological and geomorphological zoning of the Seyda river basin (east of the Bolshezemelskaya tundra) based on the ArcticDEM digital elevation model","authors":"V. Isakov","doi":"10.19110/geov.2023.10.5","DOIUrl":"https://doi.org/10.19110/geov.2023.10.5","url":null,"abstract":"The Bolshezemelskaya tundra is one of the least studied and poorly mapped territories of the European North-East of Russia. The availability of the ArcticDEM digital elevation model with a high spatial resolution allowed conducting a comprehensive joint analysis of digital, geomorphological and geological data. \u0000The results of using the ArcticDEM global digital relief model for geological and geomorphological studies of the Seyda River basin (eastern Bolshezemelskaya tundra) in its middle and lower reaches are presented. \u0000An irregular triangulation network TIN covering the Seyda River valley was constructed, and the main geomorphometric parameters of the relief were calculated: hypsometric characteristics, surface inclination angles and slope exposures. Based on the obtained morphometric indicators of the relief and the textural and structural characteristics of Quaternary sediments, the following types of relief were identified: accumulative glacial, erosion-accumulative water-glacial and erosion-accumulative alluvial types of relief. A geological and geomorphological diagram of the Seyda River valley was been constructed and the main morphogenetic features of the relief during its formation were identified.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"6 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138586584","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}
Dmitry Bushnev, N. Burdelnaya, A. Ilchenko, Ya. D. Sennikova
A sample of Domanik shale from a stratotype section along the river Chut (Ukhta District, Komi Republic, Russia) was affected to temperatures of 250—375 °C in an autoclave in the presence of water. The composition and yield of the resulting hydrocarbon gases was studied by gas chromatography. The yield of all C1—C5 hydrocarbons grew exponentially with increasing temperature in the autoclave. The total yield of gaseous hydrocarbons C1—C5 at 375 °C was 71 mg/g Corg and reached 18 mg/g Corg for methane. The increasing temperature in the autoclave resulted in decreasing ratio of methane/C2+ gases, which reflected a changing mechanism of methane formation at the corresponding stage of the thermal evolution of the Domanik organic matter.
{"title":"Formation of hydrocarbon gases in Domanik shale during hydrous pyrolysis","authors":"Dmitry Bushnev, N. Burdelnaya, A. Ilchenko, Ya. D. Sennikova","doi":"10.19110/geov.2023.10.4","DOIUrl":"https://doi.org/10.19110/geov.2023.10.4","url":null,"abstract":"A sample of Domanik shale from a stratotype section along the river Chut (Ukhta District, Komi Republic, Russia) was affected to temperatures of 250—375 °C in an autoclave in the presence of water. The composition and yield of the resulting hydrocarbon gases was studied by gas chromatography. The yield of all C1—C5 hydrocarbons grew exponentially with increasing temperature in the autoclave. The total yield of gaseous hydrocarbons C1—C5 at 375 °C was 71 mg/g Corg and reached 18 mg/g Corg for methane. The increasing temperature in the autoclave resulted in decreasing ratio of methane/C2+ gases, which reflected a changing mechanism of methane formation at the corresponding stage of the thermal evolution of the Domanik organic matter.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"62 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138587280","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}
The structural features of the rocks of the Precambrian section of the Subpolar (upper reaches of the Kozhim River) and Polar Urals (Kharbey River basin) have been studied. We revealed that the structural appearance of the formations under consideration resulted from several stages of deformation. The Precambrian of these regions is characterized by deformations and accompanying metamorphic transformations of rocks in the Early Proterozoic, associated with orogenic processes resulting from the unification of Volga-Uralia and Sarmatia and later with the development of the timanides and uralides. We found markers of an earlier stage of structural-metamorphic transformation of rocks (possibly Late Archean) in the Polar Urals.
{"title":"Structural features of Precambrian formations of Subpolar and Polar Urals: comparative analysis","authors":"I. Potapov, K. Popvasev, A. Pystin","doi":"10.19110/geov.2023.10.1","DOIUrl":"https://doi.org/10.19110/geov.2023.10.1","url":null,"abstract":"The structural features of the rocks of the Precambrian section of the Subpolar (upper reaches of the Kozhim River) and Polar Urals (Kharbey River basin) have been studied. We revealed that the structural appearance of the formations under consideration resulted from several stages of deformation. The Precambrian of these regions is characterized by deformations and accompanying metamorphic transformations of rocks in the Early Proterozoic, associated with orogenic processes resulting from the unification of Volga-Uralia and Sarmatia and later with the development of the timanides and uralides. We found markers of an earlier stage of structural-metamorphic transformation of rocks (possibly Late Archean) in the Polar Urals.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"77 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138587024","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}
V. Andreichev, Anna Soboleva, E. Dovzhikova, Y. Ronkin
The Pechora Basin is the largest tectonic structure of the Pechora Plate. It is located between the Timan and the Cis-Ural Foredeep. The Upper Precambrian sedimentary-metamorphic and igneous rocks of the basement are completely overlain by a sedimentary cover, therefore, the geological structure of the basement is known only on the basis of geophysical data and core samples from boreholes up to 5 km deep. The basement has a heterogeneous structure. It includes complexes of the Late Precambrian passive margin of the East European continent, which compose the Timan megablock (Izhma zone with Timan adjoining from the southwest) and formations formed in an active margin geodynamic setting combined into the Bolshezemel megablock (Pechora and Bolshezemel zones). The boundary between megablocks is the Pripechora fault (suture) zone. The age of igneous rocks of the basement is debatable; therefore, U-Pb (SIMS) studies of single zircon grains are undertaken to specify it. The article presents petrogeochemical data and U-Pb (SIMS, SHRIMP-RG) ages of zircon grains from plutonic rocks of the Pechora zone belonging to the Bolshezemel megablock drilled by two boreholes at depths of ~ 4.5 km. The obtained results indicated two episodes of island-arc magmatism. The first took place at the end of the Riphean, and the second was confined to the Early–Late Vendian boundary. The age of gabbrodiorites from the 1-Severny Savinobor borehole, interpreted as early island-arc rocks, is 673 ± 7 Ma. Late island-arc plagiogranites from the 1-Novaya borehole yield the age of 564 ± 5 Ma and precede the orogenic granitoids of the Pripechora fault zone which are dated (U-Pb) to 555—544 Ma.
{"title":"Two episodes of subduction-related intrusive magmatism within the Pechora zone of the Pechora Basin basement","authors":"V. Andreichev, Anna Soboleva, E. Dovzhikova, Y. Ronkin","doi":"10.19110/geov.2023.10.2","DOIUrl":"https://doi.org/10.19110/geov.2023.10.2","url":null,"abstract":"The Pechora Basin is the largest tectonic structure of the Pechora Plate. It is located between the Timan and the Cis-Ural Foredeep. The Upper Precambrian sedimentary-metamorphic and igneous rocks of the basement are completely overlain by a sedimentary cover, therefore, the geological structure of the basement is known only on the basis of geophysical data and core samples from boreholes up to 5 km deep. The basement has a heterogeneous structure. It includes complexes of the Late Precambrian passive margin of the East European continent, which compose the Timan megablock (Izhma zone with Timan adjoining from the southwest) and formations formed in an active margin geodynamic setting combined into the Bolshezemel megablock (Pechora and Bolshezemel zones). The boundary between megablocks is the Pripechora fault (suture) zone. The age of igneous rocks of the basement is debatable; therefore, U-Pb (SIMS) studies of single zircon grains are undertaken to specify it. The article presents petrogeochemical data and U-Pb (SIMS, SHRIMP-RG) ages of zircon grains from plutonic rocks of the Pechora zone belonging to the Bolshezemel megablock drilled by two boreholes at depths of ~ 4.5 km. The obtained results indicated two episodes of island-arc magmatism. The first took place at the end of the Riphean, and the second was confined to the Early–Late Vendian boundary. The age of gabbrodiorites from the 1-Severny Savinobor borehole, interpreted as early island-arc rocks, is 673 ± 7 Ma. Late island-arc plagiogranites from the 1-Novaya borehole yield the age of 564 ± 5 Ma and precede the orogenic granitoids of the Pripechora fault zone which are dated (U-Pb) to 555—544 Ma.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"57 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138587100","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}
The article examines patterns of spatial distribution of 137Cs and natural radionuclides 226Ra, 232Th, 40K in the upper (0—5 cm) layer of soils in the main functional zones of the city of Polyarnye Zori. The analysis of the general gamma activity of the territory, using RS-700 mobile gamma spectrometric complex, showed, three local anomalies of increased gamma radiation, which were confined to high-rise buildings within the city. In undisturbed peat soils in the area of the Kola Nuclear Power Plant and in the area of urban forests and parks, the maximum specific activity of technogenic 137Cs was 29.5 and 28.8 Bq/kg, respectively. In other functional zones of the city, the activity of 137Cs was 5 times less. According to the results of the correlation analysis, the technogenic 137Cs has a moderate relationship (on the Chaddock scale) with the 45 and 500 µm fraction. 232Th has a high affinity with 226Ra, and 40K with 232Th, which are statistically significant results when taking P-Value into account. It can be assumed that natural radionuclides 232Th, 40K, 226Ra have a moderate association with the 1 mm fraction due to the presence of particles of this size in the upper soil layer. There is a moderate relationship between 232Th and 40K.
{"title":"Specific spatial distribution of 137Cs, 40K, 226Ra, 232Th in soils of the city of Polyarnyye Zori (Murmansk region)","authors":"S. Iglovsky, A. Bazhenov, E. Yakovlev","doi":"10.19110/geov.2023.10.6","DOIUrl":"https://doi.org/10.19110/geov.2023.10.6","url":null,"abstract":"The article examines patterns of spatial distribution of 137Cs and natural radionuclides 226Ra, 232Th, 40K in the upper (0—5 cm) layer of soils in the main functional zones of the city of Polyarnye Zori. The analysis of the general gamma activity of the territory, using RS-700 mobile gamma spectrometric complex, showed, three local anomalies of increased gamma radiation, which were confined to high-rise buildings within the city. In undisturbed peat soils in the area of the Kola Nuclear Power Plant and in the area of urban forests and parks, the maximum specific activity of technogenic 137Cs was 29.5 and 28.8 Bq/kg, respectively. In other functional zones of the city, the activity of 137Cs was 5 times less. According to the results of the correlation analysis, the technogenic 137Cs has a moderate relationship (on the Chaddock scale) with the 45 and 500 µm fraction. 232Th has a high affinity with 226Ra, and 40K with 232Th, which are statistically significant results when taking P-Value into account. It can be assumed that natural radionuclides 232Th, 40K, 226Ra have a moderate association with the 1 mm fraction due to the presence of particles of this size in the upper soil layer. There is a moderate relationship between 232Th and 40K.","PeriodicalId":23572,"journal":{"name":"Vestnik of geosciences","volume":"48 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138588390","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}
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