A. Popov, A. Shevko, E. S. Sobolev, A. V. Yadrenkin, B. Nikitenko, A. Travin
—Petrographic and geochemical studies of igneous and volcaniclastic rocks of the middle part of the Pronchishchev Ridge and the Terpei lowland provided new data on their composition and structure. The subdivision of the Permian–Lower Triassic strata enclosing igneous and volcaniclastic bodies has been clarified by lithological/stratigraphic methods. The Lower Triassic Ulakhan-Yuryakh, Chekanovsky, Ystanakh, and Pastakh formations have been traced for the first time in the ridge area. It is shown that the studied dolerite body and adjacent breccias in the field of middle–upper Permian rocks are part of the volcanic pipe. The tuffite sandy gritstones in the field of Lower Triassic rocks are parts of an eroded tephra ring around this diatreme. The localization of tuffite bodies in the area of the Ystanakh Formation makes it possible to date the pipe at the beginning of the late Olenekian. The obtained 40Ar/39Ar dates for the dolerites of the volcanic pipe and one of the dikes of the Pronchishchev dike belt indicate the repeated tectonomagmatic activity in the studied area in the Triassic.
{"title":"Triassic Volcaniclastic and Igneous Rocks of the Pronchishchev Ridge (East Siberia, Arctic): Composition, Structure, Genesis, and Age","authors":"A. Popov, A. Shevko, E. S. Sobolev, A. V. Yadrenkin, B. Nikitenko, A. Travin","doi":"10.2113/rgg20224501","DOIUrl":"https://doi.org/10.2113/rgg20224501","url":null,"abstract":"\u0000 —Petrographic and geochemical studies of igneous and volcaniclastic rocks of the middle part of the Pronchishchev Ridge and the Terpei lowland provided new data on their composition and structure. The subdivision of the Permian–Lower Triassic strata enclosing igneous and volcaniclastic bodies has been clarified by lithological/stratigraphic methods. The Lower Triassic Ulakhan-Yuryakh, Chekanovsky, Ystanakh, and Pastakh formations have been traced for the first time in the ridge area. It is shown that the studied dolerite body and adjacent breccias in the field of middle–upper Permian rocks are part of the volcanic pipe. The tuffite sandy gritstones in the field of Lower Triassic rocks are parts of an eroded tephra ring around this diatreme. The localization of tuffite bodies in the area of the Ystanakh Formation makes it possible to date the pipe at the beginning of the late Olenekian. The obtained 40Ar/39Ar dates for the dolerites of the volcanic pipe and one of the dikes of the Pronchishchev dike belt indicate the repeated tectonomagmatic activity in the studied area in the Triassic.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45446299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
––Interpretation of magnetotelluric data within the North Caucasus marginal massif, the uplift of the Main Range, and the Stavropol Arch, performed on the basis of one- and two-dimensional inversions of the impedance tensor components and three-dimensional mathematical modeling, makes it possible to compile the starting and test models that are necessary for a three-dimensional inversion. It is shown by the three-dimensional inversion of all the impedance tensor components, carried out on a test three-dimensional model, that it is possible to estimate the parameters of conducting model blocks. The three-dimensional inversion of all the experimental impedance matrix components, performed with account for the results obtained on the test three-dimensional model, significantly corrects the parameters of the conducting blocks identified at the stages of one- and two-dimensional inversions, as well as the three-dimensional mathematical modeling of magnetotelluric fields in the central part of the North Caucasus. In the resulting three-dimensional geoelectrical model of the region, the position of low-resistance blocks correlates with the location of suture zones, deep faults, volcanic chambers, and domains with converted earthquake waves, whose velocities are reduced and whose absorption is increased. This can be explained by the dependence of the conductivity of crustal blocks on water saturation. Earthquake hypocenters are grouped near low-resistance anomalies.
{"title":"Geoelectric Model of the Central Part of the North Caucasus: Three-Dimensional Inversion","authors":"V. V. Belyavsky","doi":"10.2113/rgg20224500","DOIUrl":"https://doi.org/10.2113/rgg20224500","url":null,"abstract":"\u0000 ––Interpretation of magnetotelluric data within the North Caucasus marginal massif, the uplift of the Main Range, and the Stavropol Arch, performed on the basis of one- and two-dimensional inversions of the impedance tensor components and three-dimensional mathematical modeling, makes it possible to compile the starting and test models that are necessary for a three-dimensional inversion. It is shown by the three-dimensional inversion of all the impedance tensor components, carried out on a test three-dimensional model, that it is possible to estimate the parameters of conducting model blocks. The three-dimensional inversion of all the experimental impedance matrix components, performed with account for the results obtained on the test three-dimensional model, significantly corrects the parameters of the conducting blocks identified at the stages of one- and two-dimensional inversions, as well as the three-dimensional mathematical modeling of magnetotelluric fields in the central part of the North Caucasus. In the resulting three-dimensional geoelectrical model of the region, the position of low-resistance blocks correlates with the location of suture zones, deep faults, volcanic chambers, and domains with converted earthquake waves, whose velocities are reduced and whose absorption is increased. This can be explained by the dependence of the conductivity of crustal blocks on water saturation. Earthquake hypocenters are grouped near low-resistance anomalies.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47361147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
—We provide an analytical assessment of electrical and seismic signals of the seismoelectrical effect over a hydrocarbon deposit in the sea with seismic wave excitation using pulsed nonexplosive sources and reception by automatic underwater vehicles. The hardware complex required for the implementation of the method is described. Methods for suppressing reverberation interference are considered.
{"title":"On the Possibility of Developing a Seismoelectrical Method for Direct Hydrocarbon Prospecting in the Arctic Seas without the Use of a Streamer Cable","authors":"G. Shaidurov, V. Detkov, R. G. Shaidurov","doi":"10.2113/rgg20224480","DOIUrl":"https://doi.org/10.2113/rgg20224480","url":null,"abstract":"\u0000 —We provide an analytical assessment of electrical and seismic signals of the seismoelectrical effect over a hydrocarbon deposit in the sea with seismic wave excitation using pulsed nonexplosive sources and reception by automatic underwater vehicles. The hardware complex required for the implementation of the method is described. Methods for suppressing reverberation interference are considered.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41870022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Duchkov, D. Ayunov, P. Yan, A. Sivtsev, L. S. Sokolova
––We present results of measurements of the physical properties (thermal conductivity, porosity, permeability, and density) of 65 air-dry sedimentary-rock samples from the cores of six deep wells drilled in the Lena–Anabar interfluve. The rocks are compact low-porosity, almost impermeable siltstones, sandstones, and dolomites mainly of Paleozoic and Precambrian ages. Correlations of thermal conductivity with porosity and bulk density have been established. The available information about the thermal conductivity of rocks as well as the production thermograms recorded after drilling made it possible to estimate the geothermal gradient and heat flow (q) for the Ust’-Olenekskaya-2370, Charchykskaya-1, Khastakhskaya-930, and D’yappal’skaya-1 wells. The gradient was calculated from the temperature values at the lower boundary of the permafrost (0 ºC) and at the bottom-hole. The determined heat flow varies from 37 to 70 mW/m2. These q estimates are consistent with the available data on the distribution of heat flow in the north of the Siberian Platform. The proposed method for heat flow estimation is worthy of use in other northern regions of Siberia for obtaining more geothermal data.
{"title":"Thermal Conductivity of Rocks and Estimates of Heat Flow in the Lena–Anabar Interfluve (Siberian Platform)","authors":"A. Duchkov, D. Ayunov, P. Yan, A. Sivtsev, L. S. Sokolova","doi":"10.2113/rgg20224518","DOIUrl":"https://doi.org/10.2113/rgg20224518","url":null,"abstract":"\u0000 ––We present results of measurements of the physical properties (thermal conductivity, porosity, permeability, and density) of 65 air-dry sedimentary-rock samples from the cores of six deep wells drilled in the Lena–Anabar interfluve. The rocks are compact low-porosity, almost impermeable siltstones, sandstones, and dolomites mainly of Paleozoic and Precambrian ages. Correlations of thermal conductivity with porosity and bulk density have been established. The available information about the thermal conductivity of rocks as well as the production thermograms recorded after drilling made it possible to estimate the geothermal gradient and heat flow (q) for the Ust’-Olenekskaya-2370, Charchykskaya-1, Khastakhskaya-930, and D’yappal’skaya-1 wells. The gradient was calculated from the temperature values at the lower boundary of the permafrost (0 ºC) and at the bottom-hole. The determined heat flow varies from 37 to 70 mW/m2. These q estimates are consistent with the available data on the distribution of heat flow in the north of the Siberian Platform. The proposed method for heat flow estimation is worthy of use in other northern regions of Siberia for obtaining more geothermal data.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42510248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Galanin, I. Klimova, I. Khristoforov, Q. Wu, Zhao Ze
—The surface pattern of permafrost area in the Tibetan Plateau, with 15–20 m polygons, resembles the patterned ground of the Arctic periglacial loess plains in northeastern Eurasia and North America. However, unlike the Arctic plains, it consists of semi-stabilized modern sand dunes, up to 2.5–3.0 m high, and U-shaped epigenetic ice wedge casts inherited from an ancient polygonal network on the surface of a 10–12-m terrace of the Yangtze River. The polygonal dunes and the U-shaped sand wedges were studied in the Yangtze head-waters in the vicinity of the high-altitude research station Bei-Lu-Xe. The polygons have desert pavement floors with ventifacts, composed of Late Pleistocene alluvial gravel and debris. The dunes and wedges consist of well sorted quartz-carbonate sand with an average grains size of 2.0–2.2 mm. Ground Penetrating Radar surveys in the area revealed the permafrost table at depths varying from 2 to 4 m below the dunes. The polygonal dunes may have formed by biogenic-aeolian deposition over an ancient system of ice wedges.
{"title":"Periglacial-Aeolian Polygonal Surface Structures in the Tibetan Plateau","authors":"A. Galanin, I. Klimova, I. Khristoforov, Q. Wu, Zhao Ze","doi":"10.2113/rgg20224484","DOIUrl":"https://doi.org/10.2113/rgg20224484","url":null,"abstract":"\u0000 —The surface pattern of permafrost area in the Tibetan Plateau, with 15–20 m polygons, resembles the patterned ground of the Arctic periglacial loess plains in northeastern Eurasia and North America. However, unlike the Arctic plains, it consists of semi-stabilized modern sand dunes, up to 2.5–3.0 m high, and U-shaped epigenetic ice wedge casts inherited from an ancient polygonal network on the surface of a 10–12-m terrace of the Yangtze River. The polygonal dunes and the U-shaped sand wedges were studied in the Yangtze head-waters in the vicinity of the high-altitude research station Bei-Lu-Xe. The polygons have desert pavement floors with ventifacts, composed of Late Pleistocene alluvial gravel and debris. The dunes and wedges consist of well sorted quartz-carbonate sand with an average grains size of 2.0–2.2 mm. Ground Penetrating Radar surveys in the area revealed the permafrost table at depths varying from 2 to 4 m below the dunes. The polygonal dunes may have formed by biogenic-aeolian deposition over an ancient system of ice wedges.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49531632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
—The work considered an integrated approach to the study of deep-lying Riphean strata of the Buolkalakh–Lena region, which have certain prospects in terms of oil and gas potential. The method of revision and synthesis of acoustic and density logs is described in detail using the example of wells drilled in 80–90 for the purpose of correct reference to seismic sections. It has been shown that the Khaipakh, Debengdin, Arymas, Kyutingdinsky, and Sygynakhtakh formations of the Early and Middle Riphean eras overlook the pre-Permian surface in the middle part of the Lena–Anabar trough. The region also developed older Riphean deposits that are not exposed on the Olenek uplift and are not studied by deep drilling. The prospects for the oil and gas content of Riphean strata in the region are mainly associated with carbonate reservoirs formed in the top of the Riphean sequence and cropping out on the pre-Permian erosive surface, the most promising rocks are those constituting large carbonate platforms that were partially eroded and subjected to processes of hypergenesis and karst formation.
{"title":"Detailed Geoseismic Structure of the Riphean Deposits in Buolkalakh–Lena Area Based on Deep Drilling and Seismic Exploration Data","authors":"D. Lezhnin, M. Maslennikov","doi":"10.2113/rgg20234552","DOIUrl":"https://doi.org/10.2113/rgg20234552","url":null,"abstract":"\u0000 —The work considered an integrated approach to the study of deep-lying Riphean strata of the Buolkalakh–Lena region, which have certain prospects in terms of oil and gas potential. The method of revision and synthesis of acoustic and density logs is described in detail using the example of wells drilled in 80–90 for the purpose of correct reference to seismic sections. It has been shown that the Khaipakh, Debengdin, Arymas, Kyutingdinsky, and Sygynakhtakh formations of the Early and Middle Riphean eras overlook the pre-Permian surface in the middle part of the Lena–Anabar trough. The region also developed older Riphean deposits that are not exposed on the Olenek uplift and are not studied by deep drilling. The prospects for the oil and gas content of Riphean strata in the region are mainly associated with carbonate reservoirs formed in the top of the Riphean sequence and cropping out on the pre-Permian erosive surface, the most promising rocks are those constituting large carbonate platforms that were partially eroded and subjected to processes of hypergenesis and karst formation.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41430025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
—Experimental modeling of the interaction of eclogitic and lherzolitic garnets with CO2 fluid was carried out on a multianvil high-pressure apparatus of the “split-sphere” type (BARS) in platinum ampoules with inner graphite capsules, using a buffered high-pressure cell with a hematite container, at a pressure of 6.3 GPa and in the temperature range 950–1550 °C. It has been established that the main interaction processes at 6.3 GPa and 950–1250 °C are partial dissolution, recrystallization, and carbonation of garnet which lead to the formation of magnesian carbonate, kyanite, and coesite, a decrease in Mg contents in the recrystallized garnet, and the formation of carbonate, silicate, and oxide inclusions in it. Under these conditions, crystallization of metastable graphite and growth of diamond on the seed at ≥1250 °C were observed. In the temperature range 1350–1550 °C, the garnet underwent partial dissolution and recrystallization in CO2 fluid; no carbonation took place. These processes were accompanied by a decrease in the portion of the grossular component in the garnet and by the enrichment of the fluid phase with calcium. We have established the indicative characteristics of garnet that interacted with CO2 fluid: zoning, with low contents of CaO and MgO in the rims of crystals relative to the cores, and the presence of carbonate, kyanite, coesite, and CO2 inclusions. The compositions of the produced garnet and carbonates are consistent with the data on these minerals in mantle peridotite and eclogite parageneses and in inclusions in diamonds, which suggests a significant role of metasomatism with the participation of CO2 fluid in the evolution of deep-seated rocks and in the diamond formation. In this experimental research, we have first studied the processes of diamond crystallization and determined the boundary conditions for diamond growth in the system silicate–carbonate–CO2, which simulates natural diamond formation media. In general, the established regularities can be regarded as potential indicators of mantle metasomatism and mineral formation with the participation of CO2 fluid.
{"title":"Experimental Modeling of the Interaction between Garnets of Mantle Parageneses and CO2 Fluid at 6.3 GPa and 950–1550 °C","authors":"I. Novoselov, Y. Palyanov, Y. Bataleva","doi":"10.2113/rgg20224511","DOIUrl":"https://doi.org/10.2113/rgg20224511","url":null,"abstract":"\u0000 —Experimental modeling of the interaction of eclogitic and lherzolitic garnets with CO2 fluid was carried out on a multianvil high-pressure apparatus of the “split-sphere” type (BARS) in platinum ampoules with inner graphite capsules, using a buffered high-pressure cell with a hematite container, at a pressure of 6.3 GPa and in the temperature range 950–1550 °C. It has been established that the main interaction processes at 6.3 GPa and 950–1250 °C are partial dissolution, recrystallization, and carbonation of garnet which lead to the formation of magnesian carbonate, kyanite, and coesite, a decrease in Mg contents in the recrystallized garnet, and the formation of carbonate, silicate, and oxide inclusions in it. Under these conditions, crystallization of metastable graphite and growth of diamond on the seed at ≥1250 °C were observed. In the temperature range 1350–1550 °C, the garnet underwent partial dissolution and recrystallization in CO2 fluid; no carbonation took place. These processes were accompanied by a decrease in the portion of the grossular component in the garnet and by the enrichment of the fluid phase with calcium. We have established the indicative characteristics of garnet that interacted with CO2 fluid: zoning, with low contents of CaO and MgO in the rims of crystals relative to the cores, and the presence of carbonate, kyanite, coesite, and CO2 inclusions. The compositions of the produced garnet and carbonates are consistent with the data on these minerals in mantle peridotite and eclogite parageneses and in inclusions in diamonds, which suggests a significant role of metasomatism with the participation of CO2 fluid in the evolution of deep-seated rocks and in the diamond formation. In this experimental research, we have first studied the processes of diamond crystallization and determined the boundary conditions for diamond growth in the system silicate–carbonate–CO2, which simulates natural diamond formation media. In general, the established regularities can be regarded as potential indicators of mantle metasomatism and mineral formation with the participation of CO2 fluid.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43127221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Vinogradov, D. Metelkin, V. Abashev, V. Vernikovsky, N. Matushkin, N. Mikhaltsov
—We report results of a detailed study of the paleomagnetic record in the sedimentary rocks of the Taseeva Group of the Yenisei Ridge in three typical sections in the lower courses of the Angara, Taseeva and Irkineeva rivers. Our results confirm that the geomagnetic field was in an anomalous state at the Precambrian–Phanerozoic boundary. It is well known that Ediacaran rocks in general have preserved several different paleomagnetic directions that do not conform to the geocentric axial dipole model. For example, Siberian sections display two equally valid groups of paleopoles that cause many debates over the geometry of the geomagnetic field and whether any of the components correspond to its dipole configuration. The paleomagnetic record we studied is unique in that the rocks of the Chistyakovka and Moshakovka formations have captured both these components, which is factual evidence of a synchronous existence of two sources. To explain these findings, we propose an original hypothesis in which the bipolar component that is widely present in the rocks and corresponds to the Madagascar group of paleomagnetic poles is associated to the field of the geocentric axial dipole. The less widespread monopolar component corresponding to the Australian–Antarctic group of poles is reflective of a stationary anomalous source. The recording of this source became possible due to the abrupt decrease in the strength of the virtual dipole moment that probably was at its lowest during the accumulation of the Chistyakovka and Moshakovka formations. The new paleomagnetic pole calculated for the bipolar component – 39.2°N, 61.1°E – plots on the apparent polar wander path for Siberia and can be considered a key determination for the age ~570 Ma.
{"title":"Paleomagnetism of the Taseeva Group (Yenisei Ridge): on the Issue of the Geomagnetic Field Configuration at the Precambrian–Phanerozoic Boundary","authors":"E. Vinogradov, D. Metelkin, V. Abashev, V. Vernikovsky, N. Matushkin, N. Mikhaltsov","doi":"10.2113/rgg20224542","DOIUrl":"https://doi.org/10.2113/rgg20224542","url":null,"abstract":"\u0000 —We report results of a detailed study of the paleomagnetic record in the sedimentary rocks of the Taseeva Group of the Yenisei Ridge in three typical sections in the lower courses of the Angara, Taseeva and Irkineeva rivers. Our results confirm that the geomagnetic field was in an anomalous state at the Precambrian–Phanerozoic boundary. It is well known that Ediacaran rocks in general have preserved several different paleomagnetic directions that do not conform to the geocentric axial dipole model. For example, Siberian sections display two equally valid groups of paleopoles that cause many debates over the geometry of the geomagnetic field and whether any of the components correspond to its dipole configuration. The paleomagnetic record we studied is unique in that the rocks of the Chistyakovka and Moshakovka formations have captured both these components, which is factual evidence of a synchronous existence of two sources. To explain these findings, we propose an original hypothesis in which the bipolar component that is widely present in the rocks and corresponds to the Madagascar group of paleomagnetic poles is associated to the field of the geocentric axial dipole. The less widespread monopolar component corresponding to the Australian–Antarctic group of poles is reflective of a stationary anomalous source. The recording of this source became possible due to the abrupt decrease in the strength of the virtual dipole moment that probably was at its lowest during the accumulation of the Chistyakovka and Moshakovka formations. The new paleomagnetic pole calculated for the bipolar component – 39.2°N, 61.1°E – plots on the apparent polar wander path for Siberia and can be considered a key determination for the age ~570 Ma.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45565486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
—Magnetic field sources are sometimes approximated by magnetic dipoles or current loops. The usefulness of such approximations is not obvious at the initial stage of the study of objects. Investigating them in detail requires volumetric magnetic field sources. In this paper, they are represented by magnetized prisms. Such a model is valid due to the equivalence of current and magnetized objects. As there should be no real magnetization in the core, this property of a virtual prism to generate a magnetic field strength is referred to as virtual or effective magnetization (EM), which is determined for each prism by solving the inverse problem via the adaptive method. Initial data for solving the inverse problem are the Z vector components of the main magnetic field of the IGRF-2005 model in the geocentric coordinate system. Based on the effective magnetization and known formulas, the bulk current distribution, the bulk current density, and the magnetic moments of prisms of a two-layer core model are obtained. Their sum coincides with the magnetic moment of the virtual central dipole of the core, but, as many scientists assumed, the central dipole is not actually distinguished. At the same time, four significant inhomogeneities are identified in the core, which create the Canadian, Siberian-Asian, Australian, and negative South Atlantic global anomalies on the Earth’s surface. Based on the analysis of the results obtained, assumptions are made that the current generating the magnetic field is the motion of a positively weakly charged liquid of the core. Liquid motion is created by the rotation of the Earth and the decelerating gravitational forces of the Moon and the Sun. Arguments are given to support these assumptions. The results are illustrated in figures.
{"title":"A Detailed Model of Magnetic Field Sources of the Earth’s Core Obtained by Solving the Inverse Problem of Magnetometry","authors":"V. Kochnev","doi":"10.2113/rgg20224493","DOIUrl":"https://doi.org/10.2113/rgg20224493","url":null,"abstract":"\u0000 —Magnetic field sources are sometimes approximated by magnetic dipoles or current loops. The usefulness of such approximations is not obvious at the initial stage of the study of objects. Investigating them in detail requires volumetric magnetic field sources. In this paper, they are represented by magnetized prisms. Such a model is valid due to the equivalence of current and magnetized objects. As there should be no real magnetization in the core, this property of a virtual prism to generate a magnetic field strength is referred to as virtual or effective magnetization (EM), which is determined for each prism by solving the inverse problem via the adaptive method. Initial data for solving the inverse problem are the Z vector components of the main magnetic field of the IGRF-2005 model in the geocentric coordinate system. Based on the effective magnetization and known formulas, the bulk current distribution, the bulk current density, and the magnetic moments of prisms of a two-layer core model are obtained. Their sum coincides with the magnetic moment of the virtual central dipole of the core, but, as many scientists assumed, the central dipole is not actually distinguished. At the same time, four significant inhomogeneities are identified in the core, which create the Canadian, Siberian-Asian, Australian, and negative South Atlantic global anomalies on the Earth’s surface. Based on the analysis of the results obtained, assumptions are made that the current generating the magnetic field is the motion of a positively weakly charged liquid of the core. Liquid motion is created by the rotation of the Earth and the decelerating gravitational forces of the Moon and the Sun. Arguments are given to support these assumptions. The results are illustrated in figures.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45131826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
—The paper provides the results of experiments with sediment traps in the deep-water part of the South Basin of Lake Baikal (depth of 1366 m), installed from March 2015 to March 2016 in order to study recent sedimentation within the lake. We present new data on total fluxes of particulate matter and fluxes of biogenic components (SiO2biog, Сorg, and Ntot) at different depths of the water column both for the whole year and for individual periods of the year. Diatom analyses were carried out for all obtained samples. The total flux of sedimentary material averaged 94.9 g/m2/y; the average fluxes of SiO2biog, Сorg, and Ntot were 23.9, 11.6, and 0.94 g/m2/y, respectively. The molar C/N ratio varies from 11 to 21 and indicates a predominance of allochthonous material in almost all samples. Maximum fluxes of sedimentary matter were recorded from 20 June to 20 July 2015. This period corresponds to the bloom of diatoms of the species Synedra acus. This species amounts to >94% of the total diatom content in all samples taken during this year. The recent predominance of Synedra acus in the water column, as well as in the surface bottom sediments of South Baikal, is probably due to the climate warming.
{"title":"Fluxes and Composition of Particulate Matter in the Water Column of South Baikal (between March 2015 and March 2016)","authors":"E. Vologina, M. Sturm, S. S. Vorob’eva","doi":"10.2113/rgg20224476","DOIUrl":"https://doi.org/10.2113/rgg20224476","url":null,"abstract":"\u0000 —The paper provides the results of experiments with sediment traps in the deep-water part of the South Basin of Lake Baikal (depth of 1366 m), installed from March 2015 to March 2016 in order to study recent sedimentation within the lake. We present new data on total fluxes of particulate matter and fluxes of biogenic components (SiO2biog, Сorg, and Ntot) at different depths of the water column both for the whole year and for individual periods of the year. Diatom analyses were carried out for all obtained samples. The total flux of sedimentary material averaged 94.9 g/m2/y; the average fluxes of SiO2biog, Сorg, and Ntot were 23.9, 11.6, and 0.94 g/m2/y, respectively. The molar C/N ratio varies from 11 to 21 and indicates a predominance of allochthonous material in almost all samples. Maximum fluxes of sedimentary matter were recorded from 20 June to 20 July 2015. This period corresponds to the bloom of diatoms of the species Synedra acus. This species amounts to >94% of the total diatom content in all samples taken during this year. The recent predominance of Synedra acus in the water column, as well as in the surface bottom sediments of South Baikal, is probably due to the climate warming.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48616129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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