Pub Date : 2022-01-01DOI: 10.21638/spbu07.2022.202
E. Perova, A. Zaitsev, J. Spratt, N. Vlasenko, Nataliya Vladimirovna Platonova, O. Bubnova
The Laetoli area in northern Tanzania is an important palaeo-anthropological site, where the oldest footprints of Australopithecus afarensis reside. Aeolian tuffs are the major rock type at Laetoli and they are divided into Lower and Upper Laetolil Beds that were deposited at an interval of 4.36 and 3.63 million years. The Upper Laetolil Beds contain eight layers of air-fall tuffs known as marker tuffs. The Australopithecus afarensis footprints are observed on the surface of the white tuff, which is a part of the Upper Laetolil marker tuff 7, also known as the “Footprint Tuff.” The interpolated age of the marker tuff 7 is 3.66 million years. Two mineral assemblages are distinguished in the Upper Laetolil marker tuffs. The first assemblage consists of primary tuff minerals and includes clinopyroxene (diopside, augite, aegirine-augite), nepheline, melilite (åkermanite and alumoåkermanite), garnet (andradite and schorlomite), magnetite, and others. The second mineral assemblage consists of secondary minerals, montmorillonite, calcite, and phillipsite. They were formed during replacement of the primary minerals, volcanic glass, and ash cementation. Thermodynamic calculations show that the major primary tuff minerals (melilite and nepheline) are stable at variable sodium activity and pH values. Replacement of melilite and nepheline by montmorillonite is caused by a decrease of sodium activity in slightly alkaline, neutral and acidic conditions (рН < 10). Montmorillonite is not present in the altered nephelinitic tuff of the Sadiman volcano (which is considered as a source of the Laetolil Beds) where kaolinite is the major secondary mineral. This is explained by the difference in H2O fugacity with higher lgfH2O values in Sadiman and lower values in Laetoli. Relationships between primary and secondary tuffs minerals on the lgaHCO3 vs pH plot suggest mineral transformation within the Laetolil Beds in slightly acid and neutral con- ditions (рН = 5–7) compared with more alkaline conditions at Sadiman (рН > 10).
{"title":"Thermodynamic analysis of primary and secondary minerals stability in melilite-nephelinite tuff with Australopithecus Afarensis footprints, Laetoli, Tanzania","authors":"E. Perova, A. Zaitsev, J. Spratt, N. Vlasenko, Nataliya Vladimirovna Platonova, O. Bubnova","doi":"10.21638/spbu07.2022.202","DOIUrl":"https://doi.org/10.21638/spbu07.2022.202","url":null,"abstract":"The Laetoli area in northern Tanzania is an important palaeo-anthropological site, where the oldest footprints of Australopithecus afarensis reside. Aeolian tuffs are the major rock type at Laetoli and they are divided into Lower and Upper Laetolil Beds that were deposited at an interval of 4.36 and 3.63 million years. The Upper Laetolil Beds contain eight layers of air-fall tuffs known as marker tuffs. The Australopithecus afarensis footprints are observed on the surface of the white tuff, which is a part of the Upper Laetolil marker tuff 7, also known as the “Footprint Tuff.” The interpolated age of the marker tuff 7 is 3.66 million years. Two mineral assemblages are distinguished in the Upper Laetolil marker tuffs. The first assemblage consists of primary tuff minerals and includes clinopyroxene (diopside, augite, aegirine-augite), nepheline, melilite (åkermanite and alumoåkermanite), garnet (andradite and schorlomite), magnetite, and others. The second mineral assemblage consists of secondary minerals, montmorillonite, calcite, and phillipsite. They were formed during replacement of the primary minerals, volcanic glass, and ash cementation. Thermodynamic calculations show that the major primary tuff minerals (melilite and nepheline) are stable at variable sodium activity and pH values. Replacement of melilite and nepheline by montmorillonite is caused by a decrease of sodium activity in slightly alkaline, neutral and acidic conditions (рН < 10). Montmorillonite is not present in the altered nephelinitic tuff of the Sadiman volcano (which is considered as a source of the Laetolil Beds) where kaolinite is the major secondary mineral. This is explained by the difference in H2O fugacity with higher lgfH2O values in Sadiman and lower values in Laetoli. Relationships between primary and secondary tuffs minerals on the lgaHCO3 vs pH plot suggest mineral transformation within the Laetolil Beds in slightly acid and neutral con- ditions (рН = 5–7) compared with more alkaline conditions at Sadiman (рН > 10).","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74184717","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}
Pub Date : 2022-01-01DOI: 10.21638/spbu07.2022.203
F. Maksimov, A. Petrov, V. Grigoriev, E. Konstantinov, V. Kuznetsov, K. Arslanov, S. Levchenko, N. Karpukhina, A. Starikova, N. Baranova
This article presents new data from geochronological study the lake-bog organic-rich layer from of the “Ilya Prorok” sequence (Upper Volga Basin, Tver Region) that is a one of the reference sections located on the Russian Plain. Ideas concerning the age and climatic conditions of these organic-mineral deposits formation changed significantly over the long history of their study. As a result, the viewpoint about the belonging of this layer to the Likhvin time began to prevail. However, it is still unclear with which marine isotope-oxygen stage (MIS) the Likhvin interglacial can be compared. According to the paleobotanical study of the lake-bog from the Ilya Prorok section, it was confirmed that the lower part of the lake-bog layer can be attributed to the warm phases of the Likhvin interglacial, while its upper half was deposited during the transition to cooling after the interglacial period. For the first time, the radioisotope age of the buried lake-bog deposits of the reference section “Ilya Prorok” have obtained. According to the data of direct 230Th/U dating, the formation of the sequence probably began no earlier than ~ 326–260 Kyr ago. The 230Th/U age of the buried peat bog from its upper half, according to the results of applying the isochronous approximation, can be correlated with the interval ~256–225 Kyr ago. According to these data, the Likhvin deposits were formed no earlier than MIS-9.
{"title":"230Th/U age and paleobotanic description of the organic-rich layer from the “Ilya Prorok” section on the Bolshaya Kosha River (Upper Volga basin)","authors":"F. Maksimov, A. Petrov, V. Grigoriev, E. Konstantinov, V. Kuznetsov, K. Arslanov, S. Levchenko, N. Karpukhina, A. Starikova, N. Baranova","doi":"10.21638/spbu07.2022.203","DOIUrl":"https://doi.org/10.21638/spbu07.2022.203","url":null,"abstract":"This article presents new data from geochronological study the lake-bog organic-rich layer from of the “Ilya Prorok” sequence (Upper Volga Basin, Tver Region) that is a one of the reference sections located on the Russian Plain. Ideas concerning the age and climatic conditions of these organic-mineral deposits formation changed significantly over the long history of their study. As a result, the viewpoint about the belonging of this layer to the Likhvin time began to prevail. However, it is still unclear with which marine isotope-oxygen stage (MIS) the Likhvin interglacial can be compared. According to the paleobotanical study of the lake-bog from the Ilya Prorok section, it was confirmed that the lower part of the lake-bog layer can be attributed to the warm phases of the Likhvin interglacial, while its upper half was deposited during the transition to cooling after the interglacial period. For the first time, the radioisotope age of the buried lake-bog deposits of the reference section “Ilya Prorok” have obtained. According to the data of direct 230Th/U dating, the formation of the sequence probably began no earlier than ~ 326–260 Kyr ago. The 230Th/U age of the buried peat bog from its upper half, according to the results of applying the isochronous approximation, can be correlated with the interval ~256–225 Kyr ago. According to these data, the Likhvin deposits were formed no earlier than MIS-9.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88076056","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}
Pub Date : 2021-06-30DOI: 10.21638/spbu07.2021.304
V. Rasputina, D. Ganyushkin, Dmitrii V. Bantcev, G. Pryakhina, V. Vuglinsky, Stepan S. Svirepov, Nikolai A. Paniutin, D. D. Volkova, Mihail R. Nikolaev, Evgenii V. Siroezhko
There is a reduction in the area of glaciation of mountain massifs as a result of climate warming, which leads to the formation of lake-glacial complexes in areas of glaciation degradation. These complexes are dynamic systems that are rapidly changing over time, therefore, unstable and potentially outburst. Moraine and periglacial lakes outbursts are dangerous hydrological phenomena. As a result of outbursts catastrophic floods and mudflows can form, causing serious damage to the infrastructure of settlements located downstream and often leading to human toll. Therefore, the study of outburst-hazardous lakes is necessary and is an important applied problem associated with forecasting natural hazards. In this paper an the outburst hazard of little-studied moraine and periglacial lakes at the Mongun-Taiga mountain massif (Tyva Republic, Russian Federation) assessment was carried out using the scoring method, supplemented taking into account regional characteristics, using data from remote sensing of the Earth. The performed assessment according to satellite images showed that most of the massif's lakes have a high outburst hazard. Based on the assessment results a group of lakes was selected located in the right branch upstream of the river “Tolaity” for the purpose of a more detailed field survey (hydrological and geophysical studies were carried out). Field work carried out on the selected group of lakes allowed us to correct the performed assessment. In paper the applicability of the method based on comparing field data and data obtained from satellite images was estimated.
{"title":"Outburst hazard of little-studied lakes assessment at the Mongun-Taiga massif","authors":"V. Rasputina, D. Ganyushkin, Dmitrii V. Bantcev, G. Pryakhina, V. Vuglinsky, Stepan S. Svirepov, Nikolai A. Paniutin, D. D. Volkova, Mihail R. Nikolaev, Evgenii V. Siroezhko","doi":"10.21638/spbu07.2021.304","DOIUrl":"https://doi.org/10.21638/spbu07.2021.304","url":null,"abstract":"There is a reduction in the area of glaciation of mountain massifs as a result of climate warming, which leads to the formation of lake-glacial complexes in areas of glaciation degradation. These complexes are dynamic systems that are rapidly changing over time, therefore, unstable and potentially outburst. Moraine and periglacial lakes outbursts are dangerous hydrological phenomena. As a result of outbursts catastrophic floods and mudflows can form, causing serious damage to the infrastructure of settlements located downstream and often leading to human toll. Therefore, the study of outburst-hazardous lakes is necessary and is an important applied problem associated with forecasting natural hazards. In this paper an the outburst hazard of little-studied moraine and periglacial lakes at the Mongun-Taiga mountain massif (Tyva Republic, Russian Federation) assessment was carried out using the scoring method, supplemented taking into account regional characteristics, using data from remote sensing of the Earth. The performed assessment according to satellite images showed that most of the massif's lakes have a high outburst hazard. Based on the assessment results a group of lakes was selected located in the right branch upstream of the river “Tolaity” for the purpose of a more detailed field survey (hydrological and geophysical studies were carried out). Field work carried out on the selected group of lakes allowed us to correct the performed assessment. In paper the applicability of the method based on comparing field data and data obtained from satellite images was estimated.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85165880","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}
Pub Date : 2021-06-30DOI: 10.21638/spbu07.2021.303
A. Mikhaylova, V. Gorochnaya, I. Gumenyuk, Angelina P. Plotnikova, Andrey Sergeevich Mikhaylov
The coastal regions are increasingly in the focus of contemporary academic research as economically favorable territories with high innovative potential. The coastalization factor gets individual attention, the influence of which is registered in various countries of the world as a tendency of the population and economic activity to concentrate in the coastal zone. However, there is significant heterogeneity between the coastal areas, due to natural and climatic features and affecting their economic development. This paper focuses on assessing the differences in the readiness of the coastal regions of the European part of Russia to the innovation economy, taking into account their geographical location (northern, northwestern, southern). The study is conducted at the level of municipalities across 6 regions of Russia: Murmansk, Arkhangelsk, Leningrad, Kaliningrad, Rostov regions, and Krasnodar Krai. The research methodology included an assessment of 4 most important components of an innovative economy: human capital, business environment, knowledge production, and technological equipment. The results of the study showed a high degree of spatial divergence in terms of the level of readiness for the development of an innovative economy both between the regions of the sample and within them in the inter-municipal context. It is revealed that the concentration of innovative potential within the coastal region is largely the result of the cross-influence of the agglomeration and the coastalization factors. In the case of their complementary influence on coastal municipalities, the latter are characterized by a relatively higher level of readiness for the development of an innovative economy than inland ones. This is true for both the northern, northwestern, and southern coastal regions of the European part of Russia.
{"title":"Does the coastal location of municipalities influence their innovation development?","authors":"A. Mikhaylova, V. Gorochnaya, I. Gumenyuk, Angelina P. Plotnikova, Andrey Sergeevich Mikhaylov","doi":"10.21638/spbu07.2021.303","DOIUrl":"https://doi.org/10.21638/spbu07.2021.303","url":null,"abstract":"The coastal regions are increasingly in the focus of contemporary academic research as economically favorable territories with high innovative potential. The coastalization factor gets individual attention, the influence of which is registered in various countries of the world as a tendency of the population and economic activity to concentrate in the coastal zone. However, there is significant heterogeneity between the coastal areas, due to natural and climatic features and affecting their economic development. This paper focuses on assessing the differences in the readiness of the coastal regions of the European part of Russia to the innovation economy, taking into account their geographical location (northern, northwestern, southern). The study is conducted at the level of municipalities across 6 regions of Russia: Murmansk, Arkhangelsk, Leningrad, Kaliningrad, Rostov regions, and Krasnodar Krai. The research methodology included an assessment of 4 most important components of an innovative economy: human capital, business environment, knowledge production, and technological equipment. The results of the study showed a high degree of spatial divergence in terms of the level of readiness for the development of an innovative economy both between the regions of the sample and within them in the inter-municipal context. It is revealed that the concentration of innovative potential within the coastal region is largely the result of the cross-influence of the agglomeration and the coastalization factors. In the case of their complementary influence on coastal municipalities, the latter are characterized by a relatively higher level of readiness for the development of an innovative economy than inland ones. This is true for both the northern, northwestern, and southern coastal regions of the European part of Russia.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72579998","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}
Pub Date : 2021-06-17DOI: 10.21638/spbu07.2021.305
M. Rogov, Julia N. Savelieva, O. V. Shurekova, AO “Geologorazvedka”
The results of integrate biostratigraphic study of Upper Jurassic deposits of the clay pit near the village of Valy (Syzran district, Samara region) are presented. For the first time a bed-by-bed description was made and the subdivision of the section into zones, subzones and biohorizons by ammonites was established. Bauhini and Kitchini zones (Bayi subzone) are established in the Lower Kimeridgian, while Upper Kimmeridgian is represented by Autissiodorensis zone only. In the Lower Volgian Sokolovi and Pseudoscythica zones were recognized, while the Middle Volgian is represented by the Panderi zone. The age of the regionally developed unconformity at the base of the Trazovo Formation has been clarified. As in the sections located to the south from studied section, this unconformity is located in the base of the Autissiodorensis zone, overlying different Oxfordian and lower Kimmeridgian. For the first time for Kimmeridgian of Central Russia in the marlstone band of the Kitchini zone (bayi biohorizon) solitary corals conditionally attributed to the genus Trochocyathus were found. Along with corals other warm-water taxa (belemnites Hibolithes, rare ammonites Taramelliceras) were found in the same bed, suggesting deposition of this bed during the short-time warming event. 6 biostratigraphic units (zone and beds with fauna) were recognized by ostracods, along with 2 dinocyst-based units (assemblage and zone) which are compared with the stratigraphic subdivisions by these groups, previously proposed for the Kimeridgian and Volgian stages of the Russian Platform. The paleo-ecological analysis has allowed to assume, that sediments have accumulated in the conditions of warm shallow eutrophic basin with depth to 50 m, with gradual increase of eutrophy through time. At some levels, short-term episodes of severe shallowing or freshening are recorded by ostracods.
{"title":"Biostratigraphy of Upper Jurassic of the Valy clay pit (Samarskaya Luka) by ammonites, ostracods and dinocysts","authors":"M. Rogov, Julia N. Savelieva, O. V. Shurekova, AO “Geologorazvedka”","doi":"10.21638/spbu07.2021.305","DOIUrl":"https://doi.org/10.21638/spbu07.2021.305","url":null,"abstract":"The results of integrate biostratigraphic study of Upper Jurassic deposits of the clay pit near the village of Valy (Syzran district, Samara region) are presented. For the first time a bed-by-bed description was made and the subdivision of the section into zones, subzones and biohorizons by ammonites was established. Bauhini and Kitchini zones (Bayi subzone) are established in the Lower Kimeridgian, while Upper Kimmeridgian is represented by Autissiodorensis zone only. In the Lower Volgian Sokolovi and Pseudoscythica zones were recognized, while the Middle Volgian is represented by the Panderi zone. The age of the regionally developed unconformity at the base of the Trazovo Formation has been clarified. As in the sections located to the south from studied section, this unconformity is located in the base of the Autissiodorensis zone, overlying different Oxfordian and lower Kimmeridgian. For the first time for Kimmeridgian of Central Russia in the marlstone band of the Kitchini zone (bayi biohorizon) solitary corals conditionally attributed to the genus Trochocyathus were found. Along with corals other warm-water taxa (belemnites Hibolithes, rare ammonites Taramelliceras) were found in the same bed, suggesting deposition of this bed during the short-time warming event. 6 biostratigraphic units (zone and beds with fauna) were recognized by ostracods, along with 2 dinocyst-based units (assemblage and zone) which are compared with the stratigraphic subdivisions by these groups, previously proposed for the Kimeridgian and Volgian stages of the Russian Platform. The paleo-ecological analysis has allowed to assume, that sediments have accumulated in the conditions of warm shallow eutrophic basin with depth to 50 m, with gradual increase of eutrophy through time. At some levels, short-term episodes of severe shallowing or freshening are recorded by ostracods.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89758794","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}
Pub Date : 2021-06-17DOI: 10.21638/spbu07.2021.309
M. Petrova, S. Petrov, Mihail Iu. Kurapov
The Balagychan-Sugoi (Omsukchan) riftogeneous depression is described by different authors both as a part of Okhotsk-Chukotka volcanic belt (OCVB) and as a separate structure. The unique Dukat gold and silver deposit and a lot of others ore deposits including rare-metal, such as Arylah, Lunnoe, Askold, Mechta, Tidid, Krasin, are associated with this structure. All mentioned objects are located in the south part of the depression and from this point of view are connected with OCVB structure. Evolution of the Balygychan-Sugoi depression is closely related to the stages of magmatic evolution of the region. In the article, these stages are characterized based on the data form intrusion bodies located in the northern part (Naygain depression). This part is the most outlying from the OCVB and less investigated. For the first time, the U-Pb zircon and baddeleyite dating and the description of petrographic and geochemical composition have been carried out for Mandychan gabbro-diorite and Nayahan gabbro leucogranite intrusion complexes from the northern part of the depression and for Omsukchan leucogranite complex. The Late Jurassic – Early Cretaceous intrusions of the Mandychansk complex dated as 143-139 Ma mark the beginning of the rift depression formation. Intrusion of granitoids of the Nayahan and Omsukchan complexes dated as 84-85 Ma and 81-82 Ma correspondently is related with new stage of magmatic activity, synchronous to OCVB formation. The petrographic and geochemical compositions of these granitoids indicate their belonging to the I-type granites, which are typical for extension environments, whereas leucogranites of the Omsukchan complex have some features corresponding to the A-type granites.
{"title":"New data concerning the age and composition of intrusion complexes of the northern part of Balygychan-Sugoi rift depression (North-Eastern Russia)","authors":"M. Petrova, S. Petrov, Mihail Iu. Kurapov","doi":"10.21638/spbu07.2021.309","DOIUrl":"https://doi.org/10.21638/spbu07.2021.309","url":null,"abstract":"The Balagychan-Sugoi (Omsukchan) riftogeneous depression is described by different authors both as a part of Okhotsk-Chukotka volcanic belt (OCVB) and as a separate structure. The unique Dukat gold and silver deposit and a lot of others ore deposits including rare-metal, such as Arylah, Lunnoe, Askold, Mechta, Tidid, Krasin, are associated with this structure. All mentioned objects are located in the south part of the depression and from this point of view are connected with OCVB structure. Evolution of the Balygychan-Sugoi depression is closely related to the stages of magmatic evolution of the region. In the article, these stages are characterized based on the data form intrusion bodies located in the northern part (Naygain depression). This part is the most outlying from the OCVB and less investigated. For the first time, the U-Pb zircon and baddeleyite dating and the description of petrographic and geochemical composition have been carried out for Mandychan gabbro-diorite and Nayahan gabbro leucogranite intrusion complexes from the northern part of the depression and for Omsukchan leucogranite complex. The Late Jurassic – Early Cretaceous intrusions of the Mandychansk complex dated as 143-139 Ma mark the beginning of the rift depression formation. Intrusion of granitoids of the Nayahan and Omsukchan complexes dated as 84-85 Ma and 81-82 Ma correspondently is related with new stage of magmatic activity, synchronous to OCVB formation. The petrographic and geochemical compositions of these granitoids indicate their belonging to the I-type granites, which are typical for extension environments, whereas leucogranites of the Omsukchan complex have some features corresponding to the A-type granites.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72460799","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}
Pub Date : 2021-01-01DOI: 10.21638/spbu07.2021.401
A. Savelev, Anna A. Pazukhina, A. Pasenko
The interval of ~ 1000 - ~ 900 Ma is one of the key ones in the history of the evolution of the Siberian Platform. At this time, the formation of the neoproterozoic supercontinent Rodinia took place, which undoubtedly found its reflection in the geological annals of Siberia. A reflection of the kinematics of the Siberian platform is its apparent pole wander path (APWP), the development of which will help to clarify the geodynamic in which the platform was at the beginning of the Neoproterozoic. However, not many objects of this age are known within the Siberian Platform, suitable for performing paleomagnetic determinations. The consequence of this is a very limited number of existing reliable poles, obtained either from sedimentary rocks with very imprecise age limits, or from rocks of the Yenisei Ridge and Taimyr with an ambiguous structural position. This paper presents the results of paleomagnetic studies of the Proterozoic igneous rocks of the Sette-Daban complex of the southern Verkhoyansk region, the formation of which took place ~ 1000-970 Ma ago. Detailed thermal magnetic cleaning made it possible to reveal the high-temperature (HT) characteristic component in a significant part of the samples. It has maximum unblocking temperatures of about 580 ° C, lying in the region of the Curie point of magnetite. The average direction of the characteristic component for the sills sampled in the valley of the Yudoma, coincides with the direction obtained earlier on the same bodies. The calculated paleomagnetic pole for the intrusive bodies of the Sette-Daban magmatic complex (Plat = 5.8 °, Plong = 182.9 °, dp / dm = 9.0 ° / 14.4 °) confirms and refines the previously obtained pole for the rocks of this complex, and also indicates that Siberia in the range of ~ 970-1000 Ma was located in the northern hemisphere in tropical latitudes (~ 26 ° N). The analysis of the available geochronological and geochemical data, coupled with new paleomagnetic data, made it possible to clarify the age of the Sette-Daban magmatic event and limit it within ~ 970-1000 Ma.
{"title":"Paleomagnetism of the Sette-Daban Meso-Neoproterozoic magmatic complex of the southeastern margin of the Siberian platform","authors":"A. Savelev, Anna A. Pazukhina, A. Pasenko","doi":"10.21638/spbu07.2021.401","DOIUrl":"https://doi.org/10.21638/spbu07.2021.401","url":null,"abstract":"The interval of ~ 1000 - ~ 900 Ma is one of the key ones in the history of the evolution of the Siberian Platform. At this time, the formation of the neoproterozoic supercontinent Rodinia took place, which undoubtedly found its reflection in the geological annals of Siberia. A reflection of the kinematics of the Siberian platform is its apparent pole wander path (APWP), the development of which will help to clarify the geodynamic in which the platform was at the beginning of the Neoproterozoic. However, not many objects of this age are known within the Siberian Platform, suitable for performing paleomagnetic determinations. The consequence of this is a very limited number of existing reliable poles, obtained either from sedimentary rocks with very imprecise age limits, or from rocks of the Yenisei Ridge and Taimyr with an ambiguous structural position. This paper presents the results of paleomagnetic studies of the Proterozoic igneous rocks of the Sette-Daban complex of the southern Verkhoyansk region, the formation of which took place ~ 1000-970 Ma ago. Detailed thermal magnetic cleaning made it possible to reveal the high-temperature (HT) characteristic component in a significant part of the samples. It has maximum unblocking temperatures of about 580 ° C, lying in the region of the Curie point of magnetite. The average direction of the characteristic component for the sills sampled in the valley of the Yudoma, coincides with the direction obtained earlier on the same bodies. The calculated paleomagnetic pole for the intrusive bodies of the Sette-Daban magmatic complex (Plat = 5.8 °, Plong = 182.9 °, dp / dm = 9.0 ° / 14.4 °) confirms and refines the previously obtained pole for the rocks of this complex, and also indicates that Siberia in the range of ~ 970-1000 Ma was located in the northern hemisphere in tropical latitudes (~ 26 ° N). The analysis of the available geochronological and geochemical data, coupled with new paleomagnetic data, made it possible to clarify the age of the Sette-Daban magmatic event and limit it within ~ 970-1000 Ma.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75747844","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}
Pub Date : 2021-01-01DOI: 10.21638/spbu07.2021.307
S. Baltybaev, G. V. Ovchinnikova, A. Kuznetsov, I. Vasilieva, N. Rizvanova, I. Alekseev, P. A. Kirillova
In a study based on Pb isotopes, it has been shown that the formation of gold-sulfide mineralization in the Early Proterozoic gabbros of the Northern Ladoga region is associated with different tectonic phases. This conclusion is based on a comparative study of isotopic data for feldspars and lead sulfides in two Early Proterozoic intrusions; Velimäki and Alattu-Päkylä. The investigated intrusions have similar geological settings at the junction of the Svecofennian accretionary complex and the Karelian craton. Both massifs are characterized by manifestations of noble metal sulfide mineralization associated with zones of local shear deformations. The formation of the studied ore massifs is attributed to the Svecofennian and Caledonian tectonic stages. Feldspars of Velimäki intrusion have parameters and model age of Pb significantly older than U-Pb age of zircon (1.9 Ga), although they correspond to the Svecofennian time of magmatic crystallization of gabbro and clinopyroxenites, while sulfide pyrite-pyrrhotite mineralization is associated with gold in these rocks with the Caledonian stage of fluid-thermal processing of the Early Proterozoic magmatic mineral paracenteses. Feldspars and sulfides of the Alattu-Päkylä intrusion have similar lead isotopic parameters and Pb model age (~ 2 Ga), also somewhat older than the U-Pb age of zircon, but at the same time indicating the formation of rock-forming and ore sulfide associations with gold during the Svecofennian (Early Proterozoic) plutonic and tectonic-thermal events. The source of lead sulfides of the Velimäki massif is characterized by the parameters of the upper crust with high µ2 = 238U / 204Pb, while the µ2 parameter of the minerals of the Alattu-Päkylä massif is slightly lower, which indicates the participation of the mantle-lower crustal reservoir material in the formation of magma.
{"title":"Two stage of gold-bearing sulfide ores of early Proterozoic gabbroids in the north Ladoga area","authors":"S. Baltybaev, G. V. Ovchinnikova, A. Kuznetsov, I. Vasilieva, N. Rizvanova, I. Alekseev, P. A. Kirillova","doi":"10.21638/spbu07.2021.307","DOIUrl":"https://doi.org/10.21638/spbu07.2021.307","url":null,"abstract":"In a study based on Pb isotopes, it has been shown that the formation of gold-sulfide mineralization in the Early Proterozoic gabbros of the Northern Ladoga region is associated with different tectonic phases. This conclusion is based on a comparative study of isotopic data for feldspars and lead sulfides in two Early Proterozoic intrusions; Velimäki and Alattu-Päkylä. The investigated intrusions have similar geological settings at the junction of the Svecofennian accretionary complex and the Karelian craton. Both massifs are characterized by manifestations of noble metal sulfide mineralization associated with zones of local shear deformations. The formation of the studied ore massifs is attributed to the Svecofennian and Caledonian tectonic stages. Feldspars of Velimäki intrusion have parameters and model age of Pb significantly older than U-Pb age of zircon (1.9 Ga), although they correspond to the Svecofennian time of magmatic crystallization of gabbro and clinopyroxenites, while sulfide pyrite-pyrrhotite mineralization is associated with gold in these rocks with the Caledonian stage of fluid-thermal processing of the Early Proterozoic magmatic mineral paracenteses. Feldspars and sulfides of the Alattu-Päkylä intrusion have similar lead isotopic parameters and Pb model age (~ 2 Ga), also somewhat older than the U-Pb age of zircon, but at the same time indicating the formation of rock-forming and ore sulfide associations with gold during the Svecofennian (Early Proterozoic) plutonic and tectonic-thermal events. The source of lead sulfides of the Velimäki massif is characterized by the parameters of the upper crust with high µ2 = 238U / 204Pb, while the µ2 parameter of the minerals of the Alattu-Päkylä massif is slightly lower, which indicates the participation of the mantle-lower crustal reservoir material in the formation of magma.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89261389","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}
Pub Date : 2021-01-01DOI: 10.21638/spbu07.2021.408
E. Zakharchuk, V. N. Sukhachev, N. Tikhonova
The characteristics of storm surges in different regions of the Gulf of Finland in the second half of the XX and the beginning of the XXI centuries were investigated on the basis of tide gauge measurements of sea level, instrumental observations of the wind and data from the reanalysis of meteorological fields. A criterion for identifying storm surges, taking into account spatial changes in their intensity, is proposed. The results indicate that depending on the year and the location of the station, the number of storm surges varies in the Gulf of Finland in a wide range: from 0 - 1 to 16 - 52 cases per year. The average duration of storm surges varies from 6.7 to 9.0 hours, and the maximum reaches 26 to 96 hours. Shown that in recent decades, in most regions, there has been a tendency towards a decrease in the number of storm surges, their dispersion and sea level maximum. The distributions of the probabilities of wind and atmospheric pressure during storm surges are given. Estimates of two-dimensional probability densities indicate that during storm surges, winds blowing from the west and southwest with speeds of 4-13 m / s are most likely. At the northern coast and at the top of the bay, the most probable values of atmospheric pressure during storm surges are 995 hPa. On the southern coast of the Gulf of Finland, atmospheric pressure values of 1005 - 1015 hPa are most likely. The results obtained indicate that the atmospheric pressure over the Gulf of Finland during storm surges is not very low. This is due to the fact that the trajectories of the centers of cyclones causing storm surges pass north of the Gulf of Finland. Analysis of meteorological information also showed the presence of significant negative trends in interannual variations in the dispersion of the horizontal atmospheric pressure gradient, average values and maximums of wind speed. It is concluded that the revealed changes in the characteristics of storm surges are associated with a decrease in the intensity of cyclogenesis in the atmosphere over the Baltic Sea in recent decades.
{"title":"Storm surges in the Gulf of Finland of the Baltic Sea","authors":"E. Zakharchuk, V. N. Sukhachev, N. Tikhonova","doi":"10.21638/spbu07.2021.408","DOIUrl":"https://doi.org/10.21638/spbu07.2021.408","url":null,"abstract":"The characteristics of storm surges in different regions of the Gulf of Finland in the second half of the XX and the beginning of the XXI centuries were investigated on the basis of tide gauge measurements of sea level, instrumental observations of the wind and data from the reanalysis of meteorological fields. A criterion for identifying storm surges, taking into account spatial changes in their intensity, is proposed. The results indicate that depending on the year and the location of the station, the number of storm surges varies in the Gulf of Finland in a wide range: from 0 - 1 to 16 - 52 cases per year. The average duration of storm surges varies from 6.7 to 9.0 hours, and the maximum reaches 26 to 96 hours. Shown that in recent decades, in most regions, there has been a tendency towards a decrease in the number of storm surges, their dispersion and sea level maximum. The distributions of the probabilities of wind and atmospheric pressure during storm surges are given. Estimates of two-dimensional probability densities indicate that during storm surges, winds blowing from the west and southwest with speeds of 4-13 m / s are most likely. At the northern coast and at the top of the bay, the most probable values of atmospheric pressure during storm surges are 995 hPa. On the southern coast of the Gulf of Finland, atmospheric pressure values of 1005 - 1015 hPa are most likely. The results obtained indicate that the atmospheric pressure over the Gulf of Finland during storm surges is not very low. This is due to the fact that the trajectories of the centers of cyclones causing storm surges pass north of the Gulf of Finland. Analysis of meteorological information also showed the presence of significant negative trends in interannual variations in the dispersion of the horizontal atmospheric pressure gradient, average values and maximums of wind speed. It is concluded that the revealed changes in the characteristics of storm surges are associated with a decrease in the intensity of cyclogenesis in the atmosphere over the Baltic Sea in recent decades.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90925305","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}
Pub Date : 2021-01-01DOI: 10.21638/spbu07.2021.308
B. Gerasimov, R. Zhelonkin, Makhmutyan G. Mukhamedyarov
Typomorphic features of placer gold of conglomerates of the Ortokinskaya formation of the Early Permian age (P1or) of the Sololiy Uplift of the Olenek High and modern channel alluvium of the Ortoku Eekit river, which drains these deposits, are studied. It is found that extremely heterogeneous composition and complex inner structure are typical features of the vast majority of gold of the Permian conglomerates. There are several stages of different fineness (from 251‰ to 999‰) within a single gold particle, as a result, gold has a mosaic-block inner structure. It is proposed that such heterogeneity is formed due to epigenetic transformations of primary medium-grade gold in an intermediate reservoir of the Permian age, and also under influence of superposed hydrothermal mineralization with low-grade gold, related to the processes of the Mesozoic tectonomagmatic activation. The latter is indicated by the discovery of impregnated gold-sulfide mineralization in the Permian conglomerates. Ore mineralization is represented by gold, silver, pyrite, sphalerite, chalcopyrite, galena, argentite, native tin, and barite. Association mineralization to thin tectonic zones of conglomerate fragmentation, suggests that superposed gold-sulfide hydrothermal mineralization of impregnated type was formed as a result of manifestations of the Mesozoic tectonomagmatic activation, when gold-bearing hydrothermal solutions migrated in faults. It is determined that auriferous conglomerates of the Ortokinskaya formation of the Permian age were major sources of placer gold of modern alluvium in the studied part of the Ortoku Eekit.
{"title":"Mineralogical features of gold of the Permian conglomerates of the Sololiy uplift of the Olenek high (Northeastern Siberian platform)","authors":"B. Gerasimov, R. Zhelonkin, Makhmutyan G. Mukhamedyarov","doi":"10.21638/spbu07.2021.308","DOIUrl":"https://doi.org/10.21638/spbu07.2021.308","url":null,"abstract":"Typomorphic features of placer gold of conglomerates of the Ortokinskaya formation of the Early Permian age (P1or) of the Sololiy Uplift of the Olenek High and modern channel alluvium of the Ortoku Eekit river, which drains these deposits, are studied. It is found that extremely heterogeneous composition and complex inner structure are typical features of the vast majority of gold of the Permian conglomerates. There are several stages of different fineness (from 251‰ to 999‰) within a single gold particle, as a result, gold has a mosaic-block inner structure. It is proposed that such heterogeneity is formed due to epigenetic transformations of primary medium-grade gold in an intermediate reservoir of the Permian age, and also under influence of superposed hydrothermal mineralization with low-grade gold, related to the processes of the Mesozoic tectonomagmatic activation. The latter is indicated by the discovery of impregnated gold-sulfide mineralization in the Permian conglomerates. Ore mineralization is represented by gold, silver, pyrite, sphalerite, chalcopyrite, galena, argentite, native tin, and barite. Association mineralization to thin tectonic zones of conglomerate fragmentation, suggests that superposed gold-sulfide hydrothermal mineralization of impregnated type was formed as a result of manifestations of the Mesozoic tectonomagmatic activation, when gold-bearing hydrothermal solutions migrated in faults. It is determined that auriferous conglomerates of the Ortokinskaya formation of the Permian age were major sources of placer gold of modern alluvium in the studied part of the Ortoku Eekit.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86631038","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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