Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601809
V. G. Bondur, T. N. Chimitdorzhiev, A. V. Dmitriev
Abstract
The geodynamics at the epicenter of the destructive Mw = 6.8 earthquake that occurred in Morocco on September 8, 2023, was studied by the Stacking-InSAR method applied to 801 interferograms based on the Sentinel-1 synthetic aperure radar (SAR) data. Over the period from January 2019 to September 2023, local subsidence of the surface with an average velocity of 1.5 cm/yr was discovered. The maximum velocity obtained in 2023 reached 24 cm/yr in the areas with a developed melioration system located above aquifers. Based on the integrated analysis of variations in the water equivalent thickness measured from the 2000–2023 satellite gravimetric data and the amount of precipitation, the surface subsidence was found to be due to a significant withdrawal of water from aquifers. Assuming similar shapes of isoseists of earthquakes with close epicenters, the isoseists of the earthquakes that occurred in 2014 and 2023 were compared. The data obtained made it possible to identify the expansion of isoseist contours toward the descending surface areas of the 2023 earthquake. This process, along with the tectonic movements of the Eurasian and Nubian plates, is believed to have increased the stress–strain state between two aquifers and finally caused the Mw = 6.8 earthquake in Morocco on September 8, 2023.
{"title":"The Induced Seismicity Effect in Morocco Caused by a Reduced Aquifers Volume according to Stacking-InSAR Method and Gravimetric Data","authors":"V. G. Bondur, T. N. Chimitdorzhiev, A. V. Dmitriev","doi":"10.1134/s1028334x24601809","DOIUrl":"https://doi.org/10.1134/s1028334x24601809","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The geodynamics at the epicenter of the destructive <i>M</i>w = 6.8 earthquake that occurred in Morocco on September 8, 2023, was studied by the Stacking-InSAR method applied to 801 interferograms based on the Sentinel-1 synthetic aperure radar (SAR) data. Over the period from January 2019 to September 2023, local subsidence of the surface with an average velocity of 1.5 cm/yr was discovered. The maximum velocity obtained in 2023 reached 24 cm/yr in the areas with a developed melioration system located above aquifers. Based on the integrated analysis of variations in the water equivalent thickness measured from the 2000–2023 satellite gravimetric data and the amount of precipitation, the surface subsidence was found to be due to a significant withdrawal of water from aquifers. Assuming similar shapes of isoseists of earthquakes with close epicenters, the isoseists of the earthquakes that occurred in 2014 and 2023 were compared. The data obtained made it possible to identify the expansion of isoseist contours toward the descending surface areas of the 2023 earthquake. This process, along with the tectonic movements of the Eurasian and Nubian plates, is believed to have increased the stress–strain state between two aquifers and finally caused the <i>M</i>w = 6.8 earthquake in Morocco on September 8, 2023.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"108 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883178","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601019
Fayaz Khan, Salman Ahmed Khattak, Waseem Khan, Zaheen Ullah, Fayaz Ali, Quan Wan
Abstract
Radon in drinking water poses radiation-related health risks. Investigating water-related health problems is indispensable, so the goal of the study was to determine how much radon was present in drinking water sources close to and far from the Balakot-Bagh (B-B) fault line (the site of a 7.6-magnitude earthquake in 2005) using the alpha-spectroscopy-based active method RAD-7. The sampling timeframe for the study was from May 16 to August 15, 2020. The radon level of the well water was higher, with an average value of 20.6 BqL–1. These values were 19.5 and 9.3 BqL–1 in spring and surface waters, respectively, although they were 7.7 and 5.5 BqL–1 far away from the fault line, respectively, while in well water its content (activity) was 14.9 BqL–1. The mean values for all water sources far and close from the fault line were 9.3 and 16.5 BqL–1, respectively. The value close to the fault line exceeds the maximum contamination limit recommended in the United States of 11.1 BqL–1, although the values far from the fault line were within limits. The doses determined from the radon levels of spring, well, and surface waters were 0.053, 0.056, and 0.025 mSv per year, respectively, and the mean dose of overall water-borne radon was 0.045 mSv. Based on regional comparisons, the mean radon concentrations in the drinking water sources for this study were higher than in Romania, Turkey, Italy, Poland, and India.
{"title":"Concentrations of Radon in the Water of Balakot-Bagh Fault Line Region, Lesser Himalayas, North Pakistan","authors":"Fayaz Khan, Salman Ahmed Khattak, Waseem Khan, Zaheen Ullah, Fayaz Ali, Quan Wan","doi":"10.1134/s1028334x24601019","DOIUrl":"https://doi.org/10.1134/s1028334x24601019","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Radon in drinking water poses radiation-related health risks. Investigating water-related health problems is indispensable, so the goal of the study was to determine how much radon was present in drinking water sources close to and far from the Balakot-Bagh (B-B) fault line (the site of a 7.6-magnitude earthquake in 2005) using the alpha-spectroscopy-based active method RAD-7. The sampling timeframe for the study was from May 16 to August 15, 2020. The radon level of the well water was higher, with an average value of 20.6 BqL<sup>–1</sup>. These values were 19.5 and 9.3 BqL<sup>–1</sup> in spring and surface waters, respectively, although they were 7.7 and 5.5 BqL<sup>–1</sup> far away from the fault line, respectively, while in well water its content (activity) was 14.9 BqL<sup>–1</sup>. The mean values for all water sources far and close from the fault line were 9.3 and 16.5 BqL<sup>–1</sup>, respectively. The value close to the fault line exceeds the maximum contamination limit recommended in the United States of 11.1 BqL<sup>–1</sup>, although the values far from the fault line were within limits. The doses determined from the radon levels of spring, well, and surface waters were 0.053, 0.056, and 0.025 mSv per year, respectively, and the mean dose of overall water-borne radon was 0.045 mSv. Based on regional comparisons, the mean radon concentrations in the drinking water sources for this study were higher than in Romania, Turkey, Italy, Poland, and India.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"14 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883076","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601755
G. N. Fedotov, S. A. Shoba, D. A. Ushkova, I. V. Gorepekin, O. A. Salimgareeva, A. I. Sukharev
Abstract
Based on earlier study results, the drying process changes the soil properties and, in particular, the characteristic features of a specific soil organic material such as a humic substance (HS). HS is the basis of soil organomineral gels that cover and bind soil particles. When water is removed from soil, gels are subjected to hydrophobization and compression resulting in changes in properties of soil samples. The recovery of soil gels of air-dried samples should reduce the discrepancy between the study data obtained on the soil properties of dried and non-dried soil samples. The study objective is to find ways to recover the structure of soil gels. Samples of six soil types were studied. Vibration viscometry, laser diffractometry, scanning electron microscopy (SEM), photocolorimetry, and conductometry were used in this work. The drying of soil samples increases the size of supramolecular formations (SMFs) in the soil and reduces the soil paste viscosity, a parameter characterizing the structure and the ability of gels to swell. To recover the structure of soil gels, it is proposed to reduce the size of SMFs from HSs to the initial level. SMFs of air-dried samples were separated by soil moistening and subsequent treatment with various temperatures, by ultrasound, and by freezing. Based on the SEM data, heating and ultrasound treatment do not reduce, but enlarge SMFs. Humidification of air-dried soils, exposure to moisture for two weeks, and subsequent freezing bring the paste viscosity of a number of studied soils closer to the condition of samples that were not dried. This process is due to the return of SMFs to size values of the initial soils, as evidenced by the laser diffractometer data on the suspended particle size distribution. Hence, a method for recovery of gel structures in dried soils to the initial state is proposed.
{"title":"Recovery of Organomineral Gel Properties in Dried Soil Samples","authors":"G. N. Fedotov, S. A. Shoba, D. A. Ushkova, I. V. Gorepekin, O. A. Salimgareeva, A. I. Sukharev","doi":"10.1134/s1028334x24601755","DOIUrl":"https://doi.org/10.1134/s1028334x24601755","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Based on earlier study results, the drying process changes the soil properties and, in particular, the characteristic features of a specific soil organic material such as a humic substance (HS). HS is the basis of soil organomineral gels that cover and bind soil particles. When water is removed from soil, gels are subjected to hydrophobization and compression resulting in changes in properties of soil samples. The recovery of soil gels of air-dried samples should reduce the discrepancy between the study data obtained on the soil properties of dried and non-dried soil samples. The study objective is to find ways to recover the structure of soil gels. Samples of six soil types were studied. Vibration viscometry, laser diffractometry, scanning electron microscopy (SEM), photocolorimetry, and conductometry were used in this work. The drying of soil samples increases the size of supramolecular formations (SMFs) in the soil and reduces the soil paste viscosity, a parameter characterizing the structure and the ability of gels to swell. To recover the structure of soil gels, it is proposed to reduce the size of SMFs from HSs to the initial level. SMFs of air-dried samples were separated by soil moistening and subsequent treatment with various temperatures, by ultrasound, and by freezing. Based on the SEM data, heating and ultrasound treatment do not reduce, but enlarge SMFs. Humidification of air-dried soils, exposure to moisture for two weeks, and subsequent freezing bring the paste viscosity of a number of studied soils closer to the condition of samples that were not dried. This process is due to the return of SMFs to size values of the initial soils, as evidenced by the laser diffractometer data on the suspended particle size distribution. Hence, a method for recovery of gel structures in dried soils to the initial state is proposed.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"15 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883175","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x23603681
Zheng Yong-Sheng, Yi Hai-Sheng, Song Wei, Wu Kun-Yu, Yang Yun, Liu Yan-Xin, Ying Min, Wei Zi-Yu
Abstract
Since the Cenozoic, the Earth’s climate has experienced significant transformations, transitioning from a “greenhouse” to the current “icehouse,” where ice sheets presently cover both Antarctica and the Arctic. The thick sediments deposited in the Cenozoic stratigraphy of the Qaidam Basin hold immense significance in unraveling the uplift of the Tibetan Plateau and the paleoclimate evolution of northwestern China. To understand the process of Cenozoic paleoclimate changes in the western Qaidam Basin, the paleoclimate of the Shangganchaigou Formation, Xiaganchaigou Formation, and the Xiayoushashan Formation was reconstructed by analyzing 114 mudstone samples of the Y3 well in the Yauchazi area for major elements and n-alkanes. The results indicate that the Younanshan area of the Qaidam Basin experienced two climatic transitions of wet-dry-relatively wet during the Eocene–Miocene period. The paleoclimatic changes indicated by the results of the correlation indexes of major elements and n-alkanes are consistent and well coupled with global climate change, East Asian monsoon, uplift of the Tibetan Plateau, and the Paratethys retreat event, suggesting that the paleoclimatic environmental changes during the Eocene–Miocene period may have been affected by the combined influence of these several factors.
{"title":"Geochemical Characterization and Paleoclimatic Significance of the Xiaganchaigou Formation–Xiayoushashan Formation in the Youquanzi Area, Qaidam Basin","authors":"Zheng Yong-Sheng, Yi Hai-Sheng, Song Wei, Wu Kun-Yu, Yang Yun, Liu Yan-Xin, Ying Min, Wei Zi-Yu","doi":"10.1134/s1028334x23603681","DOIUrl":"https://doi.org/10.1134/s1028334x23603681","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Since the Cenozoic, the Earth’s climate has experienced significant transformations, transitioning from a “greenhouse” to the current “icehouse,” where ice sheets presently cover both Antarctica and the Arctic. The thick sediments deposited in the Cenozoic stratigraphy of the Qaidam Basin hold immense significance in unraveling the uplift of the Tibetan Plateau and the paleoclimate evolution of northwestern China. To understand the process of Cenozoic paleoclimate changes in the western Qaidam Basin, the paleoclimate of the Shangganchaigou Formation, Xiaganchaigou Formation, and the Xiayoushashan Formation was reconstructed by analyzing 114 mudstone samples of the Y3 well in the Yauchazi area for major elements and <i>n</i>-alkanes. The results indicate that the Younanshan area of the Qaidam Basin experienced two climatic transitions of wet-dry-relatively wet during the Eocene–Miocene period. The paleoclimatic changes indicated by the results of the correlation indexes of major elements and <i>n</i>-alkanes are consistent and well coupled with global climate change, East Asian monsoon, uplift of the Tibetan Plateau, and the Paratethys retreat event, suggesting that the paleoclimatic environmental changes during the Eocene–Miocene period may have been affected by the combined influence of these several factors.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"64 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883068","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601822
G. A. Petrov, A. V. Maslov
Abstract
The Lower Carboniferous volcanoterrigenous sequences of the eastern slope of the Central and Northern Urals are studied. It is shown that these rocks are confined to zones of regional strike–slip faults and formed under transtension conditions. The geochemical parameters of volcanic rocks are similar to those of igneous rocks of both suprasubduction and intraplate settings, which is in agreement with ideas about their formation in the rear of the active continental margin.
{"title":"Formation Conditions of the Lower Carboniferous Volcanoterrigenous Sequences of the Eastern Slope of the Central and Northern Urals","authors":"G. A. Petrov, A. V. Maslov","doi":"10.1134/s1028334x24601822","DOIUrl":"https://doi.org/10.1134/s1028334x24601822","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The Lower Carboniferous volcanoterrigenous sequences of the eastern slope of the Central and Northern Urals are studied. It is shown that these rocks are confined to zones of regional strike–slip faults and formed under transtension conditions. The geochemical parameters of volcanic rocks are similar to those of igneous rocks of both suprasubduction and intraplate settings, which is in agreement with ideas about their formation in the rear of the active continental margin.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"1 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883179","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601743
S. V. Mezhelovskaya, E. V. Asafov, A. N. Koshlyakova, D. P. Tobelko, A. D. Mezhelovsky, A. V. Sobolev
Abstract
Two primary and two subordinate age groups of detrital zircons are distinguished as a result of isotopic–geochronological studies of metasandstones of the Vilenga Formation of the Vetrenyi Belt. A zircon group with an age of 2751 ± 7 Ma was potentially sourced from late granitoids (granodiorite–granite–leucogranites) abundant in the northern part of the Vodlozero domain. No source with an age of 2823 ± 5 Ma has been identified in the adjacent part of the Karelian granite–greenschist area. The zircons with the age of 2874 Ma were sourced from rocks of the BADR (basalt–andesite–dacite–rhyolite) series and adakites of the Sumozero–Kenozero greenschist belt. Previous study of detrital zircon from basal horizons of sections of the Vetrenyi Belt (Toksha Formation), as well as the underlying rocks for the metasandstones (Kozhozero Formation), showed the same main age peaks, which may indicate a stable tectonic setting at the beginning of the Paleoproterozoic and a common provenance of clastic material. Intermediate–felsic rocks with an age of 2940 Ma could also have made a small contribution in the formation of metasandstones.
摘要通过对 Vetrenyi 地带 Vilenga Formation 的元砂岩进行同位素-地质电子学研究，区分出了两个主要和两个次要的锆石碎片年龄组。年龄为 2751 ± 7 Ma 的锆石组可能来自 Vodlozero 地区北部丰富的晚期花岗岩（花岗闪长岩-花岗闪长岩-白花岗岩）。在卡累利阿花岗岩-片麻岩地区的邻近地区，没有发现年龄为 2823 ± 5 Ma 的锆石来源。年龄为 2874 Ma 的锆石来自苏莫泽罗-基诺泽罗绿斜岩带的 BADR（玄武岩-安山岩-黑云母-流纹岩）系列岩石和闪长岩。此前对维特伦伊带（托克沙构造）剖面基底地层以及玄武岩（科佐泽罗构造）底层岩石中的锆英石进行的研究显示出相同的主要年龄峰值，这可能表明在古近纪初有一个稳定的构造环境以及碎屑物质的共同来源。年龄为 2940 Ma 的中熔岩也可能在元砂岩的形成过程中起到了微小的作用。
{"title":"Metasandstones of the Vilenga Formation of the Vetrenyi Belt: Composition, Isotopic–Geochronological Characteristic, and Provenances","authors":"S. V. Mezhelovskaya, E. V. Asafov, A. N. Koshlyakova, D. P. Tobelko, A. D. Mezhelovsky, A. V. Sobolev","doi":"10.1134/s1028334x24601743","DOIUrl":"https://doi.org/10.1134/s1028334x24601743","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Two primary and two subordinate age groups of detrital zircons are distinguished as a result of isotopic–geochronological studies of metasandstones of the Vilenga Formation of the Vetrenyi Belt. A zircon group with an age of 2751 ± 7 Ma was potentially sourced from late granitoids (granodiorite–granite–leucogranites) abundant in the northern part of the Vodlozero domain. No source with an age of 2823 ± 5 Ma has been identified in the adjacent part of the Karelian granite–greenschist area. The zircons with the age of 2874 Ma were sourced from rocks of the BADR (basalt–andesite–dacite–rhyolite) series and adakites of the Sumozero–Kenozero greenschist belt. Previous study of detrital zircon from basal horizons of sections of the Vetrenyi Belt (Toksha Formation), as well as the underlying rocks for the metasandstones (Kozhozero Formation), showed the same main age peaks, which may indicate a stable tectonic setting at the beginning of the Paleoproterozoic and a common provenance of clastic material. Intermediate–felsic rocks with an age of 2940 Ma could also have made a small contribution in the formation of metasandstones.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"21 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883180","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601810
T. M. Skovitina, A. B. Kotov, I. N. Buchnev, V. P. Kovach, S. D. Velikoslavinskii, E. V. Tolmacheva, E. V. Adamskaya, O. V. Bobrovskaya, V. A. Gorovoy
Abstract
The results of U–Th–Pb (LA–ICP–MS) geochronological studies of detrital zircon from the Quaternary sands of the Tokko Basin on the eastern flank of the Baikal Rift Zone are reported. It is shown that their main sources were Mesoarchean tonalite–trondhjemite orthogneisses and metavolcanics, as well as Meso- and Neoarchean syn- and post-collision granitoids of the Charа–Olekma geoblock of the Aldan Shield, which are located near the Tokko Basin. Moreover, the input of sedimentary material into the basin could have occurred during the melting of glaciers that covered the Udokan Ridge to the south and the Kodar Ridge to the north in the Middle–Upper Quaternary.
{"title":"Sandy Sediments in the Tokko Basin of the Baikal Rift Zone: Sources and Provenance Areas","authors":"T. M. Skovitina, A. B. Kotov, I. N. Buchnev, V. P. Kovach, S. D. Velikoslavinskii, E. V. Tolmacheva, E. V. Adamskaya, O. V. Bobrovskaya, V. A. Gorovoy","doi":"10.1134/s1028334x24601810","DOIUrl":"https://doi.org/10.1134/s1028334x24601810","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The results of U–Th–Pb (LA–ICP–MS) geochronological studies of detrital zircon from the Quaternary sands of the Tokko Basin on the eastern flank of the Baikal Rift Zone are reported. It is shown that their main sources were Mesoarchean tonalite–trondhjemite orthogneisses and metavolcanics, as well as Meso- and Neoarchean syn- and post-collision granitoids of the Charа–Olekma geoblock of the Aldan Shield, which are located near the Tokko Basin. Moreover, the input of sedimentary material into the basin could have occurred during the melting of glaciers that covered the Udokan Ridge to the south and the Kodar Ridge to the north in the Middle–Upper Quaternary.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"16 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883177","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}
Pub Date : 2024-05-02DOI: 10.1134/s1028334x24601573
S. G. Skublov, E. N. Terekhov, N. B. Kuznetsov, A. B. Makeyev, L. I. Salimgaraeva
Abstract
New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircons from granites of Bolshoi Tyuters Island (Outer Islands of the Gulf of Finland) are presented. The upper intersection of the discordia (1825 ± 11 Ma) is taken as the age of crystallization of granites cutting through secondary quartzites and thereby determines their youngest age. Subconcordant zircons located in the upper part of the discordia have growth oscillatory zoning and geochemical characteristics of zircons of magmatic origin. The age of the lower intersection of discordia and concordia is about 570 Ma. It is supported by the independent zircon generation represented by black CL domains and rims in magmatic zircons characterized by increased contents of non-formula elements (light REEs, Ca, P, Ti, Nb, etc.), up to anomalous values. The age of the lower intersection of discordia and concordia can be considered as related to the Timan (Ediacaran) or Finnmark (Early Caledonian) thermal activation of the Fennoscandian Shield discovered earlier based on zircons from Kola Group gneisses.
{"title":"U–Pb (SHRIMP-II) Age of Zircon from Granites of Bolshoi Tyuters Island (Gulf of Finland, Russia) and the Problem of the Ediacaran Thermal Event in the Region","authors":"S. G. Skublov, E. N. Terekhov, N. B. Kuznetsov, A. B. Makeyev, L. I. Salimgaraeva","doi":"10.1134/s1028334x24601573","DOIUrl":"https://doi.org/10.1134/s1028334x24601573","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircons from granites of Bolshoi Tyuters Island (Outer Islands of the Gulf of Finland) are presented. The upper intersection of the discordia (1825 ± 11 Ma) is taken as the age of crystallization of granites cutting through secondary quartzites and thereby determines their youngest age. Subconcordant zircons located in the upper part of the discordia have growth oscillatory zoning and geochemical characteristics of zircons of magmatic origin. The age of the lower intersection of discordia and concordia is about 570 Ma. It is supported by the independent zircon generation represented by black CL domains and rims in magmatic zircons characterized by increased contents of non-formula elements (light REEs, Ca, P, Ti, Nb, etc.), up to anomalous values. The age of the lower intersection of discordia and concordia can be considered as related to the Timan (Ediacaran) or Finnmark (Early Caledonian) thermal activation of the Fennoscandian Shield discovered earlier based on zircons from Kola Group gneisses.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"21 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883182","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}
Pub Date : 2024-04-19DOI: 10.1134/s1028334x24601585
A. E. Izokh, V. V. Egorova, R. A. Shelepaev, Ya. Yu. Shelepov
Abstract
Large (up to 4 cm) crystals of euhedral olivine and its intergrowths with clinopyroxene were discovered in the alkali–basaltoid dikes of the Western Sangilen region, Southeastern Tuva. The composition of olivine megacrysts (81–83 at % Mg#, 0.2–0.3 wt % NiO) is drastically different from that of olivines in mantle and gabbroid parageneses. Olivine is a liquidus phase crystallized from an alkaline basaltic melt at a pressure of 10–13 kbar in intermediate magma chambers located at a depth of 34–43 km corresponding to the level of the crust–lithospheric mantle boundary in the Western Sangilen region.
{"title":"Olivine Megacrysts in Alkaline Basalt Dikes of the Western Sangilen Region, Southeastern Tuva","authors":"A. E. Izokh, V. V. Egorova, R. A. Shelepaev, Ya. Yu. Shelepov","doi":"10.1134/s1028334x24601585","DOIUrl":"https://doi.org/10.1134/s1028334x24601585","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Large (up to 4 cm) crystals of euhedral olivine and its intergrowths with clinopyroxene were discovered in the alkali–basaltoid dikes of the Western Sangilen region, Southeastern Tuva. The composition of olivine megacrysts (81–83 at % Mg#, 0.2–0.3 wt % NiO) is drastically different from that of olivines in mantle and gabbroid parageneses. Olivine is a liquidus phase crystallized from an alkaline basaltic melt at a pressure of 10–13 kbar in intermediate magma chambers located at a depth of 34–43 km corresponding to the level of the crust–lithospheric mantle boundary in the Western Sangilen region.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"9 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140629835","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}
Pub Date : 2024-04-19DOI: 10.1134/s1028334x24601500
A. V. Chefranova, K. G. Erofeeva, A. S. Dubenskiy
Abstract
Runoff of terrigenous material involved in the structure of Neogene rare metal–Ti placers of the northeastern side of the Dniepr–Donets Basin (DDB) is determined using lithological and mineralogical methods including U–Pb geochronological and chemical study of detrital zircon. The peculiarities of an assemblage of accessory minerals of heavy fraction of placers, the morphology of individual grains, and the depletion of most zircons in U, Th, Y, and Yb indicate that the material was sourced from chemical weathering mantles, which probably developed after Proterozoic (70%) and Neoarchean (15%) metamorphic rocks. The presence of Paleozoic zircon crystals and a higher U, Th, Y, and Yb content are evidence of the erosion of igneous rocks of the Neoproterozoic–Early Paleozoic trap complexes and Devonian intrusive and volcanosedimentary rocks of the DDB. The involvement of clasts of the above rocks in sedimentary recycling was promoted by the evolution of abundant DDB salt tectonics.
{"title":"Sources of Neogene Rare Metal–Titanium Placers of the Northeastern Wall of the Dnieper–Donets Basin: First Results of U–Pb Geochronological Studies of Detrital Zircon","authors":"A. V. Chefranova, K. G. Erofeeva, A. S. Dubenskiy","doi":"10.1134/s1028334x24601500","DOIUrl":"https://doi.org/10.1134/s1028334x24601500","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Runoff of terrigenous material involved in the structure of Neogene rare metal–Ti placers of the northeastern side of the Dniepr–Donets Basin (DDB) is determined using lithological and mineralogical methods including U–Pb geochronological and chemical study of detrital zircon. The peculiarities of an assemblage of accessory minerals of heavy fraction of placers, the morphology of individual grains, and the depletion of most zircons in U, Th, Y, and Yb indicate that the material was sourced from chemical weathering mantles, which probably developed after Proterozoic (70%) and Neoarchean (15%) metamorphic rocks. The presence of Paleozoic zircon crystals and a higher U, Th, Y, and Yb content are evidence of the erosion of igneous rocks of the Neoproterozoic–Early Paleozoic trap complexes and Devonian intrusive and volcanosedimentary rocks of the DDB. The involvement of clasts of the above rocks in sedimentary recycling was promoted by the evolution of abundant DDB salt tectonics.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":"76 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140625854","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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