Pub Date : 2024-08-11DOI: 10.1134/s1028334x2460316x
E. V. Bezrukova, S. A. Reshetova, N. V. Kulagina, A. A. Shchetnikov, I. A. Filinov, M. I. Kuzmin
Abstract
The results of studying the bottom sediments of meromictic Shira Lake, located in the northern part of the Minusinsk Basin, are presented. The sediments are represented by varves, annual layered series, which make it possible to reconstruct the history of the regional natural environment with a high resolution. The age model is based on seven 14C dates. The proposed new palynological record from the upper part of the Shira-2021-II-1 core extends the previous record by 530 years, providing the reconstruction of the regional natural environment for the past 2980 calibrated years with an average resolution of 21 years. The reconstructions show a humid regional climate 2980–2650 BP, with the climate of the basin itself being more arid, providing the existence of steppe and meadow–steppe assemblages around Shira Lake for the past 2980 years. The trend of changes in the Artemisia/Chenopodiaceae pollen ratio, considered as an indicator of available moisture for plants, suggests a slight increase in the moisture level in the Minusinsk Basin in 2980‒70 BP and a noticeable decrease in the past 70 years. However, the increase was interrupted by short-term intervals of increased climate aridization. The reconstructions have shown that changes in vegetation around Shira Lake in the Late Holocene were mainly caused by large-scale circulation processes that changed the regional moisture balance. The steppe assemblages were the most sensitive to moisture changes on a decadal scale. Like the previous pollen record, the new one does not have clear pollen indicators of anthropogenic influence on vegetation. Only a noticeable increase in the birch pollen content in the past 50 years may indicate planting of greenery around the resort areas.
{"title":"Vegetation and Climate in the North of the Minusinsk Basin in the Late Holocene: A Record from Shira Lake Resolved by Decade","authors":"E. V. Bezrukova, S. A. Reshetova, N. V. Kulagina, A. A. Shchetnikov, I. A. Filinov, M. I. Kuzmin","doi":"10.1134/s1028334x2460316x","DOIUrl":"https://doi.org/10.1134/s1028334x2460316x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The results of studying the bottom sediments of meromictic Shira Lake, located in the northern part of the Minusinsk Basin, are presented. The sediments are represented by varves, annual layered series, which make it possible to reconstruct the history of the regional natural environment with a high resolution. The age model is based on seven <sup>14</sup>C dates. The proposed new palynological record from the upper part of the Shira-2021-II-1 core extends the previous record by 530 years, providing the reconstruction of the regional natural environment for the past 2980 calibrated years with an average resolution of 21 years. The reconstructions show a humid regional climate 2980–2650 BP, with the climate of the basin itself being more arid, providing the existence of steppe and meadow–steppe assemblages around Shira Lake for the past 2980 years. The trend of changes in the <i>Artemisia/</i>Chenopodiaceae pollen ratio, considered as an indicator of available moisture for plants, suggests a slight increase in the moisture level in the Minusinsk Basin in 2980‒70 BP and a noticeable decrease in the past 70 years. However, the increase was interrupted by short-term intervals of increased climate aridization. The reconstructions have shown that changes in vegetation around Shira Lake in the Late Holocene were mainly caused by large-scale circulation processes that changed the regional moisture balance. The steppe assemblages were the most sensitive to moisture changes on a decadal scale. Like the previous pollen record, the new one does not have clear pollen indicators of anthropogenic influence on vegetation. Only a noticeable increase in the birch pollen content in the past 50 years may indicate planting of greenery around the resort areas.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948944","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 : 2024-08-11DOI: 10.1134/s1028334x24603158
S. A. Reshetova, E. V. Bezrukova, M. I. Kuzmin
Abstract
The study of herbarium materials of the Ephedra dahurica Turcz. collected in the Torey Lakes region in different years has revealed the morphological variability of its pollen grains. An inverse relationship has been established between the development of the number of pseudosulci and plicae (ridge) of pollen grains and the values of temperature and humidity during the growing season. During wet seasons, the plant produces pollen grains with few pseudosulci. The number of pseudosulci increases during dry and cool growing seasons.
{"title":"Variability of Ephedra dahurica Turcz. Pollen as an Indicator of Humidity for the Modern Climate of Southeastern Transbaikalia","authors":"S. A. Reshetova, E. V. Bezrukova, M. I. Kuzmin","doi":"10.1134/s1028334x24603158","DOIUrl":"https://doi.org/10.1134/s1028334x24603158","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The study of herbarium materials of the <i>Ephedra dahurica</i> Turcz. collected in the Torey Lakes region in different years has revealed the morphological variability of its pollen grains. An inverse relationship has been established between the development of the number of pseudosulci and plicae (ridge) of pollen grains and the values of temperature and humidity during the growing season. During wet seasons, the plant produces pollen grains with few pseudosulci. The number of pseudosulci increases during dry and cool growing seasons.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948942","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 : 2024-08-11DOI: 10.1134/s1028334x24602839
V. V. Yarmolyuk, A. M. Kozlovsky, V. M. Savatenkov, E. A. Kudryashova
Abstract
The results of systematic geochronological (K–Ar) studies of rocks of the Dariganga volcanic field (DVF) composed of Late Cenozoic mafic lavas are presented. Four stages of its evolution are distinguished: the Middle–Late Miocene (>10 Ma), Late Miocene–Early Pliocene (7.8–3.5 Ma), Late Pliocene (2.8–2.6 Ma), and Pleistocene (<1.7 Ma). The products of these stages are regularly distributed within the volcanic field. The main volume of eruptions was related to the Late Miocene–Early Pliocene and Pleistocene stages. The northwestern part of the lava field as a lava plateau formed during the Late Miocene–Early Pliocene. The eruptions are related to a local structural depression, which originated under extension accompanying volcanism. The southeastern part of the DVF formed during the Pleistocene volcanic eruption. Volcanism accompanied the formation of the Khukhot-Ein-Nuru Ridge in the Nukut-Daban Uplift and was responsible for the morphological peculiarities of the volcanic cover. A typical feature of it includes the large multicentered shield volcanoes related to the axial zone of the ridge, as well as the elongated valley flows along both slopes. The peculiarities of the formation of the DVF and other volcanic areas of the Late Cenozoic intraplate volcanic province of Central and East Asia are compared. Their consistent evolution indicates that the formation of the DVF was controlled by the same geodynamic mechanisms as the formation of other volcanic areas of the province, namely, by the activity of a small mantle plume.
{"title":"Age of Rocks and Peculiarities of the Formation of the Dariganga Volcanic Field, Southeastern Mongolia","authors":"V. V. Yarmolyuk, A. M. Kozlovsky, V. M. Savatenkov, E. A. Kudryashova","doi":"10.1134/s1028334x24602839","DOIUrl":"https://doi.org/10.1134/s1028334x24602839","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The results of systematic geochronological (K–Ar) studies of rocks of the Dariganga volcanic field (DVF) composed of Late Cenozoic mafic lavas are presented. Four stages of its evolution are distinguished: the Middle–Late Miocene (>10 Ma), Late Miocene–Early Pliocene (7.8–3.5 Ma), Late Pliocene (2.8–2.6 Ma), and Pleistocene (<1.7 Ma). The products of these stages are regularly distributed within the volcanic field. The main volume of eruptions was related to the Late Miocene–Early Pliocene and Pleistocene stages. The northwestern part of the lava field as a lava plateau formed during the Late Miocene–Early Pliocene. The eruptions are related to a local structural depression, which originated under extension accompanying volcanism. The southeastern part of the DVF formed during the Pleistocene volcanic eruption. Volcanism accompanied the formation of the Khukhot-Ein-Nuru Ridge in the Nukut-Daban Uplift and was responsible for the morphological peculiarities of the volcanic cover. A typical feature of it includes the large multicentered shield volcanoes related to the axial zone of the ridge, as well as the elongated valley flows along both slopes. The peculiarities of the formation of the DVF and other volcanic areas of the Late Cenozoic intraplate volcanic province of Central and East Asia are compared. Their consistent evolution indicates that the formation of the DVF was controlled by the same geodynamic mechanisms as the formation of other volcanic areas of the province, namely, by the activity of a small mantle plume.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948941","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 : 2024-08-11DOI: 10.1134/s1028334x24601470
Sevcan Kürüm, Abdullah Sar, Muhammed Yasir Yurt, İsmail Yıldırım
Abstract
This study presents new analytical data for the Ulukale porphyritic dome located within the Neogene Tunceli volcanic rocks, as well as whole rock geochemistry and Sr–Nd isotope data for the Çağlarca radial dykes for the first time. The Ulukale porphyritic dome and the Çağlarca radial dykes, have trachyandesite composition. On trace element diagrams normalized to primitive mantle, samples from the dome and dykes have similar features. Whole-rock geochemistry data for the investigated volcanic rocks indicate they formed from low-degree of partial melting of spinel lherzolite at shallow depths. Accordingly magmatism forming the dome appears to have more acidic composition. Sr–Nd isotope data (εNd(T) value –2.0 and –1.7) for both rock groups indicate a lithospheric subcontinental mantle source. All geochemical data indicate these volcanic rocks had source magma with lherzolitic features which underwent low-degree of partial melting; however, fractional crystallization, magma mixing, contamination in the form of continental crust effects and the effect of subduction-linked sediment melts were shown to be important during magma differentiation. Additionally, all this data shows that these volcanic rocks have the same petrological features as the Tunceli Volcanics, the main product of this magmatism.
{"title":"Petrological Features of Neogene Ulukale Porphyritic Dome and Çağlarca Radial Dykes in the Tunceli Volcanic, Eastern Turkey","authors":"Sevcan Kürüm, Abdullah Sar, Muhammed Yasir Yurt, İsmail Yıldırım","doi":"10.1134/s1028334x24601470","DOIUrl":"https://doi.org/10.1134/s1028334x24601470","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>This study presents new analytical data for the Ulukale porphyritic dome located within the Neogene Tunceli volcanic rocks, as well as whole rock geochemistry and Sr–Nd isotope data for the Çağlarca radial dykes for the first time. The Ulukale porphyritic dome and the Çağlarca radial dykes, have trachyandesite composition. On trace element diagrams normalized to primitive mantle, samples from the dome and dykes have similar features. Whole-rock geochemistry data for the investigated volcanic rocks indicate they formed from low-degree of partial melting of spinel lherzolite at shallow depths. Accordingly magmatism forming the dome appears to have more acidic composition. Sr–Nd isotope data (εNd(<i>T</i>) value –2.0 and –1.7) for both rock groups indicate a lithospheric subcontinental mantle source. All geochemical data indicate these volcanic rocks had source magma with lherzolitic features which underwent low-degree of partial melting; however, fractional crystallization, magma mixing, contamination in the form of continental crust effects and the effect of subduction-linked sediment melts were shown to be important during magma differentiation. Additionally, all this data shows that these volcanic rocks have the same petrological features as the Tunceli Volcanics, the main product of this magmatism.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969824","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 : 2024-08-11DOI: 10.1134/s1028334x24602888
N. E. Kosheleva, N. B. Zhaxylykov, Yu. A. Zavgorodnyaya, N. S. Kasimov
Abstract
The content of 17 individual polycyclic aromatic hydrocarbons (PAHs) was analyzed in samples of background and urban soils obtained during a geochemical survey of the territory of Ulan-Ude in the summer of 2022 for the first time. The average content of PAHs in the urban soils is 801 ng/g, which is more than 8.5 times higher than the level in background chestnut soils. The soil cover is contaminated primarily with medium- and high-molecular-weight PAHs. The proportions of individual PAHs in the soils of Ulan-Ude range within 4–11% at an average value of 6%. The urban soil cover is found to have ten high-contrast anomalies with the sum of PAHs ranging from 3162 to 10 189 ng/g. The principal component analysis and ratios of PAHs have made it possible to identify the main types of PAH sources and their contribution to urban soil pollution.
{"title":"First Assessment of Soil Cover Pollution with Polycyclic Aromatic Hydrocarbons in the City of Ulan-Ude","authors":"N. E. Kosheleva, N. B. Zhaxylykov, Yu. A. Zavgorodnyaya, N. S. Kasimov","doi":"10.1134/s1028334x24602888","DOIUrl":"https://doi.org/10.1134/s1028334x24602888","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The content of 17 individual polycyclic aromatic hydrocarbons (PAHs) was analyzed in samples of background and urban soils obtained during a geochemical survey of the territory of Ulan-Ude in the summer of 2022 for the first time. The average content of PAHs in the urban soils is 801 ng/g, which is more than 8.5 times higher than the level in background chestnut soils. The soil cover is contaminated primarily with medium- and high-molecular-weight PAHs. The proportions of individual PAHs in the soils of Ulan-Ude range within 4–11% at an average value of 6%. The urban soil cover is found to have ten high-contrast anomalies with the sum of PAHs ranging from 3162 to 10 189 ng/g. The principal component analysis and ratios of PAHs have made it possible to identify the main types of PAH sources and their contribution to urban soil pollution.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969826","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 : 2024-08-11DOI: 10.1134/s1028334x24603389
M. A. Misyura, S. A. Bushmin, O. V. Aleksandrovich, M. E. Mamykina, E. V. Savva
Abstract
A thermodynamic model of the ternary fluid system H2O–LiCl–NaCl is proposed for the temperature range from –77 to +300°C. This model incorporates low-temperature phase transitions of freezing products of water–salt inclusions. The model is based on the Pitzer equations using new interaction parameters of Na, Cl, and the corresponding equilibrium constants of reactions involving the solid and liquid phases. Based on microthermometry data of fluid inclusions (T of phase transitions during heating after freezing), the model allows determination of the salt concentrations. The characteristics (T, wt %, LiCl and NaCl) of triple points with solid phases including the eutectic ({text{E}}{kern 1pt} '') (ice + LiCl · 5H2O + NaCl · 2H2O), peritectic ({text{P}}_{1}^{{{text{''}}}}) (LiCl · 5H2O + NaCl · 2H2O + NaCl) and ({text{P}}_{2}^{{{text{''}}}}) (LiCl · 5H2O + LiCl · 3H2O + NaCl), and the cotectic, peritectic curves separating the phase fields (ice + L, NaCl · 2H2O + L, NaCl + L), as well as solubility isotherms of ice, hydrohalite, and halite calculated by the model, showed good agreement with the experimental data. As an example of the application of a model to a natural object, we determined the salt contents in lithium-bearing brine inclusions in late quartz veins of the Bolshie Keivy area (Fennoscandian Shield).
{"title":"Thermodynamic Model of the H2O–LiCl–NaCl System for Study of Fluid Inclusions: Calculations Using the Pitzer Equations","authors":"M. A. Misyura, S. A. Bushmin, O. V. Aleksandrovich, M. E. Mamykina, E. V. Savva","doi":"10.1134/s1028334x24603389","DOIUrl":"https://doi.org/10.1134/s1028334x24603389","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A thermodynamic model of the ternary fluid system H<sub>2</sub>O–LiCl–NaCl is proposed for the temperature range from –77 to +300°C. This model incorporates low-temperature phase transitions of freezing products of water–salt inclusions. The model is based on the Pitzer equations using new interaction parameters of Na, Cl, and the corresponding equilibrium constants of reactions involving the solid and liquid phases. Based on microthermometry data of fluid inclusions (<i>T</i> of phase transitions during heating after freezing), the model allows determination of the salt concentrations. The characteristics (<i>T</i>, wt %, LiCl and NaCl) of triple points with solid phases including the eutectic <span>({text{E}}{kern 1pt} '')</span> (ice + LiCl · 5H<sub>2</sub>O + NaCl · 2H<sub>2</sub>O), peritectic <span>({text{P}}_{1}^{{{text{''}}}})</span> (LiCl · 5H<sub>2</sub>O + NaCl · 2H<sub>2</sub>O + NaCl) and <span>({text{P}}_{2}^{{{text{''}}}})</span> (LiCl · 5H<sub>2</sub>O + LiCl · 3H<sub>2</sub>O + NaCl), and the cotectic, peritectic curves separating the phase fields (ice + L, NaCl · 2H<sub>2</sub>O + L, NaCl + L), as well as solubility isotherms of ice, hydrohalite, and halite calculated by the model, showed good agreement with the experimental data. As an example of the application of a model to a natural object, we determined the salt contents in lithium-bearing brine inclusions in late quartz veins of the Bolshie Keivy area (Fennoscandian Shield).</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948946","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 : 2024-08-11DOI: 10.1134/s1028334x24602773
A. B. Vrevsky, A. B. Kuznetsov, P. A. Lvov
Abstract
New isotopic data are presented in this paper that make it possible to determine the stratigraphic position of the Talja Formation on the regional stratigraphic scale of the Early Precambrian. The U‒Th‒Pb age of 1926 ± 7 Ma obtained for the first time for metarhyodacites of the Talja Formation indicates that this formation is coeval to the Kaskama Formation, which, together with the similar isotope–geochemical composition of the type varieties of the Kaskama and Talja formations (komatiitic basalts, aluminous metabasalts, and metarhyodacites), significantly expands the understanding of the extent of the area composed of the Paleoproterozoic Kalevian Superhorizon within the Kola–Norwegian region of the Fennoscandian shield.
{"title":"New Data on the Regional Stratigraphic Scale of the Paleoproterozoic of the Fennoscandian Shield (Isotope Geochemistry and Age of Supracrustal Rock Complexes of the Inari Terrane, Kola Peninsula)","authors":"A. B. Vrevsky, A. B. Kuznetsov, P. A. Lvov","doi":"10.1134/s1028334x24602773","DOIUrl":"https://doi.org/10.1134/s1028334x24602773","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>New isotopic data are presented in this paper that make it possible to determine the stratigraphic position of the Talja Formation on the regional stratigraphic scale of the Early Precambrian. The U‒Th‒Pb age of 1926 ± 7 Ma obtained for the first time for metarhyodacites of the Talja Formation indicates that this formation is coeval to the Kaskama Formation, which, together with the similar isotope–geochemical composition of the type varieties of the Kaskama and Talja formations (komatiitic basalts, aluminous metabasalts, and metarhyodacites), significantly expands the understanding of the extent of the area composed of the Paleoproterozoic Kalevian Superhorizon within the Kola–Norwegian region of the Fennoscandian shield.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948945","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 : 2024-08-11DOI: 10.1134/s1028334x2460244x
Emad Ullah Khan, Maryam Saleem, Syed Muhammad Wasim Sajjad, Saif Ullah Khan
Abstract
This study marks the first detailed depositional, diagenetic and organic geochemical investigation of Jurassic Isha Formation in North Waziristan, Khyber Pukhtunkhuwa, Pakistan. Detailed systematic sampling was carried out from exposed outcrop along the Mirali road in North Waziristan for microfacies analysis and diagenetic studies to unravel the depositional environment and diagenetic alterations. The oraganic maturity and hydrocarbon generation potential were assessed by total organic content and Rock-Eval pyrolysis. Outcrop analogue revealed that the formation predominantly comprises of thick to thin bedded oolitic fractured limestone, bioclastic and dolomitic limestone. In the petrography, a total of eight microfacies (MF1–MF8) were constructed and were directed different depositional enviroments. Based on the integrated field data and microfacies analyses, the Isha Formation is interpreted to be deposited on a homoclinal ramp particularly in peritidal, lagoon, and carbonate shoals. Sequences stratigraphic setup shows intervallic Transgressive and Regressive Systems Tracts. The TSTs are mostly grainstone and packstone facies whereas the RSTs are wackestone and mudstone microfacies which demonstrates a single 2nd order cycle and then multiple 3rd order transgressive and regressive cycles for the deposition of Isha Formation. The total organic content and Rock-Eval pyrolysis results were ploted on VanKerevlen diagram which indicate that the source rock potential fall within the type III kerogen. The HI versus Tmax and PI versus Tmax cross plots indicate that the formation lies within the zone of maturation, generation potentiality indicate that the formation has fair to poor potential and hydrocarbons are indigenous.
摘要 本研究是对巴基斯坦开伯尔普赫图赫瓦北瓦济里斯坦的侏罗纪伊沙地层进行的首次详细沉积、成因和有机地球化学调查。对北瓦济里斯坦米拉利公路沿线的裸露地层进行了详细的系统取样，以进行微地层分析和成因研究，从而揭示沉积环境和成因变化。通过总有机物含量和岩石热解评估了岩层成熟度和碳氢化合物生成潜力。露头模拟显示，地层主要由厚层至薄层鲕粒状断裂灰岩、生物碎屑岩和白云质灰岩组成。岩相学共构建了八个微岩相（MF1-MF8），分别指向不同的沉积环境。根据综合野外数据和微岩相分析，伊沙地层被解释为沉积在同向斜坡上，尤其是在潮间带、泻湖和碳酸盐浅滩。层序地层设置显示了金属间的递变和回归系统阶地。TST主要是粒岩和包裹岩层面，而RST则是瓦基岩和泥岩微地层，这表明伊沙地层的沉积经历了一个二阶循环和多个三阶递变和回归循环。总有机质含量和岩石-评价热解结果绘制在 VanKerevlen 图上，表明源岩可能属于 III 型角质。HI与Tmax和PI与Tmax的交叉图表明，该地层位于成熟区内，生成潜力表明，该地层的潜力一般到较差，碳氢化合物是本地的。
{"title":"Depositional Environment, Diagenesis and Source Rock Characterization of Middle Jurassic Carbonates, North Waziristan, Khyber Pakhtunkhwa, Pakistan","authors":"Emad Ullah Khan, Maryam Saleem, Syed Muhammad Wasim Sajjad, Saif Ullah Khan","doi":"10.1134/s1028334x2460244x","DOIUrl":"https://doi.org/10.1134/s1028334x2460244x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>This study marks the first detailed depositional, diagenetic and organic geochemical investigation of Jurassic Isha Formation in North Waziristan, Khyber Pukhtunkhuwa, Pakistan. Detailed systematic sampling was carried out from exposed outcrop along the Mirali road in North Waziristan for microfacies analysis and diagenetic studies to unravel the depositional environment and diagenetic alterations. The oraganic maturity and hydrocarbon generation potential were assessed by total organic content and Rock-Eval pyrolysis. Outcrop analogue revealed that the formation predominantly comprises of thick to thin bedded oolitic fractured limestone, bioclastic and dolomitic limestone. In the petrography, a total of eight microfacies (MF1–MF8) were constructed and were directed different depositional enviroments. Based on the integrated field data and microfacies analyses, the Isha Formation is interpreted to be deposited on a homoclinal ramp particularly in peritidal, lagoon, and carbonate shoals. Sequences stratigraphic setup shows intervallic Transgressive and Regressive Systems Tracts. The TSTs are mostly grainstone and packstone facies whereas the RSTs are wackestone and mudstone microfacies which demonstrates a single 2nd order cycle and then multiple 3rd order transgressive and regressive cycles for the deposition of Isha Formation. The total organic content and Rock-Eval pyrolysis results were ploted on VanKerevlen diagram which indicate that the source rock potential fall within the type III kerogen. The HI versus Tmax and PI versus Tmax cross plots indicate that the formation lies within the zone of maturation, generation potentiality indicate that the formation has fair to poor potential and hydrocarbons are indigenous.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948939","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 : 2024-08-11DOI: 10.1134/s1028334x24603183
E. N. Kozlov, E. N. Fomina, M. Yu. Sidorov, A. V. Gudkov, V. V. Kolobov
Abstract
The He isotopic composition and the He and Ne ratio of fluid inclusions in magnetite and pyrite from carbonatite breccias of the Sallanlatva alkali-ultramafic complex of the Kola alkaline province (Northwest Russia) are studied using the step-crushing method. The results indicate the highly likely involvement of fluids from several sources trapped in various proportions during the formation of the Sallanlatva explosive carbonatite breccias. The R/Ra ratio, where R is the measured 3He/4He ratio and Ra of 1.382 × 10–6 is the same ratio of atmospheric air, reaches 2.3, which is a reliable indicator of the presence of mantle gases. A low (1–44) 4He/20Ne ratio allows us to suggest the involvement of atmospheric gases dissolved in paleometeoric waters. A combination of these two facts favors a hypothesis of the phreatomagmatic nature of the studied breccias, i.e., their formation at the expense of interaction between the intruding hot orthomagmatic fluids and meteoric waters with dissolved atmospheric gases.
摘要 利用阶梯破碎法研究了科拉碱性省（俄罗斯西北部）萨兰拉特瓦碱性-超基性复合体碳酸盐岩角砾岩中磁铁矿和黄铁矿中流体包裹体的 He 同位素组成以及 He 和 Ne 比率。研究结果表明，在萨兰拉特瓦爆炸碳酸盐岩角砾岩的形成过程中，极有可能有来自不同来源的流体以不同比例滞留其中。R/Ra 比率（其中 R 是测量到的 3He/4He 比率，Ra 为 1.382 × 10-6 是大气中空气的相同比率）达到 2.3，这是地幔气体存在的可靠指标。较低的（1-44）4He/20Ne 比值使我们可以推断出溶解在古史水域中的大气气体的存在。综合这两个事实，我们倾向于假设所研究的角砾岩具有岩浆性质，即它们的形成是以侵入的热原岩流体和陨石水与溶解的大气气体之间的相互作用为代价的。
{"title":"He Isotopic Composition and 4He/20Ne Ratio of Pyrite and Magnetite of Explosive Carbonatite Breccia of the Sallanlatva Massif, Kola Region","authors":"E. N. Kozlov, E. N. Fomina, M. Yu. Sidorov, A. V. Gudkov, V. V. Kolobov","doi":"10.1134/s1028334x24603183","DOIUrl":"https://doi.org/10.1134/s1028334x24603183","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The He isotopic composition and the He and Ne ratio of fluid inclusions in magnetite and pyrite from carbonatite breccias of the Sallanlatva alkali-ultramafic complex of the Kola alkaline province (Northwest Russia) are studied using the step-crushing method. The results indicate the highly likely involvement of fluids from several sources trapped in various proportions during the formation of the Sallanlatva explosive carbonatite breccias. The <i>R</i>/<i>Ra</i> ratio, where <i>R</i> is the measured <sup>3</sup>He/<sup>4</sup>He ratio and <i>Ra</i> of 1.382 × 10<sup>–6</sup> is the same ratio of atmospheric air, reaches 2.3, which is a reliable indicator of the presence of mantle gases. A low (1–44) <sup>4</sup>He/<sup>20</sup>Ne ratio allows us to suggest the involvement of atmospheric gases dissolved in paleometeoric waters. A combination of these two facts favors a hypothesis of the phreatomagmatic nature of the studied breccias, i.e., their formation at the expense of interaction between the intruding hot orthomagmatic fluids and meteoric waters with dissolved atmospheric gases.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969822","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 : 2024-08-11DOI: 10.1134/s1028334x24603286
N. G. Lyubimtseva, N. S. Bortnikov, V. M. Gekimyants, S. E. Borisovsky, P. Yu. Plechov
Abstract
Tetrahedrite-(Cd), Cu10Cd2Sb4S13, is a member of the tetrahedrite series of the tetrahedrite group with a predominance of Cd at the C position typically occupied by divalent metals. Cadmium end-members from the tetrahedrite group are rare: they have been described in 15 deposits and ore occurrences. This work reports on a new discovery site of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara mineral deposit (Southwestern Pamirs, Tajikistan) and summarizes the known data on rare Cd-bearing fahlores with a Cd content from 1 to 12.31 wt %. Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit occurs as xenomorphic segregations 10–35 μm in size in association with tetrahedrite-(Fe), tetrahedrite-(Zn), galena, polybasite, and chalcopyrite, calculated which replace bournonite. According to the EPMA data, its composition averaged over seven analyses (in wt %) is as follow: Ag 16.17, Cu 25.19, Cd 10.09, Fe 0.38, Zn 0.09, Pb 0.13, Sb 25.55, As 0.18, and S 22.34. The empirical formula calculated based on 29 atoms per unit is (Cu7.40Ag2.80)Σ10.20(Cd1.68Fe0.13Zn0.03Pb0.01)Σ1.84(Sb3.92As0.04)Σ3.96S13.00. The composition of the tetrahedrite-(Cd) from Kon-Dara is similar to those from the Tyndrum Pb–Zn mineralization in Scotland, the Clara baryte–fluorite–(Ag,Cu) mine in Germany, and the Xitieshan Pb–Zn deposit in China. The formation temperature of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit is estimated to have been at about (170–140) ± 20°C.
{"title":"Ag-Bearing Tetrahedrite-(Cd), (Cu,Ag)6(Cu4Cd2)Sb4S13, from the Galena–Fluorite Kon-Dara Mineral Deposit (Southwestern Pamirs): The First Discovery in Tajikistan","authors":"N. G. Lyubimtseva, N. S. Bortnikov, V. M. Gekimyants, S. E. Borisovsky, P. Yu. Plechov","doi":"10.1134/s1028334x24603286","DOIUrl":"https://doi.org/10.1134/s1028334x24603286","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Tetrahedrite-(Cd), Cu<sub>10</sub>Cd<sub>2</sub>Sb<sub>4</sub>S<sub>13</sub>, is a member of the tetrahedrite series of the tetrahedrite group with a predominance of Cd at the C position typically occupied by divalent metals. Cadmium end-members from the tetrahedrite group are rare: they have been described in 15 deposits and ore occurrences. This work reports on a new discovery site of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara mineral deposit (Southwestern Pamirs, Tajikistan) and summarizes the known data on rare Cd-bearing fahlores with a Cd content from 1 to 12.31 wt %. Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit occurs as xenomorphic segregations 10–35 μm in size in association with tetrahedrite-(Fe), tetrahedrite-(Zn), galena, polybasite, and chalcopyrite, calculated which replace bournonite. According to the EPMA data, its composition averaged over seven analyses (in wt %) is as follow: Ag 16.17, Cu 25.19, Cd 10.09, Fe 0.38, Zn 0.09, Pb 0.13, Sb 25.55, As 0.18, and S 22.34. The empirical formula calculated based on 29 atoms per unit is (Cu<sub>7.40</sub>Ag<sub>2.80</sub>)<sub>Σ10.20</sub>(Cd<sub>1.68</sub>Fe<sub>0.13</sub>Zn<sub>0.03</sub>Pb<sub>0.01</sub>)<sub>Σ1.84</sub>(Sb<sub>3.92</sub>As<sub>0.04</sub>)<sub>Σ3.96</sub>S<sub>13.00</sub>. The composition of the tetrahedrite-(Cd) from Kon-Dara is similar to those from the Tyndrum Pb–Zn mineralization in Scotland, the Clara baryte–fluorite–(Ag,Cu) mine in Germany, and the Xitieshan Pb–Zn deposit in China. The formation temperature of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit is estimated to have been at about (170–140) ± 20°C.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969827","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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