P. A. Solotchin, É. Solotchina, A. Maltsev, G. Leonova, S. Krivonogov, A. Zhdanova, I. Danilenko
––We present the results of comprehensive studies of Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Lake Bolshoi Bagan, located in the East Baraba lowland (south of Western Siberia). The research methods include X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, scanning electron microscopy, elemental analysis of sediments and pore water, radiocarbon (14C AMS) dating. It has been found that during the Holocene an intensive authigenic mineral formation took place in the lake basin; gypsum, halite and carbonates of calcite-dolomite series dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite and occasionally Mg-siderite have been found in the assemblage of carbonate minerals by mathematical modeling of complex XRD patterns. Mineralogical and crystallochemical studies, supplemented by the results of geochemical analyses, allowed us to identify four stages of the evolution of Lake Bolshoi Bagan in the Holocene, due to regional climate variations. The boundaries of the stages in general correspond to the boundaries of the climatostratigraphic phases by the Blytt–Sernander system: Stage I (the end of the Boreal) – the lake formation, humid climate; Stage II (Atlantic) – climate aridization, shallowing of the lake; Stage III (Subboreal) – unstable climate, frequent change of conditions; Stage IV (Subatlantic) – moderately cool and dry climate.
{"title":"Carbonate Sedimentation in High-Mineralized Lake Bolshoi Bagan (South of West Siberia): Dependence on Holocene Climate Changes","authors":"P. A. Solotchin, É. Solotchina, A. Maltsev, G. Leonova, S. Krivonogov, A. Zhdanova, I. Danilenko","doi":"10.2113/rgg20234567","DOIUrl":"https://doi.org/10.2113/rgg20234567","url":null,"abstract":"\u0000 ––We present the results of comprehensive studies of Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Lake Bolshoi Bagan, located in the East Baraba lowland (south of Western Siberia). The research methods include X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, scanning electron microscopy, elemental analysis of sediments and pore water, radiocarbon (14C AMS) dating. It has been found that during the Holocene an intensive authigenic mineral formation took place in the lake basin; gypsum, halite and carbonates of calcite-dolomite series dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite and occasionally Mg-siderite have been found in the assemblage of carbonate minerals by mathematical modeling of complex XRD patterns. Mineralogical and crystallochemical studies, supplemented by the results of geochemical analyses, allowed us to identify four stages of the evolution of Lake Bolshoi Bagan in the Holocene, due to regional climate variations. The boundaries of the stages in general correspond to the boundaries of the climatostratigraphic phases by the Blytt–Sernander system: Stage I (the end of the Boreal) – the lake formation, humid climate; Stage II (Atlantic) – climate aridization, shallowing of the lake; Stage III (Subboreal) – unstable climate, frequent change of conditions; Stage IV (Subatlantic) – moderately cool and dry climate.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46367246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Travin, M. M. Buslov, Y. Bishaev, A. A. Tsygankov, E. Mikheev
—The tectonothermal evolution of Transbaikalia is reconstructed using U/Pb, 40Ar/39Ar, and apatite fission track thermo-chronology of samples from the Late Paleozoic Angara–Vitim granitoid batholith (AVB). Successive closure of the zircon and amphibole isotope systems provides evidence that the AVB rocks cooled down rapidly soon after crystallization and 7–4 km of rocks were denuded subsequently during an extensive late Paleozoic orogeny in southern Siberia. The isotopic system of feldspar closed in the Middle Jurassic–Early Cretaceous (170–140 Ma) after a period of tectonic stability and slow closure of the biotite isotopic system in the early Permian–Middle Jurassic (295–170 Ma). The 170–140 Ma span was the time when the Mongol–Okhotsk orogen began its evolution, and the orogeny caused denudation of ~3 km of rocks. Denudation was slow in the Paleogene–Miocene (60–5 Ma) but accelerated over the past 5 million years (a ~3–2 km thick layer) during rapid cooling of rocks and activity under a far-field effect of the India–Eurasia collision.
{"title":"Late Paleozoic–Cenozoic Tectonothermal Evolution of Transbaikalia: Thermochronology of the Angara–Vitim Granitoid Batholith","authors":"A. Travin, M. M. Buslov, Y. Bishaev, A. A. Tsygankov, E. Mikheev","doi":"10.2113/rgg20234577","DOIUrl":"https://doi.org/10.2113/rgg20234577","url":null,"abstract":"\u0000 —The tectonothermal evolution of Transbaikalia is reconstructed using U/Pb, 40Ar/39Ar, and apatite fission track thermo-chronology of samples from the Late Paleozoic Angara–Vitim granitoid batholith (AVB). Successive closure of the zircon and amphibole isotope systems provides evidence that the AVB rocks cooled down rapidly soon after crystallization and 7–4 km of rocks were denuded subsequently during an extensive late Paleozoic orogeny in southern Siberia. The isotopic system of feldspar closed in the Middle Jurassic–Early Cretaceous (170–140 Ma) after a period of tectonic stability and slow closure of the biotite isotopic system in the early Permian–Middle Jurassic (295–170 Ma). The 170–140 Ma span was the time when the Mongol–Okhotsk orogen began its evolution, and the orogeny caused denudation of ~3 km of rocks. Denudation was slow in the Paleogene–Miocene (60–5 Ma) but accelerated over the past 5 million years (a ~3–2 km thick layer) during rapid cooling of rocks and activity under a far-field effect of the India–Eurasia collision.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48159566","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}
V. Tauson, S. Lipko, N. Smagunov, D. Babkin, O. Belozerova
—Distribution of a wide range of elements in the systems with magnetite, hematite and sphalerite is studied by the method of thermogradient hydrothermal synthesis combined with internal fluid sampling at 450 °C temperature and 100 MPa pressure. The distribution and cocrystallization coefficients are determined; the literature and original data on these coefficients are summarized. The possibility of obtaining the reproducible data on elements distribution in the mineral − solution system in the occurrence of many typomorphic elements is substantiated. This considerably increases the experiment efficiency. A significant advantage of using cocrystallization coefficients rather than “conventional” distribution coefficients expressed by the ratio of the element concentrations in crystal and solution (fluid) is shown. The features of behavior and occurrence of elements in hydrothermal systems are provided with physico-chemical evidence, through application of cocrystallization coefficients. The examples of the behavior of typomorphic trace elements in sphalerite are considered, which support the theoretical analysis. The major (Fe, Mn, Zn and possibly Cu) and secondary (Ti, V, Al, and Co) components of ore-forming solutions are estimated according to the compositions of magnetite and hematite from hydrothermal ore deposits of various types. The similarity in compositions of magnetite and hematite does not prove their coformation from a single fluid, quite the reverse, and this fact indicates different compositions of fluids from which the minerals were deposited.
{"title":"Distribution and Cocrystallization Coefficients of a Wide Range of Typomorphic Elements in Magnetite, Hematite, and Sphalerite in Hydrothermal Systems","authors":"V. Tauson, S. Lipko, N. Smagunov, D. Babkin, O. Belozerova","doi":"10.2113/rgg20234576","DOIUrl":"https://doi.org/10.2113/rgg20234576","url":null,"abstract":"\u0000 —Distribution of a wide range of elements in the systems with magnetite, hematite and sphalerite is studied by the method of thermogradient hydrothermal synthesis combined with internal fluid sampling at 450 °C temperature and 100 MPa pressure. The distribution and cocrystallization coefficients are determined; the literature and original data on these coefficients are summarized. The possibility of obtaining the reproducible data on elements distribution in the mineral − solution system in the occurrence of many typomorphic elements is substantiated. This considerably increases the experiment efficiency. A significant advantage of using cocrystallization coefficients rather than “conventional” distribution coefficients expressed by the ratio of the element concentrations in crystal and solution (fluid) is shown. The features of behavior and occurrence of elements in hydrothermal systems are provided with physico-chemical evidence, through application of cocrystallization coefficients. The examples of the behavior of typomorphic trace elements in sphalerite are considered, which support the theoretical analysis. The major (Fe, Mn, Zn and possibly Cu) and secondary (Ti, V, Al, and Co) components of ore-forming solutions are estimated according to the compositions of magnetite and hematite from hydrothermal ore deposits of various types. The similarity in compositions of magnetite and hematite does not prove their coformation from a single fluid, quite the reverse, and this fact indicates different compositions of fluids from which the minerals were deposited.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45828175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Persikov, P. G. Bukhtiyarov, L. Aranovich, O. Shaposhnikova, A. Nekrasov
—We report new experimental data on the interaction of igneous melts with hydrogen at temperatures of 1100–1250 °C and hydrogen pressures of 1–100 MPa in strongly reducing conditions: fO2=10−12−10−14. The experiments were conducted using an original high-gas-pressure unit equipped with a unique device that provides long-term experiments at high temperatures and pressures of hydrogen. The experiments used natural samples of igneous rocks: the magnesian basalt of the Northern Breakthrough of the Tolbachik Volcano (Kamchatka) and the andesite of the Avacha Volcano (Kamchatka). On the basis of the experiments, the following features of the process of interaction of hydrogen with igneous melts have been established: (1) Despite the high reduction potential of the H2–igneous melt system, the reactions of hydrogen oxidation and complete reduction of oxides of metals of variable valence in the melt do not go to the end. The cessation of redox reactions in basaltic and andesitic melts is due to the formation of H2O in the melt, which buffers the reduction potential of hydrogen; (2) The initially homogeneous igneous melt becomes heterogeneous: The formed H2O dissolves in the melt and in the fluid phase (at first pure hydrogen), and melts of variable, more acidic composition and small metallic isolations of the liquation structure are formed; (3) The complex process of metal–silicate liquation in magmatic melts when they interact with hydrogen can be carried out at real magma temperatures in nature (≤1200 °C), significantly lower than the corresponding melting points of iron and its alloys with nickel and cobalt; (4) The structure and dimensions of the experimentally established metal isolations are consistent with natural data on the finds of small quantities of native metals, primarily iron and its alloys with nickel and cobalt, in igneous rocks of different compositions and genesis.
{"title":"Experimental Study of the Process of Interaction of Hydrogen with Igneous Melts in the Conditions of the Earth’s Crust","authors":"E. Persikov, P. G. Bukhtiyarov, L. Aranovich, O. Shaposhnikova, A. Nekrasov","doi":"10.2113/rgg20234562","DOIUrl":"https://doi.org/10.2113/rgg20234562","url":null,"abstract":"\u0000 —We report new experimental data on the interaction of igneous melts with hydrogen at temperatures of 1100–1250 °C and hydrogen pressures of 1–100 MPa in strongly reducing conditions: fO2=10−12−10−14. The experiments were conducted using an original high-gas-pressure unit equipped with a unique device that provides long-term experiments at high temperatures and pressures of hydrogen. The experiments used natural samples of igneous rocks: the magnesian basalt of the Northern Breakthrough of the Tolbachik Volcano (Kamchatka) and the andesite of the Avacha Volcano (Kamchatka). On the basis of the experiments, the following features of the process of interaction of hydrogen with igneous melts have been established: (1) Despite the high reduction potential of the H2–igneous melt system, the reactions of hydrogen oxidation and complete reduction of oxides of metals of variable valence in the melt do not go to the end. The cessation of redox reactions in basaltic and andesitic melts is due to the formation of H2O in the melt, which buffers the reduction potential of hydrogen; (2) The initially homogeneous igneous melt becomes heterogeneous: The formed H2O dissolves in the melt and in the fluid phase (at first pure hydrogen), and melts of variable, more acidic composition and small metallic isolations of the liquation structure are formed; (3) The complex process of metal–silicate liquation in magmatic melts when they interact with hydrogen can be carried out at real magma temperatures in nature (≤1200 °C), significantly lower than the corresponding melting points of iron and its alloys with nickel and cobalt; (4) The structure and dimensions of the experimentally established metal isolations are consistent with natural data on the finds of small quantities of native metals, primarily iron and its alloys with nickel and cobalt, in igneous rocks of different compositions and genesis.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42669502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. I. Nepomnyashchikh, A. Fedorov, A. P. Zhaboedov, M. G. Volkova
—We consider high-purity quartzites of the Gargan quartz-bearing zone of East Sayan. The main productive varieties of quartzites have been identified. The structures, textures, chemical composition, and degree of enrichment of the quartzites and the mineral and fluid inclusions in them have been studied. Quartz concentrates of high and ultrahigh purity have been obtained from superquartzite and compact quartzite.
{"title":"High-Purity Quartzite from East Sayan","authors":"A. I. Nepomnyashchikh, A. Fedorov, A. P. Zhaboedov, M. G. Volkova","doi":"10.2113/rgg20234586","DOIUrl":"https://doi.org/10.2113/rgg20234586","url":null,"abstract":"\u0000 —We consider high-purity quartzites of the Gargan quartz-bearing zone of East Sayan. The main productive varieties of quartzites have been identified. The structures, textures, chemical composition, and degree of enrichment of the quartzites and the mineral and fluid inclusions in them have been studied. Quartz concentrates of high and ultrahigh purity have been obtained from superquartzite and compact quartzite.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42974455","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}
O. Khubaeva, A. Degterev, D. Kozlov, A.L. Khomchanovskii, R. Zharkov, F. Batanov
—This paper describes a set of studies performed at a thermal manifestation (Lake Utinaya Banya) on the Iturup Island (Kuril Islands). These studies include bathymetric survey of the lake basin, geometric leveling across the lake, pitting, sampling of thermal waters from the lake and springs, hydrochemical research, and isotopic analysis of oxygen and hydrogen in the lake water. It is suggested by the shape of the lake basin (close to lenticular with a significant concentric depression), the underwater gas-hydrothermal vents, the bank along the perimeter of the lake basin, and the presence of several layers of clastic deposits at the top of the rampart that the lake was formed by a hydrothermal eruption. The lake temperature has remained constant over the years and ranges on average from 25 to 15 °C, depending on the season. The water of Lake Utinaya Banya is represented by acidic, sulfate calcium, and low-mineralized waters.
{"title":"Morphology and Specific Features of Formation of Thermal Lake Utinaya Banya (Iturup Island, Southern Kuril Islands)","authors":"O. Khubaeva, A. Degterev, D. Kozlov, A.L. Khomchanovskii, R. Zharkov, F. Batanov","doi":"10.2113/rgg20234551","DOIUrl":"https://doi.org/10.2113/rgg20234551","url":null,"abstract":"\u0000 —This paper describes a set of studies performed at a thermal manifestation (Lake Utinaya Banya) on the Iturup Island (Kuril Islands). These studies include bathymetric survey of the lake basin, geometric leveling across the lake, pitting, sampling of thermal waters from the lake and springs, hydrochemical research, and isotopic analysis of oxygen and hydrogen in the lake water. It is suggested by the shape of the lake basin (close to lenticular with a significant concentric depression), the underwater gas-hydrothermal vents, the bank along the perimeter of the lake basin, and the presence of several layers of clastic deposits at the top of the rampart that the lake was formed by a hydrothermal eruption. The lake temperature has remained constant over the years and ranges on average from 25 to 15 °C, depending on the season. The water of Lake Utinaya Banya is represented by acidic, sulfate calcium, and low-mineralized waters.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46872501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A.K. Kozin, S. Stepanov, R. Palamarchuk, V. Shilovskikh, V.S. Zhdanova
—The placer deposits of the Miass valley in the Southern Urals have been known since the beginning of the 19th century. Over two centuries of mining more than 120 tons of gold have been extracted from alluvial and alluvial–deluvial placers. Despite the industrial significance of this territory, native gold of alluvial deposits is practically unstudied and there is no data on the mineral composition of concentrates. Native gold and heavy fraction minerals from seven placers of the Miass placer zone of deluvial–alluvial and alluvial types were researched. The study of the typomorphic features of native gold and distribution of heavy fraction minerals in loose deposits makes it possible to determine the genetic types of primary sources of placer formation. Chrome-spinel and ilmenite prevail in the concentrates, magnetite, epidote, rutile, titanite, clinopyroxene, hematite, zircon, garnets, and monazite are less common. Chromespinelides of various placers are represented by chromite and subferrichromite, they are characterized by a high average content of Cr2O3 (50.9 wt.%). Chromespinelide chemical composition features show evidence of its penetration into placer sediments from rocks of the ophiolitic association. The composition and morphological features of phosphates of rare earth elements (monazite and xenotime) indicate their metamorphogenic nature and penetration into placers from the Riphean strata. Native gold is characterized by a low degree of roundness. Mineral inclusions in native gold are represented by sulfides, arsenides, bismuthides, cuprous gold, platinoids. Composition of native gold from the Miass River valley placers varies over a wide range. The main admixtures are silver (4.5–23.4 wt.%) and mercury (up to 5.14 wt.%), copper (up to 2.03 wt.%) was noted in several grains. The EBSD study of native gold internal structure showed predominance of primary crystallization structures, a low degree of deformation and growth of gold-rich rims with a fine-grained mosaic structure. Formation of gold-rich rims in gold grains in placers is explained by recrystallization of the most deformed parts of gold during transportation. Placers occurred due to the destruction of primary sources located in the upper reaches of streams or near them, which is confirmed by a low degree of grains’ roundness. The composition of native gold in combination with a set of micro-inclusions indicate the gold–sulfide-quartz type of mineralization of most primary sources.
{"title":"Mineral Associations of Concentrates from Gold-Bearing Placers of the Miass Placer Zone (South Urals) and Possible Primary Sources of Gold","authors":"A.K. Kozin, S. Stepanov, R. Palamarchuk, V. Shilovskikh, V.S. Zhdanova","doi":"10.2113/rgg20234543","DOIUrl":"https://doi.org/10.2113/rgg20234543","url":null,"abstract":"\u0000 —The placer deposits of the Miass valley in the Southern Urals have been known since the beginning of the 19th century. Over two centuries of mining more than 120 tons of gold have been extracted from alluvial and alluvial–deluvial placers. Despite the industrial significance of this territory, native gold of alluvial deposits is practically unstudied and there is no data on the mineral composition of concentrates. Native gold and heavy fraction minerals from seven placers of the Miass placer zone of deluvial–alluvial and alluvial types were researched. The study of the typomorphic features of native gold and distribution of heavy fraction minerals in loose deposits makes it possible to determine the genetic types of primary sources of placer formation. Chrome-spinel and ilmenite prevail in the concentrates, magnetite, epidote, rutile, titanite, clinopyroxene, hematite, zircon, garnets, and monazite are less common. Chromespinelides of various placers are represented by chromite and subferrichromite, they are characterized by a high average content of Cr2O3 (50.9 wt.%). Chromespinelide chemical composition features show evidence of its penetration into placer sediments from rocks of the ophiolitic association. The composition and morphological features of phosphates of rare earth elements (monazite and xenotime) indicate their metamorphogenic nature and penetration into placers from the Riphean strata. Native gold is characterized by a low degree of roundness. Mineral inclusions in native gold are represented by sulfides, arsenides, bismuthides, cuprous gold, platinoids. Composition of native gold from the Miass River valley placers varies over a wide range. The main admixtures are silver (4.5–23.4 wt.%) and mercury (up to 5.14 wt.%), copper (up to 2.03 wt.%) was noted in several grains. The EBSD study of native gold internal structure showed predominance of primary crystallization structures, a low degree of deformation and growth of gold-rich rims with a fine-grained mosaic structure. Formation of gold-rich rims in gold grains in placers is explained by recrystallization of the most deformed parts of gold during transportation. Placers occurred due to the destruction of primary sources located in the upper reaches of streams or near them, which is confirmed by a low degree of grains’ roundness. The composition of native gold in combination with a set of micro-inclusions indicate the gold–sulfide-quartz type of mineralization of most primary sources.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48246992","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}
B. Damdinov, A. R. Kotelnikov, N. Suk, L. B. Damdinova, G. M. Akhmedzhanova
–The modeling experiments were conducted to study transport of ore-forming components in the lithosphere, taking into account the possibility of ore matter remobilization under endogenous conditions. The experiments, which included temperature gradient-based ones, were conducted at T = 500–680 °C and P = 1.5–5.0 kbar on high gas pressure devices (HGPD) in highly concentrated water-salt solutions of alkaline specifics. The experiments consisted of two stages. During the first stage, we tested the possibility of recrystallization of the ore matter of “black smokers” in the presence of basalt at 500 ℃ and 5 kbar and water-salt fluids at a concentration of up to 5 wt.%. At the second stage, mechanisms of ore-forming components transport (P–T parameters: 450–650 ℃ and up to 5 kbar) were studied under conditions of a temperature gradient (0.3–0.4 °C/mm). The duration of the experiments was 14 days. The test products were: oceanic basalts, granite model mixtures (Fsp + Qz), as well as various sulfide minerals, oxides and noble metals (Au, Pt). It has been shown that at T 680–650 °C, intensive recrystallization and deposition of sulfide minerals (sphalerite, galena, chalcopyrite, pyrite, cooperite, etc.) along with feldspars, micas and quartz, takes place. Intensive transport of both the main petrogenic (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K) and ore-forming elements (Ni, Cu, Zn, As, Pb, Cd, Pt, Au, Hg, Bi), and a joint transport of silicate and ore matter is established. Some ore elements are either included into compositions of solid solutions or present as impurities in ore-forming minerals: Fe, Ni, Cu → pyrite, pyrrhotite; Pb, Au, As, Bi, Zn → galena; Zn, Cd, Fe, Mn, Cu → sphalerite; As → galena, orpiment, realgar, gold; Hg → gold. The obtained data attest to the possibility of modeling ore mineralization mechanisms. The experimental results apply to explain the genesis of the Zun-Kholba gold–quartz–sulfide deposit and describe the processes of epigenetic transformations of primary ores in polymetallic deposits, on the example of the Ozernoe Pb–Zn deposit. The discussed mechanisms can be extended to explain the genesis of other ore deposits occurring in the zones of tectonic-magmatic activation.
{"title":"Experimental Modeling of Transport of Ore-Forming Components by Water-Salt Fluids at Elevated P–T Parameters","authors":"B. Damdinov, A. R. Kotelnikov, N. Suk, L. B. Damdinova, G. M. Akhmedzhanova","doi":"10.2113/rgg20234565","DOIUrl":"https://doi.org/10.2113/rgg20234565","url":null,"abstract":"\u0000 –The modeling experiments were conducted to study transport of ore-forming components in the lithosphere, taking into account the possibility of ore matter remobilization under endogenous conditions. The experiments, which included temperature gradient-based ones, were conducted at T = 500–680 °C and P = 1.5–5.0 kbar on high gas pressure devices (HGPD) in highly concentrated water-salt solutions of alkaline specifics. The experiments consisted of two stages. During the first stage, we tested the possibility of recrystallization of the ore matter of “black smokers” in the presence of basalt at 500 ℃ and 5 kbar and water-salt fluids at a concentration of up to 5 wt.%. At the second stage, mechanisms of ore-forming components transport (P–T parameters: 450–650 ℃ and up to 5 kbar) were studied under conditions of a temperature gradient (0.3–0.4 °C/mm). The duration of the experiments was 14 days. The test products were: oceanic basalts, granite model mixtures (Fsp + Qz), as well as various sulfide minerals, oxides and noble metals (Au, Pt). It has been shown that at T 680–650 °C, intensive recrystallization and deposition of sulfide minerals (sphalerite, galena, chalcopyrite, pyrite, cooperite, etc.) along with feldspars, micas and quartz, takes place. Intensive transport of both the main petrogenic (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K) and ore-forming elements (Ni, Cu, Zn, As, Pb, Cd, Pt, Au, Hg, Bi), and a joint transport of silicate and ore matter is established. Some ore elements are either included into compositions of solid solutions or present as impurities in ore-forming minerals: Fe, Ni, Cu → pyrite, pyrrhotite; Pb, Au, As, Bi, Zn → galena; Zn, Cd, Fe, Mn, Cu → sphalerite; As → galena, orpiment, realgar, gold; Hg → gold. The obtained data attest to the possibility of modeling ore mineralization mechanisms. The experimental results apply to explain the genesis of the Zun-Kholba gold–quartz–sulfide deposit and describe the processes of epigenetic transformations of primary ores in polymetallic deposits, on the example of the Ozernoe Pb–Zn deposit. The discussed mechanisms can be extended to explain the genesis of other ore deposits occurring in the zones of tectonic-magmatic activation.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43320243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Kozlov, A. Maltsev, E. Fomina, M. Sidorov, A. N. Zhilicheva, S. V. Panteeva, A. Kompanchenko, A. Chernyavskiy
—We have studied the trace element composition of apatite from several varieties of carbonatites and associated apatite ores of the Vuoriyarvi alkaline-ultrabasic carbonatite complex (Kola region, northwestern Russia), which hosts several commercial deposits of apatite–magnetite and pyrochlore ores and large-scale unexplored rare-earth mineral occurrences. The composition of apatite was analyzed by total-reflection X-ray fluorescence spectrometry (hereafter, TXRF). Verification of the obtained results was carried out by ICP-MS analysis of weighed portions of apatite monomineral samples. It is shown that during the evolution of the Vuoriyarvi carbonatites and associated apatite–magnetite ores, the contents of Sr and rare-earth elements (REE) and the degree of REE fractionation in apatite synchronously increased. The obtained TXRF data on the composition of apatite in the carbonatite complex demonstrate the efficiency of TXRF and its high potential in both applied and fundamental research concerned with apatite of various geologic objects.
{"title":"Study of the Distribution of Rare-Earth Elements and Strontium in Apatite from Rocks of the Vuoriyarvi Carbonatite Complex by Total-Reflection X-Ray Fluorescence Spectrometry (TXRF): First Results and Prospects","authors":"E. Kozlov, A. Maltsev, E. Fomina, M. Sidorov, A. N. Zhilicheva, S. V. Panteeva, A. Kompanchenko, A. Chernyavskiy","doi":"10.2113/rgg20234580","DOIUrl":"https://doi.org/10.2113/rgg20234580","url":null,"abstract":"\u0000 —We have studied the trace element composition of apatite from several varieties of carbonatites and associated apatite ores of the Vuoriyarvi alkaline-ultrabasic carbonatite complex (Kola region, northwestern Russia), which hosts several commercial deposits of apatite–magnetite and pyrochlore ores and large-scale unexplored rare-earth mineral occurrences. The composition of apatite was analyzed by total-reflection X-ray fluorescence spectrometry (hereafter, TXRF). Verification of the obtained results was carried out by ICP-MS analysis of weighed portions of apatite monomineral samples. It is shown that during the evolution of the Vuoriyarvi carbonatites and associated apatite–magnetite ores, the contents of Sr and rare-earth elements (REE) and the degree of REE fractionation in apatite synchronously increased. The obtained TXRF data on the composition of apatite in the carbonatite complex demonstrate the efficiency of TXRF and its high potential in both applied and fundamental research concerned with apatite of various geologic objects.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46290792","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}
—Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87–1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K2O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low εNd(T) from –5.1 to –10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K2O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher εNd(T) from –0.3 to –1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative εNd(T) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.
{"title":"Heterogeneous Subcontinental Lithospheric Mantle below the South Margin of the Siberian Craton: Evidence from Composition of Paleoproterozoic Mafic Associations","authors":"O. Turkina, A. Izokh","doi":"10.2113/rgg20234575","DOIUrl":"https://doi.org/10.2113/rgg20234575","url":null,"abstract":"\u0000 —Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87–1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K2O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low εNd(T) from –5.1 to –10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K2O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher εNd(T) from –0.3 to –1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative εNd(T) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.","PeriodicalId":49587,"journal":{"name":"Russian Geology and Geophysics","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44364490","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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