Pub Date : 2023-11-04DOI: 10.24930/1681-9004-2023-23-5-887-909
G. Yu. Shardakova, A. V. Korovko, N. A. Antonishin
Research subject . For the first time, the mineral composition, petro- and geochemical features, generation and metasomatic alteration conditions, fluid regime (based on the behavior of F, Sl, and S in apatites), and ore-generating potential of granitoids from the South Saryshagan intrusion (Western Balkhash) were studied. Materials and methods . X-ray fluorescence and atomic emission methods of rock analysis (drilling well core), as well as microprobe (polished sections) studies of mineral composition. Results . The rock composition was found to correspond to moderately alkaline granites, formed at a generation pressure of about 2 kbar and T = 670°C. Subsequent metasomatic transformations were mediumtemperature (313–350°C) and multistage, i.e., phyllitization followed by chloritization. The ferrous composition of chlorite and the confinement of its development area to fracture zones indicate the local scale of the process. Ore mineralization is mainly represented by chalcopyrite, occasionally containing Au. According to the morphology and composition features, apatites from granites can be divided into two groups, i.e., magmatogenic grains and products of their transformations. In a diagram of F-Cl-S ratios, most points of their composition lie in the fields of rocks productive of Cu-porphyry mineralization. Conclusions . Mineral associations and the analysis of F, Cl, and S behavior in apatites indicate changes in the composition of the fluid phase over time under the conditions of an open system. In apatites, sulfur accumulates to the maximum level (0.012 wt % S) simultaneously with an increase in the amount of Cl and a decrease in the amount of F. After S reaches this level, the Cl content in apatites decreases followed by a notable increase in F; as a result, the late portions of the fluid become depleted of F, but enriched with Cl and S. In general, the content of the latter two components is low, compared with that typical of rich Cu–porphyry systems. Since the amount of mobilized copper depends on both the contents of Cl and S in the fluid and the volume of this fluid (determined by the size of the intrusion itself; in our case, it is a small body), the predicted copper reserves in the upper horizons of the South Saryshagan intrusion are small.
{"title":"Generation and alteration conditions, fluid regime features of the ore-magmatic system of the South Saryshagan granite intrusion (Western Balkhash region)","authors":"G. Yu. Shardakova, A. V. Korovko, N. A. Antonishin","doi":"10.24930/1681-9004-2023-23-5-887-909","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-887-909","url":null,"abstract":"Research subject . For the first time, the mineral composition, petro- and geochemical features, generation and metasomatic alteration conditions, fluid regime (based on the behavior of F, Sl, and S in apatites), and ore-generating potential of granitoids from the South Saryshagan intrusion (Western Balkhash) were studied. Materials and methods . X-ray fluorescence and atomic emission methods of rock analysis (drilling well core), as well as microprobe (polished sections) studies of mineral composition. Results . The rock composition was found to correspond to moderately alkaline granites, formed at a generation pressure of about 2 kbar and T = 670°C. Subsequent metasomatic transformations were mediumtemperature (313–350°C) and multistage, i.e., phyllitization followed by chloritization. The ferrous composition of chlorite and the confinement of its development area to fracture zones indicate the local scale of the process. Ore mineralization is mainly represented by chalcopyrite, occasionally containing Au. According to the morphology and composition features, apatites from granites can be divided into two groups, i.e., magmatogenic grains and products of their transformations. In a diagram of F-Cl-S ratios, most points of their composition lie in the fields of rocks productive of Cu-porphyry mineralization. Conclusions . Mineral associations and the analysis of F, Cl, and S behavior in apatites indicate changes in the composition of the fluid phase over time under the conditions of an open system. In apatites, sulfur accumulates to the maximum level (0.012 wt % S) simultaneously with an increase in the amount of Cl and a decrease in the amount of F. After S reaches this level, the Cl content in apatites decreases followed by a notable increase in F; as a result, the late portions of the fluid become depleted of F, but enriched with Cl and S. In general, the content of the latter two components is low, compared with that typical of rich Cu–porphyry systems. Since the amount of mobilized copper depends on both the contents of Cl and S in the fluid and the volume of this fluid (determined by the size of the intrusion itself; in our case, it is a small body), the predicted copper reserves in the upper horizons of the South Saryshagan intrusion are small.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"28 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-04DOI: 10.24930/1681-9004-2023-23-5-868-886
V. R. Vetrin, S. G. Skublov
Research subject . Zircon from granitoids of the A- and I-types of the Neorchean Kola alkaline province of the Baltic (Fennoscandian) shield. Aim . To determine the trace element composition of zircon in order to characterize the conditions of its formation in different types of granitoids. To use these data, along with the available results of U-Pb dating and Lu-Hf isotope composition of the studied zircon crystals, to assess the amount of mantle and core matter in the protolith composition and the effect of crystallization conditions on the rare element composition of zircon. Materials and Methods . 50 zircon crystals from 5 samples of the main types of granitoids of the province were studied. Concentrations of trace elements were determined using a Cameca IMS-4f ion microprobe (NF FTIAN, Yaroslavl). Points for analysis were selected using optical and cathodoluminescent images. The size of the crater did not exceed 20 µm, the relative measurement error for the predominant part of the elements was set at 10–15%, the threshold for detecting elements was 10 ppb. Results . There are two main types of zircon of Neoarchean age – zircon-1 and zircon-2, formed, respectively, at the magmatic and autometasomatic stages of crystallization, zircon-4 in inclusions in zircon-1, and Paleoproterozoic zircon-3 of metamorphic genesis. The average isotopic composition of Hf in zircon-1 and zircon-2 of different arrays varies slightly, with the amount of mantle component (Xm) ranging from 23 to 30%, which may indicate a relatively constant and significantly core composition of their protoliths. Conclusions . The change in the trace element composition of Neoarchean zircons was controlled mainly by the composition of protoliths and redox crystallization conditions. Under reducing conditions, the greatest chemical activity was acquired by light (La-Nd) lanthanides, for which a direct dependence on the Ce/Ce* value was established. For heavy lanthanides with similar ion sizes relative to Zr+4, crystallochemical factors were more important and a decrease in the dependence of heavy lanthanide concentrations in zircon on Ce/ Ce* was determined.
{"title":"Trace element composition of zircon from granitoids of the Neoarchean alkaline province of the Kola Peninsula","authors":"V. R. Vetrin, S. G. Skublov","doi":"10.24930/1681-9004-2023-23-5-868-886","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-868-886","url":null,"abstract":"Research subject . Zircon from granitoids of the A- and I-types of the Neorchean Kola alkaline province of the Baltic (Fennoscandian) shield. Aim . To determine the trace element composition of zircon in order to characterize the conditions of its formation in different types of granitoids. To use these data, along with the available results of U-Pb dating and Lu-Hf isotope composition of the studied zircon crystals, to assess the amount of mantle and core matter in the protolith composition and the effect of crystallization conditions on the rare element composition of zircon. Materials and Methods . 50 zircon crystals from 5 samples of the main types of granitoids of the province were studied. Concentrations of trace elements were determined using a Cameca IMS-4f ion microprobe (NF FTIAN, Yaroslavl). Points for analysis were selected using optical and cathodoluminescent images. The size of the crater did not exceed 20 µm, the relative measurement error for the predominant part of the elements was set at 10–15%, the threshold for detecting elements was 10 ppb. Results . There are two main types of zircon of Neoarchean age – zircon-1 and zircon-2, formed, respectively, at the magmatic and autometasomatic stages of crystallization, zircon-4 in inclusions in zircon-1, and Paleoproterozoic zircon-3 of metamorphic genesis. The average isotopic composition of Hf in zircon-1 and zircon-2 of different arrays varies slightly, with the amount of mantle component (Xm) ranging from 23 to 30%, which may indicate a relatively constant and significantly core composition of their protoliths. Conclusions . The change in the trace element composition of Neoarchean zircons was controlled mainly by the composition of protoliths and redox crystallization conditions. Under reducing conditions, the greatest chemical activity was acquired by light (La-Nd) lanthanides, for which a direct dependence on the Ce/Ce* value was established. For heavy lanthanides with similar ion sizes relative to Zr+4, crystallochemical factors were more important and a decrease in the dependence of heavy lanthanide concentrations in zircon on Ce/ Ce* was determined.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-04DOI: 10.24930/1681-9004-2023-23-5-910-929
S. G. Kovalev, S. S. Kovalev, A. A. Sharipova
Research subject . Acid rock varieties of the Shatak complex were studied. Materials and methods . The reseach object included the previously unknown abundant mineralization represented by rare earth minerals. The concentration of petrogenic oxides was determined by the X-ray fluorescence method at the IG UFRC RAS (Ufa) using a VRA-30 spectrometer (Carl Zeiss, Germany) with an X-ray tube with a W-anode (30 kV, 40 mA). The amount of rare earth elements in the rocks of the studied area was determined by the ICP-MS method at the Central Research Institute of VSEGEI (St. Petersburg). The mineralogy was studied using a Tescan Vega Compact scanning electron microscope equipped with an Xplorer Oxford Instruments energy-dispersive analyzer (IG UFRC RAS, Ufa). Results . The studied rocks were diverse in chemical composition, varying from alkaline varieties (trachydacites) to low-alkaline rhyolites. These rocks belong to a highalumina type characterized by potassium specialization and a low agpaitic coefficient. It is assumed that the felsic varieties are subvolcanic formations, and the term “rhyolites” in this case characterizes the chemical composition of the rocks, but not their genesis. The amount of rare earth elements in the studied rocks is subject to significant fluctuations, varying from 60.81 g/t to 1625.39 g/t; moreover, their distribution is characterized by significant differentiation. In general, the rocks belong to a contrasting basalt-rhyolitic series, and their genesis is due to the differentiation of magma in the intermediate chamber. Numerous rare-earth minerals were found in the rocks, inlcuding allanite-(Ce), monazite-(Ce), monazite-(La), nioboeshinit-(Y), aeschinite-(Y), talena-(Dy), talena-(Nd), synchisite-(Ce) and Ce–La–Fe oxide. Conclusions . The presence of paragenetic associations of rare-earth minerals, such as allanite-(Ce) + aeschinite-(Y) + nioboaeschinite-(Y) and allanite-(Ce) + talena-(Dy) + talena-(Nd), indicate the formation of rare-earth mineralization in the course of a single process. The described type of mineralization has no analogues on the western slope of the Southern Urals, which substantiates the need for further research.
{"title":"First data on rare earth mineralization in acid rock varieties of the Shatak complex (Southern Urals)","authors":"S. G. Kovalev, S. S. Kovalev, A. A. Sharipova","doi":"10.24930/1681-9004-2023-23-5-910-929","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-910-929","url":null,"abstract":"Research subject . Acid rock varieties of the Shatak complex were studied. Materials and methods . The reseach object included the previously unknown abundant mineralization represented by rare earth minerals. The concentration of petrogenic oxides was determined by the X-ray fluorescence method at the IG UFRC RAS (Ufa) using a VRA-30 spectrometer (Carl Zeiss, Germany) with an X-ray tube with a W-anode (30 kV, 40 mA). The amount of rare earth elements in the rocks of the studied area was determined by the ICP-MS method at the Central Research Institute of VSEGEI (St. Petersburg). The mineralogy was studied using a Tescan Vega Compact scanning electron microscope equipped with an Xplorer Oxford Instruments energy-dispersive analyzer (IG UFRC RAS, Ufa). Results . The studied rocks were diverse in chemical composition, varying from alkaline varieties (trachydacites) to low-alkaline rhyolites. These rocks belong to a highalumina type characterized by potassium specialization and a low agpaitic coefficient. It is assumed that the felsic varieties are subvolcanic formations, and the term “rhyolites” in this case characterizes the chemical composition of the rocks, but not their genesis. The amount of rare earth elements in the studied rocks is subject to significant fluctuations, varying from 60.81 g/t to 1625.39 g/t; moreover, their distribution is characterized by significant differentiation. In general, the rocks belong to a contrasting basalt-rhyolitic series, and their genesis is due to the differentiation of magma in the intermediate chamber. Numerous rare-earth minerals were found in the rocks, inlcuding allanite-(Ce), monazite-(Ce), monazite-(La), nioboeshinit-(Y), aeschinite-(Y), talena-(Dy), talena-(Nd), synchisite-(Ce) and Ce–La–Fe oxide. Conclusions . The presence of paragenetic associations of rare-earth minerals, such as allanite-(Ce) + aeschinite-(Y) + nioboaeschinite-(Y) and allanite-(Ce) + talena-(Dy) + talena-(Nd), indicate the formation of rare-earth mineralization in the course of a single process. The described type of mineralization has no analogues on the western slope of the Southern Urals, which substantiates the need for further research.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"27 7","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-740-765
V. V. Murzin, К. N. Malitch, I. Yu. Badanina, D. A. Varlamov, I. S. Chashchukhin
Research subject . Minerals and mineral assemblages of noble elements in chromitites of the Alapaevsk massif. Aim . A systematic mineralogical study of high-chromium (Cr) and alumina-rich (Al) chromitites with the development of a sequence scheme for mineral formation, including platinum-group minerals (PGMs) and gold alloys. Materials and Methods. Samples of high-Cr and Al chromitites from chromite deposits in various parts of the Alapaevsk massif. Scanning electron microscopy (Tescan VEGAII XMU and JSM-6390LV Jeol with EDX INCA Energy 450 X-Max 80 spectrometers) and electron microprobe analysis (Cameca SX 100 with five wave spectrometers) were used. Results . A diagram showing the sequence of mineral formation in chromitites was designed; primary and secondary mineral assemblages were distinguished, with the latter assemblage being divided into early and late mineral associations. Primary assemblages of high-Cr (Cr 2 O 3 > 50 wt %) and Al (Cr 2 O 3 < 50 wt %) ores are represented by similar minerals, including chromespinel, clinopyroxene, and olivine, with characteristically distinct compositions of these minerals in each type of ores. Minerals of the primary assemblage are synchronous with chrome-spinel and are represented by pentlandite, Cu-bearing pentlandite, chalcopyrite, pyrrhotite, bornite, as well as PGMs (laurite RuS 2 , erlichmanite OsS 2 , native osmium) and Cu-rich gold. Minerals of the secondary early association occur in the form of polyphase inclusions within chrome-spinel. Polyphase inclusions are composed of Cr-bearing chlorite, amphibole, garnet, sulfides (millerite, heazlewoodite) and minerals of native elements, including (Ni, Cr)-bearing copper, nickel-bearing copper, (Cu, Fe, Cr)-bearing nickel, awaruite. Noble metal minerals from the secondary early association were found only in Al chromitites and are represented by laurite, Pt- and Pd arsenides and stibnides, Ru-bearing pentlandite, and high-grade native gold. The secondary late mineral association consists of native copper and awaruite, which are intergrown with serpentine in high-Cr ore. The temperature conditions for the formation of secondary assemblages were estimated using a chlorite geothermometer. The formation temperatures of the studied chlorites from chromitites fall within the range of 250–284°C. Conclusions . Noble metal minerals from secondary associations were formed at temperatures below 350°C together with garnet, amphibole, chlorite, and nickel sulfides. Grains of primary Os–Ir–Ru alloys during epigenetic processes underwent sulfurization with the formation of a fine-grained porous mixture of native and sulfide (sometimes with As) phases, and replacement by Ru-pentlandite. The presence of awaruite and native Cu and Ni in both primary and secondary assemblages of chromotites indicates the reducing conditions for the formation of noble metal minerals. The limited occurrence of high-Cr ores, along with the manifested processes of sulfurization for primary
{"title":"Mineral assemblages from chromitites of the Alapaevsk dunite-harzburgite massif (Middle Urals)","authors":"V. V. Murzin, К. N. Malitch, I. Yu. Badanina, D. A. Varlamov, I. S. Chashchukhin","doi":"10.24930/1681-9004-2023-23-5-740-765","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-740-765","url":null,"abstract":"Research subject . Minerals and mineral assemblages of noble elements in chromitites of the Alapaevsk massif. Aim . A systematic mineralogical study of high-chromium (Cr) and alumina-rich (Al) chromitites with the development of a sequence scheme for mineral formation, including platinum-group minerals (PGMs) and gold alloys. Materials and Methods. Samples of high-Cr and Al chromitites from chromite deposits in various parts of the Alapaevsk massif. Scanning electron microscopy (Tescan VEGAII XMU and JSM-6390LV Jeol with EDX INCA Energy 450 X-Max 80 spectrometers) and electron microprobe analysis (Cameca SX 100 with five wave spectrometers) were used. Results . A diagram showing the sequence of mineral formation in chromitites was designed; primary and secondary mineral assemblages were distinguished, with the latter assemblage being divided into early and late mineral associations. Primary assemblages of high-Cr (Cr 2 O 3 > 50 wt %) and Al (Cr 2 O 3 < 50 wt %) ores are represented by similar minerals, including chromespinel, clinopyroxene, and olivine, with characteristically distinct compositions of these minerals in each type of ores. Minerals of the primary assemblage are synchronous with chrome-spinel and are represented by pentlandite, Cu-bearing pentlandite, chalcopyrite, pyrrhotite, bornite, as well as PGMs (laurite RuS 2 , erlichmanite OsS 2 , native osmium) and Cu-rich gold. Minerals of the secondary early association occur in the form of polyphase inclusions within chrome-spinel. Polyphase inclusions are composed of Cr-bearing chlorite, amphibole, garnet, sulfides (millerite, heazlewoodite) and minerals of native elements, including (Ni, Cr)-bearing copper, nickel-bearing copper, (Cu, Fe, Cr)-bearing nickel, awaruite. Noble metal minerals from the secondary early association were found only in Al chromitites and are represented by laurite, Pt- and Pd arsenides and stibnides, Ru-bearing pentlandite, and high-grade native gold. The secondary late mineral association consists of native copper and awaruite, which are intergrown with serpentine in high-Cr ore. The temperature conditions for the formation of secondary assemblages were estimated using a chlorite geothermometer. The formation temperatures of the studied chlorites from chromitites fall within the range of 250–284°C. Conclusions . Noble metal minerals from secondary associations were formed at temperatures below 350°C together with garnet, amphibole, chlorite, and nickel sulfides. Grains of primary Os–Ir–Ru alloys during epigenetic processes underwent sulfurization with the formation of a fine-grained porous mixture of native and sulfide (sometimes with As) phases, and replacement by Ru-pentlandite. The presence of awaruite and native Cu and Ni in both primary and secondary assemblages of chromotites indicates the reducing conditions for the formation of noble metal minerals. The limited occurrence of high-Cr ores, along with the manifested processes of sulfurization for primary","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"30 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-785-808
S. B. Shishlov, E. Yu. Akimova, K. A. Dubkova
Research subject . Gravelites and conglomerates of the Upper Carboniferous and Permian of Western Taimyr. Aim . To reveal features of the petrographic composition of coarse clastic rocks and, on this basis, to clarify the ideas about the composition and position of the feeding province of the western part of the Taimyr sedimentary basin in the Late Paleozoic. Materials and methods . The analysis of materials collected during a layer-by-layer study of sections and microscopic description of 47 large transparent sections with the count of psephitic (more than 2 mm) fragments of quartzites, felsic and basic igneous, metamorphic and sedimentary rocks was performed. The revealed features of the petrographic composition of psephytoliths, in combination with a generalization of previously published geodynamic and paleogeographic reconstructions, were used to refine the model of the geological development of the Taimyr fold-thrust belt and adjacent areas in the Late Paleozoic. Results . It was established that the sections contain polymictic lithoclastic (83%) and petroclastic (15%) psephytoliths, with occasional inclusions of oligomictic essentially quartz varieties (2%). Minor changes in the composition of clasts over time indicate the existence of a single source of clastic material during the entire Late Paleozoic, which formed the sections of Western Taimyr. It was shown that the maturity of psephytolites increases from the southwest to the northwest and northeast. Numerous fragments of phtanites and lydites with remains of radiolarians of the Middle Devonian – early Early Carboniferous were identified, analogs of which are present in the Lemva zone of the Urals and in the basement of Western Siberia. Conclusions . The material forming the coarse clastic rocks of Western Taimyr was transported by the river for 600–1000 km from the folded structures of the “West Siberian land” located in the southwest (in modern coordinates), which formed in the Visean–Serpukhovian ages of the Early Carboniferous during the collision of the East - European, Kazakhstan and Siberian continental blocks.
{"title":"Petrographic composition and material sources of Upper Paleozoic rough-clastic rocks in Western Taimyr","authors":"S. B. Shishlov, E. Yu. Akimova, K. A. Dubkova","doi":"10.24930/1681-9004-2023-23-5-785-808","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-785-808","url":null,"abstract":"Research subject . Gravelites and conglomerates of the Upper Carboniferous and Permian of Western Taimyr. Aim . To reveal features of the petrographic composition of coarse clastic rocks and, on this basis, to clarify the ideas about the composition and position of the feeding province of the western part of the Taimyr sedimentary basin in the Late Paleozoic. Materials and methods . The analysis of materials collected during a layer-by-layer study of sections and microscopic description of 47 large transparent sections with the count of psephitic (more than 2 mm) fragments of quartzites, felsic and basic igneous, metamorphic and sedimentary rocks was performed. The revealed features of the petrographic composition of psephytoliths, in combination with a generalization of previously published geodynamic and paleogeographic reconstructions, were used to refine the model of the geological development of the Taimyr fold-thrust belt and adjacent areas in the Late Paleozoic. Results . It was established that the sections contain polymictic lithoclastic (83%) and petroclastic (15%) psephytoliths, with occasional inclusions of oligomictic essentially quartz varieties (2%). Minor changes in the composition of clasts over time indicate the existence of a single source of clastic material during the entire Late Paleozoic, which formed the sections of Western Taimyr. It was shown that the maturity of psephytolites increases from the southwest to the northwest and northeast. Numerous fragments of phtanites and lydites with remains of radiolarians of the Middle Devonian – early Early Carboniferous were identified, analogs of which are present in the Lemva zone of the Urals and in the basement of Western Siberia. Conclusions . The material forming the coarse clastic rocks of Western Taimyr was transported by the river for 600–1000 km from the folded structures of the “West Siberian land” located in the southwest (in modern coordinates), which formed in the Visean–Serpukhovian ages of the Early Carboniferous during the collision of the East - European, Kazakhstan and Siberian continental blocks.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"31 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-844-867
N. I. Maksimenko, T. G. Shumilova, V. V. Ulyashev
Research subject. Suevites from the eastern sector of the Kara astrobleme, located in the basin of the Bolshaya Vanuyta river. Aim. To identify the suevitic type and to clarify the facial features of the suevites from the B. Vanuyta River. Materials . Hand-size samples of suevites collecteed in the basins of B. Vanuyta, Anaroga, Kara, and Sopchayu rivers, as well as samples of siltstones collected outside the Kara crater (rivers Halmeryu, Sayakha, Putyu, Anaroga and the creek Lavovyi). The samples were used for preparing polished thin sections and powder specimens for analytical works. Methods . Field observations, optical and electron scanning microscopy, and silicate analysis by the wet chemical method. Results and conclusions . The structural-textural and petrochemical features of the matrix, fragments of impact glasses, and lithoclasts of suevites from the B. Vanuyta river were characterized. The suevite matrix was found to exhibit an intensely sintered character and to be presented by feldspar, quartz, calcite, chlorite, muscovite, glauconite, and titanite. Lithoclasts include siltstones, sandstones, limestones, mudstones, and shales. Vitroclasts are characterized by angular and irregular morphology with different border patterns, and spotted, fluid, and porous textures. The similarity of the chemical composition of siltstone clusters and similar target rocks confirms the genetic relationship and the leading role of this type of target rocks in the formation of the studied suevites. The proximity in the composition of the impact glasses of the studied suevites and the glasses of type I and II suevites indicates the formation of suevite vitroclasts in the river B. Vanuyta by a similar protolith – siltstones and a clay component of the limestones. The matrix lithification character, morphology and nature of the vitroclast outlines indicate that the suevites from the B. Vanuyta river are the rocks of an aerodynamic facies formed under relatively high-temperature conditions, which structurally lie at the lower part of the detrital impactites sequence of the aerodynamic facies. The studied rocks are close to the type I suevites by the composition of the protolith and differ in the conditions of their formation. With the type II suevites, they have similar facies characteristics, but differ in the composition of the target rocks fragments. It is determined that the leading factor in the typification of suevites from the Kara astrobleme is the chemical composition, at the same time, the types can be subdivided more fractionally based on the specifics of the facies environments of their formation.
{"title":"Complex characteristics of suevites at the B. Vanuyta river (Kara astrobleme, Russia)","authors":"N. I. Maksimenko, T. G. Shumilova, V. V. Ulyashev","doi":"10.24930/1681-9004-2023-23-5-844-867","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-844-867","url":null,"abstract":"Research subject. Suevites from the eastern sector of the Kara astrobleme, located in the basin of the Bolshaya Vanuyta river. Aim. To identify the suevitic type and to clarify the facial features of the suevites from the B. Vanuyta River. Materials . Hand-size samples of suevites collecteed in the basins of B. Vanuyta, Anaroga, Kara, and Sopchayu rivers, as well as samples of siltstones collected outside the Kara crater (rivers Halmeryu, Sayakha, Putyu, Anaroga and the creek Lavovyi). The samples were used for preparing polished thin sections and powder specimens for analytical works. Methods . Field observations, optical and electron scanning microscopy, and silicate analysis by the wet chemical method. Results and conclusions . The structural-textural and petrochemical features of the matrix, fragments of impact glasses, and lithoclasts of suevites from the B. Vanuyta river were characterized. The suevite matrix was found to exhibit an intensely sintered character and to be presented by feldspar, quartz, calcite, chlorite, muscovite, glauconite, and titanite. Lithoclasts include siltstones, sandstones, limestones, mudstones, and shales. Vitroclasts are characterized by angular and irregular morphology with different border patterns, and spotted, fluid, and porous textures. The similarity of the chemical composition of siltstone clusters and similar target rocks confirms the genetic relationship and the leading role of this type of target rocks in the formation of the studied suevites. The proximity in the composition of the impact glasses of the studied suevites and the glasses of type I and II suevites indicates the formation of suevite vitroclasts in the river B. Vanuyta by a similar protolith – siltstones and a clay component of the limestones. The matrix lithification character, morphology and nature of the vitroclast outlines indicate that the suevites from the B. Vanuyta river are the rocks of an aerodynamic facies formed under relatively high-temperature conditions, which structurally lie at the lower part of the detrital impactites sequence of the aerodynamic facies. The studied rocks are close to the type I suevites by the composition of the protolith and differ in the conditions of their formation. With the type II suevites, they have similar facies characteristics, but differ in the composition of the target rocks fragments. It is determined that the leading factor in the typification of suevites from the Kara astrobleme is the chemical composition, at the same time, the types can be subdivided more fractionally based on the specifics of the facies environments of their formation.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-766-784
I. R. Rakhimov, A. V. Vishnevskiy
Subject research . Morphology and chemical composition of amphiboles from ultramafic-mafic rocks of the Khudolaz complex. Methods . Morphological studies were carried out using optical (Carl Zeiss Axioskop 40A) and electron (Tescan Vega Compact) microscopes. The chemical composition of minerals was determined using CAMECA SX 100 and JEOL JXA-8230 electron probe microanalyzers . Results . The rocks under study are dominated by xenomorphic brown titanium hornblende crystals, formed mainly due to the reaction of clinopyroxene with a residual water-saturated melt at 920–1040°C. Euhedral brown hornblende, which crystallized directly from the residual water-saturated melt in the same temperature range, was found in small amounts. Green hornblende originated along the edges and cracks in brown hornblende crystals during the late magmatic stage and early hydrothermal stage (670–830°C) at the subsolidus transformation. At the hydrothermal stage (620–650°C and below), brown and green hornblende were partially replaced by actinolite and cummingtonite. Conclusions . The nature of changes in the composition of brown hornblende indicates similar petrogenesis conditions at the late magmatic stage in all intrusions of the Khudolaz complex. The process of transition from brown hornblende to green hornblende occurred with a gradual increase in oxygen fugacity (ΔNNO from –0.2…+0.4 to +0.9…+2.5), and was accompanied by decrease of Ti, Fe 2+ , Na and the increase of Si, Al VI , Mg, and K in the mineral structure. The low concentrations of F and Cl in hornblende crystals indicate their formation after migration of halogens from the melt.
{"title":"Hornblende in ultramafic-mafic rocks of the Khudolaz Complex of the Southern Urals: Crystallization conditions and petrological implications","authors":"I. R. Rakhimov, A. V. Vishnevskiy","doi":"10.24930/1681-9004-2023-23-5-766-784","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-766-784","url":null,"abstract":"Subject research . Morphology and chemical composition of amphiboles from ultramafic-mafic rocks of the Khudolaz complex. Methods . Morphological studies were carried out using optical (Carl Zeiss Axioskop 40A) and electron (Tescan Vega Compact) microscopes. The chemical composition of minerals was determined using CAMECA SX 100 and JEOL JXA-8230 electron probe microanalyzers . Results . The rocks under study are dominated by xenomorphic brown titanium hornblende crystals, formed mainly due to the reaction of clinopyroxene with a residual water-saturated melt at 920–1040°C. Euhedral brown hornblende, which crystallized directly from the residual water-saturated melt in the same temperature range, was found in small amounts. Green hornblende originated along the edges and cracks in brown hornblende crystals during the late magmatic stage and early hydrothermal stage (670–830°C) at the subsolidus transformation. At the hydrothermal stage (620–650°C and below), brown and green hornblende were partially replaced by actinolite and cummingtonite. Conclusions . The nature of changes in the composition of brown hornblende indicates similar petrogenesis conditions at the late magmatic stage in all intrusions of the Khudolaz complex. The process of transition from brown hornblende to green hornblende occurred with a gradual increase in oxygen fugacity (ΔNNO from –0.2…+0.4 to +0.9…+2.5), and was accompanied by decrease of Ti, Fe 2+ , Na and the increase of Si, Al VI , Mg, and K in the mineral structure. The low concentrations of F and Cl in hornblende crystals indicate their formation after migration of halogens from the melt.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"31 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-809-819
I. Kh. Shumilov
Research subject . The article presents the results of morphological, mineralogical, and geochemical studies into gley zones in the Devonian red-colored sediments of the Middle Timan. Aim . Determination of the timing of gleization processes in the formation history of the Devonian sedimentary strata; identification of morphological, mineralogical and geochemical features of gley zones. Methods. A macroscopic study of the morphology of gley zones in successive sections of the sediments was carried out in field conditions. Thin sections were studied using a Nikon eclipse LV100 ND polarization microscope with a Nikon DS Fi2 camera; polished samples were characterized using a TESCAN electron microscope VEGA3 with an Oxford instruments X-Max energy dispersion attachment; the chemical composition was determined by an X-ray fluorescent silicate method on a MESA-500W spectrometer; X-ray diffraction analysis was performed using a Shimadzu XRD-6000 diffractometer under the CuKα radiation. Results . In terms of size and morphological features, the gley zones under study are divided into four types: point, veined, lens-shaped, and bed-shaped. The similarity between the forms of gley zones and core organics fragments was established both in plan and vertically. The lithological heterogeneity of rocks (stratification) does not have any effect on the development of gley processes. Changes in the content of rock-forming elements during gleization are confined to intensive iron removal and a slight decrease in the potassium content; the silica content remains almost unchanged. An increase in the content of aluminum, titanium, and magnesium was observed. Among the contents of microelements, trends towards accumulation of Y and Yb, removal of Ga, V, Co, Ni are noticeable. Conclusions . Gleization processes proceeded for a very long time until the sedimentary sequence was completely formed and compacted; the main mechanism of chemical element migration was diffusion.
{"title":"Gley catagenesis of Devonian red-colored rocks on the Middle Timan","authors":"I. Kh. Shumilov","doi":"10.24930/1681-9004-2023-23-5-809-819","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-809-819","url":null,"abstract":"Research subject . The article presents the results of morphological, mineralogical, and geochemical studies into gley zones in the Devonian red-colored sediments of the Middle Timan. Aim . Determination of the timing of gleization processes in the formation history of the Devonian sedimentary strata; identification of morphological, mineralogical and geochemical features of gley zones. Methods. A macroscopic study of the morphology of gley zones in successive sections of the sediments was carried out in field conditions. Thin sections were studied using a Nikon eclipse LV100 ND polarization microscope with a Nikon DS Fi2 camera; polished samples were characterized using a TESCAN electron microscope VEGA3 with an Oxford instruments X-Max energy dispersion attachment; the chemical composition was determined by an X-ray fluorescent silicate method on a MESA-500W spectrometer; X-ray diffraction analysis was performed using a Shimadzu XRD-6000 diffractometer under the CuKα radiation. Results . In terms of size and morphological features, the gley zones under study are divided into four types: point, veined, lens-shaped, and bed-shaped. The similarity between the forms of gley zones and core organics fragments was established both in plan and vertically. The lithological heterogeneity of rocks (stratification) does not have any effect on the development of gley processes. Changes in the content of rock-forming elements during gleization are confined to intensive iron removal and a slight decrease in the potassium content; the silica content remains almost unchanged. An increase in the content of aluminum, titanium, and magnesium was observed. Among the contents of microelements, trends towards accumulation of Y and Yb, removal of Ga, V, Co, Ni are noticeable. Conclusions . Gleization processes proceeded for a very long time until the sedimentary sequence was completely formed and compacted; the main mechanism of chemical element migration was diffusion.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-03DOI: 10.24930/1681-9004-2023-23-5-820-843
F. I. Zhimulev, A. V. Kotlyarov, I. S. Novikov, N. V. Sennikov, K. K. Kolesov
Research subject . The Nenya-Chumysh basin is a long-term Mesozoic intracontinental sedimentary basin confined to the zone of a regional fault separating the Salair from the structures of Gorny Altai, Gornaya Shoria, and the Kuznetsk basin. Aim . To establish the geological and structural-kinematic characteristics of impulses of intracontinental orogeny that took place during the Mesozoic and Cenozoic in the territory of the northwestern part of the Altai-Sayan Folded Area. Materials and Methods . Geological maps of the area, geophysical data on the position of the base of the Paleozoic basement, satellite images and digital elevation models were used. The sedimentary filling of the basin is considered as a chronicle of tectonic movements in the NW part of the Altai-Sayan Folded Area at the intracontinental stage of development. Results . The Early Jurassic, Early Cretaceous, Late Cretaceous-Paleogene, and Neogene-Quaternary tectonic stages of the development of the Nenya-Chumysh basin were distinguished. In the Early Jurassic, the Nenya-Chumysh basin was a pull-apart basin in a left-hand strike-slip zone. This stage is associated with the accumulation of coal-bearing deposits of the Glushinskaya Formation, the thickness of which in the Nenya-Chumysh basin reaches about 1900 m. In the Early Cretaceous, as a result of changes in the stress field, the Nenya-Chumysh basin was transformed into a thrust basin, composed of terrigenous deposits of the Ilek Formation, forming a wedge-shaped sedimentary basin characteristic of foreland troughs. The neotectonic structure of the Nenya-Chumysh basin, formed in the stress field of the Indo-Eurasian collision, inherits an older structural plan in general terms, although differing in details. A non-inherited structure is the transverse neotectonic uplift of the Sary-Chumysh swell. Conclusions . The Early Jurassic stage is related with the closure of the Paleo-Tethys and the collision of a series of Cimmerian terranes with the southern margin of Eurasia, Early Cretaceous stage is caused with Mongol-Okhotsk collision, and the Cenozoic stage proceeds with the ongoing Indo-Eurasian collision. The geological evolution of continental sedimentary basins controlled by regional faults can be used as a source of information about the intensity and kinematic pattern of impulses of intracontinental orogeny in the geological past.
{"title":"Geological structure and Mesozoic-Cenozoic tectonic evolution of the Nenya-Chumysh basin (Southern Salair, southern Western Siberia)","authors":"F. I. Zhimulev, A. V. Kotlyarov, I. S. Novikov, N. V. Sennikov, K. K. Kolesov","doi":"10.24930/1681-9004-2023-23-5-820-843","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-820-843","url":null,"abstract":"Research subject . The Nenya-Chumysh basin is a long-term Mesozoic intracontinental sedimentary basin confined to the zone of a regional fault separating the Salair from the structures of Gorny Altai, Gornaya Shoria, and the Kuznetsk basin. Aim . To establish the geological and structural-kinematic characteristics of impulses of intracontinental orogeny that took place during the Mesozoic and Cenozoic in the territory of the northwestern part of the Altai-Sayan Folded Area. Materials and Methods . Geological maps of the area, geophysical data on the position of the base of the Paleozoic basement, satellite images and digital elevation models were used. The sedimentary filling of the basin is considered as a chronicle of tectonic movements in the NW part of the Altai-Sayan Folded Area at the intracontinental stage of development. Results . The Early Jurassic, Early Cretaceous, Late Cretaceous-Paleogene, and Neogene-Quaternary tectonic stages of the development of the Nenya-Chumysh basin were distinguished. In the Early Jurassic, the Nenya-Chumysh basin was a pull-apart basin in a left-hand strike-slip zone. This stage is associated with the accumulation of coal-bearing deposits of the Glushinskaya Formation, the thickness of which in the Nenya-Chumysh basin reaches about 1900 m. In the Early Cretaceous, as a result of changes in the stress field, the Nenya-Chumysh basin was transformed into a thrust basin, composed of terrigenous deposits of the Ilek Formation, forming a wedge-shaped sedimentary basin characteristic of foreland troughs. The neotectonic structure of the Nenya-Chumysh basin, formed in the stress field of the Indo-Eurasian collision, inherits an older structural plan in general terms, although differing in details. A non-inherited structure is the transverse neotectonic uplift of the Sary-Chumysh swell. Conclusions . The Early Jurassic stage is related with the closure of the Paleo-Tethys and the collision of a series of Cimmerian terranes with the southern margin of Eurasia, Early Cretaceous stage is caused with Mongol-Okhotsk collision, and the Cenozoic stage proceeds with the ongoing Indo-Eurasian collision. The geological evolution of continental sedimentary basins controlled by regional faults can be used as a source of information about the intensity and kinematic pattern of impulses of intracontinental orogeny in the geological past.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"11 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135874853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-02DOI: 10.24930/1681-9004-2023-23-5-721-739
P. S. Kozlov, S. V. Berzin, K. S. Ivanov, D. S. Yudin
Research subject . We studied the concentric-zonal massif (≈400 × 400 m) of amphibole-rich ultramafic rocks composed of amphibole peridotite (schriesheimite and amphibole wehrlite) with olivinite schlieren, pyroxenite and hornblendite located among gabbro at the Schrisheimite Hill in the Revdinskiy massif of the Ural Platinum Belt. The scope is characteristic of both of amphibole peridotites, which are extremely rare in the massifs of the Ural Platinum Belt, and the associated amphibole-rich ultramafic rocks. Aim. To expand the understanding of aqueous ultramafic magmatism in Ural Platinum Belt massifs. Materials and methods . To determine the age, we selected monofractions of high-alumina amphibole (pargasite-magnesiohastingsite) from two samples. Amphibole is not significantly altered by the regional metamorphism. 40 Ar/ 39 Ar dating was carried out according to the method described in (Travin et al., 2009; Yudin et al., 2021). The argon isotope composition was measured using a Micromass 5400 mass spectrometer (IGM SB RAS). Results. Amphibole peridotite has a hypidiomorphic (subhedral) or poikilitic texture. It is typical of igneous rocks, which indicates the crystallization of amphibole peridotite was by H 2 O-saturated magmas. Schlieren segregations of fine-grained schriesheimites and fine-grained olivinites are among coarse-grained schriesheimites. Amphibole peridotite, pyroxenite and hornblendite are deficient in high field strength elements (HFSE) and enriched in large ion lithophile elements (LILE) (with contrast concentration of Cs and Rb), which is typical of supra-subduction igneous formations. We obtained a 40 Ar/ 39 Ar age of 437.2 ± 6.7 Ma for an amphibole from hornblendite, which differs significantly from the ages of hornblendite determined earlier. Conclusions . Our new data indicate that hornblendite dikes in different UPB massifs formed over a fairly long time interval from the Early Silurian to the Early Devonian. These data expand modern ideas about the timing and nature of ultramafic water magmatism in the massifs of the Ural Platinum Belt.
{"title":"Amphibole peridotite and hornblendite of the Schrisheimite Hill intrusion of the Revdinskiy massif (Ural Platinum Belt)","authors":"P. S. Kozlov, S. V. Berzin, K. S. Ivanov, D. S. Yudin","doi":"10.24930/1681-9004-2023-23-5-721-739","DOIUrl":"https://doi.org/10.24930/1681-9004-2023-23-5-721-739","url":null,"abstract":"Research subject . We studied the concentric-zonal massif (≈400 × 400 m) of amphibole-rich ultramafic rocks composed of amphibole peridotite (schriesheimite and amphibole wehrlite) with olivinite schlieren, pyroxenite and hornblendite located among gabbro at the Schrisheimite Hill in the Revdinskiy massif of the Ural Platinum Belt. The scope is characteristic of both of amphibole peridotites, which are extremely rare in the massifs of the Ural Platinum Belt, and the associated amphibole-rich ultramafic rocks. Aim. To expand the understanding of aqueous ultramafic magmatism in Ural Platinum Belt massifs. Materials and methods . To determine the age, we selected monofractions of high-alumina amphibole (pargasite-magnesiohastingsite) from two samples. Amphibole is not significantly altered by the regional metamorphism. 40 Ar/ 39 Ar dating was carried out according to the method described in (Travin et al., 2009; Yudin et al., 2021). The argon isotope composition was measured using a Micromass 5400 mass spectrometer (IGM SB RAS). Results. Amphibole peridotite has a hypidiomorphic (subhedral) or poikilitic texture. It is typical of igneous rocks, which indicates the crystallization of amphibole peridotite was by H 2 O-saturated magmas. Schlieren segregations of fine-grained schriesheimites and fine-grained olivinites are among coarse-grained schriesheimites. Amphibole peridotite, pyroxenite and hornblendite are deficient in high field strength elements (HFSE) and enriched in large ion lithophile elements (LILE) (with contrast concentration of Cs and Rb), which is typical of supra-subduction igneous formations. We obtained a 40 Ar/ 39 Ar age of 437.2 ± 6.7 Ma for an amphibole from hornblendite, which differs significantly from the ages of hornblendite determined earlier. Conclusions . Our new data indicate that hornblendite dikes in different UPB massifs formed over a fairly long time interval from the Early Silurian to the Early Devonian. These data expand modern ideas about the timing and nature of ultramafic water magmatism in the massifs of the Ural Platinum Belt.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135975488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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