Litosfera最新文献

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"title":"Distribution of brachiopods in the Lower Visean deposits in the Eastern Urals","authors":"N. A. Kucheva","doi":"10.24930/1681-9004-2019-19-1-59-80","DOIUrl":"https://doi.org/10.24930/1681-9004-2019-19-1-59-80","url":null,"abstract":"Subject. This paper is aimed at investigating the distribution of brachiopods across the stratotypes of the Lower Visean regional substages and formations, as well as of the Upper Visean Zhukovsky regional substage, which are presently located in the East Uralian and Magnitogorskian megazones of the Eastern Urals. Materials and methods. Brachiopods were one of the most numerous groups of benthic organisms inhabiting the Early Carboniferous marine basins now located in the eastern Urals. This paper presents information on the distribution of brachiopods across the carbonate and carbonate-terrigenous facies of the Middle (Pokrovskoe, Zhukovo, Smolino, Brod-Kljuchiki) and Southern (Nizhnyaya Gusikha, Verkhnyaya Kardailovka, Kipchak, Ust-Grekhovka and Khudolaz) Urals sections.Results. It is found that Delepinеа lebedevi, D. comoides, Ovatia markovskii and Composita sp. were the domineering species during the Early Visean period. The Ust-Grekhovsky time marked the appearance of migrant species, which resulted not only in a decrease in the proportion of Delepinеа and Ovatia but also significantly changed the entire structure of the local brachiopod communities. The evolutionary transformation of the Ovatia genus at the Ust-Grekhovsky–Zhukovsky time boundary led to the appearance of the Linoprotonia genus and subsequently to the Globosoproductus genus (the first representative of the Gigantoproductini). The Zhukovsky period was characterized by a continuing reorganization of the composition and structure of the communities, featuring a change in the dominant taxa. The Linoprotonia and Globosoproductus genera became widespread. Rare representatives of the Gigantoproductus, Datangia and Semiplanus genera appeared.Conclusions. A direct correlation between the diversity of brachiopod associations and abiotic factors is found. The most diverse associations represented by the taxa of several orders, including Gigantoproductini, inhabited shallow-water environments with carbonate sedimentation. The evolution of brachiopods over the Early Visean and Zhukovsky periods of the Late Visean was characterized by natural succession in the composition of genera and species, with the most significant alteration having occurred in the Ust-Grekhovsky and Zhukovsky periods.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76518514","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}

{"title":"Petrography of garnet-containing rocks of the Ufalei block, the Southern Urals","authors":"L. Y. Kabanova, Vsevolod N. Anfilogov, M. A. Igumentseva, V. A. Kotlyarov","doi":"10.24930/1681-9004-2018-18-6-859-869","DOIUrl":"https://doi.org/10.24930/1681-9004-2018-18-6-859-869","url":null,"abstract":"Object of study. The article presents of the petrographic study results of the garnet-containing rocks from the Ufaleiskii complex, located on the border of the Ufaleyskii metamorphic gneiss-amphibolite block with the Main Ural Fault (GUR). Methods. Petrographic studies were conducted using a polarizing microscope Axiolab ZS и Olimpus BX 51. Chemical composition of garnets is performed on the raster electron microscope of the РЭММА-202М with an energy dispersive spectrometer LZ-5. Results. Investigations made it possible to distinguish two types of garnet-containing rocks. One type, in which garnet was formed after amphibole (amphibolites and gornbendites), and the second one, in which garnet is the primary mineral (metamorphic schists). Zoisite and chlorite are formed in rocks of the first type together with granate. CaO, MgO, FeO and Al2O3 were extracted from amphibole, in the process of crystallization of garnet, some of these components went to form zoisite and chlorite, and the released silica formed quartz. Garnet grains in these rocks are 64–68% composed of almandine. In the rocks of the second type, represented by biotite-hornblende, biotite-chlorite-quartz and double-mica schists, garnet is the primary mineral formed from the original rocks in the process of progressive metamorphism. The composition of the garnet in these rocks correlates with the composition of the original rock. Conclusion. A complex of garnet-containing rocks with a high content of granulated quartz may be of interest as a raw material for obtaining pure quartz concentrates. The paper presents the results of a detailed petrographic study of all types of rocks of the complex and discusses possible options for their genesis.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72756515","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}

{"title":"Geological structure of the Pre-jurassic basement of the Yugansk-Koltogorsk zone of the West Siberia","authors":"K. Ivanov, S. Berzin, N. V. Vakhrusheva, N. Kostrov, O. Pogromskaya","doi":"10.24930/1681-9004-2018-18-6-839-858","DOIUrl":"https://doi.org/10.24930/1681-9004-2018-18-6-839-858","url":null,"abstract":"Subject of the study.We have carried out an additional exploration on petrography, petrochemistry, geochemistry, geochronology and biostratigraphy of rock complexes of the Yugansk-Koltogorsk (central part of West Siberia).Materials and methods.The materials are core samples from wells that penetrated the Pre-Jurassic basement rock complexes The used methods are as follows: X-ray spectrum microanalysis (Cameca SX 100, JEOL-733 Superprobe); the silicate analysis of the rocks (СРМ-18 and EDX-100); mass-spectroscopy with inductively coupled plasma (ICP-MS) (ELAN-9000 and Element2); zircons were analysed with a high resolution ionic microprobe SHRIMP-II (U-Pb); Ar-Ar dating was carried out by Micromass 5400; biostratigraphy, petrochemestry.Results.A geological map of Yugan-Koltogor zone of the central part of West-Siberian plate in a scale 1:500 000 was created. The map is a set of informational geological, geophysical and other layers. It was established that age of granites is Early Permian, the basalts of the rift zone began to form 268.4 ± 7.5 Ma ago (Ar-Ar). Conclusions. Volcanism in the axial rift zones of the West-Siberian megabasin basement began earlier than it is supposed before our study and significantly earlier of that of trap basalts of Siberian platform.","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84421580","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}

{"title":"Reference sections OF Cisuralian Series (Permian System): geochemical features","authors":"G. Mizens, R. Sungatullin, G. Sungatullina, B. Gareev, G. Batalin, F. F. Sadriev","doi":"10.24930/1681-9004-2018-18-6-819-838","DOIUrl":"https://doi.org/10.24930/1681-9004-2018-18-6-819-838","url":null,"abstract":"Object.Geochemical features of rocks from the Dal’ny Tulkas and Mechetlino sections located in the southern part of the West Urals foredeep are considered and are offered as International Standards for the global correlation (GSSP) of the lower boundaries of the Artinskian and Kungurian stages.Materials and methods.The content of rock-forming oxides and other components were studied for 15 and 20 samples of carbonate, clay and sandy rocks respectively in the sections of Dalnii Tyulkas and Mechetlino. The determination of the chemical composition of rocks was performed using a wave-dispersive X-ray fluorescence spectrometer S8 Tiger (Bruker, Germany). Results. The lithological characteristics of the sections, the content of oxides in mudstones and limestones of the boundary Sakmarian-Artinskian and of the boundary ArtinskianKungurian are taken. Mudstones of different stage are almost identical in average contents of the main components, whereas limestones have some differences. Correlative connections of oxides are analyzed and conclusions about mineral composition of rocks are made. Using the petrochemical modules and diagrams, it was established that the clay rocks in considered sections have mainly a hydromica composition. Based on the analysis of the indices of chemical weathering CIA, it is shown that the climate in the Cisuralian Epoch was predominantly arid. The tectonic environment of forming demolition sources, presumably corresponded to the active and passive margins of the continents.Conclusions.The main lithochemical characteristics of the rocks of the two sections under consideration are somewhat different, however, the boundaries of the stratigraphic subdivisions of each of them are virtually indistinguishable by lithochemical parameters, which may indicate the benefit of the continuity of sedimentation at the borders of centuries of the Cisuralian Epoch in this region. The conditions of sedimentation and the nature of eroded rocks in the area of demolition remained relatively constant. This is a positive point when looking the sections as International Standards for the global correlation (GSSP) reference objects – “golden nails”. ","PeriodicalId":32819,"journal":{"name":"Litosfera","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80754181","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}