Paleozoic Age of Metaterrigenous Sequences of the Maksyutov Metamorphic Complex (Southern Urals): Results of U–Pb Dating of Detrital Zircons     

Golionko  B. G.  Ryazantsev  A. V.  Degtyarev  K. E.  Kanygina  N. A.  Kuznetsov  N. B.  Sheshukov  V. S.  Dubensky  A. S.  Gareev  B. I. 《Doklady Earth Sciences》2020,493(2):578-583

Doklady Earth Sciences - The first U–Pb (LA–ICP–MS) isotope dating of detrital zircons from quartzites of two strata of the Maksyutov metamorphic complex (Southern Urals) was...  相似文献   

The 238U/235U Ratio as an Indicator of Redox Conditions in the Ediacaran Paleobasin (Sequence of the Chaya River,Baikal–Patom Highland,Southern Part of Central Siberia)     

Chugaev  A. V.  Chernyshev  I. V.  Pokrovsky  B. G.  Mandzhieva  G. V.  Gareev  B. I.  Sadasyuk  A. S.  Batalin  G. A. 《Doklady Earth Sciences》2019,485(1):336-340

Doklady Earth Sciences - Abstract—This article is devoted to a study of variations in the U isotopic composition (238U/235U) in the section of clastic–carbonate Ediacaran sediments...  相似文献   

Variations of the 238U/235U Isotope Ratio in Metasedimentary Rocks and Evidence of Changes in Sedimentation Conditions during the Ediacarian Period of the Neoproterozoic     

Chugaev  A. V.  Chernyshev  I. V.  Budyak  A. E.  Mandzhieva  G. V.  Sadasyuk  A. S.  Gareev  B. I. 《Doklady Earth Sciences》2019,484(2):167-172

Doklady Earth Sciences - The isotopic composition of uranium is a new geochemical indicator that facilitates reconstruction of the redox conditions of geological processes. In this paper the...  相似文献   

Paleoclimate changes in the late precambrian: Evidence from the upper precambrian section of the South Urals     

A. V. Maslov  V. N. Podkovyrov  E. Z. Gareev  O. V. Graunov 《Lithology and Mineral Resources》2016,51(2):117-135

The climatic impact on the formation of fine-grained rocks from the Riphean stratotype and Vendian Asha Group on the western slope of the South Urals during the time interval lasting approximately 1200 Ma is considered. It is shown that these rocks are largely represented by “tectonosilicate-dominated” shales. This feature combined with changes in the average K₂O/Al₂O₃ values disavows the hypothesis in (Kennedy et al., 2006), according to which the growth of free oxygen concentration in the Late Riphean and Vendian atmosphere was determined by gradual intensification of the organic carbon extraction from the biosphere by clays. The average values of the hydrolyzate module, chemical index of alteration (CIA), and several lithogeochemical parameters calculated for the Riphean and Vendian clayey rocks provide grounds for the conclusion that intensity of weathering in paleodrainage areas during the accumulation of the Upper Precambrian sedimentary successions was low. The curve reflecting changes of the average CIA values in the Upper Precambrian fine-grained siliciclastic rocks of the South Urals is similar to some extent with the “standard” CIA_correct. curve (GonzalezAlvarez and Kerrich, 2012). It is assumed that changes in microand macrobiotic communities during the Late Precambrian were controlled to a variable extent by climate fluctuations as well. At the same time, these fluctuations most likely left the chemical composition of water in the ocean virtually unchanged, which is evident from analysis of the redox conditions in the ocean and the distribution of primary producers with the average CIA_correct. and CIA values.  相似文献   

Tectonic setting discrimination diagrams for terrigenous rocks: a comparison     

A. V. Maslov  V. N. Podkovyrov  G. A. Mizens  A. D. Nozhkin  A. M. Fazliakhmetov  A. I. Malinovsky  A. K. Khudoley  L. N. Kotova  A. V. Kuptsova  E. Z. Gareev  R. I. Zainullin 《Geochemistry International》2016,54(7):569-583

An attempt is made to compare discrimination diagrams of the first (mid-1980s) and second (early 2010s) generations compiled using data for sedimentary successions of different ages. Our results suggest that the diagrams of different generations allow more or less correct discrimination only between the platform, rift, passive margin, and island arc settings. The data for collision sediments do not form separate fields in these diagrams.  相似文献   

Geochemistry of Riphean terrigenous rocks in the Southern Urals and Siberia and variations of the continental-crust maturity     

A.D. Nozhkin  A.V. Maslov  V.N. Podkovyrov  O.M. Turkina  E.F. Letnikova  Yu.L. Ronkin  M.T. Krupenin  N.V. Dmitrieva  E.Z. Gareev  O.P. Lepikhina 《Russian Geology and Geophysics》2009,50(2):71-86

We consider the general and specific features of the evolution of the composition of fine-grained terrigenous rocks in the Riphean sedimentary megasequences of the Southern Urals, Uchur-Maya region, and Yenisei Ridge. It has been established that the crust on the southwestern (in the modern frame of references) periphery of the Siberian craton was geochemically the most mature segment of the Riphean continental crust. For example, the fine-grained clastic rocks and metapelites of all Riphean lithostratigraphic units of the Yenisei Ridge have higher median contents of Th than the most mature Paleoproterozoic crust, and in median contents of Y and Cr/Th values they are the most similar to it. In the Southern Urals and Uchur-Maya region, some units of the Riphean sedimentary sequences show median contents of Y and Th and Cr/Th values close to those of primitive Archean crust. Analysis of Cr/Th variations in the fine-grained terrigenous rocks of all three megasequences shows that the minimum Cr/Th values, evidencing a predominance or the abundance of felsic rocks in provenances, are typical of the Riphean argillaceous shales and metapelites of the Yenisei Ridge. The distinct Cr/Th and Cr/Sc increase in the fine-grained clastic rocks of the Chingasan Group of the ridge reflects the large-scale destruction of continental crust during the formation of rift troughs as a result of the Rodinia breakup in the second half of the Late Riphean. The Cr/Th variations in the Lower and Middle Riphean argillaceous shales and mudstones of the Bashkirian mega-anticlinorium and Uchur-Maya region are in agreement, which evidences the subglobal occurrence of rifting in the early Middle Riphean (so-called “Mashak rifting”).  相似文献   

Fine-Grained Aluminosiliciclastic Rocks of the Middle Riphean Stratotype Section in the Southern Urals: Formation Conditions,Composition and Provenance Evolution   总被引：2，自引：0，他引：2  

Maslov  A. V.  Krupenin  M. T.  Ronkin  Yu. L.  Gareev  E. Z.  Lepikhina  O. P.  Popova  O. Yu. 《Lithology and Mineral Resources》2004,39(4):357-381

General trends of the formation of Middle Riphean fine-grained aluminosiliciclastic rocks in the Bashkir Meganticlinorium are considered. It is shown that Yurmatinian shales do not contain any significant pyroclastic admixture. Judging from the relatively constant Th/Cr ratio throughout the Yurmatinian section, the tectonic regime in the study territory during the early Middle Riphean is suggested to be rather stable. The main paleoclimatic indices and indicators of the pelitic material maturity (CIA, CIW, IVC, PIA, and Ce/Y) suggest that paleodrainage systems in the early Middle Riphean were dominated by humid climate that gave way to the arid or semiarid type in the middle Yurmatinian. The low Mo/Mn ratio and some other indicators of redox conditions in shales from all Yurmatinian lithostratigraphic units show that no explicit reducing conditions existed in the basin during the early Middle Riphean. The shales were characterized by the increase in K₂O/Al₂O₃ ratio, gradual enrichment in REE, and growth of LREE/HREE and La_N/Yb_N ratios toward the middle Yurmatinian, indicating the gain of an appreciable amount of slightly weathered arkosic aluminosiliciclastic material in the sedimentary basin about 1220–1200 Ma ago. The REE distribution and the UCC- and AUC-normalized shale compositions suggest that the eroded upper crust was compositionally close to the UCC. The occurrence of mafic and ultramafic rocks is also inferred. Data points of Yurmatinian shales plotted in the Cr–Ni, Eu/Eu*–Gd_N/Yb_N, and (La/YB)_N–Yb_N diagrams are localized between the fields of Upper Archean and post-Archean rocks or within the latter field. Hence, post-Archean igneous and metamorphic complexes prevailed in paleodrainage systems of the early Middle Riphean. This is also confirmed by the model Nd ages.  相似文献   

Secular variations of the upper crust composition: Implication of geochemical data on the Upper Precambrian shales from the Southern Urals western flank and Uchur-Maya region     

A. V. Maslov  V. N. Podkovyrov  Yu. L. Ronkin  M. T. Krupenin  E. Z. Gareev  V. M. Gorozhanin 《Stratigraphy and Geological Correlation》2006,14(2):126-149

In the mid-1980s, it was concluded based on geochemical study that Th, Sc, La concentrations and ratios Th/Sc, La/Sc and Eu/Eu* did not wary significantly in the post-Archean time. It was impossible to judge about compositional variations of upper crust during the Riphean and Vendian, because data of that time characterized a limited number of samples from the post-Archean basins of Australia, New Zealand, and Antarctic. Considered in this work are variations of Eu/Eu*, LREE/HREE, Th/Sc, and La/Sc ratios in Upper Precambrian fine-grained siliciclastic rock of the Southern Urals western flank (Bashkirian meganticlinorium) and Uchur-Maya region (Uchur-Maya plate and Yudoma-Maya belt). As is established, only the Eu anomaly in the studied siliciclastic rocks is practically identical to this parameter of the average post-Archean shale. Three other parameters plot on the Riphean-Vendian variation curves with positive and negative excursions of diverse magnitude, which do not coincide always in time. It is assumed that these excursions likely mark stages of local geodynamic activity, destruction of pre-Riphean cratons, and progressing recycling of sedimentary material during the Riphean.  相似文献   

Modern Geothermochronological and Paleomagnetic Potential for Solving Mineral Exploration Problems     

V. I. Powerman  R. V. Veselovskiy  D. K. Nurgaliev  S. V. Malyshev  E. B. Degtyareva  A. M. Pasenko  D. A. Gavryushkin  D. M. Kuzina  B. I. Gareev  G. A. Batalin  A. V. Latyshev 《Seismic Instruments》2018,54(5):579-585

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Noble metal specialization of Lower and Middle Riphean terrigenous rocks in the South Urals     

S. G. Kovalev  A. V. Maslov  E. Z. Gareev 《Lithology and Mineral Resources》2016,51(6):467-483

Results of the study of noble metal specialization of Lower and Middle Riphean terrigenous rocks in the Bashkir Anticlinorium (South Urals) are reported. The study revealed their genetic differences in the relatively unaltered, i.e., “background” terrigenous rocks in type sections of the Burzyan and Yurmatau groups and in sedimentary rocks of the same stratigraphic levels from tectonic zones subjected to local dynamothermal metamorphism of the greenschist facies and intruded by mafic rocks. It has been established that Ru serves as a geochemical marker of the impact of magmatic processes on sedimentary rocks and the redistribution of noble metals during metamorphism and local metasomatism. A generalized model is proposed for the formation of noble metal geochemical specialization of Lower and Middle Riphean terrigenous rocks in the South Urals.  相似文献