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I.A. Vishnevskaya E.F. Letnikova N.A. Kanygina A.I. Proshenkin N.G. Soloshenko E.V. Vetrov V.Yu. Kiseleva 《Russian Geology and Geophysics》2018,59(11):1433-1449
U-Pb dating of detrital zircons from the sandstones of the Mamakan Formation has been made. Geochemical and isotope parameters of the carbonate deposits of the Yanguda Formation in the Vendian-Cambrian cover of the North Muya continental block have been estimated. It has been established that only the Neoproterozoic (630-915 Ma) rocks of the North Muya block were the provenances of terrigenous material. In the least altered carbonate rocks of the Yanguda Formation, the 87Sr/86Sr ratio is within 0.70814-0.70879 and δ13C varies from -0.4 to + 1.9‰. Comparison of the evaluated isotope parameters with those of carbonate rocks of typical Vendian-Cambrian sections shows that the carbonate deposits of the Yanguda Formation accumulated in the Early Cambrian, about 520 Ma. Sedimentation of the Mamakan and Yanguda Formations took place in the local sedimentary basin in the Vendian-Early Cambrian, in the absence of tectonic activity within the North Muya block. Detrital material that formed during the destruction of the rocks of the Siberian Platform basement and cover was not supplied into the basin. 相似文献
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Tretyakov A. A. Degtyarev K. E. Kanygina N. A. Letnikova E. F. Zhimulev F. I. Kovach V. P. Danukalov N. K. Lee H.-Y. 《Geotectonics》2020,54(5):605-627
Geotectonics - This work presents the results of a study of metamorphic rocks of the Bekturgan and Balazhezdy groups of the Precambrian Ulutau massif (Central Kazakhstan), which have been... 相似文献
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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
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G. V. Ovchinnikova A. B. Kuznetsov I. M. Vasil’eva I. M. Gorokhov E. F. Letnikova B. M. Gorokhovskii 《Stratigraphy and Geological Correlation》2012,20(6):516-527
The U-Pb and Pb-Pb methods were used for determining age of cap limestones from the Neoproterozoic Tsagaan Oloom Formation corresponding to the lower part of the sedimentary cover in the Dzabkahn microcontinent of Central Asia. The weighted average age value appeared to be equal to 632 ± 14 Ma (MSWD = 0.11, probability 0.74). This value allows the following assumptions: (1) the lower boundary of the Tsagaan Oloom Formation corresponds to the beginning of the Ediacaran; (2) Dzabkhan tillites are correlative with glacial sediments of the Marinoan Epoch. The low 238U/204Pb and 232Th/238U ratios observed in initial Pb sources of limestones from the Tsagaan Oloom Formation indicate that the Dzabkhan paleobasin received at its early development stages a bulk of material from eroded upper Riphean juvenile rocks. The 87Sr/86Sr ratio in fractions of Tsagaan Oloom limestones enriched with primary carbonate material and satisfying geochemical criteria of Rb-Sr systems retentivity (Mn/Sr < 0.20 and Fe/Sr < 1) varies from 0.70676 to 0.70691 and reflects this ratio in the World Ocean approximately 630 Ma ago. 相似文献
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E. F. Letnikova F. A. Letnikov S. I. Shkol’nik T. Yu. Cherkashina L. Z. Reznitskii I. A. Vishnevskaya 《Doklady Earth Sciences》2016,466(1):42-46
Isotope–geochemical studies of Mn, P, and Ba ores were performed in order to establish the influence of submarine hydrotherms on the formation of Early Cambrian sedimentary rocks of the southern environs of the Siberian Platform. Based on study of the geochemical and isotope (εNd) characteristics of the shallow-water Mn and Ba ores and phosphorites of southern environs of the Siberian Platform with similar ages, two types of sedimentary basins of the different geodynamic origins were distinguished: intraplate oceanic and those of the active continental margin, for which the sources of ore materials differ by the proportions of the mantle and contaminated crustal matter. 相似文献
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A. B. Kuznetsov E. F. Letnikova I. A. Vishnevskaya G. V. Konstantinova E. P. Kutyavin N. K. Geletii 《Doklady Earth Sciences》2010,432(1):577-582
This study uses Sr isotope chemostratigraphy to place constraints on the depositional age of carbonate rocks from the Tuva-Mongolian
microcontinent. The age of carbonate rocks of the Irkut Formation (87Sr/86Sr initial ratio equal to 0.70480–0.70485) is determined to be older than 1250 Ma, whereas carbonates of the Zabit (0.70706–0.70727
and 0.70828–0.70848) and Agarin Gol (0.70725–0.70743) formations were deposited in the interval 630–560 Ma. 相似文献
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A. V. Maslov A. D. Nozhkin V. N. Podkovyrov E. F. Letnikova N. V. Dmitrieva Yu. L. Ronkin 《Russian Journal of Pacific Geology》2010,4(5):379-397
The clarkes of concentrations (Kc) of a wide range of trace elements (Li, Be, B, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In,
Sb, Cs, Ba, REE, Hf, Ta, Hg, Tl, Pb, Bi, Th, and U) were analyzed for fine-gained terrigenous rocks (mudstones, metapelites)
from the reference Riphean sections of the Uchur-Maya region and the Yenisei Range. It was established that the shales and
mudstones of the Uchur and Aimchan groups in the Riphean hypostratotype section are characterized by moderate (2.5 < Kc < 5) and intense (Kc > 5) geochemical specialization for Li, B, and Zn. At the same time, the similar rocks of the Lakhanda and Ui groups do not
exhibit any distinct geochemical specialization, although they are notably enriched in HREE. The metapelites from the basal
formations of the Riphean sedimentary successions in the Yenisei Range are distinctly specialized for B and slightly for Li,
Rb, Be, Nb, Ta, Th, Ge, and Cd. In addition, moderate specialization for Cu is characteristic of the metapelites from the
Korda and Lopatino formations; for Bi, Sb, Hg, and V, for their analogs from the Potoskui Formation; and, for Hg and Cs, for
the similar rocks from the Lopatino Formation. The metapelites of the Lower Riphean Korda Formation from the central zone
of the Yenisei Range have elevated contents of significantly more elements (Li, Be, Sc, V, Cr, Co, Ni, Zn, As, Rb, Y, Zr,
Nb, Sb, Ag, In, Hf, Hg, and others) than their counterparts from its eastern near-platform part. The mudstones of the ore-bearing
(Pb, Zn) Gorevo Formation are characterized by elevated concentrations of several ore elements such as Pb, Cd, As, Sb, and
Bi. The elevated Kc values of the rare lithophile and of several ore elements in the metapelites of the Yenisei Range are determined by the high
geochemical differentiation of the Early Precambrian blocks constituting the western margin of the Siberian Craton, which
were eroded in the Riphean, and the syn-sedimentary riftogenic and intraplate magmatism. On the contrary, the fine-grained
and terrigenous rocks from the basal part of the Riphean section in the Uchur-Maya region are compositionally closer to the
immature Late Archean substrates or their Early Proterozoic analogs. 相似文献
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Shkol’nik S. I. Barash I. G. Belichenko V. G. Letnikova E. F. 《Doklady Earth Sciences》2011,436(1):108-112
This paper presents comprehensive geochemical characteristics of highly aluminiferous schists discovered in the Tunka Bald
Mountains and associated with the Vendian-Cambrian cover of the Tuva-Mongolian Microcontinent. The Al2O3 content varies within a wide range, the maximum being up to 36.11 wt. %. A specific feature of the geochemical composition
of these rocks is the simultaneously high contents of Cr (up to 1400 ppm), V (up to 2700 ppm), and Zr (up to 800 ppm). The
origin has been interpreted, and the conditions in which the highly aluminiferous rocks formed have been considered. Based
on geochemical data, it is assumed that the main origin could be weathering crusts formed after ultramafic and mafic rocks,
with a felsic source playing a secondary role. 相似文献
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Letnikova E. F. Izokh A. E. Kosticin Y. A. Letnikov F. A. Ershova V. B. Federyagina E. N. Ivanov A. V. Nojkin A. D. Shkolnik S. I. Brodnikova E. A. 《Doklady Earth Sciences》2021,496(1):53-59
Doklady Earth Sciences - On the basis of petrographic and mineralogical studies, we have established the presence of clastic rocks with a strong predominance of K-feldspar among the rock-forming... 相似文献