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Gorokhov I. M. Kuznetsov A. B. Vasilieva I. M. Kramchaninov A. Yu. Rizvanova N. G. Konstantinova G. V. 《Doklady Earth Sciences》2021,500(1):715-719
Doklady Earth Sciences - The first direct Pb–Pb dating of carbonate rocks of the Kamo Group has been carried out. The Pb–Pb age of carbonates of the lower units (the Madra, Jurubchen,... 相似文献
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S. G. Skublov A. V. Berezin N. G. Rizvanova A. E. Mel’nik T. A. Myskova 《Petrology》2014,22(4):381-388
The first geochemical study of titanite from eclogites and associated rocks of the Belomorian Mobile Belt (BMB) by secondary ion mass spectrometry made it possible to establish the compositional features of this mineral in the garnet-bearing and garnet-free assemblages. Titanite from garnet-bearing assemblages is characterized by upward convex REE pattern and lowered HREE content relative to LREE, as well as the average GdN/YbN ratio around 16.5. Titanite from metaultrabasic rock inherits the specific features of the host rock, which should be taken into account when comparing with titanite from metagabbro. Results of U-Pb (TIMS) dating of titanite confirms the identification of the early and late stages of the Svecofennian metamorphism in the studied areas of BMB: early metamorphism with the peak eclogite facies conditions at around 1900 Ma, retrograde amphibolite facies metamorphism at 1870–1880 Ma, and late allochemical metamorphism accompanied by the pegmatite formation with an age of 1840 Ma. 相似文献
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Doklady Earth Sciences - A new technique for the complete dissolution of cassiterite, which makes it possible to determine the age of this mineral by U–Pb isotope dilution (ID-TIMS), has been... 相似文献
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V. A. Glebovitskii O. A. Levchenkov V. I. Levitskii N. G. Rizvanova L. K. Levskii E. S. Bogomolov I. V. Levitskii 《Doklady Earth Sciences》2011,436(1):13-17
The Irkut Block with dominant rocks of the Sharyzhalgai Series and Kitoi Block with prevalence of the Kitoi Series rocks are the main structures of the Presayanian basement elevation of the Siberian Craton. Two stages of metamorphism, Neoarchean (2.6–2.7 Ga) and Paleoproterozoic (1.85–1.87 Ga), were established for the granulitic complexes of these blocks. The rocks of the Kitoi sillimanite schist deposit composed of sillimanite, andalusite-sillimanite, and garnet-sillimanite schists and gneisses underwent by intense ultrametamorphic transformations which led to the formation of sillimanite- and garnet-bearing plagioclase and feldspar migmatites, and also granites, sienites, and granite-pegmatites. The geochronological study of melanocratic schists and leucocratic plagiogneisses-the typical rocks of the Kitoi deposit-showed the manifestation of metamorphism only at the Archean and Proterozoic boundary (2450–2550 Ma). 相似文献
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Sh. K. Baltybaev G. V. Ovchinnikova V. A. Glebovitskii I. M. Vasil’eva N. G. Rizvanova 《Doklady Earth Sciences》2016,468(2):541-544
The isotopic–geochemical features of late and postorogenic granites of the S type and ambient migmatites are studied within the Russian part of the Svecofennian orogen of the Fennoscandinavian Shield. The spatial association of leucosomes of migmatites and granites of the S type and their similar petro- and geochemistry and distribution of Pb isotopes are evidence of the genetic similarity of their parental melts. The Borodinskoe pluton has a more primitive 206Pb/207Pb ratio, which indicates the presence of upper and U-poor lower crustal material in the source of granitic magmas. This conclusion is supported by the ?Nt(t) lower value of granites of this pluton relative to those of other plutons of the region. 相似文献