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Russian Geology and Geophysics
Allerton Press
Russian Geology and Geophysics

Allerton Press

1068-7971

Russian Geology and Geophysics/Journal Russian Geology and GeophysicsISTPSCIAHCI
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    Lithological Signatures of Early Carboniferous Events in the Northeastern Siberian Craton (Western Verkhoyansk Region)

    Sennikov N.V.Khabibulina R.A.Obut O.T.Gonta T.V....
    18页
    查看更多>>摘要：© 2022, Novosibirsk State University.The paper focuses on presumable sources of coarse carbonate material transported into the Visean Northern Kharaulakh basin. The sand to pebble components of the Krestyakh conglomerate unit originated by medium and distant transport by debris flows (turbidity currents) along submarine canyons from the place of their initial littoral deposition to relatively deep accommodation basins. The carbonate material was most likely derived from Ordovician, Silurian, and Devonian sediments, which are currently represented by their analogs in Kotelny Island. The sediments of the Northern Kharaulakh basin store a record of two geological events: (1) middle Visean collision of Siberia with the Laurussian supercontinent and rifting of some terranes off the Siberian сraton, and (2) late Visean collision of the Kara terrane with the northern margin of Siberia.
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    Geodynamic Formation Conditions and Age of Granitoids from Small Intrusions in the West of the Yana–Kolyma Gold Belt (Northeast Asia)

    Fridovsky V.Yu.Vernikovskaya A.E.Yakovleva K.Yu.Matushkin N.Yu....
    20页
    查看更多>>摘要：Russian Geology and Geophysics © 2022, Novosibirsk State University.We report results of geological, mineralogical-petrographic, geochemical, isotope-geochemical (Sm–Nd, Rb–Sr), and geo-chronological (U–Pb,40Ar/39Ar) studies of acid and intermediate intrusive rocks (granodiorites, leucocratic granites, subalkaline granites, and subalkaline leucocratic granites, diorites, and quartz diorites) of the Bukeschen and Samyr small plutons in the western part of the Yana–Kolyma gold belt (northeast Asia). These rocks are combined with Late Jurassic (151–145 Ma) dikes of basic, intermediate, and acid compositions into a single complex of small intrusions. They intrude the Upper Triassic–Middle Jurassic terrigenous deposits of continental margin blocks in the eastern part of the Verkhoyansk–Kolyma folded area. Our new U–Pb data for zircon (SHRIMP-II) indicate that the Bukeschen and Samyr pluton granitoids formed in the Berriasian, at 144.5 and 143 Ma, respectively. The small-intrusion granitoids have geochemical and isotope (Sm–Nd and Rb–Sr) characteristics similar to those of Late Jurassic dikes of varying composition. Therefore, they can be united into a single complex of small intrusions generated from a mixed source with the participation of mantle (OIB-and E-MORB type), lower crust, and subduction components and with Paleoproterozoic–Mesoproterozoic Sm–Nd model age estimates for the magma sources. Late Jurassic–Early Cretaceous magmatic and postmagmatic events and cooling of the intrusions played an important role in the processes of gold localization in the western part of the Yana–Kolyma gold belt. This is reflected in two tectonothermal stages (accounting for closing temperatures of the U–Pb,40Ar/39Ar, and Re–Os isotope systems for different minerals) estimated at 151–141 and 138–137 Ma. These results for the small-intrusion complex agree with the tectonic model of the evolution of an active continental margin (northeastern Siberia) in the Mesozoic era, whose final development stage in the Berriasian age saw the formation of mostly small granitoid plutons.
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    Metamorphism of the Korvatundra Structure of the Lapland–Kola Orogen (Arctic Zone of the Fennoscandian Shield)

    Kaulina T.V.Kozlova N.E.Dolivo-Dobrovol'skii D.V.Nitkina E.A....
    16页
    查看更多>>摘要：© 2022, Novosibirsk State University.We study the P–T conditions and age of metamorphic evolution of the rocks that make up the Korvatundra structure in the northeast of the Fennoscandian Shield. The rocks underwent progressive metamorphism of the amphibolite facies at 625–660 ºC and 8.7–8.8 kbar 1945 ± 34 Ma (Sm–Nd data). The pegmatite cutting the metamorphic paragenesis that formed at this stage has an age of 1917 ± 6 Ma (zircon U–Pb data). Metamorphic transformations after 1917 Ma are manifested locally as discrete zones of blastomylonites in the rocks of the northern part and some inner sites of the Korvatundra structure. Both local increases and decreases in temperature and pressure are possible in these zones. The formation of light titanite with an age of 1863 ± 44 Ma marks the next stage of shear strain. Low-temperature alterations (chloritization and silicification) took place in the zones of final deformations 1722 ± 5 Ma (Rb–Sr data). Beginning from 1.94 Ga, the general deformational and metamorphic history of the Korvatundra structure, Lapland Granulite Belt, and Tana Belt confirms the assumption of the formation of a single inverted metamorphic zoning within the Korvatundra structure and the overlying Lap-land–Kolvitsa Collision Belt in the Paleoproterozoic. The obtained data supplement the idea of the Paleoproterozoic geodynamic evolution of the Lapland–Kola orogen.
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    • NSTL