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Nevstruev V.G.,Kosygin Institute of Tectonics and Geophysics | Berdnikov N.V.,Kosygin Institute of Tectonics and Geophysics | Nechaev V.P.,Russian Academy of Sciences
Russian Journal of Pacific Geology | Year: 2014

This paper reports the geochemical characteristics of PGE- and Au-bearing carbonaceous shales of the Sutyr and Kimkan sequences from the eastern Bureya Massif in the Russian Far East. The weakly altered shales are chemically close to the average upper crustal shale (NASC) but differ in the lower contents of iron, manganese, magnesium, phosphorus, calcium, and REE. According to the discrminant diagrams, these sediments are similar to the modern sediments accumulated under the influence of the continental terrigenous runoff, suprasubduction volcanism, and seawaters, which suggest their relation either with the deep-water trench near the active continental margin or with the central part of the marginal sea. The iron-rich sedimentary rocks of the Kimkan Sequence, including the Kimkan iron ore, are characterized by a positive Eu anomaly, which probably indicates their rift origin. The superimposed hydrothermal alterations of the Sutyr Sequence, including sericitization, sulfidization, and formation of quartz veinlets, were accompanied by the removal of silica and the input of potassium, LREE, and MREE with the formation of a well expressed Eu anomaly. The rocks from the weakly altered to metalliferous sediments of the Kimkan Sequence show a decrease in alkalis and especially in potassium. The carbon isotope composition of the Sutyr shales corresponds to that of the biogenic carbon (δ13CVPDB from -20.7 to -23.7‰). The shales of the Kimkan Sequence have a heavier carbon isotope composition (δ13CVPDB from -15.6 to -19.1‰), which may indicate either partial carbon influx from an endogenous source or its formation during decarbonatization in the presence of iron. © 2014 Pleiades Publishing, Ltd.

Ernst R.E.,Carleton University | Ernst R.E.,Tomsk State University | Hamilton M.A.,University of Toronto | Soderlund U.,Lund University | And 10 more authors.
Nature Geoscience | Year: 2016

Precambrian supercontinents Nuna-Columbia (1.7 to 1.3 billion years ago) and Rodinia (1.1 to 0.7 billion years ago) have been proposed. However, the arrangements of crustal blocks within these supercontinents are poorly known. Huge, dominantly basaltic magmatic outpourings and intrusions, covering up to millions of square kilometres, termed Large Igneous Provinces, typically accompany (super) continent breakup, or attempted breakup and offer an important tool for reconstructing supercontinents. Here we focus on the Large Igneous Province record for Siberia and Laurentia, whose relative position in Nuna-Columbia and Rodinia reconstructions is highly controversial. We present precise geochronology - nine U-Pb and six Ar-Ar ages - on dolerite dykes and sills, along with existing dates from the literature, that constrain the timing of emplacement of Large Igneous Province magmatism in southern Siberia and northern Laurentia between 1,900 and 720 million years ago. We identify four robust age matches between the continents 1,870, 1,750, 1,350 and 720 million years ago, as well as several additional approximate age correlations that indicate southern Siberia and northern Laurentia were probably near neighbours for this 1.2-billion-year interval. Our reconstructions provide a framework for evaluating the shared geological, tectonic and metallogenic histories of these continental blocks. © 2016 Macmillan Publishers Limited.

Sorokin A.P.,Russian Academy of Sciences | Malyshev Y.F.,Kosygin Institute of Tectonics and Geophysics | Kaplun V.B.,Kosygin Institute of Tectonics and Geophysics | Sorokina A.T.,Russian Academy of Sciences | Artemenko T.V.,Russian Academy of Sciences
Russian Journal of Pacific Geology | Year: 2013

The evolution and deep structure of the Songliao and Zeya-Bureya basins can be divided into the rift, platform (subsidence), and neotectonic phases. The rift phase (Middle Jurassic-Early Cretaceous) climaxed at the formation of a basin-wide near N-S-oriented rift system, which was followed (Late Cretaceous) by the deposition of the deep-water organic-rich lacustrine source facies with the maximum thickness identified in the Songliao basin (up to 1100 m). The neotectonic phase was marked by the pronounced differences in the basin's development caused by the formation of a series of E-W-trending transverse structures, which eventually separated the basins, changed the drainage pattern, and blocked the rivers draining southwards from the Zeya-Bureya to the Songliao basin. The differences in the deep structure of the basins are also strongly pronounced. High heat flow values of more than 70 mW/m2 are typical of the Songliao basin, and its mantle heat flow component is higher than the crustal one, as compared to the Zeya-Bureya basin (below 50 mW/m2). The crustal thickness of the Zeya-Bureya basin is higher than that of the Songliao basin (38-42 km and 29-34 km) with a lithospheric thickness of 110-140 km and 50-75 km, respectively. The only exception is the southern Zeya-Bureya basin, which has an electrical structure similar to that of the Songliao basin. These differences have important implications for the evaluation of the hydrocarbon potential of the rift basins. It was suggested that the evaluation of the hydrocarbon potential of the sedimentary basins or parts of these basins should account for two factors: (1) the influence of the lithospheric motions and the related collisional processes and (2) the anomalies in the deep lithospheric structures (the high heat flow and the reduced crustal and lithospheric thickness). The results of this study indicate that the southern part of the Zeya-Bureya basin (in particular, the Lermontovka, Dmitrievka, Mikhailovka, Ekaterinoslavka, and Arkhara troughs) is interpreted to have a fairly high hydrocarbon potential. © 2013 Pleiades Publishing, Ltd.

Didenko A.N.,Russian Academy of Sciences | Gur'yanov V.A.,Kosygin Institute of Tectonics and Geophysics | Peskov A.Y.,Kosygin Institute of Tectonics and Geophysics | Perestoronin A.N.,Kosygin Institute of Tectonics and Geophysics | And 4 more authors.
Russian Journal of Pacific Geology | Year: 2010

A model of the formation of the Ulkan trough was specified on the basis of new geochemical and geochronological data. The volcanics of the Ulkan Group exhibit geochemical features typical of the rocks of two modern geodynamic settings: suprasubduction and within-plate ones. The combination of the components derived from the different-depth sources in the magmatic chambers explains the formation of the volcanics with mixed geochemical signatures. The age of the granitoids of three phases of the Ulkan Massif is determined within the range of 1730-1925 Ga. The granites of the first and third phases have positive e{open}Nd(T) of + 3.5 and + 0.7, respectively. The granites of the first phase of the Ulkan Complex were likely derived from the Paleoproterozoic juvenile crust with an age of 1.84-1.95 Ga. The effusive rocks of the Ulkan Group were presumably formed in a geodynamic setting of a Cordilleran-type transform continental margin. Judging from the model TNd(DM) age, these geodynamic conditions operated >1.84 Ga ago. © 2010 Pleiades Publishing, Ltd.

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