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Gablina I.F.,Russian Academy of Sciences | Popova E.A.,Gramberg All Russia Scientific Research Institute for Geology and Mineral Resources of the World Ocean | Sadchikova T.A.,Russian Academy of Sciences | Savichev A.T.,Russian Academy of Sciences | And 3 more authors.
Geology of Ore Deposits | Year: 2014

We have performed the first detailed study of hydrothermal alteration of the Holocene-upper Pleistocene sediments in the recent Ashadze-1 hydrothermal field sampled during the 26th cruise of R/V Professor Logachev in 2005. It has been established that alterations in mineralogy and geochemistry are caused by the dissolution of calcite shells in bottom sediments and their metasomatic replacement with sulfides and other hydrothermal minerals. A zone of sediments enriched in magnesian hydrothermal minerals has been revealed in the sediments of the MAR for the first time. It is suggested that metasomatism is related to diffuse percolation of hydrothermal fluids through sediments. © I.F. Gablina, E.A. Popova, T.A. Sadchikova, A.T. Savichev, N.V. Gor'kova, N.S. Os'kina, T.A. Khusid, 2014. Source

Daragan-Sushchova L.A.,Karpinsky All Russia Geological Research Institute | Petrov O.V.,Karpinsky All Russia Geological Research Institute | Daragan-Sushchov Y.I.,Gramberg All Russia Scientific Research Institute for Geology and Mineral Resources of the World Ocean | Vasil'ev M.A.,Saint Petersburg State University
Geotectonics | Year: 2014

The sedimentary cover section of the North Kara Shelf had been subdivided based on extensive seismic data, and seismic correlation was carried out. The predominant role of Upper Riphean-Middle Paleozoic rocks has been corroborated. A series of relatively deepwater basins filled with primarily terrigenous fly-schoid rocks up to 7–9 km in thickness existed in the Late Riphean-Vendian at the place of the shelf. In the Cambrian, isolated basins merged into a wide and shallow-water basin as a result of the Baikalian reactivation in southeast Severnaya Zemlya and probably in Taimyr. After the pre-Ordovician hiatus, a vast sedimentation basin with a regressive section was formed on the shelf from Ordovician to Late Devonian. Shallow-water marine and near-shore carbonate and carbonate-terrigenous sequences accumulated in this basin and gave way to continental and less frequent near-shore, marine, variegated, and red beds in the Devonian. The thickness of the Ordovician-Devonian sequence reaches 6 km. Since the Mid-Carboniferous, block emergence and deep erosion of Ordovician-Devonian complexes have occurred in the north Kara shelf as a result of Hercynian events in northern Taimyr, Severnaya Zemlya, and in the southern Kara Sea. No Permian-Triassic rifts existed on the North Kara Shelf. At that time, the shelf was an area of erosion. The thickness of the Middle Carboniferous-Cretaceous sequence was insignificant and gradually increased toward Barents Sea troughs. The newly formed Svyataya Anna and Voronin troughs arose due to opening of the Eurasia Basin of the Arctic Ocean. The terrane concept has been subjected to criticism. The available data show that a large epi-Grenvillian continental block existed, and the North Kara region was part of it. Collision of the northern continent with the Paleosiberian Platform in the Late Paleozoic resulted in the formation of the Hercynian fold arc to the south of the North Kara Shelf, and an inverted orogenic arch arose at the place of shelf basin. The individual geological features that distinguish the North Kara Shelf from the Barents Sea troughs and the South Kara Syneclise are emphasized. The ancient pre-Riphean basement, a system of Late Riphean-Vendian relatively deepwater troughs and basins, Hercynian tectonic inversion, deep erosion of the most uplifted part of the arch, and significant block motions are the distinguishing features of the North Kara Shelf. © 2014, Pleiades Publishing, Inc. Source

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