Hard fragments (crushed only by a hammer) of manganese deposits differing strongly in appearance from the regional ferromanganese crusts were sampled from depths of 3500-3200 m during the dredging of an unnamed seamount in the Central Basin of the Sea of Japan. Their surface has a black carbonaceous coating; after its removal, the crusts become steel-gray. The specific weight of these crust fragments is 3.35 g/cm(3), whereas the regional crusts have a specific weight of < 2 g/cm(3). X-ray diffraction analysis showed that the sampled fragments consist of pure pyrolusite. There are also fragments of crusts formed by todorokite and birnessite. All pyrolusite samples have an abnormally high content of Mn (up to 63%). The Mn/Fe ratio reaches 9016. The conclusion is drawn that the manganese crusts formed on this seamount are of hydrothermal genesis. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
机构:
Perm State Natl Res Univ, Biol Fac, Dept Invertebrate Zool & Aquat Ecol, Bukirev St 15, Perm 614990, RussiaPerm State Natl Res Univ, Biol Fac, Dept Invertebrate Zool & Aquat Ecol, Bukirev St 15, Perm 614990, Russia
Grischenko, Andrei V.
Chernyshev, Alexei V.
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Russian Acad Sci, Far East Branch, Natl Sci Ctr Marine Biol, Palchevskogo St 17, Vladivostok 690041, Russia
Far Eastern Fed Univ, Vladivostok 690600, RussiaPerm State Natl Res Univ, Biol Fac, Dept Invertebrate Zool & Aquat Ecol, Bukirev St 15, Perm 614990, Russia