Ferromanganese crusts of submarine Belyaevsky Medvedev volcanoes from the Sea of Japan

摘要

Ferromanganese crusts were studied from two underwater volcanoes from the Sea of Japan(Belayevsky Volcano (Central Basin) and Medvedev Volcano (Honshy Basin)). Mn crusts samples were analyzed by modern techniques and we obtained new data. (1)There are manganese breccia deposits (new morphological type of Mn crusts from the Sea of Japan), which consist of Mn clasts and micronodules cemented by Mn oxides. (2) Diatoms were found into layered Mn crusts from Belayevsky volcano, which were replaced by Mn minerals. This fact was not known in the literature before. (3) Some samples consist of pure well-crystallized pyrolusite. This mineral was pioneer found for Mn deposits from the Sea of Japan. (4) The rare earth element geochemistry indicates that the Mn crusts were formed from high temperature fluids. These samples are similar with hydrothermal manganese deposits from mid-oceanic and back-arc spreading center and hot-sport volcanoes in terms of morphology, mineralogy and geochemistry features.