Petrogeochemistry and Ore Mineralization of Sericite–Quartz Schists of the Southern Slope of the Kashevarov Bank (Sea of Okhotsk)

Data on the structure and chemical and mineral composition of sericite–quartz schists of the southern slope of the Kashevarov Bank of the Sea of Okhotsk are presented. The studied schists have a banded texture, due to the alternation of fine, from 0.2 to 2 mm, layers of sericite, quartz, and less frequently biotite–quartz compositions, microscale chlorite, and iron hydroxides. Scattered fine “ore dust” gravitates to the boundaries of layers. Schists are broken by quartz veins. The walls of small cavities are lined with quartz brushes, less frequently pyrite crusts. In all the studied schistsamples, inclusions of Fe, Mn, Ti, Cr, Ni, Cu, Sn, Zn, Pb, W, Ba, and REE are present in some quantity in native form or as oxides, sulfides, sulfates, phosphates, or intermetallic compounds. The source of ore matter was probably postintrusive fluids, possibly with a water–silicate–carbon composition. Circulating in increased fracture and discontinuous faulting zones, they mobilize and transport ore elements, followed by their deposition in schists or as ferromanganese crusts.