Silicon in ferromanganese crusts from the Sea of Japan: peculiarities of allocation and interrelation with main ore phases

The article considers the distribution features of siliceous mineralization in ferromanganese crusts of the Sea of Japan. The crusts are formed near the top parts of submarine volcanos. Both manganese crusts and ferrosiliceous crusts with manganese admixture were found on some of them, among the dredging material. The main rock-forming elements in the crusts are Mn (0.2–63.1 %), Fe (0.01–42.5 %) and Si (0.4–37.9 %). The Fe/Si value varies from 0.01 to 5.5, Mn/Si — from 0.01 to 177.5. The silicon content varies significantly not only in samples collected at different rises, but also in samples raised at the same station. In addition to ferrosiliceous crusts, formed as a result of quartz cementation of grains of presumably glauconite (celadonite), crusts where the same glauconite is cemented by manganese hydroxides have a high silicon content. The samples with amorphous silica areas along with the manganese matrix, or where the sediment is impregnated with manganese hydroxides, have an increased Si content. The general pattern of ore deposition on underwater volcanoes in the Sea of Japan is as follows: Fe-Si  Si  Mn  Ba. This pattern is distorted in some cases, which is most likely conditioned by the pulsating flow of hydrothermal fluids during subsequent volcanic activity.