Ferromanganese Crusts in the Northwestern Pacific Seamounts - A Review: Variations in Grade and Abundance on the Regional to Microscopic Scales

摘要

We carried out seafloor observation and shore-based analyses onferromanganese crusts for the last decade at a number of the Pacificseamounts, and found abundant and common occurrence ofhydrogenetic Fe-Mn oxide precipitates at a wide range of water depthsbetween 1 - 6 km. Our geological and geochemical studies indicate thatthe deposits have been formed continuously since 10 million years agoor older and building 10-cm thick piles of precipitates with variablechemical compositions, thus resulting in variable abundance and gradeon regional, small and microscopic scales. We discuss here theparameters controlling the variability.