GEOLOGICAL CONTROLS OF MARINE FERROMANGANESE DEPOSITS ON REGIONAL AND SMALL-SCALES: AN EXAMPLE IN THE NORTHWESTERN PACIFIC

摘要

Distribution patterns, compositional variation of ferromanganese deposits, and their implications to geological setting have been characterized in the Northwestern Pacific Ocean according to shipboard survey and shore-based analysis. Recent submersible observations with Shinkai's, short-core drilling with Benthic Multi-coring System, and surface ship operations provided us with more details of ferromanganese deposits together with related geological data. We have carried out ICP/ES chemical analysis, XRD mineralogical analysis, and cross-checking of age determination on hydrogenetic ferromanganese crusts collected from wide variety of marine geological environments from deep-sea basins to topographic highs of the area. The patterns of regional- to small-scale variability of the deposits are basically controlled by geological/topographic settings. The age determination indicated a close relationship of the deposits to the geological provinces controlled with tectonic evolution as well as local non-tectonic phenomena..