Distribution and mineral assemblages of bedded manganese deposits in Shikoku, Southwest Japan: Implications for accretion tectonics

摘要

Numerous bedded manganese and manganese-iron ore deposits occur in Shikoku, Southwest Japan. The mineralogy, wall rock characteristics and fossil age data of the deposits are synthesized in this paper. Their mineral assemblages correlate well with the progressive metamorphic grade of the accretionary complexes in Shikoku. Based on the plate tectonic framework of subduction-accretion process, the deposits are considered to have formed by metamorphism of Mn-Fe-nodule-bearing siliceous sediments on the ocean floor.