2020 Volume 70 Issue 2 Pages 113-119
Characteristics of ore deposits for marine mineral resources investigated by JOGMEC since 2014 was presented by Morozumi et al. (2020). Additional information for characteristics of seafloor hydrothermal deposits of the Gondou and Hakurei sites in the Okinawa area was obtained for three subjects.
1) As to the footwall rocks of ore bodies of these sites, the multiple centers of the hydrothermal alteration are characterized by illite and kaolinite respectively. The footwall alteration is accompanied by chlorite, anhydrite and gypsum, whereas the centers of illite alteration lack anhydrite and gypsum.
2) As to the footwall sediments of mound ore bodies of the Hakurei site, authigenic sulfides mineralization and exotic crystalline sulfides fragments are observed in these sediments.
3) As to microscopic ore textures of the Gondou site, growth of chimneys with collapse and reworking are suggested for the formation of ore bodies, whereas some ore textures show the flow and feather structures about chalcopy rite and pyrite.
