R7: Petrology, Mineralogy and Economic geology (Joint session with SRG)

[R7-05] Mineralogical study of massive sulfide deposits beneath the seafloor at the Gondou field in the Okinawa Trough

*Shuhei Totuka¹, Jun-ichiro Ishibashi¹, Kazuhiko Shimada¹, Takashi Miyamoto¹, Kei Ikehata² (1. Kyushu Univ. Sci., 2. Fac. of Life and Environ. Sci., Univ. of Tsukuba)

Keywords:Seafloor massive sulfide deposit, Hydrothermal alteration

The Gondou field is an active hydrothermal field in the middle Okinawa Trough. During JM17-04 Cruise, sediment cores were obtained in Southern area of the Gondou field. Massive sulfide deposits were recognized at Site GDUC06. Two distinctive types of massive sulfide were recognized; the upper one is composed of sphalerite, pyrite, galena and barite, while the lower one is composed of pyrite, chalcopyrite, quartz and illite. Occurrence of both sphalerite-rich and chalcopyrite-rich sulfide deposits is considered as a modern analogue of black and yellow ore in kuroko-type deposits.