[SVC44-P01] Geochemical study of High-T hydrothermal fluid and chimney obtained from Tarama Hydrothermal Vent Field in southern Okinawa Trough
Keywords:Seafloor hydrothermal activity, Tarama Knoll, Southern Okinawa Trough
Chimney fragment samples were obtained from active chimneys by the manipulators of DSV. The samples were observed and analyzed using the microscope, XRD, EPMA. Those samples were classified into three types; (1) arsenic sulfide-rich type, (2) anhydrite-rich type, and (3) metal sulfide-rich type. The mineral composition of each sample was similar to the chimney mineral composition reported from multiple hydrothermal systems in the Okinawa Trough (e.g., Izena Cauldron, Daiyon-Yonaguni Knoll, Hatoma Knoll).
Chemical and isotopic compositions of the sampled hydrothermal fluids and pore fluids from the both sites were measured. Those results indicate significant contribution of sedimentary organic matter, although Tarama Knoll is mainly composed volcaniclastics of felsic rocks. It also suggests that the high-T fluid venting from YZ site has no significant difference in the redox state (oxygen and sulfur fugacities) and the isotopic compositions of methane are comparable with those of other hydrothermal fluids occurring in the Okinawa Trough. In addition, the estimated endmember fluid compositions of each site are different, suggesting that those fluids are supplied from individual hydrothermal reservoirs.