Host: Abstracts of Annual Meeting of the Geochemical Society of Japan
Pages 152-
Metal sulfides in the ocean have attracted much attention for their roles on the speciation of trace metals in seawater. Although hydrothermal system is one of the most important sources of sulfides and trace metals, the behavior and fate of hydrothermally-derived metal sulfides in the ocean have not been explored yet. In this study, vertical profiles of acid volatile sulfides (AVS) concentrations in three different size fractions (＜30 nm, 30?200 nm, >200 nm) were obtained, which is the first results of sub-nanomolar levels of metal sulfides over the submarine hydrothermal field of Hatoma and Daiyon-Yonaguni Knoll in Okinawa Trough in the western Pacific. The nanometer size separation was carried out immediately after seawater sampling, and AVS concentrations in each filtrate were then determined by a purge-trap gas chromatography with an FPD. The highest concentrations of AVS-total (unfiltered AVS) were found at the depth of ~50 m above sea floors in both areas (Hatoma Knoll: 1.8?8.9 nmol/kg, Daiyon-Yonaguni Knoll: 4.8 nmol/kg). Metal sulfides in the hydrothermal plume at the Hatoma Knoll mainly existed in ＜ 30 nm size fraction, while at the Daiyon-Yonaguni Knoll, 30 ? 200 nm and ＞200 nm size fractions of sulfides significantly contributed, suggesting that different growth processes of metal sulfides during plume dispersion in two hydrothermal systems and/or different size distributions of nanoparticulate metal sulfides in their original hydrothermal fluids.
