HR: 16:30h
AN: V54A-03    [Abstracts]
TI: Behavior of trace metals in the hydrothermal plume at two sites on the Izu-Bonin-Mariana Arc
AU: * Shitashima, K
EM: shita@criepi.denken.or.jp
AF: Central Research Institute of Electric Power Industry, 1646, Abiko, Abiko, Chiba, 2701194 Japan
AB: Deep-sea hydrothermal systems play an important role in the oceanic geochemical cycles of trace metals. High concentration of trace metals of the basalt origin is discharged into the deep sea via the hydrothermal plume. The hydrothermal plume is widely diffused to the ocean by mixing with ambient seawater. The processes of input and removal in the diffusing hydrothermal plume differ by individual hydrothermal systems. In this presentation, the behavior of trace metals in the hydrothermal plume of two sites on the Izu-Bonin-Mariana Arc is compared. This study was funded by the O`Archaean ParkO_L project of MEXT. The hydrothermal plume samples were taken from the Suiyo Seamount and the southern Mariana Trough (Pika Site). The mini CTDT-RMS mounted twelve 1.2L Niskin bottles was installed onto the manned submersible. And the hydrothermal plume samples were collected with monitoring the anomaly of temperature and turbidity. The samples were immediately filtered in an onboard clean bench. Unfiltered sample for analysis of total (particulate + dissolved) trace metal and filtered sample for analysis of dissolved trace metal were acidified. Trace metals (Al, Mn, Fe, Cu and Zn) in the hydrothermal plume samples were analyzed by GFAAS. The ranges of concentration of Al, Mn, Fe, Cu and Zn in the hydrothermal plume samples collected from two sites are _`15uM, _`5uM, _`5uM, _` 0.2uM and _`0.6uM, respectively. The particulate phase is predominant form in Al, Fe, Cu and Zn, and Mn shows the superiority of dissolved form. At the Suiyo Seamount, the hydrothermal active site is located in the bottom of caldera. On the other hand, the hydrothermal active site exists on the top of off-ridge seamount at the southern Mariana Trough. The diffusion process of trace metals in the hydrothermal plume to the ocean differed by the topographic factor in two sites. It suggests that trace metals discharged from the vents are hardly diffused to the ocean surmounting the Suiyo Seamount caldera because the metals almost removed from the hydrothermal plume in the caldera.
DE: 1724 Ocean sciences
DE: 1749 Volcanology, geochemistry, and petrology
DE: 1030 Geochemical cycles (0330)
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1065 Trace elements (3670)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting