HR: 0800h
AN: V21D-0751    [Abstracts]
TI: Removal of trace elements in hydrothermal plume at submarine volcanic arc hydrothermal systems
AU: * Shitashima, K
EM: shita@criepi.denken.or.jp
AF: Central Research Institute of Electric Power Industry, 1646, Abiko, Abiko, 2701194, Japan
AB: On the study of geochemical fluxes of trace elements from the hydrothermal system, it is necessary to collect not only samples by the hydro-cast from surface ship and fluid samples using a submersible but also temporally and spatially continuous samples ranging from a fluid to a hydrothermal plume. For that purpose, the sampling method along the diluting and rising plume just after erupting from a hydrothermal vent is effective. The mini CTDT-RMS was installed onto the submersible. The hydrothermal plume samples were collected with monitoring the anomalies of temperature and turbidity by taking the distance from the hydrothermal vent gradually. Unfiltered sample for total (particulate + dissolved) trace element concentration and filtered sample for dissolved trace element concentration were analyzed on land. In V, Ni, Cu, Mo, Cd, Pb and Zn, particulate form was predominant in the fluid. The elements that are easy to form a sulfide such as Cu, Cd and Pb were removed as a sulfide precipitate from the fluid before erupting to the deep ocean. Therefore, the concentration of these trace elements in the hydrothermal plume showed superiority of a dissolved form, and was slightly high or same concentration in the deep ocean. The concentration of Fe in the fluid was extremely higher (500 - 100,000 times) than that in the deep ocean, and showed a fifty-fifty partition between dissolved form and particulate form. In the hydrothermal plume, Fe formed hydroxide mainly and was removed gradually from the plume as a particulate form in dilution and diffusion process of the plume. These hydroxides may play a role of the precipitant that coprecipitate with absorbing the other trace elements. Because Mn is hard to deposit as a sulfide, dissolved form was predominant in the fluid and Mn showed extreme high concentration same as Fe. Mn was discharged to the deep ocean as a dissolved form and removed from the plume as an oxide with increasing the particulate form gradually in dilution and diffusion process of the plume. In addition, existence of an organic trace element as one of a chemical species of dissolved form was confirmed in the hydrothermal plume, and the relationship between the hydrothermal ecosystem and the organic trace elements is very interesting.
DE: 1030 Geochemical cycles (0330)
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4825 Geochemistry
DE: 4875 Trace elements (0489)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting