HR: 14:00h
AN: V43F-02    [Abstracts]
TI: Discharge/recharge boundary of hydrothermal venting detected by closely-spaced geothermal measuremsnts
AU: * Kinoshita, M
EM: masa@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, 237-0061 Japan
AU: Kawada, Y
EM: kawada@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
AB: Hydrothermal activity within the caldera of Suiyo Seamount was investigated in detail using HOV/ROV, and by deep-tow imagery and seismic surveys. Hydrothermal regime in the Suiyo-seamount is characterized by a geochemically uniform fluid, shallow reservoir depth, very permeable seafloor, and venting without creating big chimneys. Detailed heat flow surveys were carried out through five research cruises. Heat flow is highest ($>$ 10 W/m$^{2}$) within the active area. On the western and southern periphery, some heat flow is lower than 0.3 W/m$^{2}$, only several tens of meters away from the venting area. To the east, heat flow is uniform around 4 W/m$^{2}$, indicating a uniform reservoir overlain by impermeable layer. High temperature zones below seafloor, with non-linear temperature profiles, are identified next to the isolated vents indicating a very local circulation. We believe that we obtained several lines of direct evidence for discharge and recharge activity and their interface near the vents, constrained by the precipitation structure around the vents. Hydrothermal regime at the Suiyo site consists from a 100-m scale, stable circulation to a 1-m scale local patterns. This multiple-scale circulation pattern, also identified at other hydrothermal sites, would be constrained by the distribution of heat source and hydrological properties near the seafloor.
DE: 3015 Heat flow (benthic) and hydrothermal processes
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting