Geophysical structure of a hydrothermal system in the Suiyo Seamount, the Izu-Bonin Island Arc, Western Pacific
Abstract
Surface geophysical, airgun-OBS and deep towed surveys by R/V Kairei KR01-15 cruise and heat flow measurements by submersible Shinkai 6500 (NT01-08 cruise), were conducted to characterize geophysical features of a hydrothermal system in the Suiyo Seamount as a part of Archaean Park Project. The SeaBeam2112 and proton magnetometer data were collected over the seamount area to derive bathymetry, backscatter image, crustal magnetization. The results suggest 1) the seamount was formed during Brunhes Epoch (<0.78Ma), 2) low magnetization area exits on its summit, 3) its eruption accompanied with low backscatter materials, and 4) a collapse occurred in NNE side of the caldera after its formation. 2-D ray tracing results, using four OBS data with a GI gun across the seamount in NE-SW direction, indicate 1) P wave velocity of 2.2-4.2 km/s (2km thickness) locates all over the observation line, and 2) the relatively low velocity material exits under the caldera. Three deep towed equipments (WADATSUMI, a seismic reflection system and a magnetometer) were separately towed 100-200m above the sea floor to map the hydrothermal area in the caldera. The WADATSUMI supplied side scan sonar intensity images and sub-bottom profiles which reveal 10m thickness layer in the SW side of the caldera. The SW-NE seismic reflection image indicates two layers beneath the caldera; their thicknesses are 11m and 23m at the center of the hydrothermal site and both of them become thicker in the SW side. The low magnetization area is limited only in eastern side, which probably results from higher rock alteration by the hydrothermal activity. Eleven heat flow data across the hydrothermal site indicate anomalously high (>10W∧ (m2)), high (ca.4W∧ (m2) without hydrothermal activity, and low (ca.0.2W∧ (m2)) at the center, the eastern side and the western side of the hydrothermal site, respectively. All the data show that the hydrothermal area has different features between the SW and NE sides, and we will present a model to explain these features.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.V72A1306S
- Keywords:
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- 3015 Heat flow (benthic) and hydrothermal processes