Heat Flow of the Southwestern End of the Okinawa Trough

Abstract

Detailed heat flow measurements were carried out around the ODP contingency drilling site KS-1 (24°48'N, 122°30'E) located on the southern slope of the southwestern end of the Okinawa Trough. A total of 26 heat flow values were obtained. Within about 10 km of the site, the heat flow is lower than 50 mW/m2. Heat flow increases southward to about 65 mW/m2 on the south edge of the trough. Due to the extraordinarily high sedimentation rates, the sedimentation-corrected heat flow values have increased by as much as 76%, only the most recent surface sedimentation effects are considered. Distribution of heat flow patterns shows that high heat flow values are associated with igneous activities and are observed in both the northern and southern flank and the western end of the Okinawa Trough. Heat flow values in the E-W trending central rift zone, on the other hand, appear to be lower. This is probably due to hydrothermal activities in the rift zone. The correlation between the heat flow and bathymetric contours is discernable, but with a slight southward shift in the heat flow patter. Considering the fact that abnormally high and low heat flows are observed near volcanic intrusions, extrusions and faults, and that much higher heat flows would be expected if the full sedimentation effects were eliminated, we suggest that the magma associated with the extension of the southwestern Okinawa Trough has at least extended into the southwestern end of the Okinawa Trough, in northeast Taiwan.

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