| Summary: | Marginal seas develop in the western Pacific region, with various evolutionary stages and geological characteristics. Geothermal field could provide some clues for understanding regional tectonics, thus revisiting the geothermal regime of the marginal seas in western Pacific region is in demand and available with the increasing heat flow data. Combing the updated global heat flow dataset of IHFC and other observations, heat flow and thermal structure of the marginal sea basins are analyzed. Our results demonstrate that heat flow varies much among the marginal seas, and the average values for the Okhotsk Sea, Japan Sea, Okinawa Trough and South China Sea are 80 mW/m2, 93 mW/m2, 210 mW/m2 and 75 mW/m2, respectively, indicating different ages. While the subduction zones exhibit similar geothermal patterns, with relatively low heat flow in the fore-arc regions, extremely high but variable heat flow in the volcanic arcs, and generally high heat flow in the back-arc regions. High heat flow anomalies are observed within the marginal seas, as a result of fluid circulation and recent volcanic activities. High temperature and large heat flow in the back-arc regions can be attributed to the heat contributions from the mantle. The heat flow verse age relation for marginal sea basins can be roughly expressed by Q(t)=585.8 t-1/2. It seems that this Q-t relation for marginal seas does not significantly differ from that for oceanic basins. Given the uneven coverage in heat flow data and vagueness in crustal age, this expression needs to be determined with caution in further study.
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