Characteristics of surface heat flow in the South China Sea

Abstract

A total of 592 heat flow measurements, ranging from 8 to 192 mW/m 2, 78 percent of which are between 50 and 100 mW/m 2, have been collected in the South China Sea (SCS). To overcome shortcomings such as the uneven distribution of the measurements and the occurrence of abnormal heat flow values, the tectonic evolution of different areas and their crustal thickness have been combined in analyzing geothermal characters. The results show that the oceanic basins, where they are floored by oceanic crust, the western part of the southern margin and the western fault system have high heat flow values. Heat flow along the northern margin of the SCS increases from 61 mW/m 2 on the shelf to 73–80 mW/m 2 in the slope area, and in the Xisha–Zhongsha area increases from about 70 mW/m 2 to about 85 mW/m 2 from the NW to the SE. Heat flow in the Nansha (Spratley) Islands is about 60 mW/m 2 or even higher, and decreases from the NW to SE; The average heat flow of the Mekong Basin is about 60 mW/m 2, which is similar to that of the Beibuwan Basin on the northern margin. Heat flow on the eastern margin and on the eastern part of the southern margin is lower, especially in the Luzon Trough, where the average heat flow is lower than 40 mW/m 2. Observed heat flow values in the SW subbasin are generally lower than predicted theoretically from the age of the ocean floor, unlike values in the eastern subbasin. A high heat flow zone in the lower slope area of the northern margin is recognized for the first time.