Three-dimensional thermal structure of the lithosphere and its relationship to surface structure in the South China Sea

This paper systematically studies the seafloor heat flow characteristics, the lithospheric thermal structure, and its relationship to the surface structures in the South China Sea. A three-dimensional numerical method is used to obtain the lithospheric depth of the entire South China Sea region under constraints of the newly compiled seafloor heat flow data. Then the contribution to the heat flow from the crust and mantle, respectively, and relationships between the surface tectonic units and the lithospheric thermal structure are analyzed. Results show that the depth of the lithosphere-asthenosphere boundary (LAB) in the South China Sea is 30 similar to 100 km. The shallowest LAB appears in the water depth of more than 3000 m in the South China Sea Basin, such as the northwestern sub-basin, the southwestern sub-basin, and the western side of the eastern sub-basin, as well as in the middle of the northern continental margin of the South China Sea, the Yinggehai Basin, Zhongjiannan Basin and Nanweixi Basin, reflecting the control of deep structure on different structural units on the surface. Along the Manila Trench in the east side of the South China Sea basin, the deep LAB and low heat flow are probably related to the subduction of the South China Sea and the Paleo-South China Sea. On the contrary, the Luzon Island Arc (area 119 degrees E-122 degrees E and 13 degrees N-17 degrees N), located in the intersection of the Manila trench and the extinct South China Sea spreading ridge, has a shallow LAB and high heat flow, which are probably related to the opposite subduction of the South China Sea Plate and the Philippine Sea Plate.