Heat flow and thermal structure of the South China Sea

Abstract

The South China Sea (SCS), the largest marginal sea in the western Pacific, is crucial for understanding geodynamic processes from continental breakup to seafloor spreading. The thermal state plays an important role in lithospheric deformation; however, that of the SCS remains poorly understood owing to poor data coverage and quality in early compilations. The incremental data accumulations over the decades enable an in-depth investigation of the thermal state of the SCS. A new compilation of 1338 heat flow data from the SCS indicates a high thermal condition with a mean of 75 mW/m². The central oceanic basin is uniformly hot while continental margins show strong lateral variations due to various tectonic settings and shallow environmental factors. Sedimentation correction considering both heat generation and thermal blanket was applied; the suppression on seafloor heat flow by sedimentation is as significant as 20 %–40 % in the Qiongdongnan Basin. A broad high heat flow anomaly zone is confirmed, extending from the ocean-continent transition in the northeast to the Xisha Trough and the central depression of the Qiongdongnan Basin. The combination of post-rifting magmatism and hydrothermal circulation is thought to be responsible for it. The thermal lithospheric thickness of the SCS is estimated to be 50–80 km and the mantle contributes more than 65 % of the seafloor heat flow. This compilation offers unprecedented insights into the heat flow pattern depiction and interpretation for the SCS.