Thermal Modeling of Submarine High Heat Flow Anomalies on the Southwestern Margin of the South China Sea

The southwestern margin of the South China Sea (SCS) features a well-developed strike-slip fault system. The Zengmu Basin and its adjacent areas, bounded by the Wan’an, Lupar and Tinjar strike-slip faults, exhibit prominent high heat flow anomalies that substantially exceed the regional average geothermal value of the SCS, with a maximum heat flow of 140 mW/m2. Nevertheless, the genetic mechanism governing these extreme geothermal anomalies remains poorly constrained, representing a key scientific issue in regional geothermal research. Based on integrated geological and geophysical datasets, this study conducts numerical thermal modeling to explore the effect of shear frictional heat on regional high heat flow anomalies under variable slip rates and thermophysical conditions. The results show that, under the assumed model conditions, shear frictional heating generates heat flow of 24.5–47.5 mW/m2 and accounts for approximately 22–35% of the total surface heat flow, indicating that it is a significant heat source in this region. The high heat flow anomalies on the southwestern margin of the SCS originate from the superposition of three dominant heat sources: mantle heat input driven by mantle upwelling along deep-seated faults, persistent shear frictional heat generated by continuous strike-slip activity, and crustal radioactive heat production from abundant heat-producing elements. The findings provide a robust theoretical basis for understanding the thermal evolution and maturity assessment of source rocks in sedimentary basins of the SCS.