Lithospheric thermal structure in the South China Sea and its tectonic implications based on magnetic and gravity data

Based on gravity anomalies, magnetic anomalies, and surface heat flow data from the South China Sea (SCS) and adjacent regions, this study applies a Curie point depth–constrained thermal modeling approach to construct regional-scale, spatially continuous models of lithospheric thermal structure and effective elastic thickness ( T e ) within a unified framework for the first time. Integrated analysis of the thermal models and four representative geophysical profiles (P1–P4) systematically reveals spatial variations in lithospheric thermo-mechanical structure and their tectonic controls. The results show that T e generally correlates positively with lithospheric thermal thickness at the regional scale, but exhibits pronounced variations among different tectonic settings, with local deviations influenced by lithology, tectonic stress, and evolutionary history. The central ocean basin and sub-basins are characterized by extremely thin thermal lithosphere and low T e , reflecting thermally controlled lithospheric weakening associated with seafloor spreading and mantle heat input. In contrast, the northern passive continental margin and southern compressional domains display cold, thick lithosphere and relatively high T e , primarily controlled by long-term post-rift cooling and enhanced deep mechanical coupling. The Manila subduction zone and its forearc show the lowest T e values, indicating mechanically dominated weakening related to stress concentration and slab bending, with thermal anomalies playing a secondary role. Overall, the lithospheric thermo-mechanical structure of the SCS and surrounding regions exhibits strong lateral heterogeneity, controlled by the combined effects of seafloor spreading, mantle heat supply, margin compression, and plate subduction. Through multi-parameter joint constraints and tectonic partitioning, this study identifies the dominant controls on T e across different tectonic units, providing new regional-scale geophysical constraints on the thermo-mechanical evolution of the SCS lithosphere and on marginal-sea geodynamics.