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.

The Rakhine Offshore Basin is located within an accretionary wedge in the trench setting of an active continental margin, exhibiting complex and dynamic characteristics. Its structure is notably segmented from north to south and zoned from east to west. The basin is divided into two segments along the north-south axis: the northern segment features a compressional fold belt, while the southern segment is characterized by a strike-slip belt. Along the east-west axis, the basin is divided into two zones: the eastern zone represents the early-stage, steeply folded belt, where the shallow part is disrupted by thrust faults, while the western zone is marked by later, gentle sedimentary structure. Despite these detailed structural observations, current research on the structural and evolutionary characteristics of the Rakhine Offshore Basin is still limited, and the underlying causes of its north-south segmentation and east-west zonation remain unclear. Using seismic and drilling data, we provide a comprehensive examination of the structural and evolutionary characteristics of the basin. The results indicate that the Rakhine Offshore Basin formed at the end of the Upper Cretaceous, experiencing significant deformation from the end of the Upper Miocene to the Quaternary. The structural formation progressed from east to west, occurring earlier and more intensely in the east, and later and more gently in the west. After Miocene sedimentation, the regional structure underwent inversion, with the depocenter migrating from east to west. The segmentation from north to south and zonation from east to west in the Rakhine Offshore Basin are attributed to the oblique subduction and collision of the Indian Ocean plate with the Eurasian plate. The subduction angle is gentler in the south and steeper in the north, reflecting varying stress field mechanisms across these regions.

A notable feature of volcanic activity in the Halmahera arc since the Middle Miocene is that eruptions have occurred episodically from south to north, rather than simultaneously. However, the dynamic cause of the volcanic age disparity between the northern and southern regions remains unresolved. To investigate this, thermal simulation methods were employed to calculate the temperature structures of the subducted slab and mantle wedge under varying movement rates of subduction and overriding plates. Simulation results indicate that arc magmatism is favored at lower subduction rates or higher overriding plate movement rates. During the Middle Miocene, the northward drift of the Australian plate propelled the Obi microplate southward via left-lateral strike-slip faults, accelerating its movement rate. In contrast, the movement rate of the Halmahera microplate in the north remained lower, unaffected by the Australian plate. The accelerated movement of the Obi microplate resulted in the rapid generation of a higher temperature zone, facilitating arc volcanism on Obi Island in the late Middle Miocene. Meanwhile, the lower movement rate of the Halmahera microplate delayed the formation of a favorable high-temperature zone for arc volcanism, leading to the emergence of volcanism on Halmahera Island in the late Pliocene.