Prediction of Geothermal Conditions in Zhangzhou Area Based on Gravity and Thermal Modelling

ABSTRACT The Zhangzhou area in South China, a key target for high‐temperature geothermal research, has long faced challenges in deep geothermal exploration due to its complex geological structure. This study systematically reveals the deep thermal field distribution characteristics for the first time by constructing a three‐dimensional (3‐D) geological structure model. The gravity forward modelling results show that the subsurface distribution of granite intrusions far exceeds their surface outcrops, with vertical extensions reaching up to 50% of the upper crust thickness. Numerical simulations of the geothermal field based on this model indicate a west‐high‐east‐low heat flow pattern, with maximum heat flow density of 107 mW/m 2 in the central‐western high heat flow zone. Notably, a significant high‐temperature anomaly exists in the deep Nanjing‐Pinghe‐Yunxiao tectonic zone, primarily controlled by three factors: variations in sedimentary cover thickness, 3‐D geometry of granite intrusions, and intensity of deep mantle‐derived heat flow. This finding provides new theoretical insights for locating deep geothermal resources. Notably, areas conducive to high‐temperature geothermal development encompass approximately five‐sixths of the total region. Furthermore, the density model exhibits excellent concordance with seismic interpretation profiles, while discrepancies between the thermal model and empirical temperature measurements are primarily attributable to groundwater dynamics.