Study on the genesis mechanism of geothermal resources in the Yunkai area, South China based on geophysical data

Abstract Yunkai area is located in the southwest of South China Block and is characterized by widespread granite distribution, dense hot spring occurrences, and well-developed deep faults, indicating significant geothermal resource potential. However, the establishment of a comprehensive geothermal genesis mechanism for this region has been hindered by limited geological data. In this study, geophysical data are employed to constrain the depths of faults and intrusion. Regional granite heat production rates are systematically compiled, and a typical geological profile is modeled using a two-dimensional heat conduction equation to elucidate the geothermal resource genesis mechanism of the Yunkai area. The research indicates that most faults in the study area extend to depths of 0–4 km, with only a few faults in the southwestern region exceeding 8 km. The depth of intrusions are mostly distributed at depths of 6–8 km, while those in the central region are significantly deeper, exceeding 10 km. The heat generation rate of granite ranges from 1.87 to 6.00 µW/m³, with an average value of 3.42 µW/m³, serving as a thermal source to heat underground fluids. Based on these findings, the geothermal genesis mechanism of the Yunkai area is interpreted as follows: atmospheric precipitation originating from surrounding high-altitude mountains infiltrates downward along fracture networks into deeper layers, where it is heated by the surrounding rock. Driven by pressure, this heated fluids migrate upward along deep-seaked faults, mixes with shallow cold groundwater, and undergo further heating due to the radiogenic heat production rate of granite at the surface. The fluids ultimately converge at fault intersections and discharge at the surface, forming hot spring clusters. The southeastern part of the study area shows favorable conditions for the development of high-temperature geothermal resources. This study clarifies the genesis mechanism of geothermal resource in the Yunkai area and provides a scientific basis for future geothermal exploration and development.