Abstract:

The Fujian geothermal anomaly area represents a significant geothermal anomaly region located in the southeastern coastal zone of China. The formation mechanism and composition of heat sources in this area have long been a focal point of theoretical and applied geothermal research. By utilizing thermal, seismic, magnetic, and gravity data, this study examines the heat source composition and genesis of the geothermal anomaly in the Fujian region. The analysis reveals the presence of a shear wave “low-velocity corridor” in the upper crust of the Fujian coastal area, which is associated with a regional listric thrust fault comprising the Zhenghe-Dabu fault zone and the Binhai fault zone. The eastern end of the listric thrust fault connects to the high-temperature zone in the Pacific, while the western end links to the geothermal anomaly area along the Fujian coast. The temperature gradient from the Curie depth to the Moho suggests a lack of conditions for abnormal heat source formation from modern intrusive rock masses. Notably, the radioactive heat generation from granite plays a crucial role in the thermal anomaly observed in this region, with the depth of the radioactive element heat source being less than 5 km. Groundwater acts as a conduit for absorbing radioactive heat from the surrounding rock along thermal conductivity structures, leading to the accumulation of heat and the formation of high-temperature centers. It is proposed that the geothermal anomaly area in the Fujian coastal region is influenced by both deep-seated and shallow heat sources. The deep heat source originates from the high-temperature magma in the Pacific Ocean, transmitted to the surface along the listric thrust fault. In contrast, the shallow heat source arises from the radioactive elements present in granite, with groundwater facilitating its transport to the geothermal field center. In summary, the heat in the Fujian coastal geothermal anomaly area is a result of the combined effects of deep-seated high-temperature magma and shallow radioactive heat sources. The upward transfer of heat from the deep source along the thrust fault, coupled with the collection of shallow heat by groundwater, contributes to the thermal dynamics of the region.

Key words: Fujian coastal area, heat source composition of geothermal anomaly, geophysical analysis, listric thrust fault, radioactive heat generation rate