Analysis of the Geothermal Formation Model in the Guanqiao Area, Fujian Province, China

Fujian Province in China is primarily characterized by low- to medium-temperature geothermal resources, but the deep thermal control processes and conditions remain insufficiently understood. In the area near Guanqiao Town, Quanzhou City, Fuijan Province, gravity and broadband electromagnetic methods were employed to investigate the subsurface structure. Five major faults and ten secondary faults were surveyed and the distribution of depression areas was delineated. The convective geothermal system in Guanqiao, follows a “ternary” heat accumulation model comprising heat reservoir rock bodies, heat-conducting faults, and heat-preserving cap layers. Based on this model, the intersection zones of primary faults F31 and F8 were identified as first-order geothermal target areas, while the intersections of GQ-F2 with GQ-F3 and GQ-F4, GQ-F7 with F29, F1 with F30, and GQ-F10 with GQ-F11 were classified as second-order geothermal target areas. In the first-order target area, borehole DR02 revealed that within the depth range of 0–300 m, the water temperature first increased rapidly and then slowed down, stabilizing at 48°C below 300 m depth. Geothermal verification boreholes confirmed the validity of the heat accumulation model and the delineated target areas, providing important support for the development and utilization of geothermal resources in Guanqiao, Quanzhou.