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The Southwestern area of Fujian Province in China contains a major metallogenic belt. There have been three major tectonic movements since the Late Paleozoic, and the thrusts here are the main mineral deposits. These occurred between the Early Carboniferous and Late Permian eras. Due to dramatic undulations in the surface and associated complex underground structures, a single geophysical method cannot provide reliable imaging results. This is largely due to difficulties in data acquisition and processing. Seismic exploration provides one example. Using this method, raw shot gathers have a low signal-to-noise ratio because of the undulations in the topography. Furthermore, strong lateral velocity variation makes the migration process exceedingly difficult. This means that interpretations of the resulting reflection seismic profile give rise to uncertainty. For this reason, two-dimensional reflection seismology and controlled source audio-frequency magnetotellurics (CSAMT) electromagnetic sounding techniques were performed. After initially completing conventional processing on the seismic reflection data, subsequent pre-stack depth migration (PSDM) over the rugged topography yielded a much better image. It was able to identify thrust faults and magma intrusions. Then, using CSAMT, inversion was conducted with the same topography as the seismic reflection. By combining the migrated seismic profile, inverted resistivity profile, and borehole data, a vertical geological model was constructed. This proved the existence of an overlapped thrust, and it also indicated the possible presence of deeper mineralization. [ABSTRACT FROM AUTHOR]

• Obtain 3-D resistivity structure of the Gudui geothermal field by audio magnetotelluric inversion. • Analyze the depth of heat source of the Gudui geothermal field by magnetotelluric inversion. • Establish the geothermal model and study genesis mechanism of the Gudui geothermal field. The Gudui geothermal field, situated in the Shannan region of Tibet, is classified as a shallow high-temperature hydrothermal field controlled by faults. Geothermal wells in this field can reach temperatures of up to 205 °C at a depth of 230 m, making it the highest recorded temperature for geothermal fields in China at that depth. However, the precise nature of the faults and subsurface structures within the Gudui geothermal field remains poorly understood. Therefore, to gain a deeper understanding of the structure and geothermal genesis mechanism of this field, a total of 361 audio magnetotelluric (AMT) stations were deployed, and the observed data was inverted to establish a large-scale three-dimensional resistivity structure of the study region. The obtained resistivity structure revealed multiple geothermal reservoirs underlying the Gudui geothermal field. Additionally, this structure also provided insights into the dip direction of faults, which serve as channels for water and heat flow. Furthermore, through the analysis of other existing magnetotelluric (MT) data and earthquake distribution, we were able to infer that the deep heat source of the Gudui geothermal field is a high-temperature partial melting body located approximately 5 km below the surface. The high-temperature partial melting body may originate from deep crustal heat flow. Finally, we conducted a brief discussion on the potential existence of other geothermal types in the Gudui region. [ABSTRACT FROM AUTHOR]

Analyzes magnetotelluric (MT) data from the Tibetan crust in China. Range of integrated conductivity; Indicators of presence of partial melt at shallow depths in the Tibetan crust; High conductivity layer that represents partial melt in the crust; Observations suggesting presence of aqueous fluids in the crust.