Geothermal genesis and resource potential of Kaga in Xietongmen County in Tibet

Xietongmen County is located in the alpine mountain area of the Qinghai-Tibet Plateau, where the Kaga hot spring occurs. Geothermal energy is expected to be developed to solve the local heating problem, but research on the genesis and reserves of geothermal energy has not been carried out. By analyzing the geological structure and geothermal activity law of the survey area, and carrying out detailed geological survey, audio frequency magnetotelluric sounding and soil radon measurement near the Kaga hot spring, this paper discusses the genesis and thermal reservoir characteristics of ths Kaga hot spring by comprehensively using geological and geophysical exploration data. The research results show that (1) the audio frequency magnetotelluric and soil radon measurement results clearly reveal the extension and superposition relationship of the deep NE, NW and SN trending faults in the area, indicating that the area has a good permeable channel and thermal storage space. (2) The heat source in the study area is composed of the middle and shallow Eocene Oligocene magmatic rock decay exothermic heat source and the deep high-temperature magmatic melting heat source. The fracture zone is not only a deep thermal reservoir, but also a channel for the upwelling of deep hot water. The alluvial proluvial and other accumulative layers in the upper part of the Quaternary system are good caprocks of geothermal water, while the unconsolidated sediments in the lower part of the Quaternary system and some bedrock weathering crusts constitute shallow geothermal reservoirs in the area. These indicate that the geothermal application potential in this area is large, but it should be noted that, according to the three-dimensional display of audio frequency magnetotelluric sounding results, it is found that the deep S1 and S2 abnormal areas are connected at the shallow part, and the surface hot spring vent is just above its connecting channel, so the impact of the water volume of this hot spring vent needs to be evaluated when drilling water nearby. Finally, combined with the geothermal characteristics and electrical characteristics of geothermal water in this area, the “geophysical geothermal geology” model of the survey area is constructed, providing reference and guidance for the exploration and development of geothermal resources in other regions of Tibet.