Hydrochemicalcharacteristics and genetic mechanism of Chaka-Quzhuomugeothermal in southern Tibet

The Chaka-Quzhuomu area in the southern Tibetan Plateau is characterized by complex geological conditions, structural development, and strong hydrothermal activity. The distribution of geothermal springs in the area is mainly controlled by faults in the area and presents the characteristics of zonal development. This paper takes the hot springs in the main Chaqa hydrothermal activity area and Quzomu hydrothermal activity area in the region as the object of study. The geological, hydrogeological conditions and geothermal spring exposure characteristics of the hydrothermal activity area are investigated in the field, and the geothermal springs and surface water are sampled and analyzed. The hydrogeochemical analysis method is used to analyze the water-rock reaction process and recharge source of the geothermal springs in the area. The deep geothermal reservoir temperature is calculated by using SiO₂, cationic geothermometer and silicon-enthalpy mixed model. Based on the above research results, the formation mechanism of geothermal springs in the region was further analysed, a conceptual model of the genesis pattern of geothermal springs in the region was established, and the amount of geothermal resources was evaluated, and the results showed that: (1) The temperature of geothermal springs in Chaka hydrothermal activity area is generally higher than that in Quzhuomu hydrothermal activity area. The geothermal water is mainly of Cl-Na type in Chaka, while the geothermal water is mainly of SO₄-Cl-Na type in Quzhuomu. (2) Atmospheric precipitation is the main source of recharge, and the recharge elevation ranges from 4517 to 5186 m; (3) The geothermal reservoir temperature of Chaka hydrothermal activity area and Quzhuomu hydrothermal activity area is 208 ~ 251 °C and 80 ~ 102 °C respectively, and the mixing ratio of cold and hot water is 33% ~ 47% and 34% ~ 49% respectively; (4) The annual exploitable energy of natural geothermal water reaches 8.50 × 1013 J in the study area, which has great potential for development and utilization.