The hydrochemical mechanism of multiple types of geothermal water in the same fault zone in western Guangdong, Southern China

The hydrochemical types of geothermal water is primarily influenced by the types of minerals of the surrounding rock in geothermal systems.Under the same geothermal geological and hydrogeological conditions, the hydrochemical characteristics of geothermal water are similar.However, multiple types of geothermal water with different TDS contents coexist in western Guangdong, Southern China, which is difficult to explain by a single hydrogeochemical mechanism.This paper employs hydrochemical and isotope analysis to investigate the mechanism of the different hydrochemical types of geothermal water.Hydrochemical types of geothermal water are HCO 3 -Na, SO 4 -Ca, SO 4 -Na, and Cl-Na, with the TDS values varying from 102.24 mg/L to 9343.76 mg/L.The reservoir temperature ranges from 129.7 to 132.4 estimated by the quartz geothermometer (with maximum steam loss), and the maximum circulation depth is 3.65 km.Water-rock interaction simulations illustrate that TS10, D1, and D2 have mixed with seawater.TS3 and TS4 have undergone additional dissolution of evaporite minerals.Additionally, other geothermal waters have been rapidly heated and only undergone minor mineral dissolution.The conceptual model suggests that the differences in groundwater circulation processes and water-rock interactions are the main factors for the formation of different hydrochemical types of geothermal water in the same zone.