Hydro-geochemistry and Geothermal Genesis of Hongge Hot Spring in Panxi Rift

Based on the analysis of groundwater quality and hydro-geochemistry of Hongge area,this paper discussed the geothermal genesis of the hot spring combining its hydro-geological conditions.It showed that the type of Hongge Hot Spring groundwater was Na-Cl·SO₄·HCO₃,and the groundwater of cold springs and wells in the Hongge area belonged to Ca·Mg-HCO₃.The dissolution and precipitation of carbonate,silicate and sulfate minerals in the study area restricted the main characteristics of the chemical composition in groundwater.Three kinds of geothermometer were used to calculate the reservoir temperatures respectively:Na-K geothermometer calculated the reservoir temperature of 211℃,K-Mg geothermometer calculated 72℃,and Si O₂ geothermometer calculated 114℃.The δ²H values of hot spring groundwater were-104.99‰～-103.11‰,and the δ¹⁸O values were-13.14‰～-13.02‰.The δ²H values of cold spring groundwater were 89.10‰～87.87‰,and the δ¹⁸O values were 11.70‰～11.56‰.Theδ²H values of cold well groundwater values were 86.01‰～84.76‰,and the δ¹⁸O values were 11.39‰～10.96‰.According to the hydrogeological conditions of the study area,the Xigeda fault was a heat-controlling,water-controlling and water-conducting structure of Hongge Hot Spring.The main heat source consisted of friction heat from active faults,radioactive heat generated from crustal rocks and heat from mantle.The atmospheric precipitation was the main source of groundwater recharge,and the depth of geothermal water circulation can reach 6.4 km.Geothermal water rised along fracture zone,mixed with abundant karst water in carbonate strata,and exchanged heat.At the same time,Na-Cl·SO₄·HCO₃ type groundwater was formed after chemical reaction.The study area was rich in groundwater and had huge potential for geothermal resources.It was suggested to carry out in-depth systematic investigation of geothermal resources to ensure the safety of groundwater resources,to protect the ecological environment and realize sustainable development and utilization of geothermal resources.