Study On The Chemical Characteristics And The Genesis Of Hot Springs In The Middle Section Of Xianshuihe Fault Zone

The study area is located in the middle section of the Xianshuihe fault,with complex geological conditions and strong hydrothermal activities.The hot springs in the area are characterized by regional distribution.According to the characteristics of hot springs distribution,the study area is divided into four main hydrothermal activity areas from north to south.The distribution direction of hydrothermal activity area is basically the same as that of Xianshuihe fault.In each hydrothermal activity area,the hot springs are beaded,and each hydrothermal activity area is separated by several kilometers or tens of kilometers.There are little other geothermal activities in each hydrothermal activity zone.The relationship between the main structure and the branch faults is closely related to the distribution of hydrothermal activity areas.This paper takes the underground hot water of Kangding hydrothermal activity area,Zhonggu hydrothermal activity area,Yala Shenshan hydrothermal activity area and Bamei hydrothermal activity area as research object.Based on the existing data in the research area,the field investigation was carried out on the exposure,distribution characteristics,geological and hydrogeological conditions of hot springs in various hydrothermal activity areas.Field parameter tests were carried out for geothermal wells and exposed hot springs in the study area,water samples were collected,hydrogeochemical characteristics and hydrogeochemical processes of underground hot water were analyzed,and the temperature of heat storage and recharge elevation of each hydrothermal activity area were calculated,and the genetic model of geothermal fluid in the study area was further discussed.Getting the following points:?1?From the analysis of water chemistry data,the water chemistry type of geothermal water in Kangding hydrothermal activity area is HCO₃-Cl-Na type water and HCO₃-Ca type water,of which HCO₃-Ca type water is concentrated in Kangding Erdaoqiao area.The chemical type of geothermal water in Zhonggu and Yala Shenshan hydrothermal activity area is HCO₃-Ca type water and the water chemical type of Bamei hydrothermal activity area is HCO₃-Cl-Na type water.The geothermal water temperature,pH and TDS concentration in Kangding and Bamei hydrothermal activity areas are relatively high and the content of Na and Cl in geothermal water is high.The geothermal water temperature,pH and TDS concentration in the hydrothermal activity areas of Zhonggu and Yala Shenshan are relatively low.There is a positive correlation between Cl and TDS,Na,K and HCO₃ in the hot water,and there is a positive correlation between Cl and Li and SiO₂.?2?Hydrogen and oxygen isotope characteristics show that there is obvious oxygen-18 drift phenomenon in Kangding hydrothermal activity area,and oxygen-18drift phenomenon in Zhonggu and Yala Shenshan hydrothermal activity area is not obvious.The water samples in the hydrothermal activity areas of the study area all fall near the atmospheric precipitation line,indicating that the atmospheric precipitation is the main source of underground hot water in the study area,and the recharge elevation is about 2922.7⁵162.0m.?3?The Na-K and Na-K-Ca temperature scales have higher calculation results of heat storage temperature.The Log?SiO₂?-Log?K²-Mg?map shows that the use of chalcedony temperature scale in Kangding and Zhonggu hydrothermal activity area should be more reliable and its heat storage temperature is 130.58²06.26°C and107.06¹52.49°C,respectively.The quartz temperature scale is more reliable in the Yala Shenshan and Bamei hydrothermal activity area,and the heat storage temperature is 113.96¹22.17°C and 127.1¹44.18°C,respectively.The calculation results of multi-mineral temperature scale show that the heat storage temperature of HKJ02 is160¹70°C,and the heat storage temperature of HZJ03 is 118¹28°C,which is basically consistent with the calculation result of chalcedony temperature scale.?4?The Cl-SO₄-HCO₃ triangle and the Na-K-Mg triangle show that the underground hot water in each hydrothermal activity area is affected by different degrees of mixing.The silicon-enthalpy equation method and silicon-enthalpy graphic method are used to calculate the mixing ratio of hot and cold water in the study area.The mixing ratio is 10.61⁷9.79%.According to the above research results,combined with the existing geomagnetic sounding,geothermal flow,helium isotope,earthquake,geological and hydrogeological data in the study area,the conceptual model of the underground hot water genetic model in the study area is proposed,providing a scientific basis for the development and utilization of geothermal resources in the area.