Hydrogeochemical Characteristics And Genesis Of The Geothermal Water In Shuiyindong,guizhou Province

Shuiyindong is located in the transition zone of Youjiang rift between the southwest margin of Yangtze paraplatform and the west margin of South China fold belt.It experienced multi-stage tectonic movement.There are many deep faults and secondary faults in the area.Reformed by neotectonic movement,a series of NNE and EW trending folds and faults were formed on the surface,and the geothermal geological conditions in the area are good.Taking the geothermal water in Shuiyindong area as the research object,this study analyzes the hydrogeochemical characteristics,recharge sources and runoff circulation characteristics of the geothermal water in the area by geological,hydrogeochemical and environmental isotope methods.The heat storage temperature,circulation depth and cold water mixing ratio of the geothermal water are estimated,and the genetic evolution mechanism of the geothermal water are disscussed.This study can enrich the understanding of geothermal water in this area and provide scientific basis for the exploration and rational development of geothermal water resources in the later stage:(1)The results show that the hot water in the area is mainly stored in the Permian Maokou Formation and structural alteration.The main minerals controlling ion concentration in geothermal water are calcite,dolomite,quartz,pyrite and clay minerals.The temperature of geothermal water is 33-41.5?,p H value is 7.16-7.78,TDS concentration is 903.78-1426.94 mg/L,the storage environment is restore environment;HCO₃^-·SO₄^2--Ca²⁺as the main types of water chemistry,and a small amount of HCO₃^-·SO₄^2--Na⁺type.Combined with the chemical characteristics and mineral saturation index of geothermal water,it can be seen that Ca,Mg and HCO₃ ions in geothermal water come from the dissolution of calcite and dolomite,SO₄ ions mainly come from the oxidation of sulfide,and Na ions come from the leaching of clay minerals.(2)According to the analysis of hydrogen and oxygen isotope characteristics,the source of geothermal water in the area is meteoric water,and the recharge elevation is1657-2232 m.tritium test results show that the geothermal water comes from the"ancient water"before 1952;The results of ¹⁴C dating show that the geothermal water age ranges from 8791 to 10977 a,which indicates that the geothermal water circulation time is long;the ⁸⁷Sr/⁸⁶Sr results show that the geothermal water flows from west to east to the study area,and there is a low degree of water rock interaction in the long-term runoff circulation process.The?¹³C value of CO₂ in geothermal water indicates that the carbon involved in water rock reaction may be caused by the mixture of atmospheric precipitation and organic matter,and the?³⁴S value indicates that the source of sulfur is sulfide oxidation.(3)The heat source is the earth heat flow,and the fold and fault on the deep fault and Huijiabao anticline are the main heat conduction channels.The temperature of hot water storage in the area is 60-80?,the circulation depth is 1147-1842 m,and the mixing ratio of cold water is 0.57-0.89.The genesis of geothermal water can be summarized as follows:Meteoric water is supplied laterally at the far end of Maokou Formation exposed in the west of Shuiyindong,which absorbs the heat flow of the earth along the deep fault.The hot water is controlled by the stratum and lithology,flows from west to east to the study area,and rises to the shallow along the deep fault.It is enriched in the structural alteration and Maokou Formation,and reacts with the surrounding rock.