Study On The Hydrochemical Characteristics Of Geothermal Water And Its Formation In Guanzhong Basin

Guanzhong Basin lies in the Central Shaanxi Province,with advanced Politics,economy and Culture,contains the rich geothermal water resource,geothermal water is used massively in Guanzhong Basin,by using in heating,medical bathing,swimming,planting cultivating and so on,it brings the good society,the economic efficiency. But TDS in geothermal water is high,F- content is high,if it is discharged inproperly after exploiting,it will have the significant pollution to the surface water or the shallow ground water. In order to use the geothermal water resources well in Guanzhong Basin,based on the present material and the research results by predecessors,this paper studied the hydrochemical characteristics of geothermal water in Guanzhong Basin,the formation of chemical composition of geothermal water was analyzed and discussed in detail.The research results provided scientific base for reasonable exploration and utilization of geothermal water resources.The results are summarized as following:(1)Divide geothermal reservoirs into three types based on generalized analysis the moving characteristic and buried condition:carbonate acid rocks karst geothermal reservoirs,structure break crevasse geothermal reservoir in front of Qinling mountain,cainozoic group sandstone , glutenite porosity crevasse geothermal reservoir.And the cainozoic group sandstone,glutenite porosity crevasse geothermal reservoir was subdivided into 4 kinds,that were Zhangjiapo group,Lantianbahe grou,Gaolinqun and Bailuyuan group.(2)Analysis the hydrochemistry characteristic in detail to geothermal water in each geothermal reservoir,the results show as following:1)TDS in carbonic acid rocks are low,the average is 0.941g/L,the watertype is mastered by HCO₃-SO₄-Cl-Na-Ca-Mg,F- concentration is about 1mg/L;2)TDS in front of the Qinling mountain is 0.4g/L,F- average concentration is 5.49mg/L,the watertype is mastered by SO₄-Na,HCO₃-SO₄-Cl-Na-Ca-Mg;3)The geothermal water in cainozoic group sandstone,glutenite crevasse:From top to down,their temperature and TDS raise gradually,the watertype is mastered by–Na. (3)Use the data in Lantianbahe group which has more samples and large distribution, simultaneously use the samples in in carbonic acid rocks and in front of the Qinling mountain,to analysis the level distribution of hydrochemistry characteristic.The results show that TDS increase gradually from periphery to central basin,watertypes vary from SO4-HCO3-Na-Ca-Mg around to Cl-Na in central basin,Na+,Cl-,SO42-,HCO3- increase gradually from periphery to central basin,while Ca2+,Mg2+ are bigger in the north and lower in the south.F- content is all high,SiO2 concentration is higher in central basin,while it is lower in the north and south.(4)use mass balance to simulate the formation of chemical composition of geothermal water,the chemical species in geothermal water and saturion indexes of minerals are obtained by computer,the results show that the dissolution of halite is the main effect in the north of basin,secondary,albite is dissoluted and kaolinite,chalcedony are deposited;the main chemical action in the south of basin is the dissolution of halite and the deposition of chalcedony and kaolinite,then CO2,halite,gypsum are dissoluted.