Groundwater Genesis Model of Shicheng-Xunwu Fault Zone in Southeast Jiangxi Province Based on Hydrochemical Characteristics
The Shicheng-Xunwu fault zone,which controls the distribution of red bed basin,granite intrusion and deep hot water migration,is the most densely distributed hot spring area in Jiangxi Province and the most important heat-controlling structure in southern Jiangxi Province.However,the current research is limited to scattered geothermal fields without the origin of geothermal water from the scale of regional tectonic zones.In order to find out the origin of geothermal water in the Shicheng-Xunwu fault zone,14 geothermal fields in the Shicheng-Xunwu fault zone have been studied by means of hydrochemical components and isotopes.The results show that:(1)The Shicheng-Xunwu fault zone can be divided into three parts:the Shaowu-Shicheng fault in the north,the Huichang shallow thermal rise extensional structure in the middle and the Xunwu fault zone in the south.Geothermal water is controlled by the above three main faults respectively,and the activity degree of the fault zone increases from north to south,resulting in great differences in the heat storage charac-teristics of different geothermal fields;(2)The geothermal water belongs to neutral and weakly alkaline wa-ter.In Shicheng and Huichang basin,the cations are mainly sodium and calcium ions,and the anions are mainly sulfate and bicarbonate.In the southern Xunwu fault zone,the cation is mainly sodium ion,and the an-ion is mainly bicarbonate.The hydrochemical components are mainly derived from water-rock interaction,and evaporite and silicate rock are the main source of ions;(3)Geothermal water comes from the nearby re-charge of rainwater from the surrounding mountains.The apparent age of geothermal water in the study area becomes longer,and the hot water age,the ratio of mantle source material and the heat storage temperature in-crease synchronously from north to south in the tectonic belt;(4)The hot water in the fault zone is immature water,but it tends to mature gradually as the fault zone extends southward.The heat storage temperature rang-es from 54℃to 144℃,with the lowest temperature in Mianfang,Shicheng,and the highest temperature in the east of Nanqiao,Xunwu,showing a trend of getting warm to the south,corresponding to gradual increase in depth of hot water circulation to the south,and the maximum depth can exceed 3 km(east of Nanqiao,Xunwu).The spatial differentiation of geothermal water along the fault zone is obvious.Water-rock interac-tion intensity,geothermal water maturity,heat storage temperature,circulation depth and water age,earth heat flow value,magmatic activity and seismic activity are all related to the active degree of the fault zone,and in-crease with the southward extension of the fault zone.The Nanqiao East geothermal field in the fault zone has the greatest potential and can be used as the priority area for high temperature geothermal exploration in the deep cycle of the fault zone.
Shicheng-Xunwu fault zonegeothermalhydrochemistrygenesis model
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