Hydrogeochemical features of hot spring under water-rock processes of different geologic conditions—A case in the Wentangxia hot springs of Chongqing and the hot spring at Xiaojiang fault zone of the East Yunnan

Taking the Wentangxia hot springs in Chongqing and the hot springs at Xiaojiang fault zone in the East Yunnan as the research object, the hydrogeochemic features are studied in the paper. It is found that the hydrogeochemic features of the hot springs outcrop from Wentangxia anticline are similar because of the same geologic backgrounds, and their hydrochemistry types are SO4-Ca (Mg); but that the hydrochemic features of the thermal water outcrop from Xiaojiang fault zone are quiet different for their difference of geologic conditions, their hydrochemistry types are HCO3-Na(YN1), HCO3-Ca(YN2), SO4-Ca(YN3 and YN5)and SO4-HCO3-Ca-Na(YN4). In addition, the Na-K-Mg diagram model and the Na-K-Mg-Ca diagram model evidently shows that all of the water samples have not reached equilibrium between water and rock, and only YN1 is closest to the complete equilibrium line to be close to equilibrium state. Moreover, the temperatures calculated with the silica geothermometer indicates a geothermal reservoir at 133～139℃, which is similar to the geothermal reservoir temperatures of YN1 showed by Na-K-Mg diagram and Na-K-Mg-Ca diagram (100～120℃). The analysis on hydrochemistry and Na-K-Mg-Ca diagram shows the water-rock process of YN2 is similar to the hot springs outcrop from Wentangxia anticline.