DENG Ji1, WANG Gan-lu1*, CHEN Zheng-shan1, MU Yu-liang1, LUO Mao-hui1, SHEN Xi2
(1. College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China;
2. Department of Natural Resources of Guizhou Province, Guiyang 550004, China)
Abstract: Taking the geothermal water in the Shuiyindong area of Guizhou Province as the research object, the piper three line diagram, cluster pedigree diagram and scatter diagram are made to analyze hydrochemical characteristics of the geothermal water in this area, the hydrogen and oxygen isotopes are used to analyze the source and circulation depth of the geothermal water. Combined with the PHREEQC hydrogeochemical simulation and above works, we have carried out the study on genesis of the geothermal water. The results show that the geothermal water belongs to the weak alkaline water with low and medium salinity, major cations of Ca2+ and Na+, major anions of SO42- and HCO3-, major hydrochemical type of HCO3-·SO42--Ca2+, and minor hydrochemical type of HCO3-·SO42--Na+. The hydrogen and oxygen isotopic characteristics and Na-K-Mg three line diagram show that the geothermal water was mainly sourced from atmospheric water, with the relatively low degree of water rock reaction, the recharging elevations of 1657-2232 m, the circulation depths of 1295-1790 m, and the heat storage temperatures of 56.82-74.16 ℃. Four hydrogeochemical models obtained by using the PHREEQC show that CO2 and O2 are consumed, pyrite is oxidized, a large amount of calcite and dolomite is dissolved, and the Na-Ca cation exchange is occurred in the formation process of geothermal water. It is believed that the atmospheric water was supplied to the stratigraphic aquifer by the karst pipeline and water diversion structure in the west side of Huijiapu anticline. In the migration process of cold atmospheric water passing through the strata, the cold water had oxidized sulfides in the coal measure strata and structural alteration zones to have produced SO4 ion, and had been heated by the earth heat flow transported by the deep fault. In the structural alteration zone, the interaction of hot water and wallrocks resulted in the production of Na ion, leached from silicate minerals, and of Ca, Mg, and HCO3 ions, from the dissolution of calcite and dolomite, and then the Na-Ca cation exchange in the hot water. Therefore, it is believed that good reservoir and caprock conditions, developed structures, and heat flow caused the formation of geothermal water, which is mainly composed of Ca, Na, SO4 and HCO3 ions, in the study area.
Keywords: Geothermal water; δD; δ18O; PHREEQC; Shuiyindong, Guizhou
ACTA MINERALOGICA SINICA Vol. 41, No.3, 2021, page 355-366