锂同位素地球化学在地热流体水岩反应中的应用——以川西现代富锂热泉研究为例

The chemical composition and isotopic characteristics of geothermal fluids can be carriers of deep environmental information. Based on the lithium isotope geochemistry, this study systematically analyzes the hydrochemical characteristics, recharge source, fluid-rock interaction process, temperature and circulation depth of modern geothermal water in western Sichuan. Piper diagram shows that Chaluo geothermal water belongs to HCO3-Na facies and both surface water and groundwater belong to HCO3-Ca facies. The Li isotopes temperature scale calculation results show that the fluid-rock interaction temperature of Chaluo geothermal waters is 227.80 +/- 19.84? (2 sigma, n=8), and the geothermal circulation depth is about 7348.08 +/- 684.26m (2 sigma, n=8). The chemical composition of geothermal water was controlled by fluid-rock interaction, in a state of transition from immature waters to partially equilibrated waters. The high concentration of K, Li, F, Cl and other characteristic elements related to the granite rocks shows that the fluid-rock interaction is dominated by the granite rocks, and its contribution rate is estimated to be about 75.34%. Mineral saturation index of the geothermal waters shows that dolomite, fluorite, aragonite, and calcite are in a supersaturated state; sylvite, gypsum, and anhydrite in most samples were in an unsaturated state; and halite was approaching an equilibrium state. Analysis of the lithium and lithium isotope shows that geothermal waters have high lithium concentration and low delta Li-7. Mass balance simulation figure out that the rock mass which balanced with geothermal waters has the lithium concentration of 13.43 +/- 7.04x10(-6) (2 sigma, n=13) and delta Li-7=1.14 +/- 2.06 parts per thousand (2 sigma, n=13). Based on the interaction progress, the depth of the rock mass is about 6958 similar to 7450m.