Hydrochemical Characteristics and Evolution of Hot Fluids in the Gudui Geothermal Field in Comei County, Himalayas

Abstract

Abstract The Gudui geothermal field is a typical high-temperature geothermal system characterized by tectonic control and violent hydrothermal explosions in the Himalayas. The geothermal waters are mainly Na-Cl and Na-HCO3-Cl types. The comprehensive analysis of Na-K, quartz, K-Mg geothermometers and a Na–K–Mg ternary diagram indicate that the reservoir temperature is up to 266.6\u2009°C. Except for four samples, most geothermal water samples collected from Gudui plot far from the full equilibrium line in Na–K–Mg ternary diagram, suggesting that complete chemical re-equilibrium has not been achieved as these geothermal waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters. The results of geochemical characteristics analysis indicate that Cl, Na, K, SiO2, B, As, Li, Rb, Cs, and F are the characteristic components of Gudui geothermal waters. The good linear relations between Cl and other characteristic consituents reflect the existence of a parent geothermal liquid(PGL) below Gudui. Comprehensive comparative analysis of the silica-enthalpy diagram and the chloride-enthalpy diagram suggests that the parent geothermal liquid below Gudui has a Cl− concentration of 697\u2009mg/L and enthalpy of 1250\u2009J/g. The PGL ascends to the surface through different channels and may cool by conduction of heat to reservoir host rocks, by boiling, or by mixing with cooler groundwater.