Genesis of Geothermal Waters in Suichuan County, China: An Integrated Method Constrained by the Hydrochemical and Isotopic Characteristics

Abstract

Numerous geothermal resources of medium to low temperature have been reported in southern China. Suichuan County is one of the regions where thermal manifestations are abundant. However, the study regarding the understanding of geothermal water sources, hydrochemical composition and fluid-rock interaction lacks behind. Therefore, this study has characterized the slightly acidic to slightly alkaline bicarbonate geothermal waters of medium-low temperature of the Suichuan area. Geothermal waters of the study area have been evaluated mainly as of HCO3-Ca-Na hydrochemical type with a maximum temperature of 80 °C. The results indicate the low hydrochemical concentration where HCO3− acts as a principal anion. Furthermore, the F− content in geothermal and two cold water samples have been found high with a maximum value of 13.4 (mg/L), showing high pH of 9.6 as well. Here, the compilation of deuterium and oxygen-18 isotopic data of geothermal waters showed a local precipitation origin with a recharge elevation ranging from 630–1000 m. The circulation depth and reservoir temperatures are estimated, explaining the deep thermal water behavior. Additionally, the estimation of saturation indices of various minerals shows the geothermal waters’ corrosive or scaling behavior. Subsequently, the geothermal water points in the study area represent a fracture convection formation pattern. Finally, by integrating conventional hydrochemistry along with isotopic data, and considering the geological framework, a conceptual genetic model of the Suichuan thermal ground waters has been discussed. Hydrochemistry and isotopic features along with a conceptual circulation model have been provided by the foundation towards the sustainable management of hydrothermal resources in Suichuan. Proper management policies and practices are required for further development of Suichuan hydrothermal waters.