Research on the Hydrochemistry and Fault Control Mechanism of Geothermal Water in Northwestern Zhangzhou Basin

Abstract

The Zhangzhou Basin (ZB) is one of the most important hydrothermal regions in the southeast coast of China, with abundant underground thermal water resources. The hydrothermal region is located within widely scattered acid igneous rocks. Because of the low permeability of granitoids, the geothermal water flow is strongly controlled by fault structures. Previous studies mainly focused on the center of ZB and provided little understanding on the geochemistry and fault controlling mechanism of peripheral areas of the basin. In this study, the chemical compounds and elements of both thermal and cold underground waters of the Northwestern Zhangzhou Basin (NZB) were tested. Using cluster analysis, geochemical analysis, chemical geothermometers, silica vs. enthalpy mixing model, and structural interpretation of remote sensing, this study found that the thermal water in the research area mixes with shallow cold water in different proportions. The reservoir temperature ranges from 106°C to 147°C and differs between different sides of the Tianbao-Jinshan Fault (TJF) due to fault control. The difference in the circulation depth of underground thermal water causes this reservoir temperature disparity. The circulation depth of underground thermal water in research area ranges from 3.65 km to 5.44 km, which means the circulation depth of thermal water of the northwestern area is deeper than that of the central area of the basin.