Genesis of Geothermal Waters in Zhongshan City, China: Hydrochemical and H-O-C Isotopic Implications

Investigations of the geochemical compositions of geothermal water, as well as their movements and geneses, are of great significance for the exploration and exploitation of hydrothermal resources. In Zhongshan City, a southern city in Guangdong Province, large amounts of geothermal heat have been discovered. The results of investigations show that the hydrochemical types of geothermal water in the study area are Cl-Na·Ca and Cl-Na. H-O isotopes are basically near the atmospheric precipitation line, and the calculated recharge elevation of geothermal water ranges from 716 to 822 m, which is close to the altitude of the North Peak Mountain in Taishan City. The deep thermal storage temperature ranges from 95.32 to 149.71 °C, and the depth of the thermal cycle ranges from 2638.57 m to 4581.07 m. The genetic model of the geothermal water in this area is that, at favorable structural positions with satisfied water storage conditions, the mixture of atmospheric precipitation and seawater that circulates deep in Earth is heated by terrestrial heat flow under actions such as deep heat exchange and water–rock reactions to leach the salt, finally forming the highly mineralized geothermal water that uplifts out of the surface along faults and crops. The formation of the genetic model of geothermal water will provide a geological basis and technical support for the efficient development and utilization of geothermal resources in Zhongshan City and the coastal area of Southeast China.