Hydrochemical Characteristics and Formation-Evolution Analysis of Medium-Low Temperature Geothermal Systems with High Salinity in Coastal Western Guangdong
Lei Yunkai
Wang Shuai
Huang Xuelian
Lin Jingyu
Han Yongjie
Cheng Zihao
Qi Shihua
Abstract：Coastal geothermal systems are prone to seawater intrusion,which can increase the salinity of geothermal water,reduce its utilization efficiency,and raise operational costs.As a significant region for medium-low temperature geothermal resources in China,the coastal areas of Guangdong Province still lack systematic research on seawater intrusion into geothermal systems and its impacts.This study investigates the hydrochemical characteristics,seawater intrusion extent and formation mechanisms based on physicochemical data from 35 geothermal water samples,one cold groundwater sample and one seawater sample in western Guangdong Province.Comprehensive analyses including hydrochemistry,isotopes and multivariate graphical interpretation methods,are employed to explore these aspects.The research results indicate that coastal geothermal water exhibits visible seawater intrusion characteristics with high salinity levels,demonstrating a maximum mixing proportion reaching 41.88％.The hydrochemical types evolve from bicarbonate-type in inland areas to chloride-type in coastal zones.The geothermal water is primarily recharged by atmospheric precipitation.During the Late Pleistocene to Holocene period,infiltrated meteoric water from the Yunkai Mountain and Tianlu Mountain areas interacted with geothermal reservoir rocks at a temperature of 90-126℃,undergoing gradual temperature elevation.Subsequently,marine transgression events induced large-scale paleo-seawater mixing into the geothermal system,where seawater migration was accelerated by thermal convection"pumping effects".Thereafter,sustained seawater intrusion has persistently affected coastal areas,ultimately forming medium-low temperature geothermal water with high salinity characteristics.
Keywords：medium-low temperature geothermal waterhydrochemistryseawater intrusionhigh salinitygeothermal energyisotopes
Publication Date：2025-09-30
Online Publishing Date：2025-10-15(First online date of this platform, not the publication date of the document)
Pages：15( 3616-3630 )