Hydrogeochemical Characteristics of Low to Medium Temperature Groundwater in the Pearl River Delta Region, China

This study investigates the chemical and isotopic characteristics of low to medium temperature groundwater hosted by the Heyuan deep fault zones and the Zijin-Boluo large fault zones in Dongguan and its adjacent regions. Four thermal springs are of the Na-HCO3 type and contain minor elements (Si, Sr, F, Li, Cs), while other water samples (including eleven well samples and five cold springs with temperatures ranging from 22.2 °C to 28.4 °C, named cold groundwater) have more complex hydrochemical characteristics. The results show that all water samples are of meteoric origin. Most water samples can be grouped into two groups in a plot of oxygen and hydrogen isotope data.Thermal water, all cold springs, and part of the well water samples fall into the same group. A simple binary mixing model based on oxygen and hydrogen isotopes was used to calculate the mixing ratio of groundwater with thermal water.