Karst groundwater samples were collected in the Xiongxian geothermal field for the δ18O and δ2H data analysis. Both the oxygen (-8.4‰ to -8.6‰) and hydrogen (-72.4‰ to -73.0‰) isotopes were found enriched than the precipitation (-9.4 to -11.7‰ for δ18O and -76‰ to -85‰ for δ2H, respectively) in the late Pleistocene, when the karst groundwater was recharged. The enriched oxygen isotope is attributed to water-dolomite interaction in low-middle temperature geothermal field. The water-dolomite ratio was calculated as 0.3, based on the oxygen isotope exchange. The enriched hydrogen isotope is deduced to be caused by bacterial SO42− reduction.
