Resumen
Geothermal water samples taken from deep aquifers within the city of Kaifeng at depths between 800 and 1650 m were analyzed for conventional water chemical compositions and stable isotopes. These results were then combined with the deuterium excess parameter (d value), and the contribution ratios of different carbon sources were calculated along with distributional characteristics and data on the migration and transformation of geothermal water. These results included the conventional water chemical group, hydrogen, and oxygen isotopes (dD-d18O), dissolved inorganic carbon (DIC) and associated isotopes (d13CDIC). The results of this study show that geothermal water in the city of Kaifeng is weakly alkaline, water chemistry mostly comprises a HCO3-Na type, and the range of variation of dD is between -76.12? and -70.48?, (average: -74.25?), while the range of variation of d18O is between -11.08? and -9.41? (average: -10.15?). Data show that values of d vary between 1.3? and 13.3? (average: 6.91?), while DIC content is between 91.523 and 156.969 mg/L (average: 127.158 mg/L). The recorded range of d13CDIC was between -10.160? and -6.386? (average: -9.019?). The results presented in this study show that as depth increases, so do dD and d18O, while d values decrease and DIC content and d13CDIC gradually increase. Thus, dD, d18O, d values, DIC, and d13CDIC can all be used as proxies for the burial characteristics of geothermal water. Because data show that the changes in d values and DIC content are larger along the direction of geothermal water flow, so these proxies can be used to indicate migration. This study also shows demonstrates that the main source of DIC in geothermal water is CO2thathas a biological origin in soils, as well as the dissolution of carbonate minerals in surrounding rocks. Thus, as depth increases, the contribution of soil biogenic carbon sources to DIC decreases while the influence of carbonate dissolution on DIC increases.