Geochemical features of the geothermal CO2-water-carbonate rock system andanalysis on its CO2 sources - Examples from Huanglong Ravine and Kangding,Sichuan, and Xiage, Zhongdian, Yunnan

Taking Huanglong Ravine and Kangding, Sichuan, and Xiage, Zhongdian, Yunnan , as examples, the authors summarize the hydrogeochemical and carbon stable isotopic features of the geothermal CO2-water-carbonate rock system and an alyze the CO2 sources of the system. It was found that the hydrogeochemical and carbon stable isotopic features of such a system are different from th ose of shallow CO2-water-carbonate rock system, which is strongly influence d by biosphere. The former has higher CO2 partial pressure, and is rich in heavy carbon stable isotope. In addition, such a geothermal system is also different from that developed in igneous rock. The water in the latter syst em lacks Ca2+, and thus, there are few tufa deposits on ground surface, but it is rich in light carbon stable isotope. Further analysis shows that CO2 of the geothermal CO2-water-carbonate rock system is a mixture of metamorp hic CO2 and magmatic CO2.