A re-recognition of the main controlling factors for δ18O enrichment in deep geothermal water of Guanzhong Basin

The research on the origin of deep geothermal water in Guanzhong Basin has a great significance for promoting the sustainable development and utilization of geothermal water. Deep geothermal water, which is circulating geothermal water, is intimately related to modern circulating water in most regions of China, About this phenomenon, experts both in China and abroad have different opinions concerning the main factors for the enrichment of the δ¹⁸O in the deep geothermal water in Guanzhong Basin. In this paper, the authors combined tectonic evolution and isotope geochemistry approaches to explore the main factors for the enrichment of δ¹⁸O in different deep tectonic units in Guanzhong Basin. The results show the factors are diverse, because of the difference of thermal storage circumstance exploitation level, and the main factor is the water-rock interaction under relatively closed geothermal reservoir condition. The underground water evaporation experiments show that, before the geothermal water as the source pours into the geothermal reservoir, there usually occurs some degrees of evaporation. When the supplied water comes into the geothermal reservoir, the enrichment of δ¹⁸O has been affected by water-rock reaction, and the influence degree of water-rock interaction in different tectonic units is in order of Gushi depression > the east of Xianli terrace > Xi' an depression and the west of Xianli terrace.