Hydrogeochemical Characteristics and Genesis of Rujiao Geothermal Active Area in Saga County,Xizang

Zhao Haihua; Guan Hui; Zhao Xiaoyun; Danzeng Guojie; Zheng Yadong; Gesang Pingcuo; Banba Duoji; Zeng Qifeng; Zhang Linjie

doi:10.3969/j.issn.1004-3403.2025.06.003

Abstract：The geochemical characteristics of underground thermal water can reveal deep geothermal processes.Ru-jiao Town of Gaqiong Village,in Saga County is rich in geothermal resources,but the current research level is rela-tively low.In order to further ascertain the occurrence state of geothermal resources and heat source in the Rujiao geothermal active area,reveal the mechanism of thermal circulation,and quantitatively evaluate the geothermal res-ervoir temperature and the depth of thermal circulation,water samples were collected for hydrochemical and hydro-gen-oxygen isotope analysis.Quantitative calculation was carried out,and the evolution process of underground thermal water in the study area was analyzed.The results show that:the underground thermal water in the Rujiao geothermal active area is mainly of the HCO3·Cl-Na type.The geothermal water is mainly replenished by atmo-spheric precipitation and ice-snow meltwater,with the replenishment altitude above 5,501.00 m.The geothermal res-ervoir temperature calculated by geothermometers is 123.85℃,and the circulation depth of the geothermal water in the thermal reservoir is approximately≥2,000m.There is a good positive correlation between SiO2,B,Na+,HCO3-,TDS and Cl in the thermal water within theactive area,with relatively high content.The correlation diagram of Cl content also indicates that there may be deep magmatic water mixed into the thermal water in the study area,with the magma mainly originating from crustal materials.Judging from the water-rock mineral equilibrium,the water samples are basically immature water.During the ascent of thermal water to the surface,it is affected by the mixing of a large amount of shallow cold water,which leads to certain deviation in the geothermal reservoir temperature cal-culated by geothermometers.