Hydrochemistry and H‐O‐C‐S Isotopic Geochemistry Characteristics of Geothermal Water in Nyemo‐Nagqu, Tibet

Nyemo‐Nagqu, Tibet, is rich in high‐temperature geothermal resources. The geothermal fields in Yangbajain and Yangyi as well as 11 unexplored geothermal fields along the geothermal belt from Nyemo to Nagqu were systematically investigated and the hydrochemistry data were collected from the whole field. Meanwhile, H‐O‐C‐S isotope data were obtained for the new fields, and H‐O isotope data for the Yangbajain and Yangyi fields. A comparison of the Nyemo‐Nagqu geothermal fields with those in the Yangbajain area shows that the types of high‐temperature geothermal water are dominated by Cl‐Na and Cl·HCO3‐Na, while the types of medium‐high‐temperature geothermal water are dominated by HCO3‐Na. The concentrations of Li, F, SiO2, and HBO2 in the geothermal water are positively correlated with Cl content, indicating possible mixing with magma water. The reservoir temperatures range from 90 to 270°C by geothermometers. Slight drifting of 18O was recorded at the Dongweng and Nyingzhong high‐temperature geothermal fields, while more significant drifting was recorded at Gulu. The geothermal water is mainly replenished by atmospheric precipitation. The low tritium contents (