Origin and Classification of Geothermal Water from Guanzhong Basin, NW China: Geochemical and Isotopic Approach

Combined with tectonic evolution,a multi-isotopic method(δD,δ18O,87Sr/86Sr and 14C)and hydrochemistry data have been used to study the origin and classification of geothermal water in the Guanzhong Basin.The study shows that geothermal water of Xianli terrace primarily came from northwest direction when accepting recharge.A small amount supply source of geothermal water in Xi’an City is from Qinling Mountain and the principal supply source comes from the west direction,but geothermal water of Chang’an District mainly accepts supply from Qinling Mountain.Based on geothermal environment is open or not,the degree of water-rock interaction,and the origin of geothermal water,geothermal water of the study area can be divided into four types:A,geothermal water of Gushi depression,perfect closed thermal environment and significant water-rock interaction,belonged to residual sedimentary water origin;B,geothermal water of Xianyang City,good closed environment and relatively significant water-rock interaction,belonged to residual sedimentary water origin mixed with fossil leaching water;C,geothermal water of Xi’an City,half closed environment and some water-rock interaction,belonged to fossil leaching water origin;D,geothermal water of Chang’an District,open environment and mixed with modern precipitation,belonged to fossil leaching water origin.