Hydrochemical characteristics of geothermal waters in Xianyang, China

摘要

Xianyang City, located about twenty kilometers to the north of Xi'an, the capital city of Shannxi,China, is rich in geothermal resources. Geothermal resources are characterized by relative high temperature,high hydraulic pressure, and high quality. Our hydrochemical study shows that: (1) Geothermal anomaly is controlled by faults; (2) Na+ is major cation in the thermal waters, order of anions based on their concentration is [Cl-] ＞^s[HCO3-] ＞^s[SO42-] and, as a result, Na-Cl type accounts for 50% of sampled thermal waters; (3)Evolution law of hydrochemical characteristics shows a general trend: Na-Cl type of high TDS water mainly distributes near the intersection of fractures; from southern to northern part of the field, with increase of [HCO3-]and [SO42-], water type evolves from Na-Cl type of high TDS to Na-HCO3-SO4 and Na-SO4-HCO3 type of intermediate TDS.