搭格架温泉水化学特征及其约束因素研究

搭格架地热区温泉水DJ1-DJ116号样品于2009年采集,阳离子及微量元素含量采用ICP-OES法测试,Cl-含量采用滴定法测试,其余阴离子含量采用紫外-可见光分光光度法测试。通过对温泉水化学指标的分析,研究温泉的水化学特征及约束因素。其温泉水化学类型为HCO3-Na型,平均矿化度为1 524 mg/L,具有较高的Na/Cl值,温泉水演化程度较高,为完全平衡水,热储中的水岩反应达到了平衡状态.温泉水中PO2极低,PCO2较高;大部分温泉水中玉髓、石英和无定形态SiO2三种硅质热液矿物的饱和度指数大于0。K-Na温标计算热储平均平衡温度为251.36℃;泉水中的Na＋、K＋离子活度主要受到钠、钾长石的约束。微量元素组合表现出花岗岩源的特征。总体上搭格架地热区温泉水化学特征受到区域地质背景的约束。

Hydrochemical Characteristics and Constraints of Hot Springs in Dagejia Geothermal Field, Tibet, China

The hot water samples DJ1-DJ116 were collected in 2009.Cations and trace elements were analyzed by the ICP-OES method,Cl-content was tested by the titration method,and the other anions were tested by the UV-visible spectrometry method.Through analyzing the chemical indicators of hot springs we study the characteristics and constraints of the water.The hydrochamical type of the hot springs is HCO3-Na,the average salinity is 1 524 mg/L and Na/Cl value is high.The evolution level of the water is equilibrium water and water-rock reaction in thermal reservoir has reached equilibrium.The waters are with very low partial pressure of oxygen and higher partial pressure of dioxide carbon.The saturation index of three kinds of silica minerals in most water samples are >0.The average equilibrium temperature of thermal reservoir is 251.36℃,which is calculated by K-Na geo-thermometer.The activities of Na+,K+ are constrained by albite and K-feldspar minerals.The characteristics of trace elements portfolio show that they are originated in granite.Take the whole,the hydrochemical characteristics of the hot springs in Dagejia geothermal field are constrained by the regional geological background.