贵德盆地地下热水水文地球化学特征

研究工作对完善区内高温地热系统成因机理和后期勘探及钻探工作提供一定的参考意义.为进一步研究贵德盆地地热资源赋存状态及热源来源，在充分了解贵德盆地地热地质条件的基础上，采集区内地热流体样品，进行水化学全分析和氢氧同位素分析，得到该区地热流体化学特征和氢氧同位素特征，估算了区内高温热田-扎仓寺热田的热储温度.分析结果表明:该区高温地下热水的水化学类型主要为SO₄·Cl-Na型，低温水水化学类型较为复杂，主要为SO₄-Na、SO₄·HCO₃-Na型；扎仓寺热田地下热水中Li+、F-、Sr2+、As3+与Cl-存在很好的正相关性，显示了相同的物质来源，SiO₂2-与Cl-极高的正相关性进一步验证了扎仓寺地热为深部热源；氢氧同位素数据都集中在当地大气降水线附近，说明地下热水主要为大气降水补给.选用合理的水文地球化学温标计算了扎仓寺热田的热储温度，并利用硅-焓模型分析了该热田地热流体中冷水混入比例及冷水混入前的热储温度，分析认为扎仓寺热田4 000 m以内存在两个热储层，第一热储层热储温度约为133 °C，热循环深度为1 800 m；第二热储层热储温度约为222 °C，热循环深度约为3 200 m. 

Hydrochemical Characteristics of Geothermal Water in Guide Basin

In order to further study the occurrence state and origin of geothermal resources in Guide basin, the hydrochemistry, hydrogen and oxygen isotope data from the study area are collected to analyze the geochemical properties and evolution of geothermal water and to calculate the geothermal reservoir temperature of high-temperature field. Hydrochemistry analysis of geothermal fluids show that the high-temperature thermal water is mainly of SO₄·Cl-Na type, and the low-temperature thermal water is mainly of SO₄-Na、SO₄·HCO₃-Na. There is a positive correlation between Li, F, Sr, As and Cl in Zhacangsi thermal field, which indicates the possible same origin, and the positive correlation between SiO₂ and Cl confirms the deep hot source of geothermal resources. The δD values range from-59‰ to-87‰, the δ18O values range from-8.6‰ to 12.2‰, and they are all distributed near the local meteoric water line, which suggests the thermal water in study area is recharged from the atmospheric precipitation mainly. The temperature and depths of geothermal reservoir of Zhacangsi thermal field are calculated using reasonable geothermometers. The Na-K-Mg equilibrium diagram reflects that the cold water mixing action occurred in Zhacangsi thermal field during the hot water rising process, the cold water mix proportions and the geothermal reservoir temperature before the cold water mixed are obtained using Si-enthalpy model. The geothermal reservoir temperature of Zhacangsi thermal field is about 133 °C calculated by multi mineral balance method and geothermometers, which is close to the shallow reservoir temperature, the depth of the thermal cycle is about 1 800 m; while the geothermal reservoir average temperature of Zhacangsi geothermal field is 222 °C before the cold water mixed and the cold water in geothermal fluid mixed with 60%-68% analyzed by Si-enthalpy model, which is close to the deep geothermal reservoir temperature, the depth of the thermal cycle is about 3 200 m. It is concluded that there are two geothermal reservoirs in Zhacangsi thermal field within the depth of 4 000 m This paper can facilitate further study of genetical mechanism of the high-temperature geothermal systems and provide guidance for exploration and drilling in the area.