四川巴塘地热田水文地球化学特征及成因

地下热水的地球化学特征能够揭示深部地热过程。川西巴塘地区域地热资源丰富，但当前研究程度较低。为进一步查明川西地区地热资源赋存状态及热源来源，揭示热循环机理，定量评估研究区热储温度、冷水混入比例、热循环深度等，利用巴塘热坑和巴塘热水塘两处地热田共20组温泉水样进行水化学分析和氢氧同位素分析，进行定量计算，并分析巴塘地区地下热水的演化过程。结果表明:巴塘地区地下热水主要为HCO3—Na型；水中Sr2+、Li+和F-与Cl-的相关性不佳；主要受大气降雨补给；冷水混入比例为64%~68%，未混入冷水时深部热储温度为218~229 ℃，热储循环深度4 546.32~4 777.89 m；Na+、HCO-3、SiO2浓度在热水循环过程中变化相对较大。说明Sr2+、Li+和F-只来自于水岩作用的矿物溶解，且该地区地下水补给主要来自于大气降水，川西地区地热水于围岩发生水岩作用，进行离子交换，在完成一系列水化学作用及水岩作用后，升至地表，最终形成温泉水。研究成果可为川西巴塘地区地热研究提供数据支撑及理论支持，同时也为川西整体区域地热研究提供方法借鉴，为研究区地下水开发利用研究提供参考。

Hydrogeochemical characteristics and genesis of the geothermal fields in Batang of Sichuan

Geochemical characteristics of geothermal water can reveal deep geothermal processes. The Batang area in western Sichuan is taken as an example, where geothermal resources are relatively abundant, but few studies were carried out previously. Based on the existing researches, this paper aims to further identify the occurrence and source of geothermal resources in western Sichuan, reveal the mechanism of thermal cycle, and quantitatively evaluate the temperature of the geothermal reservoirs, the mixing ratio of cold water and depth of thermal cycle in the study area. Hydrochemical analyses and hydrogen and oxygen isotopes of 20 hot spring water samples from two geothermal fields in Batang are used to calculate quantitatively and analyze the evolution process of thermal groundwater in the Batang area. The results show that the thermal groundwater is mainly of HCO3-Na type in the Batang area. F-, Li2+, As+ and Cl- in the hot water have poor correlation, indicating that F-, Li2+, As+ only come from the dissolution of minerals in the rocks. The hot water is mainly recharged by atmospheric rainfall. The temperature and depths of geothermal reservoirs before mixture with cold water are obtained by the Si-enthalpy model as 218-229 ℃ and 4 546.32-4 777.89 m and the mixing ratio of cold water ranges from 64% to 68%. The changes in concentrations of Na+, HCO-3 and SiO2 in the Batang area are relatively large, indicating that the geothermal water only comes from the dissolution of minerals in rocks, including dissolution of calcium feldspar and silicate precipitation. Water-rock interactions and ion exchange occur between the geothermal water and surrounding rocks in western Sichuan. After completing a series of hydrochemical action and water-rock interaction, the hot water rises to the land surface and eventually emerges in the form of hot springs. The above analyses of the characteristics of the geothermal reservoirs can provide data support and theoretical support for the future geothermal research in the Batang area in western Sichuan, and can also provide methodological references for the overall regional geothermal research in western Sichuan, which is of important reference significance for the study of groundwater development and utilization in the study area.