藏南茶卡—曲卓木温泉水化学特征与成因机理

Hydrochemicalcharacteristics and genetic mechanism of Chaka-Quzhuomugeothermal in southern Tibet

关键词:  藏南温泉  地热流体  水化学特征  成因模式  地热资源

Key words:  South Tibetan gethermalsprings  geothermal fluids  hydrochemical characteristics  genetic model  geothermal resources

摘要:

位于青藏高原南部的茶卡—曲卓木区域地质条件复杂，构造发育，水热活动强烈，区内温泉展布主要受区内断裂控制，并呈现出分区发育的特征。本文以区内主要的茶卡水热活动区和曲卓木水热活动区的温泉为研究对象，通过对水热活动区地质、水文地质条件和温泉出露特征开展野外调查，并对温泉和地表水进行采样分析，并运用水文地球化学分析方法，对区内温泉水岩反应过程和补给来源进行了分析研究，同时利用SiO₂、阳离子地热温标和硅-焓混合模型方法计算了深部热储温度。基于以上研究成果，进一步分析了区内温泉的形成机制，建立了区内温泉成因模式概念模型，并对地热资源量进行了评价，结果表明：（1）茶卡水热活动区温泉温度普遍高于曲卓木水热活动区，其温泉水化学类型为Cl-Na型水，曲卓木水热活动区则主要为SO₄-Cl-Na型水；（2）大气降水为主要补给来源，补给高程范围在4517～5186 m；（3）茶卡水热活动区、曲卓木水热活动区热储温度分别为208～251℃、80～102℃，冷热水混合比分别为33%～47%、34%～49%；（4）研究区内天然地热水的年可开发能量达到8.50×10¹³J，具有显著的开发利用潜力。

Abstract:

The Chaka-Quzhuomu area in the southern Tibetan Plateau is characterized by complex geological conditions, structural development, and strong hydrothermal activity. The distribution of geothermal springs in the area is mainly controlled by faults in the area and presents the characteristics of zonal development. This paper takes the hot springs in the main Chaqa hydrothermal activity area and Quzomu hydrothermal activity area in the region as the object of study. The geological, hydrogeological conditions and geothermal spring exposure characteristics of the hydrothermal activity area are investigated in the field, and the geothermal springs and surface water are sampled and analyzed. The hydrogeochemical analysis method is used to analyze the water-rock reaction process and recharge source of the geothermal springs in the area. The deep geothermal reservoir temperature is calculated by using SiO₂, cationic geothermometer and silicon-enthalpy mixed model. Based on the above research results, the formation mechanism of geothermal springs in the region was further analysed, a conceptual model of the genesis pattern of geothermal springs in the region was established, and the amount of geothermal resources was evaluated, and the results showed that: (1) The temperature of geothermal springs in Chaka hydrothermal activity area is generally higher than that in Quzhuomu hydrothermal activity area. The geothermal water is mainly of Cl-Na type in Chaka, while the geothermal water is mainly of SO₄-Cl-Na type in Quzhuomu. (2) Atmospheric precipitation is the main source of recharge, and the recharge elevation ranges from 4517 to 5186 m; (3) The geothermal reservoir temperature of Chaka hydrothermal activity area and Quzhuomu hydrothermal activity area is 208 ~ 251 ℃ and 80 ~ 102 ℃ respectively, and the mixing ratio of cold and hot water is 33% ~ 47% and 34% ~ 49% respectively; (4) The annual exploitable energy of natural geothermal water reaches 8.50 × 1013 J in the study area, which has great potential for development and utilization.