Genesis of the Xifeng Low-Temperature Geothermal Field, Guizhou, SW China: Constrains From Geology, Element Geochemistry, and D-O Isotopes
Genesis of the Xifeng Low-Temperature Geothermal Field, Guizhou, SW China: Constrains From Geology, Element Geochemistry, and D-O Isotopes
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DOI：
10.3389/feart.2021.782943
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发表时间：
2021-12
影响因子：
5.2
通讯作者：
Yanyan Li;J. Dor;Chengjiang Zhang;Guiling Wang;Baojian Zhang;Fangfang Zhang;Yifei Xing
中科院分区：
文献类型：
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作者：
Yanyan Li;J. Dor;Chengjiang Zhang;Guiling Wang;Baojian Zhang;Fangfang Zhang;Yifei Xing
西峰地热田位于长江中下游，是我国最具代表性的低温地热田之一。广泛的热异常，温泉，地热威尔斯井已被以前的研究报告。然而，该领域的性质和形成机制仍然知之甚少。对西峰地热田不同位置的温泉、地热流体、河流和冷泉的元素地球化学（离子、稀土元素）和稳定同位素（D、O）组成进行了分析。离子类型研究表明，除西峰温泉为Ca-Mg-HCO 3-SO 4型外，其余样品均为Ca-Mg-HCO 3-SO 4型。根据石英地质温度计，估计储层温度为77°C。稳定同位素（D、O）结果表明，西峰地热系统自SW向NE方向海拔1, 583 m处，接受大气降水补给。稀土元素研究表明，其富集特征和明显的Eu正异常是通过水-岩相互作用继承于含长石储集岩的。结合这些观测资料、地质背景和前人的研究，认为西峰地热田的形成是大气降水沿断裂沿着补给、深循环和二次上升的结果。首先，大气降水通过断层和裂缝带渗透到深处。其次，深层渗透水受到放射性热、深层热和构造摩擦热的加热。最后，由于升温的沃茨在水库中经历了相当深的循环，它再次沿着主要断层上升，并与地表附近的地下水混合。综合以上分析，认为西峰地热系统应归属于一个控制断裂、深循环的低温大气降水系统。
The Xifeng geothermal field is located in the Yangtze Craton, SW China, and is one of the most representative low-temperature geothermal fields in China. Widespread thermal anomalies, hot springs, and geothermal wells have been reported by previous studies. However, the nature and forming mechanisms of the field remain poorly understood. Element geochemical (ions, rare earth elements) and stable isotopic (D, O) composition of hot springs, geothermal fluids, rivers, and cold springs from different locations of the Xifeng geothermal field were analyzed in this study. The ions studies revealed that most samples featured the Ca-Mg-HCO3 type, except Xifeng hot springs, and which were characterized by the Ca-Mg-HCO3-SO4 type. Based on quartz geothermometers, the estimated reservoir temperature was 77°C. The results of stable isotopes (D, O) manifest that the Xifeng geothermal system was recharged by meteoric water at an elevation of 1,583 m from SW to NE. The research of rare earth elements (REE) revealed that their accumulation characteristics and obvious positive Eu anomaly were inherited from host feldspar-bearing reservoir dolomites through water-rock interactions. Combined with these observations, geological setting, and previous studies, it was concluded that the formation of the Xifeng geothermal field resulted from recharge, deep circulation, and secondary rising of the meteoric water along the faults. First, meteoric water infiltrated to depth through faults and crack zones. Second, the deep-infiltrated water was heated by radioactive heat, deep heat, and tectonic frictional heat. Finally, as the warmed-up waters underwent considerable deep circulation in the reservoir, it rose again along the main faults, and mixed with groundwater near the surface. Taken together, we suggest that the Xifeng geothermal system should be assigned as a faults-controlling, and deeply circulating meteoric water of low-temperature category.