Genesis of the Xifeng Low-Temperature Geothermal Field, Guizhou, SW China: Constrains From Geology, Element Geochemistry, and D-O Isotopes

Yanyan Li,Baojian Zhang,Ji Dor,Yifei Xing,Fangfang Zhang,Guiling Wang,Chengjiang Zhang

doi:10.3389/feart.2021.782943

Abstract

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.

Highlights

Geothermal resources are well developed in China and contribute significantly to the global supply of total resources
Based on the topographic features and geological conditions (Figures 1, 2), we propose the basic conceptual model for the genesis of the Xifeng geothermal system, as illustrated in Figure 12 and discussed
The geothermal fluids in the Xifeng geothermal field are hosted in dolomite from the Sinian Dengying Formation, and are capped by sedimentary rocks of the lower Cambrian Jindingshan, Mingxinsi, and Niutitang formations

Summary

Introduction

Geothermal resources are well developed in China and contribute significantly to the global supply of total resources The occurrence of high-temperature types is limited and mainly formed in South China, e.g., southern Tibet, western Sichuan and Yunnan, as well as the south-east coastal area (Duo, 2003; Guo et al, 2007; Zhang et al, 2016; Guo et al, 2017a, b; Tian et al, 2018; Cheng et al, 2021; Zheng et al, 2021) These distribution characteristics mean that research on geothermal resources in South China mainly focuses on the high-temperature type, whereas studies on the medium-low type are limited. With the increased need for renewable energy, a new round of exploration work and scientific study has been conducted to Geothermometer

Results

Discussion

Conclusion