Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (1): 123-133.DOI: 10.13745/j.esf.2020.1.14

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Geochemical characteristics of geothermal fluids and water-rock interaction in geothermal reservoirs in and around the Gonghe Basin, Qinghai Province

MA Yuehua(), TANG Baochun, SU Shengyun, ZHANG Shengsheng, LI Chengying   

  1. 1. Qinghai Key Laboratory of Hydrogeology and Geothermal Geology, Xining 810008, China
    2. Qinghai Survey Institute of Hydrogeology and Engineering & Environmental Geology, Xining 810008, China
  • Received:2019-06-20 Revised:2019-10-20 Online:2020-01-20 Published:2020-01-20

Abstract:

Investigations of the geochemical compositions of geothermal fluids as well as their movements and geneses are of great significance for the exploration and exploitation of hydrothermal resources. Currently, the exploitation and utilization of geothermal resources in Qinghai Province are not well developed, and more seriously, there is a lack of systematic studies on the geochemical features of the geothermal fluids there. The Gonghe Basin of Qinghai Province, located in the northern margin of the Qinghai-Tibet Plateau, is a rift basin formed in the early Cenozoic where abundant geothermal resources occur. With the geothermal areas in and around the basin as the study areas, we determined the geochemical compositions of the geothermal fluids and investigated the water-rock interactions occurring in the reservoirs based on systematic geochemical sampling and subsequent hydrochemical analyses. The results showed that the SiO2 concentrations of the geothermal waters displayed an increase trend from the Lower Pleistocene and Neogene reservoirs within the Gonghe Basin to the Ela and Waligong tectonic-magmatic belts, implying that the reservoir temperatures increased in the same way. The dissolution of primary aluminosilicate minerals and the formation of hydrothermally altered minerals in the reservoirs are the predominant hydrogeochemical processes controlling the concentrations of major cations in the geothermal waters, while the leaching of salty minerals during the infiltration of the recharging waters and the runoff and upflow of the geothermal waters made a substantial contribution to the occurrence of major anions, especially SO 4 2 - and Cl-.

Key words: geothermal fluid, hydrogeochemical characteristics, water-rock interaction, Gonghe Basin

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