Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (6): 173-195.DOI: 10.13745/j.esf.sf.2024.7.17

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Distribution and hydrogeochemical characteristics of hot springs in northeastern Tibetan Plateau

LIU Lingxia1,2(), LU Rui3,4, XIE Wenping3,4, LIU Bo3,4, WANG Yaru1,2, YAO Haihui5, LIN Wenjing1,2,*()   

  1. 1. Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang 050061, China
    2. Technological Innovation Center of Geothermal & Hot Dry Rock Exploration and Development, Ministry of Natural Resources, Shijiazhuang 050061, China
    3. Qinghai Geological Survey Bureau, Xining 810000, China
    4. Technology Innovation Center for Exploration and Exploitation of Strategic Mineral Resources in Plateau Desert Region, Ministry of Natural Resources, Xining 810000, China
    5. School of Civil Engineering, Xuchang University, Xuchang 461000, China
  • Received:2024-02-25 Revised:2024-05-24 Online:2024-11-25 Published:2024-11-25

Abstract:

The Tibetan Plateau is the most active geothermal area in China, and its northeastern region is traditionally considered to be on a relatively stable landmass with average geothermal endowment conditions. Within this region, Qinghai Province possesses a complete range of geothermal resources. Previous studies have been mainly focused on the areas with high levels of exploration or with high-temperature hot springs, yet the overall distribution characteristics of geothermal resources and the heat sources are poorly understood. In this paper, the hot springs are divided into 11 districts from NE to SW according to the main heat-control activity fractures and hot springs areas, and the distribution characteristics and formation of hot springs are comprehensively studied by means of hydrogeochemistry and isotope analysis. The results showed that atmospheric precipitation and snow/ice melt were the source of hot springs recharge. The chemical characteristics of hot spring water were related to the stratigraphy of the hot springs. In granite, chert and sandstone hot springs the dominant cation/anions were Na+/ SO 4 2 --Cl-, Ca2+-Mg2+/ HCO 3 - and Ca2+-Na+-Mg2+/Cl-- SO 4 2 -- HCO 3 -, respectively. Hot springs were mainly distributed along the fracture lines-resembling a string of beads, and concentrated at intersections of different tectonic units, or at bends of tectonic units. Areas between the primary and secondary fractures had the largest thermal-storage depth, the longest runoff path, and more adequate water-rock reactions; whilst the opposites were found along the ternary fractures. From NE to SW, the temperatures of geothermal reservoirs were high in the central areas and SW, and low in the S and NE, and the medium- and high-temperature reservoirs mainly distributed in Gonghe, Guide, Wulan and Tanggula Mountain areas, with the reservoir temperatures ranging from 89.0 ℃ to 139.0 ℃, averaging 117.7 ℃. The heat sources of hot springs included heat gain by conduction of Earth heat flow; heat from the decay of radioactive elements; residual heat from magma; frictional heat from fault ruptures; and heat from low-velocity-high-conductivity melts and mantle channel flow. With focuses on the distribution pattern of hydrothermal resources and heat source of hot springs, this study can provide a reference basis for the later development and utilization of geothermal resources in Qinghai.

Key words: northeastern Tibetan Plateau, hydrogeochemistry, geothermometer, silica-enthalpy diagram, thermal control fractures

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