Origin of the enrichment of B and alkali metal elements in the geothermal water in the Tibetan Plateau: Evidence from B and Sr isotopes |
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| Institution: | School of Earth Sciences and Engineering, Hohai University, Nanjing 210098, China |
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| Abstract: | Geothermal fields distributed in the southern Tibet Plateau rifts such as Yangbajing - Dangxiong basin, and the Yaluzangbu suture are characterized by intensive hydrothermal activity and high enrichment of trace elements (e.g., Li, Rb, Cs, B and Br) in geothermal springs. However, the origin of these elements and their enrichment mechanisms in those geothermal waters remain unclear. This study presents data for the enriched elements, incompatible elements, and B and Sr isotopes, in the geothermal water in the Tibetan Plateau and compares them with some typical geothermal fields worldwide, in an attempt to provide new insights into the origin and mechanism of the enrichment of these trace elements. The results indicate that all geothermal water samples from the Tibetan Plateau show more negative δ11B values than those from local precipitation and rivers. Considering the wide existence of a high-conductivity zone in the middle or even upper-crust interpreted to correspond to re-melt magmatic fluids in the Tibet, the main sources of the typical chemical composition of geothermal waters in the Tibetan Plateau can be classified into two main types: residual magmatic fluids derived from crustal partial remelting and deep circulated groundwater modified by water–rock interactions. In particular, the possible source of magmatic fluids may play a more significant role for special geochemical compositions of geothermal water in the Tibet. Such resources are beneficial for the development and utilization of the geothermal water itself and also serve as a stable source for feeding the salt lake resources. |
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