Origin mechanism of thermal springs and their supply of minerals to the salt lake(Li-Rb-Cs) in the Tangqung Co watershed of Tibet

This paper is the result of mineral exploration engineering.

Objective The Tangqung Co area in Tibet is located in the north of Tangra Yum Co-Xuru Co rift. The presence of geothermal springs in locations like Qurebaima and Zhariqusheng has prompted the need for a comprehensive study of their hydrochemical characteristics and origin, particularly regarding their contribution of Li and Rb substances to the Tangqung Co salt lake.

Methods This study involved the collection and analysis of six spring water samples to determine their chemical composition and stable isotopes. Various chemical coefficients and mineral saturation indices were calculated, and cluster analysis was performed on the chemical components of the springs.

Results The findings reveal that Qurebaima spring waters exhibit enrichments in elements such as Li, B, Rb, and Cs. These springs are influenced by atmospheric rainfall and snowmelt, displaying shallow circulation characteristics. The springs' extended flow path and substantial water-rock interaction contribute to the predominance of HCO₃^- originating from carbonate rocks and CO₂ produced by magmatic activity. Moreover, the calculated thermal reservoir temperature based on SiO₂ geothermometers falls within the range of 123.33 to 128.22℃ for Qurebaima samples.

Conclusions Geothermal activity in the Tangqung Co area is governed by the N-S trending Tangra Yum Co-Xuru Co rift valley, wherein the geothermal water acquires Li, Rb, Cs, and other trace elements through interactions with silicate minerals. Additionally, the water-rock interaction extends to the Permian and Cretaceous carbonate rocks, ascending along active faults in the region, and ultimately mixing with water from the Tangqung Co lake. This phenomenon suggests that the formation of Li and Rb-rich salt lakes in Tibet may be associated with extensive N-S rift activities, which not only provide geographic space for the accumulation and mineralization of salt lakes but also act as conduits between deep sources and surface environments.