Statistical analysis of the spatial distribution and genesis of lithium in geothermal water in the Yangbajing-Gulu rift, Xizang

In the Yangbajing-Gulu rift, located in Xizang, the lithium concentration in geothermal water exceeds the average level of thermal springs in Xizang. However, the hydrochemical genesis of lithium in geothermal water in this rift remains controversial, and one primary reason for this is the unclear spatial distribution pattern of lithium. Common methods for analyzing spatial distribution patterns include Ordinary Kriging and CO-Kriging. Nevertheless, the former suffers low precision. For the latter, it is difficult to obtain suitable auxiliary variables. Given this, this study determined two auxiliary variables: (1) the Cl⁻ concentration, a physicochemical parameter exhibiting the strongest correlation with lithium, and (2) comprehensive index F, as determined using principal component analysis. Integrating these two auxiliary variables separately into the CO-Kriging method formed the Cl⁻-CO-Kriging and F-CO-Kriging methods, which were employed to analyze the spatial distribution patterns of lithium in geothermal water in the Yangbajing-Gulu rift. The results indicate that, compared to Ordinary Kriging, both F-CO-Kriging and Cl⁻-CO-Kriging demonstrated significantly elevated prediction accuracy, with the former increasing E_MA and E_RMS by 30.3% and the latter by 28.5% on average. Furthermore, both methods revealed that lithium in geothermal water exhibits a spatial distribution consistent with faults and notable enrichment in the Yangbajing-Gulu geothermal area. This study further explored the hydrochemical genesis of the spatial distribution of lithium in geothermal water using hierarchical clustering and factor analysis. The results show that an alkaline environment characterized by high temperatures, high total dissolved solids (TDS), low Ca²⁺ and Mg²⁺ concentrations, and elevated born concentrations presents high lithium concentrations. The findings of this study will lay the groundwork for exploring the origin of high-concentration lithium and other rare metals in geothermal water on the Qinghai-Xizang Plateau and conducting relevant resource evaluation.