Geochemical evolution of geothermal waters in Trans-Himalayas: Implications for critical mineral deposition

Abstract

The hydrothermal fluids of the Trans-Himalayan region host rich deposits of critical elements (e.g. Li, Cs, B, W, etc.), that forms critical energy minerals. We characterize geochemical evolution of hydrothermal waters in Trans-Himalayan region, delineating the origin and dissemination of critical energy minerals as epithermal deposits in the region. Thermal fluids exhibit enrichment in W with maximum value of 1603 μg/L and rare alkalis like Cs and Li, whose peak concentrations reach upto 6976 μg/L, and 6.8 mg/L, respectively. Similarly, soils/altered rocks are characterized by significant levels of Li (116–911 mg/kg), Cs (632.56–3317 mg/kg), Cu (181–343 mg/kg), Hg (11–2540 μg/kg), Sb (108.94–6602 mg/kg), BaSO<inf>4</inf> (27.49–71.13 %), S (37.3 %), and F (84–3848 mg/kg). This study identifies Li-bearing mica minerals in considerable concentrations, alongside epithermal minerals attributing to a paleo-high-temperature regime in the Himalayan geothermal field. A conceptual model has been developed to trace the origin of critical minerals in thermal fluids and spring deposits, suggesting that metals and metalloids degas from felsic magmatic melts, through less-denser geological vapours, primarily as vapour-soluble chloride and sulfide complexes, which mixes with genetically evolved secondary fluids undergoing gas-solution-rock interactions and gets enriched in liquid phase after steam segregation, mainly due to decompression boiling. © 2025 Elsevier GmbH