Polymetallic Enrichment of Lithium, Cesium, and Rubidium in Borax Deposits of the Puga Geothermal System, Eastern Ladakh: A Geochemical and Fluid Evolution Perspective

The Puga geothermal system in eastern Ladakh, India, is emerging as a highly promising target for critical and strategic mineral exploration. This high-altitude geothermal field hosts significant deposits of borax (Na₂[B₄O₅(OH)₄]·8H₂O), a borate mineral typically associated with evaporitic and geothermal environments. Recent geochemical investigations have unveiled multi-element enrichment in borax samples, with notably high concentrations of lithium (Li), cesium (Cs), rubidium (Rb), and potassium oxide (K₂O)—underscoring Puga’s potential as India’s first geothermal critical mineral resource. Sampling and analytical data indicate average concentrations of 2,154 ppm Li, 1,481 ppm Cs, 184 ppm Rb, and 2.39% K₂O in borax, with trench/pit samples revealing exceptional Cs anomalies up to 6,860 ppm. These elements are essential to modern technologies—lithium and potassium for energy storage, cesium for quantum computing and atomic clocks, and rubidium for specialized electronics and optics. The co-enrichment of Li–Cs–Rb–K₂O suggests a poly-metallic exploration model, shifting the focus from single-element targeting to multi-commodity resource development. This approach is particularly suited to the geothermal context, where mineral extraction could be powered by sustainable geothermal energy, minimizing the environmental footprint and enabling low-carbon, integrated resource development. Geologically, the enrichment is attributed to deep geothermal fluids enriched through prolonged interaction with boron-rich leucogranites and volcanic lithologies, followed by concentration through surface evaporation in Puga’s arid, high-altitude basin. The integration of geothermal energy with critical mineral extraction could establish Puga as a model for sustainable and strategic resource development in the Himalayas.