Cesium and Hg-Sb mineralization in Puga geothermal system, Ladakh, J & K, India

Puga, the most promising geothermal system of the Indian subcontinent with over a hundred thermal manifestations spread over an area of 5 km², is located at an altitude of 4400 m above m.s.l. in the vicinity of the NW-SE trending Indus Suture Zone. The geothermally anomalous area is covered by borax-mixed encrustations with Cs concentrations averaging around 730 mg.kg ^-1. Surface samples also yield Hg and Sb values up to 45 and 500 mg kg^-1, respectively. Drillcores from three shallow boreholes show relatively low values for Cs and higher Hg values in the depth range of 2 to 20 m (highest value being 325 mg kg^-1). The abundance of Sb is notable at least to a depth of 50 m. Arsenic and traces of Au are associated with Hg-Sb mineralization. The Puga geothermal system thus exhibits a rather unique near surface enrichment of Hg, Sb and Cs. While Hg and Sb mineralization is clearly product of the on-going epithermal environment, similar to the one at Steamboat Springs, Nevada, U.S.A., Cs enrichment has evidently been brought about by vapors emanating from the deeper part of the system.