Integrated Geological, Geochemical, and Reserve Estimation of the Gwani Talc Deposit, Darchula, Nepal

Abstract

Talc occurrences in the Lesser Himalaya are associated with carbonate-rich rocks, and their economic viability depends on mineral quality, deposit continuity, grade, accessibility, overburden thickness, and extraction conditions. This study evaluates talc occurrences in Gwani, Sailesikhar Municipality, Darchula District, Sudurpashchim Province, Nepal, through geological mapping, sampling, chemical analysis, site-suitability scoring, and volume estimation. The deposit occurs within dolomite of the Galyang Formation of the Lesser Himalayan Midland Group, associated with limestone, slate, and schist. The site-suitability assessment gave Gwani a score of 18/24. Fifteen samples yielded SiO₂ contents of 59.36–65.59% (mean ≈ 61.9%) and MgO contents of 28.29–35.65% (mean ≈ 32.5%), indicating low- to medium-grade talc. Six geological cross-sections gave an estimated 2,631,219 m³ (7,104,290 tonnes) of talc and 1,121,934 m³ (3,052,781 tonnes) of associated dolomitic muck. A semi-mechanised mine plan with benching and sequential extraction, assuming 1,600 tonnes/day of combined material over 300 working days per year, gives a mine life of about 21 years. The findings demonstrate the potential for systematic development of industrial talc resources through integrated geological, geochemical, and mine-planning approaches.