Petrography and geochemistry of magnesite and talc deposits of Jhiroli, Kumaun Lesser Himalaya

Abstract

The Veitsch type magnesite mineralization in association with talc from Jhiroli is confined within the stromatolitic dolomite of Deoban Formation. The dolomite represents many microlithotypes and characterized by nodules and bands of chert. Microtextures suggest a tidal flat environment where different phases of replacement of dolomite by magnesite were observed. Grain boundary relations, replacement features and different phases of reactions between magnesite and silica explain development of talc in the system. There is a noteworthy similarity in geochemical signatures of dolomite, magnesite and talc except a few major and minor elements, which suggest an external chemical flux is not responsible for the magnesite and talc mineralizations. On the basis of field relation, petrography and geochemistry it can be inferred that the marine, sparry magnesite deposits are product of diagenetic replacement of early dolomite in a protected intertidal carbonate flat environment whereas the associated talc deposits resulted from incipient/low grade regional burial metamorphism of these siliceous, magnesium bearing carbonates.