Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Rajesh Sharma ¹, Prabha Joshi ², P. D. Pant ²

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN
2 Department of Geology, Kumaun University, Nainital - 253 002, IN

Abstract

Talc deposits of Rema area in the Kumaun Inner Lesser Himalaya are hosted within high magnesium carbonates of the Proterozoic Deoban Formation. These deposits occur as irregular patches or pockets mainly within magnesite bodies, along with impurities of magnesite, dolomite and clinochlore. Textures represent different phases of reactions between magnesite and silica to produce talc. Petrography, XRD and geochemistry reveal that the talc has primarily developed at the expense of magnesite and silica, leaving dolomite largely un-reacted. Early fluid inclusions in magnesite and dolomite associated with talc are filled with H₂O+NaCl+KCl± MgCl₂ ± CaCl₂ fluids, which represent basin fluid system during diagenesis of carbonates. Their varied degree of re-equilibration was although not pervasive but points to increased burial, and hence requires careful interpretation. H₂O-CO₂ fluid with X_CO2 between 0.06 and 0.12 was equilibrated with talc formation. The reaction dolomite+quartz → talc was not extensive because T-X_CO2 was not favourable, and talc was developed principally after magnesite+quartz.

Keywords

Talc, Fluid Inclusions, Re-Equilibration, Kumaun Lesser Himalaya.

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