A Note on the Metamorphism of the Carbonate Rocks of the Sausar Group in the Northwestern part of the Nagpur District

The Sausar Group rocks (Precambrian) from the highest grade region contain wollastonite in the impure dolomitic marbles (Bichua Stage), but not in the isogradic Lohangi (Sub-stage) calcitic marbles which are characterised by the calcite-quartz association with or without diopside, grossularite and scapolite. The low-variance assemblage of grossularite-plagioclase-wollastonite-calcit ± quartz in the Bichua marbles, together with the muscovite-free sillimanite-biotite ± cordicrite paragenesis in the adjacent schists and their association with migmatites, suggest metamorphic temperatures ncar 650° C at about 3 kb pressure, inferred from geological and petrological evidence. The spatial distribution of the wollastonite-bearing assemblages and their occurrence with amphibole and vesuvianite in the Bichua-Stage marbles, unlike the Lohangi calc-silicate bands. provide evidence for lowering of XCO₂ by H₂O , F and Cl in the fluid phase which controlled the development of wollastonite in the investigated area.