Abstract

Manganese silicate rocks interbedded with manganese oxide ores occur enclosed in phyllites of Precambrian Aravalli Group at Kajlidongri, Madhya Pradesh, India. The phyllites are metamorphosed up to the biotite zone of regional metamorphism. In the bedded deposits the ore minerals are bixbyite, braunite and hematite of two generations and jacobsite associated with spessartite and alurgite. In the epigenetic veins cutting across bedded deposits and in the wall rocks surrounding them, hollandite, micaceous hematite, cryptomelane and pyrolusite are present associated with brown manganese pyroxene, blanfordite, winchite, tirodite, alurgite, manganophyllite and piemontite. The origin of the bedded deposits is attributed to metamorphism of original manganese-rich sediment interbedded with pelitic and psammitic rocks. The problems of selective formation of bixbyite and braunite, the appearance of bixbyite in the biotite zone and jacobsite in the chlorite zone are discussed. The unusual mineral assemblage in and around the veins is explained as due to reconstitution of manganiferous sediments by processes associated with the epigenetic veins.

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