Magnesite in the Palaeoproterozoic metasedimentary carbonate sequence of Aravalli Supergroup in Gujarat, western India

摘要

Carbonate rocks form a substantial part of the Palaeoproterozoic Aravalli Supergroup in western India. They are good repositories of stromatolitic rock phosphate at Jhamarkotra 1 and Sallopat areas (S. K. Trivedi, unpublished), Cu–Au–Fe mineralization in Banswara 2 and Zn–Pb– Ag in Zawar area 3 in southern Rajasthan. During large-scale mapping and sampling of a phosphate prospect in Champaner Group at Chalvad–Ranjitpura area in Panchmahals district, Gujarat 4 , chemical analyses of a few samples yielded high MgO content beyond the compositional limit of pure dolomite (< 21.7 wt% MgO). In the absence of any significant amount of serpentine and talc, the high magnesia content was suspected to be periclase-brucite and/or magnesite. XRD analyses performed on high-MgO samples confirmed the presence of magnesite as a major carbonate phase. Here we report the discovery of magnesite in the Precambrian metasedimentary sequence of northern Gujarat.