Banded Iron-Formation and Associated Manganiferous Horizons of the Sargur Supracrustals, Southern Karnataka

High-grade Archaean Sargur supracrustals are made up of quartzites, pelites, carbonates, BIF and manganiferous horizons and have been metamorphosed to upper amphibolite facies. The BIF and manganiferous horizons form thin but persistent bands. Iron-manganese-carbonate association is characteristic. Ten samples of BIF and spessartine-rich manganiferous horizons were analysed for major, trace and rare earth elements. Low trace and REB abundances characteristic of these bands agree well with the data of Archaean iron-formations elsewhere. Chemistry of Sargur BIF is distinctly different from that of the Algoma and Superior types. The positive Eu anamoly shown by the iron-formation indicates oxygenic conditions. The low content of some trace elements indicates shallow water environment of deposition. The REE concentrations of manganiferous-horizons are relatively higher than that of the BIF with anomalous behaviour of Ce and Eu. The present data show that the iron and manganese separation had taken place even in the Early Archaean.