Abstract

 The Greenstone belts of Karnataka are enriched in BIFs in Dharwar craton, where Iron formations are confined to the basin shelf, clearly separated from the deeper-water iron formation that accumulated at the basin margin and flanking the marine basin. Geochemical data procured in terms of major, trace and REE are plotted in various diagrams to interpret the genesis of BIFs. Al2O3, Fe2O3 (T), TiO2, CaO, and SiO2 abundances and ratios show a wide variation. Ni, Co, Zr, Sc, V, Rb, Sr, U, Th, ΣREE, La, Ce and Eu anomalies and their binary relationships indicate that wherever the terrigenous component has increased, the concentration of elements of felsic such as Zr and Hf has gone up. Elevated concentrations of Ni, Co and Sc are contributed by chlorite and other components characteristic of basic volcanic debris. The data suggest that these formations were generated by chemical and clastic sedimentary processes on a shallow shelf. During transgression, chemical precipitation took place at the sediment-water interface, whereas at the time of regression. Iron ore formed with sedimentary structures and textures in Kammatturu area, in a setting where the water column was oxygenated.

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