Geochemistry of Banded Iron Ore from Obulapuram Area of Sandur Schist Belt, Southern India

ABSTRACT The southeastern part of the Sandur Schist Belt, particularly the Obulapuram area, was investigated to understand the genesis and geochemical evolution of iron ores along with associated volcano-sedimentary sequences. The iron ore bodies up to 5 km long and 50 to 100 m wide are strata-bound and comprise Banded Magnetite Quartzite (BMQ), Banded Hematite Quartzite (BHQ), massive hematite, and friable hematite of Precambrian age. Major, trace, and Rare Earth Element (REE) geochemistry of BHQ suggests a mixed origin involving deep-sea pelagic sediments and hydrothermal input, while BMQ exhibits signatures predominantly of hydrothermal derivation. The massive and friable hematite ores likely formed through extensive silica leaching and hydrothermal alteration of precursor BIF units, producing hematite-martite assemblages. Despite regional metamorphism and post-depositional fluid activity, the preserved geochemical patterns, particularly the REE distributions, suggest a depositional environment in a back-arc basin, possibly near immature island arcs, with geochemical affinities to mid-ocean ridge basalts (MORB). These interpretations integrate primary depositional features with subsequent overprints to reconstruct the complex genesis of the Obulapuram iron ores.