A submarine hydrothermal origin of banded iron formations from Archean Kiriburu-Meghahatuburu iron ore deposit, Singhbhum Craton, eastern India

Abstract

The high-grade (>62 wt% Fe) iron ores of Kiriburu-Meghahatuburu deposit (KMID) of the Singhbhum-Orissa region, eastern India are mainly hosted by banded hematite Jasper (BHJ) and shale. These BIFs belong to oxide facies (hematite ± martite) iron formations without sulfidic/carbonitic signatures. These BIFs have low concentrations of Al2O3 (0.86 wt%), TiO2 (0.13 wt%) and trace HFSE [(high field strength elements such as Zr (13 ppm), Hf (0.30 ppm), Ta (5 ppm), Pb (7 ppm) and Th (0.45 ppm)], reflecting minor amounts of clastic contamination. The SiO2-Zr/TiO2 ratios and the binary plots between certain trace elements, e.g., Hf-Zr and Zr-Y indicate clastic contamination derived from various sources. The weak positive chondrite normalized Eu anomaly (average 1.13) in BHJ, associated with low V (7 ppm) and Ni (17 ppm) contents are analogous to the Superior-type BIFs worldwide, and are consistent with deposition in a submarine hydrothermal environmental setting under low oxygenated environment. Positive Eu anomalies and the Y/Ho vs Eu/Sm relationships indicate mixing of seawater with a small amount of high-temperature hydrothermal fluids (<0.1 %). Based on the field studies, ore mineralogical and geochemical signatures, a “polygenic-supergene- hydrothermal” model has been proposed for the genesis of Kiriburu-Meghahatuburu BIFs that can be used in understanding the mineralogical variations in the iron ores and their genetic aspects at KMID which has implications for exploration.