Provenance Characteristics of Au+U Bearing Archean Quartz Pebble Conglomerates of Singhbhum Craton

Abstract

Summary Quartz pebble conglomerate (QPC) hosted gold mineralization has been previously reported from the Dharwar and Singhbhum Cratons in India. However, the nature of gold mineralization within such QPC’s have not been worked upon. In this study we report the presence of refractory gold occurrences within Archean-Proterozoic QPC’s of the Eastern Iron of Group and Dhanjori volcano sedimentary basin, Singhbhum craton, India. These invisible gold particles occur as solid solution within the crystal lattices of arsenic rich pyrite. Presence of refractory gold within QPC’s is rare and makes this work all the more significant. These gold nanoparticles have been identified and analyzed using the micro-probe, BSE images and X-ray compositional maps. Provenance studies for these conglomerates have been carried out whole rock geochemical data using the ICP-MS. Various Geochemical proxies based on REE and trace element data have been used to decipher the nature of the source rocks. These geochemical proxies were coupled with rutile geochemistry to further constrain the provenance characteristics of these QPC’s. These data point towards a mixed nature of source rocks, viz. felsic and mafic/ultramafic. The Singhbhum granite complex along with the mafic/ultramafic enclaves within appear to be the probable host rocks for the studied QPC’s.