Gold provenance of the Black Reef conglomerate, West and East Rand, South Africa

The origin of the gold, the uranium and the PGEs in the basal conglomerate of the palaeoproterozoic Black Reef Formation of the Transvaal Supergroup in South Africa is currently debated due to its economic significance as a gold ore body. Both the heavy mineral spectra and the geochemical trace element fingerprint of the Gold are used to unravel the origin of the Black Reef Gold. Based on EMP, LA-ICP-MS and SR-mu-XRF measurements Black Reef and Witwatersrand gold can be distinguished by means of their different degree of true fineness, the Hg and Cu concentrations, and the S, and Ni trace element content. Among the elements which are correlatible with gold, Sn, Sb, Pd, and Pt, possibly in combination with Mn, Se, Pb, and Ir appear to be the most effective element distinction of gold sources. The Black Reef at Consolidated Modderfontein on the East Rand appears to have a different gold source than the underlying Witwatersrand reefs.