Characterisation of quartz and pyrite in Witwatersrand gold-bearing conglomerates by minor and trace elements

An understanding of the distribution and concentration of gold within the Witwatersrand conglomerate reefs is of fundamental importance to the gold mining industry. The ability to finger print goldbearing reefs would have an important bearing on mine planning and the development of new methods of mining. From sedimentological studies it is possible to establish the environment in which deposition of gold and associated minerals took place. However, it is not possible to identify sources supplying detrital material on account of the nature of the preserved conglomerates. One possible way of overcoming this problem is to geochemically characterise those detrital minerals associated with the gold. As quartz and pyrite are predominant components of the reef, they are ideal for such a study. In this paper it is demonstrated that detrital pyrite and quartz have specific geochemical signatures which may be used to characterise individual reefs. Furthermore, evidence is provided of the presence of more than one population of detrital components within reefs such as the Ventersdorp Contact Reef and the Steyn Reef. The recognition of different detrital components suggests that a number of source areas were responsible for providing the detritus to the Witwatersrand basin