Archaean granitic sources for the detrital mineral assemblage in Witwatersrand conglomerates

A granite-greenstone terrain has been proposed as a model source area for the Witwatersrand detritus. Recent investigations into the heavy mineral content of some Archaean granites along the north-western margin of the Witwatersrand Basin revealed the presence of small amounts of gold particles in a number of granite exposures. Larger amounts of pyrite in granites are usually accompanied by nodules of carbonaceous matter. These nodules are often intergrown with sulphide minerals and contain small inclusions of thorianite or uraninite and rare earth minerals. Data is given on the energy dispersive spectra of uraninite inclusions in carbon nodules from an Archaean granite and the Ventersdorp Contact Reef