The Tshepong Operations are situated in the Free State Goldfield, on the southwestern margin of the Witwatersrand Basin of South Africa, one of the most prominent gold provinces in the world. The major gold bearing conglomerate reefs are mostly confined to the Central Rand Group (CRG) of the Witwatersrand Supergroup.
Tshepong Operations exploited primarily the Basal Reef, which occurs within the Harmony Formation of the Johannesburg Subgroup of the CRG.
Mineralisation also occurs within the stratigraphically higher A and B Reefs of the Kimberley (formerly Aandenk) Formation, within the Turffontein subgroup of the CRG. However, only the B Reef can be economically extracted.
Mineralisation is associated with the presence of medium to coarse, clast-supported oligomictic pebble horizons. The presence of allogenic pyrite and detrital carbon is also common.
The principal gold-bearing ore body at the Tshepong and Phakisa sections is the stratiform and stratabound Basal Reef (known as the Basal Reef Zone or BRZ). This unit comprises a thin conglomerate at the base of the BRZ, overlain by clean ‘placer’ quartzites. The BRZ is underlain by a thick series of siliceous and argillaceous quartzites comprising the Welkom Formation and is overlain by shales and quartzites of the Harmony Formation, both of the Johannesburg sub-Group of the Central Rand Group. Although not apparent within the Mines Lease, the BRZ sits unconformably on the Welkom Form ........
