Gold and uranium deposits in the Witwatersrand Basin are hosted by quartz-pebble conglomerates, which are generally less than 2 m in thickness and developed on laterally continuous unconformity surfaces. These reefs are generally characterised by shallow dips of between 10° to 25° and thicknesses of 1.0 m to 2.5 m that make them suitable for exploitation by means of typical narrow stoping techniques.

The gold deposits of the Witwatersrand Basin are considered to be associated with coalesced fluvial braidplains, where gold was concentrated within braided stream gravels developed on unconformities which have been correlated around the basin.

Most early theories on the origin of gold believed the gold to be deposited syngenetically (placer theory) with the conglomerates or by epigenetic means (hydrothermal origin), but subsequent research by Kirk et al (2004) concluded that metamorphism caused the post depositional local redistribution of gold (modified placer theory).

Generally, gold occurs in native form often associated with pyrite (less commonly pyrrhotite) and carbon, with quartz as the main gangue mineral.

At Blyvoor, two economic placer horizons have been exploited. These are namely the Carbon Leader and Middelvlei Reefs and occur in quartzites of the Main Reef Conglomerate Formation of the Johannesburg Subgroup of the Central Rand Group. The auriferous conglomerates dip uniformly at 22°S.

The Carbon Leader is a high ........

The mining strategy for the Blyvoor Mine is to extract both the Carbon Leader Reef and Middelvlei Reef utilising the No. 5 Shaft Complex via conventional ledging and opening up to the required stoping width of 160 cm for Selective Blast Mining (SBM). The first month of production on each panel will consist of conventional ledging (approximately 8 m linear advance) and conventional opening-up from a 117 cm stoping width to the planned SBM stoping width of 160 cm.

It is expected that a 2 m linear face advance will be required to open-up the stoping width from 117 cm to 160 cm (43 cm). The conversion to SBM stoping will require an additional 4 m linear face advance using conventional stoping, to create sufficient volume in the back area for waste packing once SBM commences. It has been estimated that 50% of the waste within the 4 m advance will be packed, and the remaining 50% will contribute to dilution.

There after SBM stoping will be implemented. Some of the targeted workings cannot currently be accessed and opening-up with re-equipping will be required prior to mining.

Planned mining will initially take place between 15 Level and 27 Level. A ramp up of 17 months has been planned to reach steady state production of approximately 20,000 m², which equates to approximately 40 ktpm. This production rate will be sustained for a period of 15 months followed by a second ramp up. The second ramp up to a steady state production rate of approximately 4 ........

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