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Assignment no. 2

eEveline KEKANA
Mining and exploration Geology IV
Student no. 209027135
19 August 2013

Goldfields South Deep Mine

Sampling procedures for grade control and ore reserve estimation.

The South Deep underground gold mine is situated approximately 45km southwest of Johannesburg and is established in the Witwatersrand Basin to exploit the Venterdorp Contact Reef, the upper and lower Elsburg reefs.
The Central Rand Group hosts most of the gold bearing conglomerates and is thought to have deposited in a more restricted basin, specifically in a foreland tectonic setting and is dominated by fluvial braid plain deposits, however trangressive shallow marine sandstones are commonly noted in close association. The Elsburg reef at South Deep comprise of the following reefs at South Shaft:   EB, ECBA, ECBAQ, ECB, ECBQ, ECMC, ECMQ, ECT, ED, MAC, MAS, MAD, MIT, MIC, MBB, MBT, VCR and LAVA. The UE’s are also found at the Twin Shaft at South Deep.

A coarse conglomerate facies comprises a high proportion (>70%) with large to cobble sized clasts and host economic gold mineralisation within all reefs while a sandy conglomerate facies comprises a low proportion (<30%) with small to medium clasts and host uneconomic gold concentrations. The high potential geological domains closely follow the lobes of coarse conglomerates while low potential geological domains follow the lobes of poor and sandy conglomerates.
High gold grade can be associated with poor sedimentary concentrating processes such as debris flow deposits. The behaviour of gold grades in different areas relates to the broadly homogeneous areas as recognized through the changes in the regression factors. Parameters indicating gold concentration are lithofacies, packing, pebble size, pebble assemblage, type of pyrite, amount of pyrite and pyrite grain size. Better concentrations of gold are usually found in well packed, pebble supported conglomerate,...