Orkney Gold Mine

 mine, gold mine

Orkney is a large 7 shaft mine on a mining right that covers an area of 10,561.7 ha. It was originally owned by Anglo American, which later became AngloGold Ashanti Limited, and was art of their Vaal Reef Operations. African Rainbow Minerals (ARM) then purchased the mine from Anglo and in 2003 ARM merged with Harmony Gold. In 2008 Pamodzi Gold bought the operations from Harmony but due to financial problems they were provisionally liquidated in March 2009 with final liquidation granted in October 2009.

During the liquidation bidding process Aurora Empowerment Systems bid for the Pamodzi assets was accepted and they planned to invest R600m on the assets. However Aurora had severe financial problems and workers at the mine went without salaries for months. There was also illegal stripping of mine assets and thus Aurora was removed from the mine and the accepted bid was cancelled on May 26, 2011, putting the mine back in the liquidation process.

In 2011 China African Precious Metals (CAPM) entered into an R150-million (US $15 million) agreement to purchase the mine but that deal was not completed until October 2012. CAPM is owned by Superb Gold with 74% and a black economic-empowerment consortium led by Elias Khumalo with 26%. Superb is owned by SSC Mandarin of Hong Kong. On June 20, 2016 CAPM submitted an amended EMPR report and applied to recommence mining at the Number 6 and 7 shafts. Part of the application was to produce a heritage report on the shafts to determine what, if any, needed to be preserved as heritage resources.

Infrasture includes 7 shaft complexes, 2 gold plants, and 5 tailings storage facilities. CAPM plans to establish initial production at shafts 6 and 7, and once they have been operating for around 2 years the plan is to restart mining at shafts 1 and 4, then investigate the potential for opening shaft 2. Shaft 5 will not be restarted as most infrastructure except the shaft headgear was removed and will be fully decommissioned and rehabilitated. It was found that Shaft 3 had a twisted shaft barrel therefore it was decommissioned and all infrastructure was removed. However, it was found that that the decommission was done without a permit.

Conventional cycle mining will be utilised and each crew will work two panels with one panel will be blasted and the other one cleaned. Conventional scattered breast mining method consisting of the standard deep level underground stoping layout will be used at 7 Shaft. Off-reef haulages and crosscuts will be developed, with travelling ways and step overs to access the reef. Raises will be blasted from one level to the next which will act as the centre gully. Blasted panels will be cleaned by means of gully and face winches which will pull the rock into the centre gullies. Centre gully winches will be utilised to pull the blasted rock into orepasses, from where it will be pulled into hoppers by means of chutes. All mined ore will be transported to 6 shaft for hoisting to surface.

Once ore is produced no processing will be done at the Orknew gold plants as they will not be refurbished back to operational capacity. 1.56Mtpa of Stockpiled ore will be transported to the Nicolor South Plant at Buffelsfontein which still processes ore from other mines even though mining has ceased. The process used employ typical steps of milling, thickening, leaching, adsorption in the carbon in pulp (CIP) section, elution and electrowinning, then smelting where the gold coated wire wool is removed from the electro-winning cell and then calcined. After calcination the resulting material is the smelted to produce a gold bar. If there are any issues with Nicolar South processing CAPM has the alternative to contstuct a new plant or refurbish one of the existing gold plants.

Upon takeover of the mine by CAPM it still had a good reserve base with the mineral resource statements from a Minxcon, 2014 report being used. The resources are determined by shaft and include measured, indicated, and inferred to come up with a total. Shaft 2 has 1.52 Moz, shaft 4 has 6.03 Moz, shaft 6 has 4.96, and shaft 7 has 2.72 Moz. The estimated time periods are 0.5 years for recommissioning, a life of mine operation of 9 years, and 1.5 years to close and rehabilitate the mine.

Regionally Orkney is located in the Witwatersrand Basin which is a late Archean-aged basin that is comprised of an inter-bedded sequence of arenaceous and argillaceous sediments. The basin is located on the Kaapvaal Craton and is 6 km thick, 300 km wide from northest to southwest, and 100 km wide northwest to southeast. All sections of the basin except the northern section are overlain by 4km of volcanic and sedimentary rocks from the Archaean, Proterozoic and Mesozoic period.

Locally Orkney mines from 3 primary reefs that occur at depths between 80 to 4000 meters. Those reefs are the Vaal Reef, Ventersdorp Contact Reef (VCR), and the Elsbug reef, and not all reefs are mined at each shaft. Several major faults occur in the mine area and typically have throws of tens of metres and further divide the reef into blocks of up to 100 m in width. The horsts and grabens are further disturbed by faults sympathetic to the major faults and typically have throws of tens of meters.