Great Noligwa

Overview

Great Noligwa gold mining operation is located about 15 km southeast of the town of Orkney, in the southern part of the Kleksdorp Goldfield of North West Province of South Africa. It adjoins the Kopanang and Moab Khotsong mines near the VaalRiver. The Vaal Reef, the primary reef, and the Crystalkop Reef, a secondary reef, are mined here.

This mining operation consists of a twin-shaft system and operates over eight main levels at an average depth of 2,400m below surface. The first gold was poured in 1972.

Given the geological complexity of the orebody at Great Noligwa, a scattered mining method is employed. The mine shares a milling and treatment circuit with Moab Khotsong and Kopanang, which applies conventional crushing, screening, SAG grinding and carbon-in-leach (CIL) processes to treat the ore and extract gold.

Location

Great Noligwa adjoins Kopanang and Moab Khotsong and is located close to the town of Orkney near the Vaal River in the North West Province of South Africa.

The mining lease area is 49 sq km and is adjoined to the north by Aurora mine, to the east by Buffelsfontein mine, to the south by the Moab Khotsong and the Jersey, and to the west by Kopanang mine.

Geology & Mineralization

The Vaal Reef (VR) is the principal economic horizon at Great Noligwa and the Crystalkop Reef (C Reef) is the secondary economic horizon. Both reefs are part of the Witwatersrand Supergroup and are stratigraphically located near the middle of the Central Rand Group. The C Reef forms the top of the Johannesburg Subgroup, while the VR is about 265m below the C Reef.

The VR unit can reach a maximum thickness of 2m and consists of a thin basal conglomerate (the C facies) and a thicker sequence of upper conglomerates (the A facies). These two sedimentary facies are separated by the B facies, which is a layer of barren orthoquartzites. The A facies is the principal economic horizon within the VR, but remnants of the C facies are sporadically preserved below the A facies. High gold values in the VR are often located at the base of this unit and are associated with high uranium values as well as the presence of carbon. Uranium is a very important by-product of Great Noligwa.

The C Reef has been mined on a limited scale in the central part of Great Noligwa, where a high-grade, north-south orientated sedimentary channel, containing two economic horizons, has been exposed. To the east and the west of this channel the C Reef is poorly developed with relatively small areas of economic interest. As in the case of VR, high uranium values are also often associated with high gold values and the presence of a 5mm to 2cm thick carbon seam at the base of the conglomerate. To the north of the mine the C Reef sub-crops up against the Gold Estates Conglomerate Formation and in the extreme south of the mine the C Reef has been eliminated by a deep Kimberley Erosion Channel and the Jersey fault.

Mineral reserves were estimated at 4.74 million tonnes grading 7.37 g/t gold for 1.12 million ounces. Uranium reserves at Noligwa amounted to 2.06 million tonnes containing 0.30 million pounds uranium oxide.  (December 2011)

Mining & Operation

The economic horizons are exploited between 1,500m and 2,600m below surface through a mining method that gains access to the gold-bearing reefs with footwall haulages and return airway development.

Beacuse of extensive faulting the mining method devloped here is scattered mining.

Cross-cuts are developed every 180m from the haulages to the reef horizon. Raises are then developed on-reef to the level above and the reef is mined out on strike.

In 2011, mining reached its boundary limits and the mining process shifted from conventional underground mining to pillar extraction.

Processing

Conventional crushing, screening, SAG grinding and carbon-in-leach (CIL) processes to treat the ore and extract gold.

Moab Khotsong, Great Noligwa and Kopanang material is milled at the Noligwa gold plant and treated in the South uranium plant for uranium oxide extraction by the reverse leach process. The resulting ammonium diuranate is transported to the Nufcor plant where the material is calcined and packed for shipment to the converters.

In 2011, Great Noligwa produced 94,000 oz gold at $1,194/oz total cash costs. Increased uranium production helped mitigate some of the losses generated by challenging gold mining in difficult ground and geological conditions.

Environment & Community

Great Noligwa was restructured during the year with the aim of reducing its overall operational footprint and to return it to profitability. Employees were offered the opportunity to apply for voluntary severance packages or transfer to other business units within the company. Labour unions were consulted on strategic matters throughout the process.

There were no fatalities during 2010, with the mine achieving 1 million fatality-free shifts on 5 November 2010. The mine also achieved 269 white flag days, signifying the number of full days without a lost-time injury being reported on site. The all injury frequency rate deteriorated to 21.63 per million hours worked recorded for the year (2009: 17.51). Great Noligwa maintained its OHSAS 18001 and ISO 14001 certification in 2010. Unfortunately one fatality was recorded in January 2011 during scraper winch operations.

Great Noligwa remained active in the community with various outreach projects. 

The mine retained its ISO 14001 certificate during the first advanced DQS audit conducted in August 2010. No environmental incidents were reported during the year.