May - June, 2010
Modikwa Mine a valuable link in the Anglo
Platinum Chain
A 50:50 Joint Venture between Anglo Platinum and African Rainbow Minerals (ARM), Modikwa Platinum Mine is located about 15km from Burgersfort, along the border between the South African provinces of Mpumalanga and Limpopo.
The mine is an underground operation that produces approximately 300,000 ounces of platinum group metals (platinum, palladium, rhodium and gold) annually, of which 135,000 ounces are platinum concentrate.
For Anglo Platinum, the world’s largest producer of platinum group metals (PGMs) and an owner of mines throughout the Bushveld Igneous Complex, the Modikwa mine plays a vital role in ensuring the company’s ability to meet any increase in demand for PGMs in the market place. The mine also assists Anglo Platinum in its mission to stimulate Black Economic Empowerment – 8.5 percent of its joint venture partner ARM’s 50 percent shareholding is held by the ARM Mining Consortium, which represents the communities of seven villages surrounding the mine.
Location and Geology
Situated on the Eastern Limb of the Bushveld Igneous Complex, Modikwa Platinum Mine exploits the chromitite seam known as the Upper Group 2 (UG2) reef. The north/ northwesterly-tending ore body is approximately 28 km on strike, outcropping on the surface, and extends to an unknown depth. The mine currently extends over an area of 14,278ha, and holds the mineral lease over five farms: Driekop, Maandagshoek, Hendrikplaatz, Onverwacht and Winterveldt. The mine area contains up to 48.4 million tonnes of mineral reserves, while measured and indicated resources are estimated at between 115.2 and 145.7 million tonnes – sufficient for at least fifty years.
Both the UG2 and Merensky reef are found within the mine area. At present only the UG2 is being mined, though some trial mining has been done on the Merensky Reef Horizon. The UG2 reef is present as a chromitite layer of an average thickness of nearly 60cm, which undulates across the mine area at an amplitude of less than 2m. Geological challenges include randomly distributed potholes of various sizes mainly in the north shaft area, and large ultramafic pegmatoid intrusions on the Onverwacht farm.
Mine Overview
Currently 450m deep, the mine was established in the year 2000 and the first stope production commenced in March 2002, on the south shaft. Expansion has been limited to dip extensions of the north and south shafts in 2008, but further growth is planned for the medium term. Difficult geological conditions necessitated a change in 2006 from dip to breast mining, which reduced the amount of reef development required and increased the stoping tonnes produced.
According to Sean O’Connor, Business Leader at Modikwa, the ore body is accessed by two decline shaft systems – a north shaft and a south shaft – each with a conveyor belt, a chairlift for mine personnel, and material declines for heavy vehicle access. “We have a unique hybrid mining system with the use of trackless footwall development and conventional narrow on-reef strike scraper mining,” says O’Connor. Heavy vehicles are used for the loading and tramming of ore, while the stoping is done on a narrow reef of some 100cms by conventional strike scraper cleaning of breast panels.
“We mine some 90 thirty-metre-long panels, producing some 40,000 m2 per month and milling some 200,000 tonnes per month,” O’Connor continues. Run-of-mine processing is carried out at the Modikwa concentrator, after which the platinum group element (PGE) rich concentrate is sent to Anglo Platinum’s Polokwane smelter.
Safety Second to None
Asked about significant milestones, O’Connor cites the mine’s safety performance as its greatest achievement. “Modikwa achieved 6,000,000 fatality-free shifts on the 2 December 2009, and we are on target to achieve 7,000,000 fatality-free shifts in September 2010. We completed four fatality-free years on 12 April 2010.” That’s no mean feat, considering that the mine employs some 3,700 employees and 800 contractors.
O’Connor attributes the mine’s excellent safety record to its well-educated workforce (which uses English as the main medium of communication) and to the fact that its employees “Do not come from a traditional mining culture where mine accidents are accepted as an inherent risk associated with the work.
They believe all accidents can be prevented.” Another boost for general health and safety is that Modikwa’s employees live with their families and are bussed to work and back each day, rather than living in single-sex hostels.
Ongoing Challenges
The deterioration in global economic markets and the steep decline in the prices of PGMs have had an inevitable impact on the mine, resulting in the temporary curbing of major capital expenditure.
“Costs remain an ongoing challenge, though,” O’Connor continues, “and we are currently designing to mine with strike conveyor belts to overcome the high cost of the underground fleet of loading and tramming using LHDs and ADTs respectively.”
Looking Forward
“We believe we have a bright future as we have a large ore reserve which can permit us to increase our volume of production and offset the ever-increasing unit costs we are faced with. We have plans in place to increase this volume in the medium term,” concludes O’Connor. If Modikwa’s successful – and profitable – management of the challenges so far is anything to go by, they have every reason to look forward to the future.
