A new reef may alter the economics of platinum mining in South Africa, reports Bronwen Jones
FOUR Chinese geochemists, visiting their South African partners in a platinum exploration joint venture, have found evidence of a significant new platinum reef close to the surface.
In an exclusive interview, project manager Yao Wensheng said: “The co-operation between the Chinese Institute of Noble Metals’ Henan Laboratory and the South African Council for Geoscience has produced very satisfactory results. We have established a quick and efficient method to find minerals and are convinced there is very good potential for platinum ore deposits.”
The mining houses have so far shown an exceptional lack of enthusiasm. Aki Wilhelm, scientific officer with the council, believes this negative response is owing to “fears that the platinum price might drop, especially with the potential for this reef to be mined opencast”.
The maps, resulting from the combined work of the Chinese and South Africans, are astonishingly accurate portrayals of known geological structures, and also show likely new sources of minerals, particularly in an area eight kilometres south-east of the Pilanesberg. They also indicate sometimes disturbing levels of pollution around mineral smelters and similar industrial activities.
Owing to the high cost of the research and commercial confidentiality, the maps cannot be reproduced here, but it is expected that some will be made public next April.
In light of this work, it is surprising how dismissive mining houses have been about the potential for further significant projects within South Africa. Most seem to be focusing future activity almost exclusively outside the country. And yet neighbouring nations have already demonstrated faith in the geochemical testing methods that are believed to have indicated the new platinum reef.
A major commercial study for gold has been carried out in Mozambique by the Council for Geoscience. And discussions have been held with Zimbabwe over potential studies along the Limpopo (dependent on foreign investment), as well as talks with representatives of the Botswanan government.
According to Wilhelm: “The important thing is that the Bushveld research has been going on since 1924. Everyone says we know everything. Now, 10 years after a South African called Martin Sharpe said there must be a third reef, we find it.”
Zhang Hong, a senior research geochemist, agrees: “The deposit is not a localised thing. It has been followed over the strike for 100km.”
The team is confident it will trace the deposit for several hundred more kilometres as the stratigraphy (rock sequence) of the Bushveld is to a large extent very uniform.
Says Wilhelm: “We haven’t gone to the Eastern Bushveld yet, but believe we’ll trace this mineralisation there as well.
“If Anglo American had drilled a borehole in 1985, they’d have found it. They just don’t believe Martin Sharpe.”
Another source in the council commented: “Their reluctance is because the market is saturated. If the platinum price falls you can forget about Northam.
“Big mining houses think that South Africa is a mature mining area, that there is nothing to be discovered anymore. Some people are upset that they missed this information. There has been long- standing animosity between the council and the mining houses.”
Only Gold Fields is showing any serious interest in the ground-breaking work.
The results of last year’s study led to follow-up sampling every 125m or so over a 20km2 area. Once results from these samples are available in August, this could be followed with five test drills every 200m following the rock’s downward dip. This would produce the most detailed information yet available through one kilometre of maybe the richest rocks on earth.
Existing geological horizons in South Africa where platinum concentrations are already proven include the “MG chromitite layer” and the “Merensky Reef”. Both these layers show a significant change in the ratios of two isotopes, strontium 87 and strontium 86.
Yao said: “The third mineralisation that we have identified is also related to the change in these strontium isotope ratios.”
The minute changes in elements’ mass numbers are picked up in tests of tens-of-thousands of surface samples collected from soils and streams. Analysis is so accurate that minerals are identified when there are only a few parts in every billion parts of more mundane material.
In the past, geochemists used to search for high- value deposits by looking at collections of less valuable but more abundant elements in the soil, using them to indicate likely associations of minerals. However, when the scientists started looking directly for tiny quantities of the precious metals themselves, they met with more success.
It was the patience of researchers in Xiaoqinling, China, who collected and analysed 6 900 samples, that then successfully defined two gold ore anomalies there.
The chemical spectrometry method was refined by Chen Fang Lun and over a seven-year period moved from the identification of a single gold deposit to 115 gold deposits. Says Chen: “China is already the sixth biggest gold producer in the world. We believe we can become fifth or better.”
Analysis of samples for platinum, palladium and gold has to be carried out in China as there are no suitable facilities anywhere in Africa to handle the thousands of samples required.