Mining Mirror July 2019 | Page 35

The Barberton Greenstone Belt hosts some of the oldest turbidites in the world. In the stope Johan Paul Hunt This implies that Barberton has more potential for discovery, but the targets are expected to be smaller. Barberton would be ideal for a small- to medium-sized business to explore, while the expected prizes still to be found would probably not interest the majors. In other words, they would only be interested in looking for the big deposits? Yes, the majors have much higher value thresholds that need to be met, so their focus either has to be on the acquisition of Tier 1 mineral assets or to be first-mover in new terrains and jurisdictions where the possibility of finding world-class deposits is higher, given the right geological conditions, of course. When looking at the residual potential for the discovery of a deposit, are there other factors that can have an influence? If an exploration company is able to change the search space, it can have a positive effect. This is, in effect, the idea of looking www.miningmirror.co.za where others have not or could not look before. There’s an over-arching principle in mineral exploration that the largest (and by extension the most valuable) deposits are often found early in the exploration process because they tend to have the largest geological footprints. If one can be first mover on a new technology or new geological model, one can unlock unrealised potential in old districts. For example, the introduction of airborne magnetic surveying in the 1940s permitted the search for lithological and mineralogical signatures of large areas and under cover, which was followed by a flurry of discoveries. The other ways that a company may change its search space is either by changing the conceptual understanding of the mineralisation or by changing the mining or beneficiation method. Moving from a high-grade ore-shoot emphasis to a bulk tonnage operation, for example, has been done successfully in other parts of the world, and this change in mining approach has the same effect as creating a new search space. Having said this, some ore deposit types are more amenable to bulk mining methods than others. What has been done in Barberton historically and are there opportunities for exploration companies in the area? Historically, mining companies working in the Barberton Greenstone Belt were only interested in deposits of, let’s say, at least 10g per tonne or higher. Often sample results yielding less than 5‒10g per tonne were ignored. In other words, there is potentially a lot of metal in the ground. So a shift in how one thinks about what constitutes an orebody involving a change in mining method or application of a different lower-cost beneficiation technique could unlock this and hence reduce the cut-off grade. That’s one of the opportunities in Barberton — look for lower grade bulk-mineable resources. Another is looking under the headframes of historic deposits which were stopped for non- geological reasons. Is there land available for new mining companies to still explore in the Barberton area? There is a lot of prospective land in the hands JULY 2019 MINING MIRROR [33]