Discovery of the Kamoa Copper Deposit, Central African Copperbelt, D.R.C.
D. W. Broughton, T. Rogers, 2010. "Discovery of the Kamoa Copper Deposit, Central African Copperbelt, D.R.C.", The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, Richard J. Goldfarb, Erin E. Marsh, Thomas Monecke
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The recently discovered Kamoa deposit is a laterally extensive and relatively undeformed sediment-hosted stratiform copper deposit that lies approximately 25 km west of the Kolwezi district in the Central African Copperbelt of the Neoproterozoic Katangan basin. The deposit was discovered by systematic application of conventional stream-sediment and soil geochemical surveys, airborne magnetic-radiometric surveys, and drilling. Widely spaced drilling has identified inferred and potential resources grading >1 percent Cu over widths of >3 m over an area of 81 km2, which remains open to expansion. The Kamoa deposit represents a major copper discovery beyond the previously known northwestern limit of the Central African Copperbelt.
The classic sediment-hosted stratiform copper deposits of the Central African Copperbelt, including those of the Congolese Copperbelt within the Kolwezi district, all occur at the stratigraphically lowermost redox boundaries in the oldest part of the basin fill, the Roan Group. Tectonically they occur within the External fold and thrust belt of the Lufilian arc. In the Congolese Copperbelt, sediment-hosted stratiform copper deposits occur within tectonically disrupted fragments of Mine Subgroup rocks at the base of the Roan Group. The Kamoa deposit occurs within the adjacent Western foreland tectonic domain. In the Kamoa area the Roan Group stratigraphy is condensed to approximately 200 m or less adjacent a prominent basement inlier, the Nzilo block, and comprises only oxidized hematitic sandstones and conglomerates of the Mwashya Subgroup. Kamoa mineralization occurs above these oxidized rocks in the overlying reduced basal diamictite of the ~750 Ma Grand Conglomerate (Nguba Group). The deposit thus occurs at the stratigraphically lowest redox boundary in the Kamoa part of the Western foreland. Disseminated copper sulfides replace diamictite clasts and matrix, form a gently dipping stratiform zone and show vertical chalcocite-bornite-chalcopyrite-sphalerite-pyrite zoning typical of sediment-hosted stratiform copper deposits.
Two main factors appear to have contributed to the Kamoa deposit remaining undiscovered during the long history of exploration and mining in the area. The deposit lies stratigraphically ~1 to 2 km above the usual level of ore in the Central African Copperbelt, in host rocks that elsewhere in the Congolese Copperbelt do not contain economic mineralization. The deposit also is distinct in having a strongly pyritic hanging wall and a paucity of carbonate, which resulted in development of a leached capping, atypical of the Central African Copperbelt where most deposits had outcropping mineralization.
The location of the Kamoa deposit within the ~750 Ma Grand Conglomerate places important minimum constraints on the timing of sediment-hosted stratiform copper mineralization in at least this part of the Katangan basin. Although there are similarities in the style of mineralization at Kamoa and in Kolwezi, it is unknown whether they were formed by the same event.
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The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries
There seems to be general consensus throughout much of the global mining industry that the supply of base and precious metals and some other commodities (e.g., ferrous metals, uranium) is reasonably well assured into the oreseeable future because increases in total resources continue to keep pace with or outstrip global consumption. The basic assumption is that market forces and technological advances will combine to promote and perpetuate this trend (e.g., Tilton, 2003; Crowson, 2008). Others disagree, however, andpredict that shortages are inevitable if metal consumption continues to escalate (Beaty, 2010).
It is already becoming clear that many known resources seem unlikely to be mined, irrespective of commodity prices, because of their low grade and/or quality. Hence, many mineral resources that were uneconomic in the early 2000s are likely to remain so, both today and into the foreseeable future because of increases in both the direct (e.g., energy, labor) and indirect (e.g., environmental, social) production costs. This situation is being further exacerbated by the perceived decrease, over at least the past decade, in the discovery rate of base and precious metal resources measured in terms of both the number of major discoveries made and the exploration dollars spent per discovery (e.g., Dummett, 2000; Horn, 2002; Schodde, 2004). There is also a suggestion that the discoveries made are, on average, becoming both smaller and lower grade. Therefore, it seems reasonable to ask whether current exploration practices and success rates are going to be adequate to provide for the massive increases in metal consumption that world population growth, rising living standards, and rapid industrialization and urbanization in China, India, and other emerging markets appear to portend. For example, Rio Tinto's projections suggest that "by 2030 the additional supplyrequired will be equivalent to replicating the iron ore output of the Pilbara region of Australia every five years, adding another aluminium production complex the size of Canada's Saguenay every nine months, and developing another copper mine the size of Escondida in Chile each year. Future energrequirements are such that an entire Hunter Valley coal supply chain needs to be created each year plus a uranium mine the size of Ranger every four years" (Albanese, 2010, p. 7). Clearly, the exploration business has to become increasingly effective if it is to rise to the challenge of finding mineral resources of the right caliber to assure that this burgeoning demand can be adequately satisfied.