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Book Chapter

Discovery of the Kamoa Copper Deposit, Central African Copperbelt, D.R.C.

By
D. W. Broughton
D. W. Broughton
1
Ivanhoe Nickel and Platinum Ltd., Forum Building, 10th Floor, 2 Maude Street, Sandton 2146, South Africa
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T. Rogers
T. Rogers
2
African Mining Consultants, 1564 Miseshi Road, Kitwe, Zambia
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Published:
January 01, 2010

Abstract

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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Contents

Special Publications of the Society of Economic Geologists

The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries

Richard J. Goldfarb
Richard J. Goldfarb
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Erin E. Marsh
Erin E. Marsh
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Thomas Monecke
Thomas Monecke
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Society of Economic Geologists
Volume
15 (1)
ISBN electronic:
9781629490397
Publication date:
January 01, 2010

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