Abstract The Zambian Copperbelt accounts for approximately 46 percent of the production and reserves of the Cen tral African Copperbelt, the largest and highest grade sediment-hosted stratiform copper province known on Earth. Deposits in the Zambian Copperbelt are hosted by the Neoproterozoic Katangan Supergroup, a rela tively thin (~5 km) basinal succession of predominantly marginal marine and terrestrial metasedimentary rocks that lacks significant volumes of igneous rocks. The stratigraphic architecture of the Katangan Supergroup in the Zambian Copperbelt is comparable to that of Phanerozoic rift systems. The basal portion of the sequence (Lower Roan Group) contains continental sandstones and conglomerates deposited in a series of restricted sub-basins controlled by extensional normal faults. These largely terrestrial sediments are abruptly overlain by a re gionally extensive, variably organic rich marginal marine siltstone/shale (Copperbelt Orebody Member, or “Ore Shale”) that contains the majority of ore deposits. This horizon is overlain by laterally extensive marine car bonates and finer grained clastic rocks that evolved through time into a platformal sequence of mixed carbon ate and clastic (Upper Roan Group) rocks with abundant evaporitic textures, including widespread breccias thought to record the former presence of salt, now dissolved. Rocks of the overlying Mwashia and Kundelungu groups are dominantly shallow marine in origin. Three significant tectonic events affected the basin. Extension associated with early rifting led to the devel opment of isolated fault-controlled basins and subsequent linkage of these basins along master faults at the time of Copperbelt Orebody Member deposition. A later period of extension occurred during late Mwashia to early Kundelungu time (~765–735 Ma) and is associated with limited mafic magmatism. Basin inversion and later compressive deformation (~595–490 Ma) culminated in upper greenschist-facies metamorphism (~530 Ma) in the Zambian Copperbelt. The majority of ore deposits in the Zambian Copperbelt occur within a 200-m stratigraphic interval centered on the rocks of the Copperbelt Orebody Member. Deposits are broadly stratiform and are grouped into argillite- (70% of ore) and arenite-hosted (30% of ore) types. The distribution, geometry , and size of deposits are fundamentally controlled by early subbasin fault architecture and the availability of both in situ and mobile reductants, the distribution of which is linked to basin structures. Argillite-hosted deposits occur within rela tively dark and locally carbonaceous siltstones and shales, suggesting the former presence of an in situ organic reductant. These deposits are laterally extensive with strike lengths up to 17 km. Arenite-hosted deposits occur in both the footwall and hanging wall of the Ore Shale and have maximum strike lengths of 5 km. They occur at sites that were geometrically favorable for mobile hydrocarbon or sour gas accumulation. Both argillite- and arenite-hosted deposits contain so-called barren gaps of weakly to unmineralized strata that are typically asso ciated with the fault-bounded shoulders of early subbasins. Two mineralization assemblages occur in the Zambian Copperbelt. The volumetrically dominant type con sists of prefolding disseminated and lesser vein-hosted Cu-Co sulfides. The most typical sulfide assemblage in the deposits is chalcopyrite-bornite with subsidiary chalcocite and pyrite. The Zambian Copperbelt is unusual among sediment-hosted stratiform copper districts in having abundant Co and low Ag, Zn, and Pb. The Cu-Co sulfide carrollite is widespread in the district, although cobalt is present in economic quantities in only some deposits on the western side of the district. The Zambian Copperbelt also contains ubiquitous, but volumetri cally minor, Cu-U-Mo-(Au) mineralization in postfolding veins. Cu-Co sulfides display complex textural relationships that are best explained by multistage ore formation. Diagenetic to late diagenetic mineralization is indicated by the typically nonfracture-controlled distribution of both sulfide and gangue phases, replacive textures of Cu-Co sulfides after diagenetic cements and pyrite, and an approximate 815 Ma Re-Os isochron age for sulfide precipitation at the Konkola deposit. Brines ca pable of mobilizing metals were most likely generated during development of evaporitic environments in units of the Upper Roan Group, and/or subsequent dissolution of these evaporites to form the Upper Roan Group breccias. Late diagenetic to early orogenic mineralization is recorded by prefolding bedding-parallel veinlets and tex turally and compositionally comparable disseminated Cu-Co sulfides. An Re-Os isochron age on Cu-Co sul fides from two arenite- and one argillite-hosted deposits of 576 ± 41 Ma is consistent with early orogenic hy drocarbon or sour gas production. The minor Cu-U-Mo-(Au) mineralization event occurred following postpeak metamorphism, at approximately 500 Ma. The Zambian Copperbelt ore province is characterized by stratigraphically and laterally widespread meta somatism that records a protracted history of basinal brine migration. Although the alteration history is com plex, it can be broadly categorized into an early Ca-Mg-SO 4 , anhydrite- and dolomite-dominant stage involv ing brine reflux below the level of Upper Roan Group evaporites; a second, K-dominant stage characterized by widespread and commonly intense development of K-feldspar and locally sericite, best developed in rocks of the Lower Roan Group and associated with ore; and a third, Na-dominant stage characterized by development of albite, commonly at the expense of earlier-formed K-feldspar. Albite dominates in Upper Roan Group brec cias and Mwashia-Lower Kundelungu strata. It is also locally associated with a late Cu-U-Mo-(Au) vein event. Although none of these alteration types are direct guides to ore, they demonstrate widespread brine circula tion within the lower parts of the Katangan Supergroup.

Abstract Glaciogenic sediments of the Katanga Supergroup are represented by two units. The syn-rift Grand Conglomerat Formation (<765±5 Ma to >735±5 Ma) occurs within the Nguba Group, and the Petit Conglomerat Formation defines the base of the Kundelungu Group deposited in the earliest foreland basin of the Lufilian orogenic belt located between the Congo and Kalahari cratons. Their glacial origin is inferred on the basis of the following features: the common and widespread occurrence of thick polymictic conglomerates and diamictites with faceted and striated clasts, massive structure, abundant poorly sorted fine-grained matrix, and the presence of planar-laminated shales (laminites) with dropstones. Glaciomarine facies associations prevail over most of the geographic extent of both units, but at the northern periphery of the depository, continental glacial facies are present. The glaciomarine units are succeeded by carbonates: the Kakontwe Limestone and ‘Calcaire Rose’ respectively. The clasts in the glaciogenic units are of extrabasinal and intrabasinal provenance. Lower boundaries, conformable in the basin centre, evolve to unconformities in the marginal areas to the N and S. The palaeomagnetic evidence suggests deposition in low latitudes.

Abstract The Kansanshi Cu(-Au) deposit is located approximately 160 km west of the stratiform copper-cobalt deposits of the Zambia Copperbelt, in Zambia's Northwest province. Indigenous peoples mined outcrops of high-grade copper veins at Kansanshi hill for at least 1,500 years before the arrival of Europeans in 1899. Commercial exploitation of the Kansanshi mineralization rapidly ensued, and focused on under-ground mining of the veins in the immediate vicinity of the exposures. This approach persisted through several short-lived underground and open-pit mining ventures until 1997. Recognition of the potential for a major, open-pittable orebody led to the acquisition and exploration of the Kansanshi property by Cyprus Amax Minerals Co. The Kansanshi deposit was recently estimated to contain 267 million tonnes grading 1.28 percent Cu and 0.16 g/t Au, making it one of the largest Zambian copper deposits outside the copper belt. The Kansanshi deposit occurs within the Lufilian arc, a Pan-African fold-and-thrust belt that was active from Late Proterozoic to Late Cambrian. The deposit is hosted within Late Proterozoic phyllites, schists, and marbles of the Kundelungu series, which forms the upper part of the Katangan Supergroup. Miner-alization consists of late- to postmetamorphic, undeformed, high-angle quartz-carbonate-sulfide veins and their associated albite-ferroan carbonate-sulfide alteration halos. The mineralization includes Cu, Au, U, Th, Mo, and V and forms part of a ca 500 Ma mineralization event that is recognized throughout the Lufilian arc. The Kansanshi deposit is distinct in metal content, morphology, associated alteration, and stratigraphic position from the well-known, stratiform-type deposits of the Zambia Copperbelt. Kansanshi-type mineralization represents an attractive exploration target in the Lufilian arc, and in other deformed and metamorphosed sedimentary successions prospective for copper deposits.

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 km 2 , 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.