Petrographic and mineralogical study of the sediment-hosted Cu-Co ore deposit at Kambove West in the central part of the Katanga Copperbelt (DRC)

Kambove West is a sediment-hosted Cu-Co deposit in the Neoproterozoic Mines Subgroup, which is mainly composed of dolomitic shales and dolostones. Key factors and processes responsible for high-grade mineralization were identified by studying multiple cores. The stratigraphic position of the mineralized zones adjacent to the Roches Siliceuses Cellulaires and brecciated zones are the most important factor controlling the formation of a high-grade mineralization as they most likely acted as conduits for the mineralizing fluids. The presence of organic matter, stromatolite fragments and anhydrite pseudomorphs promoted mineralization. The organic matter caused a reducing environment required for the precipitation of the sulfides. Sulfate-reducing microorganisms, which were main components of Precambrian stromatolite communities, could also have caused the necessary reduction reactions. In addition to sulfate from the pores of the sediment, anhydrite formed a sulfate source. A paragenesis with six stages was established based on microscopic observations and cold cathodoluminescence petrography. Two major hypogene mineralization phases, which consist of pyrite, chalcopyrite, bornite, chalcocite and carrollite, formed during diagenesis and low-grade metamorphism, and were succeeded by supergene remobilization, of which chalcocite forms the dominant Cu-phase in the cementation zone. The distinction between hypo- and supergene chalcocite is based on the identification of multiple microtextures, chalcocite polymorphism, and the association with iron and other (hydro)oxides or late generations of dolomite. However, none of the features are conclusive. The combination of them is highly suggestive for a supergene remobilization.