At Kamoto and in other Katangan deposits, copper and cobalt occur as sulfides (mostly digenite, chalcocite, bornite and carrollite) in two stratiform orebodies. The host rock is dolostone, chert and shale. There is no metamorphism. Mineralization was emplaced before major tectonic deformation.The two stratiform orebodies are separated by a barren interval. The lower one rests a few feet above an erosional surface which developed over consolidated red dolostone beds completely devoid of sulfides. Above the upper orebody, a sulfide fraction is present, consisting mostly of pyrite with some chalcopyrite.The mineralized sedimentary rocks present some of the features commonly observed in tidal-flat sediments. However, they have undergone a complex sequence of diagenetic transformations. Several authigenic (or partly authigenic) minerals have crystallized: dolomite, perhaps in part from hydromagnesite + CaC03; magnesite, from the remaining hydromagnesite; quartz; chlorite and other phyllosilicates; colorless tourmaline; pyrite; other sulfides: chalcopyrite, bornite, digenite, chalcocite, carrollite, etc ... New evidence is presented to show that this diagenesis took place at first in an environment devoid of copper and cobalt and then proceeded while the metals were brought in from an outside source.The features described may have resulted from a reaction between a hypersaline brine (with high pH and high Eh) flowing through the lower part of the Kamoto Dolostone, and a modified connate water (reducing and less alkaline because of abundant organic matter) present in the upper part.

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