Abstract

The Bou Azzer cobalt deposits, which have produced to date 50,000 tons of cobalt metal, are apparently unique; they are associated with serpentinites of an upper Proterozoic ophiolite, and they consist of cobalt (Ni-Fe) arsenides with accessory sulfoarsenides, copper sulfides, molybdenite, and gold in a quartz-carbonate gangue. The ore has undergone several phases of brecciation and recrystallization related to late Pan-African and Hercynian deformations which produced the varying shapes of the orebodies: lodes, veins, stocks, complex shells, and flat lenses. The cobalt ore is mainly controlled by tectonic structures along the borders and top of the Precambrian serpentinite massifs. The orebodies which are buried under the Infracambrian volcanic cover may be localized by geochemical zoning.The serpentinites are the most obvious source rock for cobalt. The quartz-carbonate gangue grades laterally into a weathering crust of late Proterozoic age. However, the origin of the arsenic is not yet resolved; it may be consanguineous with the serpentinites or derived from an unknown hydrothermal source.

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