THE GEOLOGY OF THE CENTRAL ZONE, SENTINEL COPPER DEPOSIT, NW ZAMBIA

Sentinel is a low grade, high tonnage sediment-hosted stratiform copper deposit. It is located on the southeast margin of the Kabompo Dome, which is one of several Mesoproterozoic basement inliers that define the Domes region in northwest Zambia. The stratigraphy at Sentinel comprises a 450 m thick, conformable sequence of Neoproterozoic siliciclastic metasedimentary rocks of the Katangan Supergroup. Regionally, this sequence is stratigraphically equivalent to the Roan Group and overlying Mwashya Sub-group. Copper mineralization is restricted to within a dark grey phyllite up to 200m thick, and concentrated in a fine grained carbonaceous unit that is discontinuous along strike. Potential controls on the distribution of the phyllite include deposition of reduced sediments in a half graben, or preservation of reduced rocks of originally limited areal extent by folding and low angle faulting. Chalcopyrite is the dominant copper sulfide and occurs in foliation parallel and discontinuous stringer veins, and as centimeter-scale clots. Sulfides are spatially and temporally associated with kyanite-phlogopite alteration. Copper mineralization at Sentinel occurred during Lufilian aged deformation and metamorphism at ca 520 Ma.