Pan-African structural evolution of Paleoproterozoic basement gneiss and Cu-Co mineralized shear zones in the Domes Region of the Lufilian Belt, Mwombezhi Dome, Zambia
A B S T R A C TIn the Domes Region of the Lufillian Belt, world-class stratiform Cu (±Co,±Ni,±U,±Pb,±Zn) deposits areclosely associated with tectonized pre-existing basement unconformities, viz. the pre-Katanga-basementdécollement (KD). In the KD footwall on the Mwombezhi Dome, the Lumwana Mine exploits mineralizationwithin<60m thick, laterally-extensive shear zones beneath kilometer-scale thrust sheets of Paleoproterozoicgneiss and schist. New field data and structural analysis highlight
... sis highlight preferential strain localization, kinematics andsequential reactivation of multiple shear zone generations (D1-3) under high- to medium-grade, metamorphicconditions and clockwise P-T-t path during the Lufillian Orogeny (ca. 550-500). Regional, progressive, top-tothe-NNE fore-thrusting is assigned to D1, while D2 represents localized, opposite, top-to-the-SSW kinematicsattributed to under-thrusting by dome-scale fore-thrusted basement slivers. Subsequent D3 shear zones transposedD1-2 structures and represent overall top-to-the-NNE extensional detachment and NNE-SSW-elongationalong a maximum principal extension axis (L3) which defines kilometer-scale shear- or asymmetrical-boudins ofcompetent gneiss in the KD footwall. A pre-existing NNE-SSW prolate dome asymmetry (L1-2) dictates adownlimb-directed sense of shear on the short axes of D3 asymmetrical boudins (WNW-ESE). D3 shear zones arepreferentially localized along relict pre-Katanga anisotropy and D1-2 mylonitic horizons, while Cu–Co bearingore shoots are associated with passive fold hinges in these asymmetrical boudin necks.