Stratiform and vein-type deposits in the Pan-African Orogen in Central and Southern Africa: evidence for multiphase mineralisation
Centre of Excellence for 3D Mineral Mapping, Earth Science and Resource Engineering, CSIRO, Dick Perry Avenue 26, 6102 Kensington, WA, Australia
Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, K.U.Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium
Abstract
Stratiform deposits in the Pan-African Orogen are of the Cu-Co type and are restricted to carbonates and siliciclastic sediments that are stratigraphically close above the basement. The stratiform Cu-Co deposits formed during early diagenesis (possibly around 820 Ma) and during late diagenesis/metamorphism and the Pan-African Orogeny (~580 to ~520 Ma). The early diagenetic Cu-Co sulphides were partly remobilised into the second stratabound Cu-Co mineralisation, with precipitation of Cu-Co sulphides in nodules, veins and as breccia cements.
Vein-type Cu-Pb-Zn mineralisation occurs at two distinct levels, higher in the stratigraphy. The lower level vein-type deposits occur in dolomite and are dominantly of the Zn-Cu type. The higher level vein-type deposits occur at the contact between dolomite and sandstone and are dominated by massive Cu. The Cu-dominated deposits that have been dated, developed during the waning stage of the Pan-African Orogeny (~530 to ~500 Ma). The Zn-dominated deposits for which a mineralisation age has been established, formed after the Pan-African Orogeny. Some of these vein-type mineralisation have been remobilised after their formation, with the precipitation of massive Cu(-Ag) sulphides.