Summary Metavolcanic and metasedimentary rocks of late Middle Proterozoic age are preserved in basins along the northern margin of the Kalahari Craton. Three broad stratigraphic divisions are recognized: a lower acid extrusive unit, a basic extrusive/red bed unit and a shallow marine unit. The basalts of the basic extrusive/red bed unit are interpreted to be continental within-plate basalts. Copper mineralization occurs as native copper in amygdaloidal altered basalt, and as sediment-hosted, stratiform sulphide deposits at the base of the shallow marine unit. The rocks have been strongly altered during regional metamorphism which reached temperatures up to 350°C. Massive domains were metamorphosed to oligoclase-chlorite-epidote-haematite rocks. In permeable zones such as flow top breccias, amygdaloidal zones, and regions of secondary, tectonically induced fracturing, the basalts have been altered to epidote-quartz-chlorite-haematite-muscovite rocks. During this epidote alteration copper, zinc and cobalt were leached from the basalts, thus providing a possible metal source for the sediment-hosted deposits. A model for multiphase ore genesis is presented in which basalt alteration is the main metal source for epigenetic mineralization.