Stable isotope and geochemical studies of the role of early diagenesis in ore formation, Konkola Basin, Zambian copper belt.

Sulphur, oxygen and carbon isotope data are reported for the ore shales and underlying clastic rocks from the NW end of the Zambian copper belt. The sulphides and accompanying carbonates were formed by bacterial reduction of sea-water sulphate during early diagenesis. Sulphur isotopes correlate with sea-water involvement, being lighter with transgressive rocks and heavier with regressive rocks. Carbon and oxygen isotope patterns in carbonates are inferred to represent a sea-water source for the footwall rocks and groundwater and organic matter sources for the ore shale. These patterns also show that cobalt in footwall carbonates has a marine origin, whereas copper in the ore shale may have been derived from porphyry copper deposits and mineralized gneisses in the basement. -G.J.N.