 Trace element geochemistry as well as Pb + Nd isotope characteristics of the SMZ are similar to those of the Kaapvaal Craton, with low Th and U concentrations around 2 and 0.7 ppm.Low U concentrations in the SMZ are not a consequence of high grade metamorphism.The NMZ, with high Th, U concentrations (10.8 and 2.5 ppm) and radiogenic Pb, resembles the adjoining Zimbabwe craton more.