ABSTRACT
Komatiites and basalts from two locations in the Ngezi Group of the Belingwe Greenstone Belt define parallel Pb-Pb isochrons with ages of 2692±9 Ma and 2675±173 Ma, and µ1 values of 8.2 and 8.4. Data from a third location scatter and do not give useful age information. The Pb-Pb ages are consistent with reliable ages from other greenstone belts in Zimbabwe, and are believed to be correct. Nd isotopic data on the same samples form a linear array in the Sm-Nd diagram with a slope corresponding to about 2.9 Ga. Initial εNd values, calculated at 2.7 Ga, range from +3.2, to+0.4 and show a negative correlation with the upvalues. The anomalously old Nd age and the co-variation in initial εNd and µ1 lvalues are explained by contamination of the lavas by old surrounding basement.
