Geochronological studies on Archaean and Proterozoic formations of the Foreland of the Namaqua Front and possible correlates on the Kaapvaal craton

This study focusses on the granites and volcano-sedimentary sequences within the Foreland region, in an attempt to more accurately delineate the actual craton / mobile belt boundary. Twelve suites of samples from the Foreland region were examined. A multi-method geochronological approach was adopted using the Rb-Sr, Pb-Pb, and U-Pb whole-rock methods. Of these the Pb-Pb method produced the best results in terms of satisfying the criteria required for isochron determinations, and would appear to be the least susceptible to secondary alteration processes. This was a surprising result, and as such it was considered desirable to check the method on the Bushveld Complex, the age of which had been established by other techniques. Although the U-Pb method did not yield any precise ages, these data did throw same light on the timing and nature of the open-system geochemical behaviour of U and Pb in the fine-grained volcanics