Detrital zircon mineral chemistry and U-Pb geochronology of coastal mineral sands, South Africa: provenance and exploration implications

Cenozoic heavy mineral placer deposits along the west and east coast of South Africa have been studied with the aim to determine the relationship between the U-Pb age and mineral chemistry of individual detrital zircons. Provenance characteristics of the geologically complex basement rocks will have an influence on the abundance and quality of zircons supplied to the coastal depocentres and ultimately contribute to the economic viability of heavy mineral concentrations. To this end zircons from two operating mines and a brown- and green-field deposit, were separated and then analysed by LA-ICP-MS. The results show that zircons werederived from a magmatic provenance representative of the Mesoproterozoic to the Cambrian periods. Significant quantities of Cretaceous zircons however are limited to the west coast whereas Permian zircons are more prevalent along the east coast. The age-mineral chemistry relationship shows that the Cretaceous zircons are the best quality and Neoproterozoic zircons a heterogeneous population of low quality with respect to deleterious trace elements. Exploration should focus on placers located near ancient and relatively young granitoid intrusives and avoid terranes dominated by Neoproterozoic lithologies in southern Africa.