Detrital zircon in sandstones from the palaeoproterozoic waterberg and nylstroom basins, south africa: Provenance and recycling

Laser-ablation ICPMS U-Pb and Lu-Hf isotope data on detrital zircon in sandstone from the Palaeoproterozoic Waterberg Group in the Waterberg and Nylstroom basins of northeastern South Africa contain a dominant Palaeoproterozoic (2 000 to 2 150 Ma) age fraction and minor, late Archaean zircon (2 650 to 2 780 Ma). Zircon in the 2 200 to 2 350 Ma age range is very scarce. There are no statistically significant differences in detrital zircon age distributions of sandstones in the two basins. In contrast, conglomerate from the northern margin of the Waterberg basin (Mogalakwena Formation) is dominated by a late Archaean age fraction (2 600 to 2 700 Ma, with minor 3 200 to 3 300 Ma), which resides in quartzite clasts. Zircon ages alone cannot distinguish between potential sources of detritus in the Kaapvaal Craton and Limpopo Belt. Hf isotope data, however, suggest that the main input to the basins was from recycled Archaean to Palaeoproterozoic sedimentary cover successions on the Kaapvaal Craton, supplemented by material from late Archaean granitic intrusions and the felsic igneous rocks of the Rooiberg Group and / or felsic members of the Bushveld Complex. The only known source of a prominent group of ca. 2.0 Ga detrital zircon with epsilon-Hf = 0 to-3 would be the youngest generation of granites in the Limpopo Belt (e.g. Mahalapye Granite). The Waterberg Group or its equivalents have provided only minor amounts of detritus to the Neoproterozoic to Cambrian basins at the western margin of the Kalahari Craton, directly or through recycling of intermediate deposits. However, erosion of the rocks in the Waterberg and Nylstroom basins provided material to the lower stratigraphic levels of the adjacent, Karoo-age Ellisras and Springbok Flats basins.