Zircon U-PB Age Data and HF Isotopic Signature of Kaapvaal Basement Granitoids from the Archaean White Mfolozi Inlier, Northern Kwazulu-Natal

Abstract

Three distinct types of granitoids, and intrusive contacts between them, are exposed in the central White Mfolozi Inlier, northern KwaZulu-Natal, where they form the basement on which the Mesoarchaean Pongola Supergroup had been deposited. In order to assess the position of these granites within the geochronological framework of Archaean felsic magmatism in the southeastern Kaapvaal Craton, to clarify the precise age relationships between these granitoids, and to examine their early petrogenesis, zircons extracted from these three granitoids have been analysed by LA-MC-ICPMS for their U-Pb and Hf isotopic compositions. The three U-Pb ages obtained from upper concordia-discordia intercepts are 3254 ± 7 Ma, 3245 ± 5 Ma and 3234 ± 5 Ma, which are taken to reflect magmatic crystallisation. Hence, all three granitoids belong to the late Palaeoarchaean group of Kaapvaal intrusives that appear to be prominent in the southeastern Kaapvaal Craton. In terms of Hf isotopes, the samples studied overlap with ~3.25 to 3.20 Ga granitoids from the southeastern part of the Kaapvaal Craton, the Barberton North and South terranes and coeval granitoids from Swaziland. The average Hf isotopic signature ( e Hf ~ 0) points to early magma extraction processes from an original mantle source prior to ~3.3 Ga.