Geochronology of the Sikombe Granite, Transkei, Natal Metamorphic Province, South Africa

Abstract

A new U-Pb SHRIMP zircon date of 1181 ± 15 Ma has been obtained from a sample of the syntectonic, gneissose Sikombe Granite from northeastern Transkei (Eatern Cape Province). The outcrops form the most southerly exposures of the ~1.1 Ga Natal Metamorphic Province (NMP). Previously, these isolated outcrops have been regarded as possibly forming a separate southerly, amphibolite facies terrane of the NMP, as the lithological assemblage is somewhat different from those of the granulite grade Margate terrane to the north. The new data do not conclusively demonstrate this, but they do show that the accretion age of the southerly terrane of the NMP is not significantly younger than the more northerly terranes. Sm-Nd analyses of three samples of the Sikombe Granite give consistent, positive End values (+4 at t = 1180 Ma) showing that, like the rest of the NMP, the granite was derived from juvenile Mesoproterozoic crust, with little or no involvement of older material in its genesi