Metamorphic history and U-Pb Zircon (SHRIMP) geochronology of the Glenmore Granite: Implications for the tectonic evolution of the Natal Metamorphic Province

Abstract

A new SHRIMP U-Pb zircon age of 1091 ± 9 Ma has been acquired for the gneissic, S-type Glenmore Granite from the Margate Terrane of the Natal Metamorphic Province. The Glenmore Granite contains two foliations and mineral textures indicate it underwent two metamorphic episodes separated by a period of retrogression. The presence of a folded S1 foliation in the Glenmore Granite indicates that it was either pre- or syntectonic relative to D1, thus providing a maximum age constraint of 1091 ± 9 Ma on the D1 event in the Margate Terrane. This is ~60 Ma later than the completion of the main tectonism (D1–3) documented from the Tugela Terrane, suggesting diachronous arc accretion. Syntectonic granitoids with ages of ~1090 Ma have also been documented from the Mzumbe terrane, as well as from Western Dronning Maud Land (east Antarctica), and the Cape Meredith Complex in the Falklands, which on reconstruction of Gondwanaland, lie adjacent to the Natal Metamorphic Province.