Lithostratigraphy of the Palaeoproterozoic Verena Granite

Abstract

Abstract The Verena Granite forms part of the Palaeoproterozoic Lebowa Granite Suite of the Bushveld Complex and was named after the village of Verena in the Mpumalanga Province of South Africa. It occurs over an area of ~600 km2 and is intrusive into the Rooiberg Group, the Rashoop Granophyre Suite and the Klipkloof Granite. It is in turn intruded by the Makhutso Granite, the youngest known granite of the Lebowa Granite Suite. The Verena Granite is characterised by its coarse to very coarse-grained nature, its pinkish to reddish colours and its porphyritic texture defined by the presence of large perthitic K-feldspar phenocrysts within a finer grained groundmass of plagioclase (An8-15) and quartz. Geochemically it can be classified as an A-type granite that straddles the boundary between metaluminous and peraluminous compositions. The granite is enriched in REEs relative to chondrite and shows strong fractionation of the LREEs, a distinct negative Eu anomaly and little fractionation of the HREEs. U-Pb dating presented here places the age of the Verena Granite at 2052 ± 9 Ma, which is the same as that of the published 2054 ± 2 Ma age of the Nebo Granite. Currently no consensus exists regarding the petrogenesis of the Verena Granite. Doubts have been cast on a genetic link between the Verena Granite and the remainder of the Nebo Granite. A genetic link between the Klipkloof Granite and the Verena Granite appears likely, with the former possibly representing the rapidly chilled roof of the magmas that crystallised to form the latter. Lu-Hf isotope data on zircons are consistent with that from other units of the Lebowa Granite Suite. It also supports the unconventional model involving a common enriched mantle origin for all mafic and felsic units of the Bushveld Complex, with minimal input from older crust.