Archaean Granitoid–Greenstone Geology of the Southeastern Part of the Kaapvaal Craton

Abstract

The southeastern Kaapvaal Craton is a Palaeoarchaean granitoid–greenstone terrain. Supracrustal rocks are dominated by metamorphosed mafic–ultramafic volcanic rocks intercalated with minor felsic volcanic and chemical sedimentary rocks, including carbonaceous chert and minor iron formation. Siliciclastic sedimentary rocks are rare. The greenstones occur in the Schapenburg and Dwalile fragments close to the Barberton greenstone belt, the Assegaai, De Kraalen, Witrivier and Commondale fragments in the vicinity of Piet Retief, and the Nondweni and Ilangwe greenstone belts together with several smaller fragments in the southern part of the craton. The greenstones are locally in tectonic contact with compositionally layered grey gneisses as old as ~3.5 Ga and, in the southern part, are intruded by the ~3.25 Ga Anhalt granitoid suite, providing a minimum age for the greenstones. The oldest felsic volcanic rocks so far identified are 3.53 Ga in age. The belts show evidence of polyphase deformation, with metamorphism at greenschist- to amphibolite-facies grade, the peak of which was at ~3.2 Ga. Ore deposits are restricted to sub-economic gold and rare massive sulphide Cu–Zn deposits.