Abstract
PhD. (Geology)
The lithology, stratigraphy, metamorphism and structure of the rocks in a highly deformed and metamorphosed terrain, some 5 000 km 2 in extent, south of the Soutpansberg in the Northern Transvaal, are described. The Bandelierkop Formation, which is comprised of Ultramafic-, Mafic- and Pelitic gneisses occur as deformed and metamorphosed remnants in tonalitic grey granitoids known as the Baviaanskloof Gneiss. The Ultramafic- and Mafic gneisses of the Bandelierkop Formation, in which granulite grade mineral assemblages exist, are chemically equivalent to peridotitic and basaltic komatiites and basaltic tholeiites of Archaean greenstone terrains. The greenstone origin for the gneisses is also indicated by the Hout River traverse in which material, at the
lower to middle amphibolite facies, becomes progressively metamorphosed and deformed over a distance of 10 km to the granulite grade of metamorphism. The Pelitic gneiss of the Bandelierkop. Formation is chemically similar to greywackes and shales of the Fig Tree Group and Belvue Road Formations of the Swaziland sequence.
The area of investigation is divided into two high-grade metamorphic zones separated by an eastnortheast trending Orthopyroxene isograd. The rocks of the Orthopyroxene zone to the north of the isograd were subjected to two events of regional metamorphism (M 1 and M2 ). The area south of the isograd, known as the Orthoamphibole zone, is characterised by the presence of silverygrey anthophyllite blades in Pelitic gneiss which formed during the M3 event. The southern limit of the Orthoamphibole zone, in the south-eastern portion of the area is poorly exposed and thus less well defined.