M.Sc. (Geology) / Rocks of the Witwatersrand Super group in the northern portion of the East Rand Goldfield have been examined on surface and in underground exposures in an attempt to establish the chronology, movement vectors, amount of strain and displacement associated with bedding parallel faults. It was found that more than one age of movement occurred along most of the non-bedding parallel fault planes with normal, reverse and strike-slip senses of motion. The ductile bedding plane faults are manifested in all lithologies, but the shale units have, in particular, acted as a locus for shearing and it is suggested that they should be regarded as phyllonites. Bedding parallel faults are generally characterised by the presence of quartz veins and the development of phyllosilicates. They are categorised as mylonitic quartz schists. Syntectonic fault restricted quartz veins generally parallel the foliation, developed in the plane of flattening, and aided the movement of overlying strata during fault formation. Kinematic indicators imply a broad northerly up dip movement on the bedding parallel faults; implying they are thrust faults. Directionally specific kinematic indicators display at least two directions of thrust movement in the Central Rand Group, one to the NE and a second to the N to NW. The second group may represent two overlapping directions of movement. Only NE thrust movement are indicated in the West Rand Group. The NE thrust event occurred after emplacement of Ventersdorp dykes and before deposition of the rocks of the Black Reef Quartzite Formation. The N thrust fault event occurred after deposition of the Black Reef Quartzite Formation and before deposition of Karoo age rocks. A possible third event of Bushveld Igneous Intrusion age may be manifested as thrust faults towards the NW. The contact between the Central and West Rand Groups has acted as a major decollement during the N thrust event. The folds in this region may initially have been the result of thrust faulting towards the NE. Tilting of the fold axes during the postulated NW event is possible.

Most of the economic gold and uranium placers are developed on low angle disconformities in the Central Rand Group and concentrations of gold and uranium are usually at their optimum on unconformity surfaces. Examples include the Kimberley Reef and South Reef of the East Rand, the Main Reef Leader of the Central Rand, the Carbon Leader of the Carletonville goldfield, the Vaal Reef of the Klerksdorp goldfield and the Basal/Steyn placers of the Welkom goldfield. The individual goldfields represent fluvial fans which are composed of a large number of tectonogenetic sedimentary packages separated by unconformities. The tectonic responses between cycles of sedimentation produced unconformities and tectonically controlled cyclic sedimentation is one of the key factors culminating in the preparation and deposition of auriferous placers within the Witwatersrand succession. Unconformities, which represent breaks in sedimentation, result in the preconditioning of palaeosurfaces and redistribution of sediments and heavy minerals on them. Winnowing of sands produced heavy mineral residual accumulations on erosion surfaces which were generally preserved by small-pebble lags or algal mats. Reworking of units truncated by the unconformities provided additional gold, uranium and heavy minerals to unconformity surfaces.

D.Phil. (Geology) / This study examines the nature, distribution and origin of a distinctive chert-like fault rock in the West Rand Goldfield of the Witwatersrand Basin in South Africa. These fault rocks, termed pseudotachylites, are characterized by an aphanitic groundmass enclosing subangular to rounded clasts of the host rocks. No glass has been observed in the matrix but features such as spherulites, coronas and altered margins to the host rocks as well as geochemical evidence, suggest that the pseudotachylite formed as a result of melting of the host rocks due to the heat generated by friction on faults. The colour of the pseudotachylite is a function of its chemical composition and parentage. The pseudotachylite has abrupt contacts with the host rocks which comprise a lower Proterozoic to Archaean succession of rocks belonging to the predominantly sedimentary Transvaal Sequence, the predominantly volcanic Ventersdorp Supergroup and the predominantly . sedimentary Witwatersrand Supergroup. The orientation of many of the pseudotachylite fault veins parallels a pre-existing set of mylonitic faults. These pseudotachylite fault veins most commonly occur in sub parallel southward dipping pairs and are accompanied by injection veins. If treated on a statistical basis, the vergence concept can be extended to injection veins to give the approximate movement direction of the fault system. The pseudotachylite is thought to be genetically related to brittle or semi-brittle extensional faulting of post-Transvaal age.

M.Sc. / Doornfontein Gold Mine is the westernmost member of a group of mines in the West Wits Line, extending from Westonaria to Carletonville. A study of the sedimentology and gold distribution of the Middelvlei Reef was carried out with the aim to acquire an understanding of the processes responsible for the economic concentration of gold ...

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, / The Ventersdorp Contact Reef(VCR) is a major gold-bearing reef in the Witwatersrand Basin. It occurs between the overlying Klipriviersberg Group lavas and the underlying Central Rand Group sediments, and was strongly altered by hydrothermal fluids circulating in the Witwatersrand Basin. A detailed study of the mineralogy, geochemistry of rocks and minerals, physicochemical conditions, stable isotopes and ages of hydrothermal alteration zones associated with the VCR were carried out at Western Deep Levels South Mine, South Africa. ( Abbreviation abstract) / Andrew Chakane 2019

D.Phil. (Geology) / A specific geological event has been characterized with the aid of an integrated metamorphic and fluid inclusion study of data obtained from syn-tectonic vein-quartz associated with thrusting and bedding-parallel shear along the northern margin of the Witwatersrand Basin. The vein-quartz associated with this event occurs as boudin-shaped bodies with their long and intermediate axes orientated within the foliation-, bedding- or fault-planes. The length of the quartz lenses which are spatially confined to shear zones often exceeds the thickness of the shear zones. These phenomena and the fact that quartz-fibres are orientated parallel to and not at right angles to the foliation confirms the syn-tectonic nature of the quartz veins. Heterogeneous P-T condition is indicative of imbrication, i.e. crustal thickening which is also substantiated by the random growth of pyrophylite and kyanite in shear zone assemblages, indicating that metamorphism outlasted deformation. Metamorphic studies of aluminous schists and vein-quartz with pyrophylliteand pyrophyllite - kyanite selvages established the development of two critical mineral assemblages: 1 Kaolinite + 2 Quartz = 1 Pyrophyllite + 1 H20 ... (1) and at higher P-T conditions 1 Pyrophyllite = 1 Kyanite + 3 Quartz + 1 H20 ... (2). The schists and quartz vein assemblages are quartz-oversaturated in contrast to the study material of Wallmach and Meyer (1990) which is quartz-undersaturated. Peak metamorphic conditions, therefore, are closely constrained by the position of the reaction curve (2) in P-T space, as is also substantiated by the presence of coexisting kyanite and pyrophyllite which are closely associated with syn-tectonic vein-quartz at the Florida Lake, Monarch Shaft and Krugersdorp localities. The nature of and circumstances under which the equilibrium aSsemblage pyrophyllite + kyanite + quartz has formed support an univariant situation, i.e. this assemblage can only coexist along the pyrophyllite kyanite isograd. The mineral assemblages that equilibrated during peak metamorphism are still present in the rocks of the shear zones, and show only incipient rehydration. The quartz-oversaturated nature of the rocks in the shear zones and the fact that kyanite formation is ascribed to reaction (2), cannot explain the abundance of quartz veins. Accordingly it is concluded that there must have been an external source from which Si02 was imported into shear zone to give rise to the formation of the large quantities of vein-quartz.