A stratigraphic and structural study of the Archaean Pongola Sequence on the southeastern Kaapvaal Craton centred on the area around the Klipwal Gold Mine is described. The lower predominantly volcanic Nsuze Group is overlain with a gradational transition by the upper clastic Mozaan Group in which six formations are recognized. The Sinqeni, Ntombe, Thalu, Hlashana, Odwaleni and the Kulphiso Formations. The Sinqeni and Hlashana Formations are predominantly arenaceous while the Ntombe and Kulphiso Formations are mainly argillaceous. The Odwaleni Formation contains a diamictite which is interpreted as a tillite, and is therefore the oldest glacial rock on record. The stratigraphic position of the Kulphiso Formation is problematic. The Mozaan Group was deposited in a deepening epeiric sea which was invaded periodically by storm generated deposits. Dolerite and ultramafic dykes and sills of various ages are represented. Three phases of deformation are recognized in the Klipwal area. Early compression from the south-southeast initiated a major zone of bedding-parallel shear, the Izermijn shear zone, along the Nsuze-Mozaan contact and an oblique ramp, the Klipwal shear zone, at a higher stratigraphic level. An extensional phase caused reactivation of the Klipwal shear zone and the development of a major low-angle normal fault, the Gu'nsteling fault, above the Sinqeni Formation. The main phase of deformation, related to northeast-southwest compression is the most complex and most widely developed. Early northwest-trending subhorizontal upright folds were disrupted by contemporaneous north-striking dextral or dextral reverse shearing and northwest-striking sinistral or sinistral normal shearing. The obtuse relationship of these shear zones to the compression direction is probably the result of reactivation of basement structures with similar orientations. Northwest-trending folding continued during and after the shearing. The structural styles and orientations observed in the Klipwal area are recognized regionally in the main Pongola basin, highlighting the need for further detailed studies before basin-wide correlations are made. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1993.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1987.

The Bien Venue massive sulphide deposit is associated with a felsic volcanic succession developed in the north-eastern part of the Barberton Greenstone Belt, Eastern Transvaal. The deposit is situated 8km east-north-east of Louw's Creek between the Lily Syncline to the south and the Stentor Pluton to the north. The stratigraphy of the Onverwacht, Fig Tree and Moodies Groups in the vicinity of the deposit is poorly documented, and the exact stratigraphic position of the host felsic volcanics is not known. They are tentatively correlated with the felsic volcanics from the Theespruit Formation, Onverwacht Group. The felsic volcanics have undergone low-grade greenschist facies metamorphism and occur as quartz-sericite schists. Detailed petrography enables sub-division of the volcanic succession into distinct units. A lapilli metatuff unit hosts the base metal and precious metal mineralisation. The sulphides are best developed in the upper part of this unit, together with intercalated barite-rich horizons and cherts. A series of structural events have modified the attitude of the lithological units and disrupted the continuity of the orebody. The orebody comprises stratabound lenses of massive to semi-massive and often banded sulphides, as well as disseminated sulphide mineralisation. The dominant base metal mineralogy consists of pyrite, sphalerite, chalcopyrite, galena and tennantite. Native silver and various copper-silver sulphides are also associated with the base metal sulphides. A vertical zonation of the mineralisation exists, from pyrite-chalcopyrite-rich ore in the footwall, to pyrite - chalcopyrite-sphalerite-galena-barite-rich ore towards the hanging wall. Geochemical studies indicate that the Bien Venue lithologies are rhyolitic to rhyodacitic in composition and show a calc-alkaline affinity. The mobility of some elements at Bien Venue has been clearly demonstrated. This is believed to be associated with hydrothermal alteration that has led to SiO2 and MgO enrichment, as well as K2O depletion, in the wall rocks of the deposit. The geological setting and nature of the mineralisation at Bien Venue suggest that it is an example of a volcanogenic exhalative sulphide deposit. In terms of the classification scheme suggested by Hutchinson (1973, 1980), Bien Venue would best be described as a Primitive type deposit that contains barite. / Thesis (M.Sc.)-University of Natal, 1990