Bibliography: leaves 100-104. / The key objectives of this study are, firstly, to determine the extent and effects of the S contamination and secondly, to determine an effective means of ameliorating the site.

Word processed copy. / Includes bibliographical references.

Bibliography: pages 147-161. / This study deals with the physical aspects of sedimentation in Saldanha Bay and Langebaan Lagoon. On the basis of detailed textural investigations the depositional history of the study area has been established. The sediments in the bay and in the lagoon consist of a fine terrigenous quartz population and a coarser skeletal carbonate population, which have been mixed in various proportions. In order to gain size parameters that are more closely related to the hydraulic nature of depositional processes observed in the marine environment, grain size analyses were performed with an automatically recording settling tube system. The instrument was developed in the course of this study. Construction costs were kept extremely low without, however, impairing the scientific requirements of the instrument. Over 500 sediment samples were recovered on a closely-spaced grid; in each case, a size analysis was performed on the total sample and on the insoluble, terrigenous fraction. By subtracting the terrigenous size distribution from that of the total sediment, the relevant size parameters of the bioclastic component were calculated. In this manner 1500 individual size distributions were available for interpretation.

Includes bibliographical references (leaves 213-231). / Fractals and scaling laws abound in nature, and it is said that geometry of river networks and basins is an epitome of this. This study investigates how on the tectonically unique African continent, scaling parameters, and in particular deviations from 'perfect fractal patterns' relate to parameters like underlying geology, climate, and vegetation through which the river flows. Stream and basin patterns are also used to reconstruct the past network geometry of rivers, and to shed some light on the drainage evolution of major African rivers.

Includes bibliographical references (leaves 132-141). / The Maningoza Suite is a set of Mesozoic igneous sub-volcanic to volcanic complexes situated in the Mahajanga sedimentary and volcanic basin in central-west Madagascar. The Maningoza Suite is exposed in an area roughly 50 x 80 km and consists of the Ambereny, Ambohitrosy, Ankibobozaka, Berevo, Fonjay and Maningoza Complexes. The Maningoza Complex also consists of the Ambolodia, Antanetilava and Sambao Formations.

This thesis documents a microseismicity study in the interior of South Africa. The study area is centred on Leeu Gamka in the Western Cape province, a tectonically stable intraplate setting and is therefore expected to be seismically quiet. The International Seismological Centre (ISC) catalogue reported localised anomalous seismicity in the region between 2007 and 2013 with local magnitudes up to 4.5. The short apparent duration and time history of this anomalous reported seismicity is likely a reporting artefact. An array of 23 geophones was deployed for three months (March - June) in 2015, covering an area of 60 km - 65 km centred on the zone of anomalous seismicity. Using this array, I identified a total of 106 earthquakes over this period, with almost all events clustering in a surprisingly small area (75% of the epicentres fall within a one square kilometre block). Double-difference relocation resolved the hypocentres onto a structure with an apparent NW - SE orientation, consistent with large-scale fabric that can be recognised in satellite imagery. The focal mechanisms display strike-slip faulting with the fault plane likely in a NW - SE orientation, consistent with the distribution of the earthquakes. The velocity model was tested by varying the thickness of the Karoo supergroup to investigate the sensitivity of the depths of the earthquakes. An average hypocentral depth of approximately 6 km was calculated for the earthquakes, assuming a depth to the base of the Karoo of 5km. This places the earthquakes just below the base of the Karoo in the Cape Supergroup. The magnitudes of the earthquakes recorded range from -1.5<ML<0.4, with a magnitude of completeness of -0.8, and follow a Gutenberg-Richter distribution with the b-value range of 1.23 - 2.07 calculated within a 90 % confidence range. The presence of such a structure has implications for shale gas exploration in that wastewater pumping in an area with active faulting could trigger larger and more frequent earthquakes, as seen in case studies in the central states of America, in particular, Oklahoma.

Summary in English. / Bibliography: leaves 157-163. / Former evaporite horizons in metamorphic terrains have frequently been referred to as a source for highly saline fluids associated with base metal ore deposits in various parts of the world. Data on the nature of these former evaporites and their associated connate fluids, however, is frequently quite sparse, and the link between the ore deposits and the source evaporites is usually intuitive, at best. In an attempt to characterise such evaporite-derived fluids and their source evaporites, a study of former evaporites in the Duruchaus Formation in the Southern Marginal Zone (SMZ) of the Damara Belt was carried out. The lithological units that make up the evaporite sequence within the Duruchaus Formation were mapped and sampled, along with discordant quartz-dolomite plugs intruding at various levels in the Duruchaus Formation stratigraphy, and in the overlying Bakos Group.

Bibliography: pages 157-167. / The Ventersdorp Contact Reef (VCR) is an auriferous conglomerate which unconformably overlies the rocks of the Witwatersrand Supergroup. It acted as a palaeo-aquifer and is capped by relatively impermeable metabasalts of the Ventersdorp Supergroup. Three post-depositional alteration events, which form an alteration halo in the footwall and hangjngwall rocks around the VCR, can be recognised. The first of these alteration events is attributed to regional metamorphism and is identified by the formation of pyrophyllite in the footwall quartzites and a lower green schist facies mineral assemblage in the hangingwall metabasalts. The second and third alteration events are interpreted as metasomatic fluid in filtration events which were focused along the VCR horizon. The second alteration event involved K⁺metasomatism which affected the footwall and hanging wall rocks up to a distance of several metres away from the VCR The third alteration event, during which the muscovite was partially replaced, was associated with the formation of chlorite in and immediately around the VCR-Chlorite thermometry suggests a temperature of 307 ± 14°C for this event. The close mineralogical association of gold with chlorite, secondary pyrite and secondary quartz in the VCR is interpreted to indicate that gold remobilisation was associated with the chlorite forming alteration event. The inhomogeneity found in gold particles within a hydrothermal quartz vein indicates a sharp drop in temperature after gold precipitation, suggesting a very short period of hydrothermal fluid infiltration.

Bibliography: leaves 80-95.

Bibliography: pages 73-77. / The sediments in Zoar Vlei act as a considerable sink for Pb and Zn derived from the adjacent Paarden-Eiland semi-industrial area and the Milnenon-Rugby residential area. Through elemental analysis of 34 sediment samples by WDXRF spectroscopy, the sediments were shown to be significantly enriched in Pb and Zn.Lead and Zn concentrations are highest at the entrance to the southern pan, and decrease nonhwards through the vlei system. Kaolinite, quanz, illite and smectite are present in the clay fraction of the sediment, as was shown by analysis of a clay separate by XRD. The results of the sorption experiments revealed that both Pb and Zn are sorbed by the sediments. The selective affinity of the sediments for Pb exceeds that for Zn, as Pb sorption was shown to displace Zn from (he sediment while Zn sorption did not induce Pb release. The high degree of irreversibility of both Pb and Zn sorption indicates that sorption is specific in nature, and that under the present environmental conditions, the sediments act as a suitable storage facility for these metals. Acidification of the vlei water in equilibrium with the sediments caused Zn release through neutralisation reactions. Total water analyses were performed on 72 vlei water samples using high performance ion liquid chromatography and ICP-AES. Zinc concentrations in the vlei were elevated compared to natural background values, and decrease in a northerly direction through the vlei system, however remain elevated at the outflow into the Milnerton Lagoon. Zinc appears to be entering the vlei via storm water drains from both the industrial and residential areas.