Bibliography: leaves 74-77. / The increase in urbanisation and the use of metal compounds and products domestically and in industry has resulted in the production of by-products and wastes, which needs to be evaluated in the urban environment. The discharge of some of these wastes into urban rivers should be evaluated to determine the potential effects, for example, toxicity and mobility. The effects may, in part, be determined by the chemical states in which these wastes manifest themselves, and by the chemical associations they have.

Bibliography: leaves 117-128. / Namibia's south western coast, the Sperrgebiet, hosts one of the world's largest diamond placer deposits. Diamond distribution in this placer deposit is directly related to the presence of a diamond-carrying gravel, the degree of reworking of the gravel and the quantity and quality of the diamond trapsites. The diamond-carrying gravel is present in the form of palaeo-beaches. Six Plio-Pleistocene beaches have been identified lying onshore between the Orange River mouth and Chameis Bay. The Plio-Pleistocene beaches are underlain by Late Proterozoic footwall. The Late-Proterozoic footwall has undergone extensive marine erosion and development of marine platforms during different sea-level stillstands. Diamond trapsites in the form of potholes and gullies are incised into palaeo platforms formed during the sea-level stillstands. The marine erosion palaeo-platforms have been cut into the predominantly siliciclastic rocks of the Gariep Belt. The Late Proterozoic Gariep Belt is divided into an eastern para- aulochthonous passive continental margin zone, the Port Nolloth Zone, and a western allochthonous Marmora Terrane. Previous work suggested that the Marmora Terrane had been thrust on top of the Port Nolloth Zone in a south-easterly direction and that the Marmora Terrane could be subdivided into three tectonostratigraphic units: the Schakalsberge Complex, the Oranjemund Complex and the Chameis Complex. In addition, previous work indicated that the Oranjemund Complex had been stacked tectonically between the Chameis Complex in the northwest and the Schakalsberge Complex in the southeast. However, this study questions the subdivision of the Marmora Terrane into three separate tectonic complexes. The rocks in the study area forms part of the newly defined Oranjemund Group, Oranjemund Sub-terrane.

Includes bibliographical references (leaves 89-102). / A petrological and metamorphic comparison of Mesoproterozoic metabasic rocks on the easern margin of the Archaean Grunehogna Craton and the adjacent Maud Belt in western Dronning Maud Land, East Antarctica, revealed a difference in peak metamorphic conditions from T = ~275° to 730°C and P=2 to 10.7 kbar over a distance of only 30 km across a major glacial valley. The lower grade constraints were derived from average P-T calculations using THER-MOCALC and thermodynamic modeling of phase equilibria together with chlorite geothermometry. The high-grade P-T constraint for the westernmost part of the Maud Belt closest to the glacier, derived from hornblende-plagioclase thermometry and geobarometric calculations with a garnet amphibolite assemblage, is very similar to that reported for the eastern Maud Belt and, therefore, does not support the concept of a westward decreasing metamorphic field gradient as previously proposed. In conjunction with a recent geochronological study on the eastern Maud Belt, this study suggests that the inferred sub-glacial boundary between the Grunehogna Craton and the Maud Belt, known as the Pencksökket-Jutulstraumen Discontinuity, may represent a major thrust that developed during Pan-African orogenesis (possibly as the continuation of the East African Mozambique Belt into East Antarctica) prior to extension and its development as a normal listric fault or succession of fault slices during the Mesozoic break-up of Gondwana.

There is some controversy in terms of the basement geology of Malawi which ultimately stems from the overall lack of metamorphic studies conducted in the area. The geological complexity of Malawi comes from that fact that it sits at the intersection of three major orogenic belts: The Palaeoproterozoic Ubendian Belt, Mesoproterozoic Kibaran/Irumide Belt, and Pan African Mozambique Belt. Its complexity makes it difficult to unravel, especially in terms of identifying features of older orogenic events which have already experienced multiple metamorphic overprinting from subsequent events. This thesis provides a more detailed pre-rift evolution of the Malawian basement rocks by reporting ages and P-T conditions from four localities surrounding Lake Malawi, namely Chilumba, Mlowe, Maganga, and Mangochi. Results reveal that at 1985-1974 Ma, garnet-cordierite granulites were equilibrated under conditions of 760°C at 4.5-5 kbar possibly as a result of subduction-related magmatism. Subsequently, at 1100 Ma, charnockites were emplaced and metamorphosed under peak conditions of 770-780°C at 4.3-6 kbar due to Kibaran-age magmatic underplating. Remnants of the Irumide/Kibaran Orogeny is relatively scarce throughout Malawi and although the Mangochi charnockites were emplaced during Kibaran-age tectonism, it also experienced at least two different metamorphic events thereafter. The first occurred either during early stages of the East African orogen or Rodinia break-up at 900-800 Ma while the second occurred during the late stages of the East African orogen at 650-600 Ma. Possible remnants of the Kuunga Orogeny are recorded in Chilumba and Maganga as an amphibolite facies metamorphic event which took place around 570 Ma under peak conditions of roughly 660-670°C at 6-8 kbar. Findings of this study have not only provided a more detailed metamorphic history of Malawi but also paved way for future studies in the area to further explore why similar rocks found in such close proximity to each other preserve vastly different tectonic environments.

Includes bibliographical references. / Changes in circulation and productivity in the southeastern South Atlantic Ocean over the last 850 kyr are investigated through the multiproxy study of two giant piston cores, MD962080 and MD962084, retrieved from the Agulhas Bank and Olifants River continental slopes of South Africa. The stable oxygen isotope record of the benthic foraminifer, Cibicidoides wuellerstorfi, and the planktonic taxon, Globorotalia inflata, provide the stratigraphic framework from which the age models were created. The results indicate that biotic responses to surface hydrological changes in the study area are complex and involve both high- and low-frequency variations.

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