Electronic Theses and Dissertations (Masters)

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Subject: search.filters.subject.SDG-11: Sustainable cities and communities

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    Baseline Hydrogeology of Dolerite Dykes in Lesotho, Mafeteng District as a Case Study
    (University of the Witwatersrand, Johannesburg, 2024-06-10) Monyane, Napo Shadrack; Shakhane, Teboho; Abiye, Tamiru
    Groundwater is a vital alternative resource due to the increasing demand for water supply in Lesotho’s rural and urban areas as surface water faces threats from population growth and climate variability. For instance, groundwater serves the demands of Lesotho's growing textile industry and agricultural sectors. The 3D form of the dolerite dykes widespread throughout the Karoo rocks in Lesotho may have an impact on the groundwater occurrence, flow, and yield characteristics of the region. However, specific research on their hydrogeology has not been extensively undertaken. This study aimed at characterising the hydrogeology of the dolerite dykes in the lowlands of Lesotho using selected places namely, Boluma-Tau, Ha Lumisi, Ha Mofota, Ha Maoela, Ha Mofo, Malumeng, Qalabane, Matlapaneng, Thabana Mohlomi, Ha Mohlehli, Malimong, Tsoeneng and Ha Lenonyane as case studies for the research. This research adopted the desktop and walkover survey in developing information on the region’s broad geological and hydrogeological setting within the Karoo lithologies. Included also was the use of ground magnetics in ascertaining the existence and determining the geometry of the dykes, using the D-8 algorithm for flow directions, and drilling and pumping tests for aquifer analysis. The dykes dominating the focal area in the Mafeteng District generally trend NE-SW, NNE-SSW and NW-SE. The magnetic results outlined negative anomalies along the dyke’s contact with the country rocks as surveyed from Qalabane, Mafeteng Lesotho, these magnetic lows imply fracture gaps along the strike of the dyke. A generalised dip, width, and depth could not be easily inferred due to inconsistent magnetic anomaly shapes, but forward modelling indicated a thin (10 m wide) shallow (10°) dyke trending NE-SW intruding both the Burgersdorp and Molteno Formations at Qalabane, Mafeteng. As per the D-8 results, the dolerite dykes in Mafeteng are distributed in the intermediate basin flow values due to a gentle hydraulic gradient. Certain dyke sites exhibit a groundwater flow direction towards the north, whilst others display a radial groundwater flow direction. The derivative analysis revealed the boreholes were drilled in a fractured dyke system, also the dominant radial flow regime and double porosity dip at different pumping durations, and the possible recharge boundary were revealed in some drilled dyke sites. Further analysis from the drawdown versus time curves resulted in average yields of 0.1 – 1.25 l/s with transmissivities ranging from 1 – 14 m2/day, insinuating that a limited extraction of the local water supply is suggested from the dolerite dyke lithologies in the lowlands of Mafeteng Lesotho, given the groundwater yielding capacity and magnitude of the transmissivities. Even though the drilled boreholes from the dyke sites indicated a fractured dyke setting, estimated transmissivity values are variable and low, this is indicative of the inconsistent apertures and lack of interconnectivity of the available secondary hydrogeological features in the lowlands of Lesotho.
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    Accessory REE mineralization of the Nokeng fluorite deposit as distal facies of the adjacent Vergenoeg pipe, Bushveld Complex, South Africa
    (University of the Witwatersrand, Johannesburg, 2024-10) Makhema, Relebohile Edward; Yudovskaya, Marina; Madlakana, Nonkuselo
    The Nokeng Plattekop deposit forms part of the Paleoproterozoic Bushveld Complex and it is located near Rust de Winter, approximately 80 km northeast of Pretoria. This deposit belongs to the Vergenoeg Igneous Complex, which is associated with a violent gas-vapour-rich rhyolitic eruption. The complex comprises the Vergenoeg discordant breccia pipe and a pyroclastic rock suite. Within the breccia pipe and associated pyroclastic rocks, rare earth element (REE) mineralization is observed in minerals like allanite, apatite, bastnasite, monazite, and xenotime. The Plattekop fluorite deposit, which lies 1000 m south of the breccia pipe, is postulated to represent spill-over remnants of the Vergenoeg volcanic edifice. This study performed a comprehensive petrographic and geochemical analysis of ore and pyroclastic breccia of the Nokeng Plattekop deposit, utilizing various analytical techniques, including optical microscopy, XRF, ICP-MS, and SEM. The aim is to characterise the style of accessory REE mineralization at Nokeng as a provisional distal facies of the Vergenoeg volcanic field. The findings of this study suggest that the Nokeng Plattekop deposit comprises a hematite-fluorite unit overlying an ignimbrite unit. Hematite-fluorite ores of the upper unit resemble the Vergenoeg ore, exhibiting elevated CaO concentrations and reduced SiO2 content attributed to high fluorite and hematite proportions. Conversely, the ignimbrite unit displays reduced CaO and elevated SiO2 concentrations, corresponding to lower fluorite content and higher rhyolitic lava fragments. The basal ignimbrite is proposed to have formed during the early stages of rhyolitic volcanism, while Nokeng and Vergenoeg ores formed during later stages dominated by Ca- and F-rich ferruginous magma. Petrographic evidence suggests hematite pseudomorphs after magnetite, indicating mineral assemblage evolution. REE mineralization in the Plattekop fluorite deposit is represented by bastnasite, monazite and xenotime, mostly associated with quartz, goethite, aegirine, hematite and fluorite. The highest REE + Y content (~ 5 890 ppm) is associated with Plattekop hematite-fluorite ores. Comparative analysis of REE distribution patterns suggests similar styles of mineralization between Vergenoeg and Nokeng, indicating both deposits as potential sources of REEs as by-product.
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    Reconstructing locomotor behaviour of Southern African plio-pleistocene cercopithecoids: evidence from functionally-related inner structural arrangement of the trabecular bone
    (University of the Witwatersrand, Johannesburg, 2023-07) Babutsi, Mosarwa; Beaudet, Amélie; Zipfel, Bernhard; Jakata, Kudakwashe
    Because of their abundance in African Plio-Pleistocene hominin-bearing sites and their stratigraphic association with fossil hominins, cercopithecoids represent a relevant “control group” for contextualising hominin evolution. often considered as ecological and biochronological indicators, particularly their ecological sensitivity is valuable in reconstructing southern African hominin bearing site’s palaeoenvironment and environmental changes. Since biomechanical loadings on trabecular bone produced throughout locomotor activities shape the structure of the skeleton, particularly at locomotor key joints, the expectation is that investigation of the trabecular bone of fossil cercopithecoids key joints like femur, humerus, Tibia and calcaneus would provide further evidence for eloquent discreet disparity in their locomotor behaviour and reconstructing their paleohabitats. This study used trabecular bone, described as meshwork or sponge with porous network within long bones joints and inside footbones contains red bone marrow. Its preferred orientation in is the basis of Wolff’s law, relating bone structures and its ability to adapt to mechanical load alignment in the direction of loading stress, as such recoding informative locomotor signals. Forty one (41) fossil cercopithecids from the Cradle of Humankind World Heritage sites that include Sterkfontein, Swartkrans, Makapansgat, Taung and Bolt’s Farm as well as forty (40) extant cercopithecoids specimens were scanned using a micro-focus X-ray computed tomography (CT) scanner. Trabecular bone parameters that include trabecular bone fabric anisotropy, volume fraction, thickness and spacing were quantified in ImageJ. These Plio-Pleistocene cercopithecoids recorded more arboreal locomotor signals with occasional terrestrial locomotion, suggesting transitional palaeoenvironment from long trees with cool climatic conditions to a more open grass land savanna type with dry climatic conditions believed contributed significantly to extinct of archaic humans and the emergence of the successful Homo.