Electronic Theses and Dissertations (Masters)

Permanent URI for this collectionhttps://hdl.handle.net/10539/38012

Browse

Start date: 2023

Search Results

Now showing 1 - 10 of 28
  • Thumbnail Image
    Item
    Characterisation of the Platinum Group Minerals in the Ombuku North intrusion peripheral to the Kunene Complex: Insights into its PGE potential
    (University of the Witwatersrand, Johannesburg, 2024-03) Mothobekhi, Lorraine Masoko; Milani, Lorenzo; Hayes, Ben
    The Kunene AMCG (Anorthosite-Mangerite-Charnockite-Granite) Complex, located in the southern part of Angola and northern part of Namibia, is known as one of the most extensive Proterozoic anorthosite complexes worldwide, with an extent of the area ≥ 18 000 km2, and positioned along the southwest margins of the Congo craton. The mafic-ultramafic intrusions within the vicinity of the Kunene Complex are mineralised with nickel, copper, and platinum group elements (PGEs). The area has not been extensively explored, and only minor exploration work has been conducted to search for magmatic sulphide deposits, particularly nickel deposits. The PGE potential of the mafic-ultramafic intrusions in the area and their potential mineral system has not previously been extensively studied. The available geochemical assay data of the Ombuku North intrusion in northern Namibia was sourced from African Nickel Limited (ANL) and was used in this study to assess its PGE potential and to better understand its potential mineral system. Petrographic work demonstrated Ombuku North intrusion was commonly associated with magmatic sulphides (pentlandite, pyrrhotite, chalcopyrite), formed from a Mono Sulphide Solution, and magnetite. Samples were selected for further detailed platinum group mineral (PGM) investigations on the basis of their PGE contents. Ombuku North is characterised by slightly anomalous PGE values and the available thin sections from Ombuku North with corresponding bulk rock PGE values of >80 parts per billion (ppb) were selected for the identification and characterisation of the PGMs, and for detailed petrographic analyses. In this study, PGM mineral analyses were done using a Tescan Integrated Mineral Analyser (TIMA) which is a fully automated instrument, whereas previous mineral analyses for PGMs in Ombuku North and some of the other mafic-ultramafic intrusions in this region were collected using Scanning Electron Microscopy Energy Dispersive Xray Spectroscopy (SEM-EDS) method, which is only partially automated. TIMA could identify the PGM in the selected samples from Ombuku North. The identified PGMs included sperrylite, michenerite, stibiopalladinite, and vincentite, all associated with serpentinised rocks. The platinum arsenides (sperrylite) are mainly hosted in magnetite and in pyrrhotite. The palladium bismuthotellurides (michenerite and vincentite) and a platinum antimonide (stibiopalladinite) are hosted in pentlandite. The origin of these PGMs can be associated with both magmatic and hydrothermal processes. Magmatic processes are primarily responsible for the initial formation and crystallisation of silicate minerals within the mafic-ultramafic intrusions, including primary magmatic sulphide assemblage. Late hydrothermal processes are related to the alteration of these rocks, where fluids circulated through the rock leading to the formation of secondary minerals such as serpentine, talc, and the redistribution of PGE. Although PGE data are also provided also for other intrusions, this study mainly focused on Ombuku North intrusion due to the limited availability of assay data. We infer that amongst all the mineralised mafic-ultramafic intrusions related to the Kunene Complex, the most prospective for PGE anomalies are the altered ultramafic lithologies at Ombuku North.
  • Thumbnail Image
    Item
    Intergrated Geophysical Methods to Delineate R21 Sinkholes Near Olifantsfontein, Gauteng, South Africa
    (University of the Witwatersrand, Johannesburg, 2024-09) Mabele, Nondumiso; Manzi, Musa
    The Gauteng province in South Africa is known for having a significant portion, at least 25%, of its land is underlain by dolomite rocks. An integrated approach of non-invasive geophysical methods was utilised to map the geometry (shape, size and extent) of the R21 highway sinkhole that formed near Olifantsfontein. These methods include seismic (reflection and refraction), multi-channel analyses of surface waves (MASW), electrical resistivity tomography (ERT), and ground penetrating radar (GPR). The objectives of the investigation were three-fold: (1) to understand the geology and formation of sinkholes in Gauteng; (2) to use geophysical techniques to map and characterize sinkholes in the study area, including determining their geometry, lateral and vertical extents; and (3) to determine the effectiveness of each method in mapping sinkholes. Despite the high level of noise along the highway, the geophysical surveys were conducted successfully and provided a good basis for the integrated interpretations. This study showcases the importance of utilising multiple geophysical methods to obtain a comprehensive understanding of sinkholes and their subsurface characteristics. It also demonstrates the practical application of these methods in real-world scenarios for improved hazard assessment and risk mitigation. The GPR results suggest that a sinkhole extends by ~2.5 m further into the R21 highway surface with a depth of ~8-10 m (top to bottom). The refraction seismic method suggests that the sinkhole is ~20 m wide, while the ERT results suggest that the sinkhole starts at 10 m and extends to 15 m depth. The results from reflection seismics indicate that the R21 sinkhole is structurally controlled and it is characterised by fracturing and faulting that manifest as diffractions on the seismic sections. Understanding the extent and characteristics of sinkholes is crucial for infrastructure planning and hazard mitigation, especially in areas prone to subsidence and sinkhole formation like in Gauteng. These findings can inform decision-making processes related to road maintenance, construction, and land use planning in sinkhole-prone regions. The success of the integrated geophysical approach in this study highlights its potential for similar investigations in other areas with karst geology and sinkhole risks.
  • Thumbnail Image
    Item
    The nature and characteristics of sulphide mineralisation at the Kamoa - Kakula copper deposit of the Katanga basin, Central African Copperbelt, Lualaba, Democratic Republic of Congo
    (University of the Witwatersrand, Johannesburg, 2024-08) Kaemba, Robert Ntokwa; Yudovskaya, Marina A.
    The Kamoa-Kakula deposit is a world-class stratiform copper deposit located in the southern part of the Democratic Republic of Congo (DRC) approximately 25 km from Kolwezi town and close to the border of DRC and Zambia. The ore deposit is in the southern area of the western foreland domain of the Congolese Copperbelt (Central African Copperbelt). The structural setting of the deposit is characterised by the West scarp fault, binding Kamoa to the west whilst it is bounded by faults of the Kansoko Sud trend to the east. The mineral resource footprint of the deposit envelopes the Makulu dome and wraps around the southern edge of the Kamoa dome. The main sedimentary lithologies hosting copper mineralisation are diamictite and interbedded siltstones of the Grand Conglomérat Formation at the base of the Nguba Group overlying sandstones of the Mwashya Subgroup (Roan Group). Previous studies within DRC and Zambia showed that the glaciogenic diamictite (Grand Conglomérat Formation) is a laterally extensive regional marker. The geological interpretation and literature data reveals a distinct stratigraphic correlation of several copper deposits across the Central African Copperbelt confirming multiple occurrences at various stratigraphic levels. Furthermore, this analysis identifies the Fishtie deposit (Lusale basin, Zambia), which occurs on the eastern margin of the Katanga basin, as the closest geological analogue to Kamoa – Kakula. At Kamoa-Kakula, hydrothermal sulphide mineralisation occurs mainly towards the base of the Grand Conglomérat with the dominant sulphide mineral assemblage composed of pyrite – chalcopyrite – bornite - chalcocite, and minor covellite . Optical microscopy demonstrates the multi-stage crystallisation of few generations of pyrite including the earliest diagenetic framboidal pyrite. The widespread development of the symplectic texture linked to bornite and chalcocite intricate intergrowths and regular rimming of clasts by sulphide overgrowth, as well as the occurrences of framboidal chalcopyrite and bornite argue for the sulphide paragenesis being linked to sulphide replacement. This is consistent with the apparent mineral zonation progressing downwards from pyrite → chalcopyrite → bornite ± covellite → chalcocite. The S isotope variations suggest that a significant portion of S at Kamoa originated from early bacterial sulphate reduction, which resulted in precipitation of fine-grained framboidal and sooty pyrite with the negative δ34S values as low as -19.9 ‰. The similar, while narrower, range of δ 34S values for chalcopyrite is due to inheritance and homogenization of the S isotopic signature of diagenetic sulphides during ore stage replacement, whereas the highly negative δ 34S values for chalcocite (down to -35.1 ‰) indicate the subsequent extreme isotope fractionation under low-temperature conditions. The study includes a comprehensive overview of the regional stratigraphic and geological correlation, in conjunction with detailed mineralogical and isotopic observations, contributing to further understanding of Cu mineralisation at Kamoa-Kakula as well as on a scale of the entire Central African Copperbelt.
  • Thumbnail Image
    Item
    Assessing the Magmatic Ni-Cu-(Co-PGE) Sulphide Potential of the Kunene AMCG Complex
    (University of the Witwatersrand, Johannesburg, 2024-08) Manuel, Agex Cordeiro Ferreira; Bybee, Grant; Hayes, Ben
    Not Available
  • Thumbnail Image
    Item
    South Africa’s earliest giant: The systematics and palaeobiology of a new species of sauropodomorph
    (University of the Witwatersrand, Johannesburg, 2023) Moopen, Atashni; Choiniere, Jonah N.; Botha, Jennifer
    Sauropodomorph dinosaurs are characterized by their gigantic body size and quadrupedal postures, but they evolved from small, bipedal ancestors. Transitional non sauropodan sauropodomorphs from the Norian are key to understanding this evolutionary transition. A new Norian sauropodomorph (BP/1/8469) discovered in 2018 in the lower Elliot Formation of Qhemegha, Eastern Cape consists of a well-preserved, well-represented associated postcranial skeleton of a relatively large individual. This specimen provides novel information about the Norian transition in sauropodomorph body plan. This study presents the results of BP/1/8469, using comparative anatomical study, quantitative body mass and postural estimation, osteohistological enquiry, and phylogenetic systematics assessment. BP/1/8469 is a 1.8 to 3.1 metric tonne, facultative quadrupedal sauropodomorph. It was an adult that displays rapid, interrupted growth, similar to other sauropodiforms. Phylogenetic analysis of BP/1/8469 highlights incongruencies in sauropodomorph character datasets, flags considerable homoplasy in sauropodomorph evolution, and underscores the need for accurate homology statements.
  • Thumbnail Image
    Item
    Physical property studies, tunnel numerical simulations and in-mine seismic experiments to image the gold orebody at South Deep Gold Mine
    (University of the Witwatersrand, Johannesburg, 2024-09) Mulanduli, Omphulusa; Manzi, Musa
    The investigation endeavors to assess the physical characteristics of deep borehole cores within the Upper Elsburg Reefs (UER) of the South Deep gold mine of the West Rand goldfield. Specifically, these cores are sourced from three boreholes situated approximately 2.6 km beneath the surface within the confines of the South Deep gold mine. The focal point of this study lies in non-destructive testing methods aimed at elucidating the intrinsic attributes of these rocks, with particular attention directed towards seismic velocities and densities. These measurements hold paramount importance in conducting numerical simulations to designing the in-mine (or tunnel) seismic reflection surveys acquired at South Deep gold mine, as part of the ERA-Min3 FUTURE (Fiber-optic sensing and UAV-platform techniques for innovative mineral exploration) project. Cultivating a profound comprehension of the seismic velocities and densities across diverse rock formations can significantly augment the interpretation of seismic reflections, thereby facilitating more refined assessments of subsurface geology and structural configurations. In pursuit of this goal, our study endeavors to delve into the fundamental acoustic properties of the gold-rich UER, with the overarching aim of deepening our understanding of its seismic reflectivity. To realize this objective, a comprehensive array of physical measurements, encompassing ultrasonic velocities and bulk densities, were conducted on drill-core specimens. To accurately portray the physical attributes of the lithological units under scrutiny, a total of twenty-four samples were subjected to exhaustive analysis for density and seismic velocity utilizing a spectrum of methodologies. Density determinations were procured through a diverse set of techniques, including dimensional assessments, employment of the KT20 MagSus tool, and utilization of the SNOWREX AHW-3 Professional Weighing Scale boasting a heightened sensitivity of 0.01 g. Ultrasonic measurements were undertaken employing the Proceq Pundit PL 2000 ultrasonic pulser velocity tester, equipped with two pairs of transducers boasting a center frequency of 54 kHz. The in-mine seismic survey was acquired to delineate geological structures that crosscut and displace the orebody. The study locale encompasses three distinct rock formations: the UER, gold-bearing conglomerate units (termed reefs), basaltic lava, and dyke specimens. The UER primarily comprises quartzites, exhibiting a P-wave velocity range of 5202-5802 m/s, an S-wave range of 3037-4768 m/s, and bulk densities spanning from 2.66 - 2.71 g/cm³. Conglomerate reefs exhibit a P-wave velocity range of 4467-5970 m/s, an S-wave range of 4040-4854 m/s, and bulk densities ranging from 2.67-2.94 g/cm³. Lava samples extracted from the boreholes showcase a P-wave velocity range of 5916 - 6711 m/s, an S-wave range of 3275-5659 m/s, and bulk densities spanning from 2.75-2.90 g/cm³. Singular dyke samples were encountered, exhibiting a P-wave velocity of 5921.5 m/s, an S-wave velocity of 5385 m/s, and a density of 2.85 g/cm³. The study employed the synth-seis code to simulate 1D seismic responses based on borehole data collected from the mine, aiming to validate findings from velocity and density measurements. Analysis of the seismograms indicated notable contrasts between conglomerates and quartzites, particularly evident in density and S-wave measurements, suggesting potential for improved rock discrimination with alternative seismic sources. Additionally, 2D numerical simulations were conducted to model wave propagation in the Upper Elsburg Reef (UER), revealing discrepancies between simulated and synthetic seismogram results, indicating potential limitations in seismic imaging. Furthermore, ray tracing was used to design a seismic survey inside the mine along the tunnel floor to image VCR (Ventersdorp Contact Reef) orebody and other geological structures. The real seismic survey was finally conducted inside the tunnel (SDT1), demonstrated the value of in-mine reflection seismic surveys for mapping geological structures at significant depths, which would otherwise be costly and logistically challenging. Despite noise interference from mine operations, processing algorithms enabled extraction of reflections and structural mapping from the dataset, underscoring the importance of such surveys in mining exploration and planning.
  • Thumbnail Image
    Item
    The Stratigraphy of the New Tuli Basin Fossil Sites in Zimbabwe
    (University of the Witwatersrand, Johannesburg, 2024-09) Zondo, Michel; Choiniere, Jonah; Broderick, Timothy; Munyikwa, Darlington
    This thesis investigated new fossil-bearing outcrops of the Mpandi Formation of Zimbabwe, exposed at Sentinel Ranch in the Tuli Basin, at sites named “Wedding Hill “and “Pimwe Hill”. The Mpandi Formation exposures at Sentinel Ranch reveal strata that were deposited in fluvial environments that occasionally experienced flooding in otherwise usually dry and hot climatic conditions. These fluvial systems deposited facies that are mostly dominated by fine sediments and their facies have similarities with those found in the main Karoo Basin of South Africa. The use of borehole data helped establish the thickness of the Mpandi Formation and the explorable portion of the formation was estimated to be around 54 metres. Detrital zircons collected from main Sentinel outcrops were used to estimate the maximum depositional age of the sediments using inductively coupled plasma mass spectrometer (LA-ICPMS) methods. Although sparse, the youngest zircons in these samples yielded ages of 199.2 ± 5.1 Ma and 200.8 ± 5.8 Ma, with error bars suggesting maximum depositional ages in the earliest Jurassic or possibly the latest Triassic. A bonebed at the Wedding Hill site produced many postcranial bones of sauropodomorphs, including the articulated leg of a very large individual sauropodomorph, and the first theropod bones recorded from the Mpandi Formation at Sentinel. The discoveries improve our knowledge of the fauna diversity of the Mpandi Formation, permitting more accurate biostratigraphic correlation and enhancing our understanding of the Triassic- Jurassic interval.
  • Thumbnail Image
    Item
    Taphonomy and palaeoecology of a monospecific microvertebrate bonebed: behavioural implications for the late Permian (Lopingian) parareptiles
    (University of the Witwatersrand, Johannesburg, 2024-06) Mukwevho, Lutendo; Choiniere, Jonah; Smith, Roger
    Sociality in the vertebrate fossil record is a dynamic and fast-expanding area of research. Natural history observations of living animals are crucial for understanding and categorizing sociality, but these observations are not feasible for extinct species. Monotaxic bonebeds provide unique opportunities to conceptualize the social behaviours of these extinct animals. An unusual bonebed (SAM-PK-K11289) discovered in the uppermost Permian strata of the Balfour Formation, Karoo Supergroup, in the Eastern Cape presents a window into the sociality of Late Permian reptiles. The use of propagation phase-contrast synchrotron X-ray microcomputed tomography permitted the 3D reconstruction of skeletal elements in SAMPK-K11289, allowing the taxonomic identification of the individuals in the bonebed as most likely belonging to Owenetta. This is the largest aggregation of Owenetta individuals known to date, with a minimum number of 31, which are all very similar in body size. The ontogenetic profile of SAM-PK-K11289 was interpreted by analysing the size distribution of duplicate elements and by making comparisons with other Owenetta and procolophonid specimens. The specimens in the bonebed are all osteologically immature, indicating that they are juveniles. The bonebed occurs in a pedogenically modified ripple cross-laminated siltstone suggesting that a low-energy fluvial sedimentation likely contributed to the modification, disturbance and disarticulation of elements before the bonebed was buried at or very close to the death site. This bonebed provides novel information that directly challenges the popular belief that reptiles and their ancestors are non-social or asocial. Considering the overall circumstances of the bonebed, I hypothesize that Owenetta rubidgei juveniles were socially gregarious and this behaviour may have been induced or influenced by environmental changes during the early extinction phase of the end Permian mass extinction in the Karoo Basin.
  • Thumbnail Image
    Item
    Nutrient and Salinity Loading Based On The Temporal And Spatial Water Quality Data In The Upper Crocodile River Basin
    (University of the Witwatersrand, Johannesburg, 2024-03) Mistry, Nikhil Jayant; Ali, K. Adam; Abiye, Tamiru
    The Upper Crocodile River Basin has undergone a drastic change through anthropogenic factors such as rapid urban growth, industrial activities, agriculture and mining in the past thirty-eight years. This has led to an increase in nutrient and salinity loads with decreasing water quality. The Upper Crocodile River Basin wastewater treatment works struggle to maintain loading rates, causing partially treated wastewater to enter the river systems that increased the salinity loads. Water chemistry and discharge data from the DWS were collected, cleaned and processed; data were summated across the necessary river channels in which they are located to determine the nutrient and salinity loads in all rivers in the Upper Crocodile River Basin. The results indicated that the Hennops, Jukskei and Crocodile Rivers are responsible for the largest nutrient and salinity loading rates. Changes in land use activities and climate over the past thirty-eight years, since 1980, have drastically impacted the rate at which nutrient and salinity loads enter into the UCRB. During the early 1980s to 1990s a significant drop was observed in nutrient and salinity loading rates, spiking in the late 1990s and early 2000s, influenced by changes in water management and climatic events like the La Niña and the El Niño phenomena. The inter-basin transfer in the early 2000s and subsequent two decades have led to an overall rise in nutrient and salinity loading rates, posing serious water quality and health risks to people in the UCRB area. Mining activities, poor landfill management and leaking tailing storage facilities have resulted in increased sulphate loading rates into the UCRB. Nitrogen loading has risen due to uncontrolled waste disposal from informal settlements, industrial activities and sewage spills in the Johannesburg region. Phosphorus loading rates have risen due to agricultural fertiliser runoff, with the Jukskei River being the largest contributor to these loads in the Upper Crocodile River Basin. The loads entering the Hartbeespoort dam during summer and winter seasons in the 2016-2018 period for sulphate is 6819.24 kg/hr, 4873.62kg/hr; for nitrogen 4179.24 kg/hr, 4021.55 kg/hr and for phosphorus 40.08 kg/hr, 34.724 kg/hr, respectively. Salinity loads entering the Hartbeespoort dam during summer and winter are 42952.87 kg/hr and 27548.39 kg/hr, respectively. According to the findings, water resource management must act quickly to improve the overall quality of the water; in the upcoming ten years, as loading rates are expected to rise exponentially as a result of increased demand and stressed water use, which will lead to poor water quality. This will pose serious health and economic risks to the people of the Upper Crocodile River Basin and the populace of South Africa.
  • Thumbnail Image
    Item
    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.