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A comparative functional analysis of spinous process, transverse process and articular facet morphology of the upper thoracic spine in extant hominids and fossil hominins
(2024) Yelverton, Christopher James
This study utilized three focus areas to evaluate and compare the variation in morphology of the spinous processes and articular facets of the upper thoracic spine (T1-T6) in African apes, contemporary humans, Later Stone Age (LSA) humans, baboons and fossil hominins, with the goal of finding and explaining potential functional differences. Further questions included if the spinous process deviations observed were specific to the structure or included changes to articular surface orientation and size (i.e., were changes noted only structural, or were there additional functional changes that occurred simultaneously). A skeletal sample consisting of hominines—chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), LSA humans and contemporary humans—and baboons (Papio ursinus) were compared to each other (as examples of varying locomotor propensity or lifestyle) and to relevant fossil hominins including Australopithecus africanus (Sts 14), Australopithecus sediba (MH1 and MH2), Australopithecus afarensis (A.L. 288-1) and Australopithecus prometheus (StW 573). A novel process for photography of samples was established and demonstrated to be reproducible. Specimens were photographed and linear and angular measurements taken utilizing ImageJ software and non-metric visual observations. Comparisons of hominines and baboons demonstrated statistically significant differences between species and sex. Spinous process deviations demonstrated a lower than anticipated overall incidence when evaluating the entire vertebrae sample, although the presence within an individual’s sequence of T1-T6 was significantly higher and was more prevalent in males in all groups. Morphological presentations of spinous iv process deviations were classified into five patterns based on the region of deviation identified. Age in the contemporary humans, and locomotor propensity when all selected primates were compared did not appear to have an impact on frequency of occurrence of this feature. In relation to the comparison to fossil hominins, there did not appear to be sufficient consistency in presentation to allow for this feature to be proposed as a developmental feature in the upper thoracic vertebrae related to bipedalism. The LSA humans sample group demonstrated an increased likelihood of spinous process deviations in the upper thoracic vertebrae and may be related to lifestyle and activity levels that were significantly different to contemporary humans. In summary, the study found morphometric measurements and spinous process deviation to relate more to species differences and sexual dimorphism than to locomotor differences, with lifestyle and activity levels in humans potentially increasing the frequency of spinous process deviations. It may be concluded that spinous process deviations are a consequence of various related factors that may interact in their development, or in many cases may be the result of random normal variations between individuals. Spinous process deviation in the upper thoracic vertebrae is therefore not a reliable indicator of postural or locomotor behavior in the extant comparative sample or in fossil hominins but may be an indicator of lifestyle and activity levels in humans.
A machine learning approach for assessing sedimentological data's potential for in-situ gold grade prediction in the Witwatersrand basin, South Africa
(2024) Mombe, Tariro
Mineral resource estimation is one of the most crucial factors in the mining industry because it extracts information about the quantity and quality of a mineral deposit. Mining operations have traditionally taken a purely geostatistical approach to resource estimation; however, the global technology boom has significantly improved estimation techniques. Machine Learning (ML) has only recently proven relevant in geoscience. Several studies have alluded to it being a revolutionary resource estimation tool with the potential to improve overall prediction accuracies. ML enables the incorporation of geological properties (e.g., lithology, grain size); consequently, resource estimation models produced with geological context are expected to be of higher accuracy. This research aimed to investigate how incorporating sedimentological properties enables in-situ gold grade prediction in the Witwatersrand Basin. Sibanye-Stillwater provided a gold assay database comprising sample information collected from their Kloof mining operation (South Africa). This dataset was refined and used to produce ML models; geostatistical (kriging) models were later produced for comparison. The experimental component of this dissertation was programmed in Jupyter Notebook using the Python programming language. The Random Forest (RF), AdaBoost, K-Nearest neighbours (KNN) and Elastic Net (EN) were the machine learning algorithms (MLAs) of choice for this study. The original dataset comprised 55 304 datapoints, with sample properties including spatial coordinates, four sedimentological properties (Channel Width, Internal Waste, Conglomerate Percentage and Basal Contact), and the gold grade property. In this study, a sample area was selected; consequently, the final dataset used for predictive modelling comprised 10 682 datapoints (19.31% of original). The predictive modelling results proved that it is possible to produce high-accuracy mineral resource models when predicting gold grades using MLAs; however, the quality of the data plays a significant role in the extent to which sedimentological properties can be useful in this regard. An extensive quality assurance and quality control (QAQC) workflow had to be implemented to attain good predictions from what was originally a very poor model. Investigations into the spatial distribution of the well-predicting and poor-predicting datapoints revealed a spatial pattern in the ‘bad’ dataset while the ‘good’ dataset had none, suggesting that the poor-predicting samples may have been extracted off-reef. Analysing the differences between the ‘good’ and ‘bad’ datasets thus revealed a prominent data quality issue that may have resulted from errors during sampling. Overall, this study has produced a resource estimation methodology that can be replicated and used on any gold deposit in the Witwatersrand Basin, where similar types of data exist. Therefore, similar deposits in other locations can also use the same methodology.
A regional comparative study of Middle group and lower group chromitites in the critical zone of the Bushveld Complex
(2022) Hasch, Maximilian
The present study focuses on Lower Group (LG1-7) and Middle Group (MG0-4) chromitites in the Critical Zone of the Bushveld Complex and aims at gaining new insight into their genesis. Field observations have been made in open pit and underground mines at a multitude of locations in the Eastern and Western Lobes of the Bushveld Complex. These allow for a description of the morphology and field relations of chromitites on a regional scale and for a regional perspective on their formation. Furthermore, a vertical chemical profile was drawn through the LG6 chromitite in a drill core from the Eastern Lobe, which is used to back some of the claims made from field observations. Chromitites exhibit distinct morphologies at different locations, as they appear as one, two or three chromitite layers and vary in thickness. It is inferred that this represents a regional structure of bifurcating chromitites. Owing to the significant size of this structure, bifurcations are seldom observed in outcrop. The LG6 chromitite contains up to five sublayers. Chemical data suggest that these sublayers are of magmatic origin and it is inferred that they formed in a similar fashion to the multiple chromitite layers of the MG chromitite packages. Evidence for magmatic erosion of footwall rocks to chromitites was documented in the form of chromitites transgressing their footwall and the presence of large erosional footwall remnants in chromitite layers. Furthermore, two potholes, roughly circular depressions, have been observed. The potholes contain chromitite layers and transgress their footwall rocks, suggesting that chromite deposition was preceded by magmatic erosion. The lateral thickness differences in silicate layers suggest that this erosion was regionally heterogeneous. Depending on the rate of erosion, it may have removed part of the footwall, the entire footwall or even part of the underlying chromitite. Upon cooling, the magma deposited a chromitite layer. The relations between chromitites and their host rocks suggest that the chromitites crystallised on the erosion surface. Depending on the degree of magmatic erosion, a few separate chromitite layers or a single chromitite layer would form from several influxes of fresh magma into the chamber.
An investigation into the effects on leaching select low-grade gold ores in the Witwatersrand Basin
(2024) Alex, Samira N.
The mining industry currently faces challenges including, but not limited to: gold price volatility, declining ore grade, complex ores, escalating production costs and increasing pressure to be environmentally responsible. As green mining becomes a strong focus of the 21st Century mining industry, an opportunity exists to explore non-cyanide green leaching alternatives. In the past, several non-cyanide reagents such as thiosulfate, chloride, bromide, ammonia, thiourea have been proposed to replace cyanide, however all present unique shortcomings. Glycine is a promising green alternative due to its ease in handling, affordability and recyclability. This research project aims to determine how complex and low-grade Middelvlei Reef from the Witwatersrand Basin in South Africa can be successfully leached using the glycine system. The selected Witwatersrand ore was characterised by using optical microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), quantitative X-ray diffraction (QXRD), Tescan integrated mineral analyser (TIMA) and micro-X-ray computed tomography (MicroXCT). Experimental results shows that gold is semi-refractory due to it being physically associated with gangue minerals (e.g., pyrite, carbonaceous matter) and the presence of electrum has been detected which is known to influence leaching kinetics. The occurrence of minerals such as quartz, pyrite and carbonaceous matter in the ore impedes leaching by displaying preg-robbing behaviour, reagent consumption or lowering gold recoveries. A multi-elemental analysis, conducted prior to glycine leaching, highlighted the presence of deleterious base metals such as of Cu = 67.57 ppm and Co = 97.80 ppm. These results highlight that the traditional method of processing needs to be reconsidered. Leaching experiments were aimed at optimizing gold recoveries while remaining sustainable. Results demonstrate that the optimum parameters that yielded high gold recoveries are: 1) glycine to permanganate ratio of 1:1, 20% solids (ore) and 80% liquids, pH 10. 5 and a temperature of 25 °C. Experiments demonstrate that glycine as a reagent yields average recoveries of 66.7% from all the different experiments conducted. The lowest recovery was 56% and the highest recovery was 92%. The implications of the results are that the Middelvlei Reef shows great potential for glycine leaching, however vital pre-treatment steps should follow prior to leaching. An ore pre-treatment will ensure that the correct measures are put in place to counteract the refractory and complex nature of the ore and obtain higher recoveries.
An investigation into the mineralogy and processing characteristics of the Elsburg reefs at South Deep Gold Mine, South Africa
(2024) Notole, Viwe
Gold ores of the Witwatersrand Supergroup in South Africa are known to be amenable to metallurgical recovery through the process of cyanidation. However, the continuous decline in gold ore grade, increased environmental liability caused by residual cyanide in tailings and an increase in the complexity of ore composition calls for an alternative processing route. This is important to ensure that low-grade ore recovery is profitable while producing environmentally benign waste residue. Process mineralogy provides a systematic approach for the practical application of mineralogical knowledge, aiding ore characterisation and predictive behaviour, thus optimising how ores can best be mined, blended and processed. This study used mineralogical data and environmentally friendly leach reagent (i.e., glycine) to diagnose and predict processing characteristics of the composite Elsburg reefs at South Deep Gold Mine, South Africa. The mineralogy of these reefs is dominated by quartz and sulphide minerals, with pyrite, arsenopyrite, chalcopyrite and pyrrhotite being the common sulphides. More than 85% of gold in these reefs is locked or hosted in pyrite and quartz. The geochemistry shows high concentrations of siderophile (e.g., Cu, Ni and Co) and chalcophile (i.e., Cu and Zn) elements that can form stable complexes with glycine. A moderate to strong correlation of these elements (Cu, Co, Ni, Zn, etc.) with gold is conformable with the sulphide minerals-gold association. The poor liberation characteristics of Elsburg reefs ore and its geochemistry negatively influence gold recovery using glycine leaching. Sequential or multi-stage leaching is best to process ore with moderate to high Cu concentration and unliberated gold. The outcomes of this study demonstrate that Elsburg reefs gold ore responds well to sequential glycine leaching, with gold recoveries up to 95%, depending on which method or conditions are used. At low glycine dosage (e.g., 300 ppm), leaching duration of 50 hours, and ambient temperature (~23°C), bottle roll leaching of the Elsburg reefs yield low gold recovery (i.e., 30%), while at higher glycine dosage (e.g., 1500 ppm) and same leaching conditions (duration and temperature), a higher gold recovery (i.e., 41%) is attainable. Sequential leaching at a higher concentration of glycine (1500 ppm) with a leaching duration of 101 hours, yield cumulative gold recovery of up to 86%. Furthermore, at higher glycine concentration (1500 ppm) and elevated temperature (i.e., 40°C), Elsburg reefs yield considerably higher gold recovery (95%). The leaching solution was recharged at different time intervals from the beginning to the end of the leaching process. The increase in glycine was complemented by an increase in oxidant concentration (potassium permanganate). The ratio of potassium permanganate to glycine was kept at 2:1 (potassium permanganate: glycine).
Application of Micro Computed-Tomography in the characterisation of Early Triassic coprolite microstructures and microfossils from the Burgersdorp Formation (Tarkastad Subgroup, Beaufort Group) of South Africa
(2022) Montgomery, Chandelé
Driefontein 11, a farm in the Free State province of South Africa, is a fossiliferous Early Triassic locality with a diverse and prolific coprolite assemblage. This study used micro-CT to characterise the coprofabrics and coprolite inclusions of 47 coprolites from this assemblage, and assesses how well these variables correlate with their respective morphotype assignations. Three different coprofabrics were characterised: homogenous massive, heterogenous massive and heterogenous zoned. Homogenous massive coprofabrics are indicative of coprolite perpetrators with high digestive efficacy, whereas both types of the heterogenous coprofabrics are indicative of individuals with varying digestive strategies. The coprolites document several microfossil inclusions including fish, tetrapods and the second instance of Early Triassic beetles and freshwater bivalves. The coprolite ordination shows that there is no unambiguous correlation between morphotypes or coprofabrics and microfossil inclusions. This contribution is a first step in the understanding of the fauna that inhabited this Early Triassic ecosystem and their feeding ecology.
Assessing the strategy and performance of selected JSE listed mining companies on their contribution to the United Nations Sustainable Development Goals
(2024) Hlongwane, Dumisani Gift
The Sustainable Development Goals (SDGs) are part of the United Nations (UN) 2030 Agenda for Sustainable Development, which defines an ambitious plan for people, planet, and prosperity. The UN has acknowledged that the SDGs cannot be achieved without the contribution of the private sector. The mining sector is regarded as one of the critical players with the potential to advance the achievement of the SDGs by 2030. The aim of this study was to examine the extent of corporate engagement with the SDGs of 10 selected mining companies in the Johannesburg Stock Exchange’s (JSE) Top 100 listed firms in advancing the 2030 Agenda for Sustainable Development. The objectives of this study were based on the recontextualisation of the five steps from the SDG Compass, an international guideline aimed at steering particularly large companies on engaging with the SDGs through integration, appraisal, and reporting of progress on the SDGs. This study was based on the companies’ 2019 annual reports for gathering secondary data afterwards semi-structured interviews with sustainability managers of the same selected mining companies. Content analysis coupled with a rating scale were utilised for data analysis to determine the extent of corporate engagement with the SDGs. The results of the study show that only four of the ten mining companies have made considerable progress on engaging with the SDGs, including integrating the SDGs into the core of their strategy and business models. Most mining companies failed on setting SMART objectives to support their priority SDGs, which resulted in inadequate reporting of performance to advance the SDGs. Additionally, the results of the study point to limited involvement of top management for mining companies that lagged behind. Finally, if the mining sector is to significantly contribute towards the achievement of the 2030 Agenda for Sustainable Development, then top management of mining companies must fully embrace the SDGs and provide leadership in steering the integration of the SDGs into strategy and business models of mining companies.
Butchering patterns and the implication for hominin feeding behaviour at HWK EE in Olduvai Gorge, Northern Tanzania
(2022) Kimambo, Jackson S.
Meat-eating by early hominins played an important role in the biological and cultural evolution of humans. Butchery marks such as cut and percussion marks are the direct evidence of meateating by early human ancestors, dating back to at least 2.6 Mya. However, the manner in which early hominins obtained carcasses, particularly during the Early Stone Age (ESA), is highly debated. While some researchers proposed hunting, others have suggested that early hominins were scavenging carcasses from large felids. Consequently, the two views have stimulated debate concerning the primary and secondary access of carcasses by the early hominins. The frequency of butchery and carnivore marks left on the faunal remains has been one the criteria used to understand the order of hominins’ and carnivores’ feeding on the carcass. Although there isa voluminous publication on this topic, the majority of them focus on a few sites due to a lack of well-preserved fossil remains. The recent excavation at the HWK EE site in Olduvai has revealed rich and well-preserved fossil remains with evidence of both carnivore and hominin modifications marks. Bone surface modifications (butchery, carnivore, and crocodile marks) were analysed using a 16x hand lens under strong light. These marks were recorded by a simple tally of absent or present and interpreted based on the established model of hominin feeding behaviours. The results of hominin butchery and carnivore modification marks demonstrate that hominins at the site exploited a range of small to large mammal taxa and a variety of carcass resources including meaty appendicular elements, crania, and ribs. The study also revealed that hominins at the site were selective on long bone depending on the quantity of marrow content for different taxa. The study of traces of butchery marks and percussion marks on the faunal sample support that hominins gained primary access to small mammals and secondary access to most of the medium and large mammals. These resources were likely obtained from large felids kills of carnivores such as lions and leopards. The study has also shown that in the absence of limb elements, butchery marks on well-preserved ribs and crania elements can be used to infer the order of hominin access to carcasses. Moreover, the data also show that butchery patterns are consistent in both LAS and LEMUTA interval
Geology of selected sites along the northern margin of the Barberton Greenstone Belt
(2022) Mashele, Nonkululeko Phumelele
An increasing number of UNESCO World Heritage Sites are recognised for their geological significance. One such site forms part of the Barberton Greenstone Belt (BGB), which has been widely acknowledged as an outstanding site for Archean geology research. Though members of the geoscience community are familiar with the outstanding universal value of the Barberton Greenstone Belt, the people who live on it often do not. With the World Heritage Status (2018) comes an obligation to unpack the geological heritage of the Barberton region to local people and visitors, and to promote further research so the true value of the geological importance of the region may be better understood. For this reason, this project set out to interpret and contribute to concepts formulated from studies of BGB rocks to produce a thesis usable for generating various science communication media and topics for further research. Themes discussed in this thesis include granite-greenstone relationships, alteration of ultramafic rocks and the associated economic products, as well as deformation of various lithologies. Ease of access guided the selection of eight mostly roadside outcrops along the R38 secondary road linking Barberton to the southern gate of the Kruger National Park. These sites link up to form a geological trail along the northern margin of the Barberton Greenstone Belt, allowing visitors to easily interact with outcrops on their way to other popular attractions. By driving along the R38 with science communication media produced from this project, locals and visitors will learn how geology shaped their world. They will gain insight on how mineable concentrations of verdite, talc and magnesite occur in certain ultramafic bodies. They will also learn of different ways in which rocksrespond to stress as a common perception of rocks among laypersons is that they are solid, stable and unchanging.
Geomorphic adjustment, sensitivity, and connectivity of the lower Mara River and its floodplain wetlands, Tanzania
(2024) Gomes, Megan
The Mara River in semiarid East Africa traverses one of the world’s most important wilderness conservation regions. Like many other dryland rivers, the Mara sustains wetland and terrestrial ecosystems that provide essential ecosystem services to local human and wildlife populations. However, the hydrological and geomorphological diversity and complexity of dryland rivers, including the Mara, makes comprehensive understanding of their development and prediction of future biophysical changes difficult, representing major challenges in fluvial geomorphology and wetland management. This thesis examines the key geomorphic controls that drive dryland river morphology and floodplain wetland formation, as well as the intrinsic processes that lead to channel and wetland adjustment, within the Mara system. Morphometric analysis based on satellite imagery mapping and discharge modelling is used to assess the valley-scale controls and hydrogeomorphic forms and processes of the river and its palaeochannels, as well as recent historical geomorphic adjustments (last 32 years) along the lower Mara River. The river and palaeochannels have marked downstream declines in channel capacity and changes in sinuosity due to declines in discharge and stream power, coincident with a reduction in valley confinement. While several large palaeochannels extended further downstream than the modern river, likely driven by higher-energy hydrological regimes in the past, the river now exhibits a nonequilibrium response to rapidly declining fluvial energy resulting in avulsions, channel diminution, and channel breakdown in the wetlands. Geomorphic sensitivity analysis of the lower Mara River for the recent historical period indicates that the upper and lower reaches are ‘Passive sensitive’, the former with limited adjustments, the latter with numerous cut-offs and palaeochannels, and both reaches having low migration rates. In contrast, the middle reach is ‘Fragile’ with numerous lateral migration features, cut-offs, and higher migration rates. The lower reach appears to be close to a threshold and may switch to a Fragile state where avulsions become dominant, while the other reaches may be more resilient and maintain their present states. These complex geomorphic responses are likely related to spatiotemporal patterns of hydrogeomorphic connectivity in the catchment. Modelling of contributary hydrogeomorphic connectivity indicates that the upper catchment (source zone) is consistently well-connected and is responsible for the greatest inputs of water and sediment to the fluvial network. The middle 4 section (transfer zone) has lower and more variable seasonal, inter-annual and decadal connectivity, while the lowland reaches (deposition zone), where large floodplain wetlands occur, have relatively consistent, low connectivity. These trends are associated with downstream sedimentation resulting in river and wetland adjustments and avulsive behaviour. Together, these findings provide novel insights into dryland river character and behaviour, as well as the valley- and catchment-scale conditions that contribute to geomorphic adjustments in internationally significant fluvial systems. Under increasing pressure from anthropogenic and climate change impacts the Mara River and its wetlands are likely to undergo future geomorphic changes, and thus an understanding of the biophysical controls, forms, and processes of river adjustment as well as states of sensitivity and patterns of connectivity are imperative for guiding conservation and management efforts.
Integration of 3D seismic data analysis techniques and mining-induced seismic data to elucidate the mechanical behaviour of the rock mass in the gold mines of the Witwatersrand Basin
(2022) Masethe, Richard Terence
In many hard rock underground mines worldwide, seismicity is observed as stress increases due to increasing mining depth. The rock mass in the hard rock underground mines is generally composed of high strength brittle rock types, so the risk of violent failures increases with increasing mining depth due to increasing stress levels. Seismicity poses a significant geotechnical challenge to the mines as it may damage excavations mining equipment and infrastructure, and cause injuries or even deaths of mining personnel. Mining operations within the Witwatersrand area have mostly taken place at depths of 1.5–3.5 km, but are now migrating to ultra-depth as mines mature. This transition is met with different complexities in the local geology, rock mass conditions, thickness and dip of the reef (ore body). Mining at these greater depths will result in higher mining-induced stresses, induced seismicity and rockbursts. All these complexities affect mining standards and procedures. This study attempts to mitigate the risk of rockburst by integrating 3D reflection seismic images of geological structures (especially dykes and faults) with the source mechanisms of mininginduced earthquakes to better understand the main drivers of seismicity. The seismicity data covering the Kloof Extension Area (KEA) was investigated in this study. Moderate to large mining-induced seismic events (ML≥1.5) within the defined seismic volume were analysed in an area where mining was taking place. The effects that these complexities (high stress, complex structural geology, mining elements, etc.) have on current mining operations was studied to understand the impact on future mine planning and ore reserve evaluation. High-resolution images of the gold-bearing orebody, the Ventersdorp Contact Reef (VCR), were extracted using seismic attributes. The images are the result of an interpretation of the seismic reflection data. The investigation includes the formulation of a workflow for the computation and interpretation of seismic attributes. The 3D reflection seismic data is undersampling a series of minor structures (e.g., small faults with a throw less than 5 m and mainly the dykes) that have been identified by the in-stope underground geological mapping. Comparison indicates that the faults determined by the underground mapping generally correlate with those mapped in the 3D reflection seismic data. Mining-induced seismic events frequently occur close to the in-stope identified mapped structures. Numerous faults not detected or visible on the VCR depth structural map and seismic sections were successfully imaged using horizon-based seismic attributes, viz. edge detection and dip-azimuth. The dip azimuth attribute provides a better delineation of faults. The source mechanisms of seventy-five ML≥1.5 seismic events were studied in detail. Focal plane solutions were calculated, interpreted, and compared with the geological model derived from underground mine mapping and the interpretation of the 3D seismic reflection data and elements of the mining layout such as abutments, back areas, and pillars. When comparing mining-induced seismic events occurring on mining elements and on geological structures, it was found that they release approximately equal amounts of seismic energy. It was found that moment tensor inversion generally yields fault plane solutions that align with the mining geometry and geological structures. The Es/Ep ratio, routinely used to classify seismic events, was not consistent with the source mechanisms produced by the moment tensor calculations. This study indicated that the parameter is not sufficiently stable to be used for classification. The data analysis indicates that mining activities may lead to a rockburst (a mining-induced seismic event that causes damages underground) or a slip on pre-existing geological planar structures. However, the geological structures are not the only driving factors of these large seismic events within the 3D reflection seismic volume. Mining elements, such as pillars, remnants and abutments, are sometimes implicated. All seismic data recorded since the extraction of the Thuthukani shaft pillar commenced in January 2007 has been analysed. We compared seismicity in two five-year periods (1 January 2007 to 30 November 2012 and 1 December 2012 to 31 July 2017) and found an increase in the rate of seismicity and the maximum magnitude (Mmax) from 2.7 to 3.2. An assessment of seismic hazard using intermediate term probability of occurrence indicates an increase in seismic risk for M≥1.0 seismic events in period 2 as compared to period 1. Strategies to mitigate the seismic risk during shaft extraction are discussed.
Investigating an optimized approach to the teaching and learning of genetics & evolution in South African schools
(2024) Bodhania, Aneesa
This study explores teachers’ experiences of teaching genetics and evolution according to the grade 12 Life Sciences CAPS curriculum in Gauteng Public High Schools. Research has shown that learners are only achieving a 40-50% average in the genetics and evolution sections of their final examinations (DBE, 2017,2018,2019,2020,2021,2022), however, few studies have been undertaken to explore how learners’ conceptual understanding and performance could be improved. In this regard, this study investigates whether the enacted might be a contributing factor to poor performance. To address this, 3 teachers from three different quintile 5 and 2 teachers from 2 different quintile 4 public (1 teacher per school), CAPS abiding high schools, as well as 1 genetics and 1 evolution lecturer to pre-service Life Science teachers, were purposively selected and interviewed to evaluate the topics of genetics and evolution in the enacted curriculum. The data collected from the interviews, participant sequencing suggestions and participant concept maps was analysed through inductive and deductive thematic analysis. In terms of threshold concepts, the data showed conclusively that an understanding of certain genetic concepts (such as DNA, meiosis, mutations, variation, etc.) is essential to the understanding of certain evolution concepts. Regarding the annual teaching plans, it was found that although teachers abide by the proposed plan, they suggest that resequencing evolution to directly follow genetics may improve learner understanding. Lastly, the genetics and evolution lecturers agreed that while the university curriculum is tailored to cover the school curriculum, there are still some areas which are not adequately covered a university level which may result in teachers having some knowledge gaps regarding the school curriculum. Based on the data, a recommendation is made for the reconsideration of the sequencing of genetics and evolution for optimized linking between the topics. However, further research still needs to be done to determine the most effective pedagogical methods for teaching and learning genetics and evolution content in high schoo
Metallogeny of the Boschhoek base metals occurrence and its geological context with respect to the polymetallic mineralization of the Stavoren Fragment of the Bushveld Complex, South Africa
(2024) Chauke, Rames
The Boschhoek Prospect is an epigenetic mesothermal copper, lead, zinc and silver deposit within repeatedly fractured Nebo granite of the Lebowa Granite Suite. The Prospect is exposed as hilly gossanous bodies that grade vertically downwards into siderite-calcite-quartz veins system. Similar deposit occurred at Mutue Fides Tin deposit comprising predominantly of tin and fluorite within miarolitic Bobbejaankop granite. These deposits are associated with local scale structures and they are spatially separated by a regional sinistral strike-slip Wonderkop Fault. The study examines the spatial relationships and possible structural control the Wonderkop Fault bears on local scale structures. It investigates metallogeny of base metals and evaluates the petrological character of the Boschhoek Prospect in relation to the Mutue Fides deposits. Extensive fieldwork characterising tectonic structures and structural analysis in the study areas suggest strong link between the Wonderkop Fault and the local scale structures. In syn- and post-BIC intrusion period, the northeast-southwest striking Wonderkop Fault underwent a compressional event directed at northwest-southeast that resulted in splay morphologies on the Transvaal inliers and the felsic plutonic bodies along the fault. Several warping events and rheological failures in response to this reactivation created small-scale faults and veins adjacent to the fault that are associated with polymetallic deposits. The local scale structures mimic morphologically and geodynamically the regional scale Wonderkop Fault. Petrographic studies show pervasive sericitization of the Nebo granite is characteristic of mineralised zones. The varied nature of siderite-calcite-quartz-hematite veins suggest metalliferous fluids emanate from numerous sources including the LGS, the nearby inliers and the connate waters. Greisenization and albitization characterises the mineralised zones in the Bobbejaankop granite. The metals source emanate from magmatic-hydrothermal fluids concentrated in cupolas. Geochemistry results suggest that the Nebo and Bobbejaankop granite are cogenetic and possibly share the same continental source as ascertain by normalised La/Yb ratios. The Bobbejaankop granite experienced higher fractionation degrees accompanied by intensive magmatic-hydrothermal alterations as ascertain by TEDI (Ba x (Sr/Rb)), Zr/Hf versus Y/Ho, Yb/Nb ratios and normalised REE plots. Normalised iv REE plots and petrographic studies suggest that Bobbejaankop granite melt assimilated the Stavoren granophyre and gave rise to the granophyric and the hydrothermally unaltered variety of the Klipkloof granite.
Petrography, ore mineral paragenesis, and gold deportment of the Twin Hills Gold Deposit, central Namibia
(2024) Sales, Johannes
The Twin Hills Gold Deposit is an orogenic gold deposit hosted within the metamorphic turbidites of the Kuiseb Formation in the Southern Central Zone of the Damara Belt. This study aimed to understand the petrography of the host rocks, the formation of the ore minerals and asses the deportment of the Twin Hills Gold Deposit. Methods used in this study included drill core logging, transmitted and reflected light microscopy and scanning electron microscopy (SEM) based TESCAN Integrated Mineral Analyzer (TIMA). The host rocks are characterized by graded bedding with gradations ranging from pelitic mica-rich interbeds to psammitic quartz-rich interbeds, together forming interbedded metagreywacke. The interbedded metagreywacke is the main host unit of the gold mineralization and is made up of quartz, biotite, muscovite, plagioclase, orthoclase and cordierite. The ore mineral assemblage at the Twin Hills Gold Deposit is characterized by the prescence of gold and three major sulphide minerals namely, pyrrhotite, arsenopyrite, and pyrite. Gold mineralization at the Twin Hills Gold Deposit is associated with two main hydrothermal alterations, namely, potassic alteration and silicification. This research suggests at least three stages of mineralization within the Twin Hills Gold Deposit. The first stage is the diagenetic stage, which involved the enrichment of diagenetic arsenian pyrite (Py0) in the turbiditic sediments with gold and other trace elements via the exhalation of reduced, deep-seated Au-As enriched H2S-rich basinal brines onto the sea floor. The second stage involved the release of gold initially locked up within the arsenian pyrite (Py0) crystal lattice into the metamorphic fluids and the subsequent precipitation of free gold (Au1) from the gold bearing fluids via phase separation due to a drop in fluid pressure. This resulted in the formation and concentration of disseminated gold to economic grades within the metagreywacke. The third stage is the quartz veining stage, which was characterized by increased permeability and advanced fluid flow due to progressive metamorphism and deformation. This stage was responsible for the remobilization of fine gold grains (Au1) that were disseminated within the groundmass of the metagreywacke and concentrating them into the biotite selvages. This stage is also presumed to be responsible for the exsolution of gold from the arsenopyrite crystal lattice resulting in very fine gold (Au2) grains included within arsenopyrite crystals (Asp2). The third stage led to the further upgrading of the gold grades to higher economic levels. The gold deportment analyses revealed three modes of occurrences of gold within the Twin Hills deposit. This includes gold disseminated within the groundmass, gold grains disseminated within biotite selvages associated with quartz veinlets and gold grains included within arsenopyrite crystals. This study recommends a two stage recovery procedure to ensure optimum gold recovery, this includes gravity separation methods followed by cyanide leach process. The outcomes of this research further reiterate the importance of the Kuiseb Formation meta-turbidites as a significant fertile source for gold and mineralizing fluids in sediment hosted gold deposits in the Damara Belt. A sediment hosted gold deposit model should be adopted in conjunction with the mineral systems approach in identifying targeting vectors in exploration programs. This exploration approach should also be applied to other meta-sediment hosting stratigraphic sequences within the Damara Belt such as the Arandis and the Okonguarri Formations. These stratigraphic horizons have proven gold fertility as they host the only two currently producing gold mines in Namibia, the Navachab gold mine and the Otjikoto gold mine
Raw material procurement analyses at Olieboomspoort rock shelter and Mwulu’s cave (Limpopo)
(2022) Masia, Dineo
The purpose of this study is to determine the provenance of Middle Stone Age lithics, and the procurement strategies employed to obtain them, at Olieboomspoort Rock Shelter (OBP) and Mwulu’s Cave. Macroscopic (and stereomicroscopic) analysis, portable X-ray fluorescence, thin section petrography, and Inductive Coupled Plasma Mass Spectrometry are used to achieve this purpose by identifying and comparing the lithics to the geological samples collected from formations around the sites. Quartzite, shale, sandstone, dolerite and quartz lithic raw materials from OBP may have been procured from the Mogalakwena Formation locally and non-locally although the provenance of chert lithics remains unknown. At Mwulu’s Cave, quartzite and quartz lithics were possibly made from raw materials procured from local outcrops in the Black Reef Quartzite Formation (BRQF) and chert lithics were possibly made from local or semi-local BRQF raw materials. Duitschland Formation shale raw materials may have been procured semi-locally from Mwulu’s Cave. These are preliminary hypotheses on the provenance and procurement of lithics at these sites and more petrography and ICP-MS analyses need to be conducted to verify them.
Seismotectonic and seismic hazard studies for Madagascar
(2022) Rakotondraibe, Tsiriandrimanana
Madagascar is an island that was once situated in the centre of the Gondwana supercontinent but is now located 1000 km from the East African Rift and about 2000 km from the mid-ocean ridge of the Indian Ocean. Its separation from the African continent (ca. 165-130 Ma) and the Indian sub-continent (ca. 90 Ma) and mantle upwelling that gave rise to the recent volcanism (ca. 28-0.5 Ma) has had significant impact on the geological structure and neotectonics of the island. This thesis focuses on the seismotectonic evolution of Madagascar and assesses the seismic hazard. Data for this project was derived from the 28-station MAdagascar – COmoros-MOzambique (MACOMO) array, as well as stations from the concurrent SEismological signatures in the Lithosphere/Asthenosphere system of SOuthern MAdagascar (SELASOMA) and Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel (RHUM-RUM) projects, and permanent stations of the national seismological network. The combined 56 stations provided a better distribution and density than any previous study. The thesis is presented in three main parts. The first part focuses on seismicity and focal mechanisms. The 695 events recorded and located during the 23-month period of MACOMO observations in 2011-2013 have magnitudes that vary from M1 to M5.3. Twenty-three focal mechanism solutions were determined using Pwave first motion polarities and some clear S-wave polarities. In agreement with previous studies, it was found that central Madagascar is the most seismicallyactive region. Most earthquakes are located near known faults. Normal faulting dominates the central area, while strike-slip and reverse fault mechanisms are predominantly observed near the Antsaba and Sandrakota shear zones in the north, and the Bekily and Ampanihy shear zones in the south. The focal mechanism studies revealed extensional faulting in central Madagascar, which can be explained by the reactivation of older faults by a thermal bulge underlying the region. The faulting style was not well defined in the northern and southern parts as few solutions were determined due to the lower density of stations. In the second part of this thesis, 182 focal mechanism solutions were used to study the characteristics of the stress field. Calculations were performed using a linear inversion technique based on the Michael (1984) method and using a recently calculated velocity model of Madagascar. Results give shape ratios (i.e., relative magnitude of stress axes) that vary from 0.7 to 0.9; a maximum principal stress axis (σ1) that is near-vertical and a minimum principal stress axis (σ3) that is nearhorizontal with a NW-SE orientation. This corresponds to a normal faulting regime. The regional variation of stress and the characteristics of the shape ratio and friction values were determined. The average direction of the stress field is approximately NW-SE in central Madagascar, and trends W-E in the southern and northern parts of the island. In central Madagascar the shape ratio and friction vary from 0.83 to 0.97 and 0.45 to 0.65, respectively; while in the northern and southern parts of Madagascar they vary from 0.3 to 0.5 and 0.5 to 0.7, respectively. The third part of the thesis reports on the assessment of the seismic hazard in Madagascar using data from a catalogue that combines data from the NDC (National Data Center), bulletins produced by the current study for the period between 1975 and 2016, as well as historical earthquake data. The analysis reveals that Madagascar has moderate seismic activity with local magnitude ML ≤ 6. The relationship between the moment magnitude MW and local magnitude ML values was estimated in order to unify magnitude characteristics and create the homogeneous catalogue that is required for seismic hazard studies. A Probabilistic Seismic Hazard Assessment approach (PSHA) was performed using the Kijko and Sellevoll (KS) and Cornell-McGuire methods with two different ground motion models. In order to implement the alternative parameter values in seismic hazard calculation and to attribute uncertainties associated to the input parameter, a logic tree formalism was applied. The Peak Ground Acceleration (PGA) values near major towns in the central region for 10% and 2% probability of occurrence in 50 years are 0.04 g and 0.11 g, respectively. The spectral acceleration for 1.0 s and 3.0 s vary from 0.001 g to 0.01 g and 0.001 g to 0.005 g for 10% probability of vii occurrence in 50 years, respectively; and from 0.02 g to 0.10 g and 0.002 g to 0.01 g for 2% probability of occurrence in 50 years. This work demonstrates that the deployment of additional temporary seismic stations significantly improved our understanding of the seismotectonics of Madagascar, particularly in the northern and southern regions. In summary, we obtained a new magnitude relation, more accurate epicenter locations, better focal mechanism descriptions, and improved the assessment of seismic hazard.
Structural analysis and geological modelling of a stratiform copper-cobalt deposit at Konkola, Central African Copper Belt, Zambia
(2024) Mulonda, Sitwala
The Konkola east mining block is one of the six mining blocks at Konkola mine owned by Konkola Copper Mines (KCM) in Chililabombwe Zambia. A structural analysis was carried out on the Konkola east mining block that assessed the main geological structures in the area and how they fit into the regional deformation history. The impact of the geological structures on short term mine planning was also assessed. The second part of this study involved creating a geological model and documenting the steps taken to create a workflow that can be applied to other parts of the mine. Geological mapping was carried out on underground crosscuts and 23 boreholes were logged. Ten thin sections were studied using an Olympus BX53M/DP74 microscope. Old mine working plans containing historical geological information were scanned and digitized. A database was created and validated data was used to create a geological model of the ore bearing rock; the ore shale unit using Surpac mining software. This study established that Konkola east has major normal faults striking north-south and low angle reverse faults striking east-west and sub- parallel to the regional fold axis. Parasitic folds were also identified. This configuration led to the interpretation of Konkola east as part of a larger dextral strike-slip fault system formed by north-south directed compression and east-west extension. Three main deformation phases were identified in this study and correlated with previous regional work. The earliest deformation resulted in the development of a bedding-parallel foliation due to burial. The second phase of deformation included the development of bedding parallel veins and the main folding event. The third phase involved the development of brittle structures including faults and three main joint sets. The main faults identified in this third deformation phase are thrust faults where the hangingwall block is observed to have moved up relative to the footwall block and normal faults where the hangingwall is observed to have moved down relative to the footwall. These structures were found to have major implications for the short-term mining plan especially regarding ground stability and the mine hydrogeological environment. A geological model was successfully created and the total volume of the ore shale unit was estimated to be 1,032,199 m3 .
Textural variations in uranium-bearing sheeted leucogranites, with specific attention to “oxidation halos” from the Rössing mine, Namibia
(2022) Shaba, Timothy
The Rössing Uranium Mine is ~60 km northeast of Swakopmund, Namibia, and it is one of the largest sheeted leucogranite-hosted primary uranium deposits in the world. The sheeted leucogranites (SLGs) are divided into six different types (A-F) based on field characteristics of colour, grain size, structural setting and mineralogy. Three pre-D3 A-C types are barren, while post-D3 D-F alaskites are undeformed and have potential for uranium mineralisation, especially types D and E. The E-type SLGs have notable diagnostic features; oxidation halos which occur in almost all uranium deposits in the southern Central Zone of the Damara Orogen, and have been mined for uranium since the establishment of the Rössing Uranium Mine in 1976. This project aims to document the textural variations of oxidation halos in relation to uranium mineralisation and distribution. The Rössing uranium deposit is found within the southern Central Zone of the Damara Orogen which is composed of the Abbabis Metamorphic Complex (AMC) a Damaran-aged metasedimentary sequence and various granitic intrusions. The geology of the Rössing area comprises the Etusis, Khan, Rössing Formations and granitic intrusions. The primary uranium ore minerals at the Rössing Mine are uraninite and U-silicates. The mineralised uranium SLGs are typically found within the stratigraphic intervals of the Khan and Rössing Formations. Four techniques were used to analyse the rock samples: hand specimen observations; thin section petrographic analysis; Micro-XRF analysis to determine major element distribution of the whole E-type SLG rock sample and TIMA studies to determine mineral phases, elemental distribution, textural and alteration variations of the oxidation halos and their host rocks. The results show that the grain size of the oxidation halos and their host rocks varies from fine to pegmatitic. In the oxidation halo sample, the D-type section and the oxidation halo core zone are pegmatitic; the E-type section has a coarse texture with centrimetric crystal sizes and the oxidation halo transition zones have a fine-grained texture. In the D-type SLG rock sample, TS1 sections 1, 3 and 6 have a fine texture, TS1 sections 2 and 5 exhibit pegmatitic textures and TS1 section 4 has a coarse-grained texture. Rock texture controlled uranium mineralisation and distribution, alteration rates and colour of the oxidation halo and their hosting rocks. The pegmatitic sections are less altered and have less abundant uranium (U)-bearing minerals. Whereas, the fine-grained textured sections are highly altered and they have abundant U-bearing minerals such as uranophane, uraninite and zircon. The pegmatitic-fine-grained textured interface acted as fluid traps, retaining more fluids for a long period causing intensive alteration of mineral phases characterising the finelytextured sections. In the pegmatitic sections, hydrothermal fluids were not retained for a long period, hence their low alteration. High abundance of U-bearing minerals in the fine-textured sections resulted in the presence of smoky quartz, which is responsible for light-dark variation in the D-type SLG rock sample. In the oxidation halo sample, red colouration is due to unequal distribution of iron oxides such as haematite and magnetite. The various alteration processes both rock samples were subjected to had three major effects: iron rich and primary U-bearing minerals were oxidised to form iron oxides and secondary U-bearing minerals, respectively; this promoted the rock permeability which in turn resulted in an uneven redistribution of U-bearing minerals across the rock samples; and controlled the rock colour variations. High abundance of uranium-bearing minerals in the oxidation halo transitional zones is a result of abundant biotite phases, whose alteration helped to provide Fe2+ to the REDOX system to reduce and precipitate more uranium-bearing minerals, and forming iron oxide phases such as haematite, magnetite, rutile and titanite as by-products.
The baseline assessment of radiological levels of water in the West Rand Region, Gauteng
(2022) Nkopo, Zandile Odessa
Gold mining is one of South Africa’s economic injectors. Given South Africa’s unique geology, acid mine drainage (AMD) formed by mining activities allows for the dissolution and leaching of radionuclides into groundwater and potentially other drinking water sources under the right conditions. The aim of this study was to establish the baseline radiological levels of drinking water in the West Rand region of the Gauteng Province, South Africa. 23 water samples were collected from 9 towns within the study area and a liquid scintillation counter and Liquid Water Isotopes Analyzer (LIWA) model 45-EP were used for the analysis of tritium and stable isotopes respectively. Moreover, alpha spectrometry was employed for radionuclide analysis. Gross-α and gross-β activity concentrations were measured to determine the composition of radionuclides and identify the dominant radionuclides. The lowest activity concentration results reported were 15.3 mBq/L, 0.218 mBq/L, 4.73 mBq/L for uranium isotopes (234U, 235U, 238U); 2.28 mBq/L, 4.73 mBq/L, 18 mBq/L, 2.71 mBq/L for thorium isotopes (227Th, 228Th, 230Th, 232Th); -9.8 mBq/L, -34 mBq/L, -6.4 mBq/L for radium isotopes ( 223Ra, 224Ra, 226Ra); 1.2 mBq/L 210Pb, -16 mBq/L and -1100 mBq/L gross-α and gross-β respectively.. The highest activity concentrations reported were 210 mBq/L, 2.85 mBq/L, 62.0 for uranium isotopes (234U, 235U, 238U); 50.5 mBq/L, 33 mBq/L, 86.4 mBq/L and 23.5 mBq/L for thorium isotopes (227Th, 228Th, 230Th, 232Th); 13 mBq/L, 25 mBq/L and 19.5 mBq/L for radium isotopes (223Ra, 224Ra, 226Ra); 135 mBq/L 210Pb; 341 mBq/L and 13500 mBq/L for gross-α and gross-β respectively. The effective dose calculated from activity concentrations of all samples was within the allowed range (1 mSv/L to 3 mSv/L) of the WHO, UNSCEAR and DWAF drinking water guidelines. The low activity concentrations measured from the radionuclides suggest that the consumption of groundwater within the study area poses very little threat to human health but may cause severe health effects if it accumulates in the human body. The environmental isotopes results showed multiple moisture sources from global circulation, depleted δ 18O and δ 2H (-6.9‰ and -32.2‰, respectively) indicating that the recharging water underwent evaporation prior to recharge. Tritium was used to estimate the groundwater residence times and its activity concentration ranged from 9.44 to 28.32 mBq/L. Low 3H activity concentrations are indicative of new to relatively young waters.
The geology and structural influences on copper mineralisation, distribution and spatial occurrence in the Lubambe copper deposit, Central African Copperbelt, Zambia
(2022) Taruvinga, Tapiwa
The genetic relationship between copper mineralisation, stratigraphy and basin architecture in the Central African Copper Belt is very important as it plays a critical role in controlling and localising mineralisation. Evidence from basinal geometrical studies in most Zambian Copper Belt deposits suggests that major thrust faults and folded structures were developed during the Lufilian orogeny, which involved inversion of basement structures during periods of compression. The Konkola Dome and the Kirila Bombwe anticline are examples of major basement units where re-activation of extensional faults resulted in the generation of major structures later used as channel ways by copperbearing fluids. The presence of undeformed sulphides often hosted within structures shows that deformation predates mineralisation and critically played a major role in preparing the ground and structures for mineralisation. An integration and re-interpretation of geophysical and geological data in the Lubambe Mining Area has resulted in a significantly improved understanding of the geology of the area and potential controls on ore distribution. Despite limited subsurface information from the geophysical datasets, the exercise has provided significant confidence to detailed mapping of poorly exposed parts of the area. Interpretation outcomes from this mapping and geophysical (aeromagnetic and gravity) suggest that the distribution of major folds reflects an early extensional, basement architecture which is thought to be key to ore deposit formation in the Lubambe License Area. Additionally, geological modelling of the Lubambe-Konkola Area has shown that a relationship potentially exists between ore distribution, fold axes and stratigraphic thickness trends. Specifically, the model suggests that both copper grades and Ore Shale 1 Member thickness trends are controlled by NE-trending growth faults which can be traced to the eastern-side of the property. There is modest correlation between the traces of faults interpreted from geophysical surveys and the occurrence of structures seen in drill core in the selected holes which provides evidence of faults during and immediately after sedimentation. This suggests that the depocentres were fault-bounded basin into which mineralising fluids flowed to deposit ores in the OS1 Member. Copper ore within the Lubambe License Area includes very fine-grained chalcopyrite and chalcocite with some bornite, malachite, chrysocolla and limonite staining. Hypogene copper mineralisation in the Lubambe license area occurs as disseminated and along bedding planes adopting similar grain sizes as the host rock. This is accompanied by secondary copper minerals and iron oxides filling veins, fractures and joints. The Ore Shale 1 Member within the Lubambe License area thickens towards the southeast and can be correlated to the regional structure. Copper grades in the rich zones can be correlated with two small sub-basins in the East and South limbs and another around the Extension Area. Significant structural control on copper distribution can be observed on copper grade distribution maps superimposed on structural maps showing major and intermediate structural features. There are significant concentrations of chalcocite near surface and also down dip in the East and South Limbs and the Extension Area. Chalcopyrite is widely distributed except near surface. Bornite is concentrated in the centre of the East Limb. Malachite and chrysocolla are well correlated with Acid Soluble copper and are found mainly near surface. Evidence also suggests that metal concentration and upgrading of the ore deposit was influenced by macro and meso-scale structural features during supergene processes as highly mineralised areas were coinciding with faulted and folds zones. A spatial relationship between the distribution of mineralisation and sedimentary architecture has been demonstrated to show a strong correlation in the Lubambe License Area. This interpretation is consistent with ore genesis models of sedimentary-hosted copper deposits.

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