Theses and Dissertations

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Browsing Theses and Dissertations by Author "Amponsah-Dacosta, Francis"

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    Evaluation of Nebulas Gold Deposit in Giyani Greenstone Belt, Limpopo Province, South Africa
    (2018-05-18) Mavhungu, Mbofholowo Emmanuel; Amponsah-Dacosta, Francis; Mhlongo, Siphiwe
    Giyani Greenstone Belt is known to host significant amount of gold of which about 10 tonnes were extracted from the belt in the 19th century. Due to increased gold price and mining practices that make it economic to mine low-grade ore deposits, major gold deposits within the belt have been the main targets for exploration while Nebulas Prospect remain unnoticed. To make the Nebulas Prospect attractive for investment, its gold mineralization potential needed to be investigated. The main purpose of this study was to conduct assessment of the probable gold mineralization in the Nebulas Prospect and its economic viability. The specific objectives were to establish the gold mineralized zones within the Nebulas Prospect, develop a geological model showing the geometry and placement of gold in the subsurface, establish gold grade distribution and its economic implication, and select the most appropriate and practical mining method for exploitation of the established gold deposit. The research approaches used in achieving these objectives comprised of knowledge driven predictive modelling of Nebulas Prospect to derive prospectivity map demarcating the area with the potential of hosting gold mineralization. Magnetic survey was conducted in geological permissive areas, thereby establishing boundaries of mineralization, both lateral and vertical. Geological and subsurface gold grade distribution were carried out by means of trenching and pitting. The integration of the geological, geophysical and geochemical data using Geosoft 8.5 and ArcGIS 10.5 assisted in development of a gold deposit model that model illustrates distribution and concentration of gold. Results of the investigation reveals that Banded Iron Formation (BIF) dominates the southern part of the study area while quartz vein and schist dominate the northern part. The application of knowledge driven predictive modelling established mineral prospectivity map for Nebulas Prospect, which narrowed the potential area for further investigation. The area located outside the boundary of prospective area indicated low mineralization potential compared to highly mineralized zone within geological permissive boundary. The two mineralize zones which exits in the Nebulas Prospect are separated by pegmatite intrusion which is observed from magnetic data presentation. The gold is hosted within BIF, schist and quartz vein. The highest concentration observed value of 10.65 g/t is hosted in serpentine schist and lowest significant of 1.24 g/t in BIF. The gold grades are higher in schists than in BIF and quartz veins. The Nebulas Prospect present significant measured iv gold mineral resource with substantial economic potential. The evaluation of the technical aspects of the Nebulas Gold Deposit, which include grade and tonnage was estimated through longitudinal vertical section method. The gold hosted within Banded Iron Formation (BIF) comprise a measured gold resource of 6957.6 t at an average weighted grade of 2.22 g/t Au. However, the gold mineralization hosted within tremolite-mica schist, serpentine schist and quartz veins comprise a measured gold resource of 3919.37 t with average grade of 3.8 g/t Au. The Nebulas Gold Deposit contain a significant grade and tonnage. At an assumed currently economically mineable cutoff grade 1 g/t Au, Nebulas Prospect has a measured resource of 10877 t at a weighted average grade of 2.79 g/t Au. Analytical hierarchy process (AHP) was used to prioritize the factors affecting mining method selection and ranking of potential mining method, technically appropriate for the established gold deposit in Nebulas Prospect. Open pit mining method was identified as appropriated for extraction of the Nebulas Gold Deposit.
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    Evaluation of strata conditions and performance of support systems of the Emerald Shaft Gold Mine in Gauteng Province of South Africa
    (2025-09-05) Mphaphuli, Sathiel; Amponsah-Dacosta, Francis; Mhlongo, Sphiwe Emmanuel
    The creation of underground excavations causes disturbances in the rock mass, leading to geotechnical uncertainty and increased risk of fall of ground or backbreak. The incompetency of the rock mass, high tensile fractures, and concentration of horizontal virgin and mining-induced stresses pose significant threats to both safety and production, highlighting the need for effective strata control measures. This study aimed to evaluate the strata conditions and performance of support systems of the Emerald Shaft Gold Mine to ensure long-term stability. The objectives of the study included reviewing the mine design and layout, determining geological conditions and their influence on the rock strata, examining the performance of the support systems used in the raise and production stopes of the Emerald Shaft Gold Mine., and recommending appropriate strategies for strata control. A comprehensive geotechnical investigation was conducted at the Emerald Shaft Gold Mine to characterize the rock mass and inform mine design. The study applied a multi-disciplinary approach including field profiling, geological and geotechnical mapping, field test and laboratory analysis, field observations, and analytical and numerical modelling. The investigation involved a detailed analysis of rock mechanic data, geological conditions, and raise and stope support systems to evaluate the stability of the mine. The study revealed complex geological conditions, variable rock competency, and distinct mechanical properties. The rock mass quality was compromised by regional geological features, such as dykes and faults. The findings highlighted the importance of site-specific characterization, comprehensive support design, and targeted support measures to ensure safe and efficient mining operations. The study also identified areas prone to rockfalls, fall of ground incidents, and stope instability, emphasizing the need for robust support design and regular monitoring. The study concluded that a tailored support design approach, considering tendon performance, ground conditions, and stress loading, is essential to ensure optimal ground stability and prevent rockfalls. The recommended support measures include the installation of grouted dowels, pre-stressed elongates, and fibre-reinforced shotcrete. Regular monitoring and maintenance of support systems are crucial to ensure their effectiveness and prevent accidents. The study's findings and recommendations provide valuable insights for mine design, support strategies, and safety protocols at the Emerald Shaft Gold Mine, and can be applied to similar mining operations. This study contributed significantly to the understanding of strata conditions and support systems in Emerald Shaft Gold Mine. The research provided new insights into the complex geological conditions and variable rock competency of the mine, highlighting the importance of site-specific characterization and tailored support design. The findings of the study and recommendations offered valuable contributions to the existing knowledge on strata control and support systems, providing a framework for improving mine safety and efficiency. Specifically, this research demonstrated the effectiveness of a multi-disciplinary approach in evaluating rock mass quality and designing optimal support systems and highlighted the need for regular monitoring and maintenance to ensure the effectiveness of support measures.