ETD Collection

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Has files: YesSubject: search.filters.subject.Mines and mineral resources--Evaluation

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    Mineral resource evaluation of a platinum tailings resource: a case study
    (2017) Muthavhine, Mashudu Innocent
    The project investigated the application of geostatistical techniques in evaluating a mechanically deposited platinum tailings resource. The project was undertaken on one of the Anglo American Platinum tailings dams, the identity of which cannot be revealed, due to the agreement in place or permission given. Remnant unrecovered minerals of economic potential still exist in tailings dams. These unrecovered minerals have influenced several mining companies to turn their attention to the economic potential that still exists in tailings, making them a key strategic component of their resources and reserves. Geostatistics has been developed and thoroughly tested or improved to address challenges experienced in estimating in situ geological ore bodies. The main aim of this Research Project is to test whether these fundamental principles and theories of geostatistics are relevant and appropriate in evaluating man-made ore bodies, such as a Platinum tailings dam, without any significant changes needed on the underlying principles or estimation algorithms. The findings on the Case Study tailings resource can be applied in the evaluation of other tailings dams, as well as any other man-made structures such as low grade rock dumps, muck piles, with related characteristics. A standard approach (methodology) was followed to evaluate the Case Study tailings resource. Drilling and sampling was conducted through sonic drilling. It is a dry drilling technique that is suitable for sampling unconsolidated particles such as tailings. Thereafter, 2 samples were sent to the laboratory to establish grade (concentration) of Platinum Group Metals (Platinum, Palladium and Rhodium), Gold and Base Metals (Copper and Nickel). Density was also measured, and comprehensively analysed as part of variables of interest in this research. Statistical analyses were performed on all variables of interest contained in the dam: which are Platinum (Pt), Palladium (Pd), Gold (Au), 3E (two PGMs plus Gold), Copper (Cu), Nickel (Ni) and Density. The underlying statistical distributions of all metals and density were found to be non-symmetrical and slightly positive skewed. The skewness of the distributions was established to be marginal. Differences between raw data (untransformed) averages and the log-normal estimates were analysed and found to be insignificant. As such Ordinary Kriging of untransformed data was concluded to be the appropriate geostatistical technique for Case Study tailings resource. Analysis of mineralisation continuity (variography), a pre-requisite for geostatistical techniques such as Ordinary Kriging applied on the case study tailings resource, was also performed. Reasonable and sufficient mineralisation continuity was established to exist in the Case Study tailings resource. Although characterised by high nugget effect, these spatial correlations were established to be continuous with ranges of influence well beyond 450 m in all variables. Anisotropic variograms were modelled for all variables and are comprised of nested structures with two to three spherical models. Resource estimation was conducted through Ordinary Kriging in Datamine. All the seven variables were successfully interpolated into each cell of the 5m x 5m x 5m block model. Rigorous validation of the resource model was performed to establish the quality and reliability of the estimation carried out. Estimated resource model was analysed against the original borehole data, through comparison of grade profiles, statistical analysis, QQ Plots and histograms. The grade profile was recognised to be similar between boreholes (5 m composites) and the adjacent cells that have been estimated. Furthermore, statistical analyses revealed minimal differences between means of the estimated model and the original borehole data: the highest difference being 1.7% realised on 3E, followed by 1.1% on Density and Gold (Au). The rest of the variables (Pt, Pd, Cu, and Ni) have differences that are below 1%. 3 QQ plots and histogram were plotted from resource model with 5m x 5m x 5m cells and 5 m composited boreholes. Although these data sets are of different (slightly incompatible) supports, the intended purpose of comparing distributions was achieved. QQ plots and histograms revealed approximately identical shaped distributions of the two data sets, with some minor deviations noticeable in graphs of only two variables (Au and Density) that are underlain by two populations. The validation process carried out gave a compelling assurance on the quality and reliability of the resource model produced. The Case Study tailings resource therefore is successfully estimated by Ordinary Kriging. The results achieved on the Case Study tailings dam has successfully proved that geostatistical principles and theories can confidently be applied, in their current form or understanding, to any man-made tailings resource
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    A framework to harmonise mineral asset valuation methodologies with existing and emerging financial reporting requirements
    (2017) Njowa, Godknows
    One of the consequences of globalisation in the extractive industries is the necessity to apply uniform accounting and valuation standards that are clearly understood and consistently applied by the global stakeholder community. At the beginning of the 20th century it was realised, mainly by the major mining countries that the extractive industries is one of the biggest sectors globally. In the extractive industries the single most important asset is the Mineral Resources and Mineral Reserves, yet this is not reflected anywhere in the financial statements. The major mining countries, through their mining institutes, realised that there was a need to develop standards and guidelines to align and standardise the definitions of Exploration Results, Mineral Resources and Mineral Reserves, which was achieved through the CRIRSCO template. From the accounting fraternity, several organisations also realised the need for an accounting standard specific to the extractive industries, specifically for financial reporting. Attempts by the IVSC and IASB to develop a global accounting standard for the extractive industry attests to the global requirement to develop internationally recognised valuation guidelines or a global framework for the valuation of mineral assets. Both the mining institutions and accounting standards setting boards have been working in isolation to develop a globally acceptable standard or guideline for the extractive industries, and neither has been successful due to the inherent complexities. The harmonisation of the national codes for reporting of Mineral Resources and Mineral Reserves through the CRIRSCO template, provides global common understanding. However, the national mineral asset valuation (MAV) codes, are needed to develop a similar international template. The CRIRSCO template provided a strong foundation on which the IMVAL template was developed. As part of this research a framework was developed to harmonise the national MAV Codes. Various authors have argued that there is no globally accepted standard or guideline for the valuation of extractive industries assets, nor is there a specific accounting standard for extractive industries. MAV is still an emerging discipline, coupled with the fact that financial reporting in the mineral industry is not yet fully developed, as IFRS 6 appears to be the only mineral specific financial reporting standard. This is supported by the fact that currently there is a lack of a comprehensive accounting standard for the extractive industries to guide the accounting, recognising and presenting these assets in the primary financial statements. This thesis argues that there is a gap between reflecting and accounting for Mineral Resources and Mineral Reserves in the financial reporting systems, and how these mineral assets are valued and reported. These identified gaps between MAV methodologies and financial reporting requirements formed the basis of this work. Hence this thesis develops a framework to harmonise the existing and emerging financial reporting requirements and MAV methodologies. This framework is applicable to developmental projects and operating mines, and was validated by applying the framework to a real life case study. Turquoise Hill Resources (Turquoise), which owns Oyu Tolgoi copper-gold mine in Mongolia, was selected as a good case study, due to the fact that Turquoise owns and operates this single multicommodity mineral asset, with information available in the public domain. Hence the value of Turquoise on the stock exchange is driven by the fundamental value of the mineral asset only. The results of the proposed framework showed the highest correlation coefficient of 0.77, meaning that there is a strong correlation between proposed framework and the proxy company value selected. It is concluded that the proposed framework to harmonise MAV methodologies and the emerging financial reporting requirements can be applied to estimate values for companies in the mineral industries.