3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Three dimensional geometry of the bushveld complex derived from potential field modelling(2018) Cole, JanineTwo dimensional gravity models and a few magnetic models limited to short profiles in the eastern sections of the BC have been used to propose conflicting geometries for the Rustenburg Layered Suite (RLS), especially between the western and eastern lobes; one school argued for completely separate intrusions, while the other proposed that the outcropping lobes are connected at depth. These competing models suggest different emplacement models. They provide a valuable starting point, but, 2.5D potential field modelling is not well suited to modelling complex three dimensional geology. Also, in previous work the magnetics or only the gravity data were modelled independently. Here I present the first full three dimensional potential field forward modelling of the central and southern Bushveld Complex (BC) which has been used to test the geometry of the Bushveld Complex in areas obscured by younger geological cover. Both gravity and magnetic data have been used to develop a geological model that is consistent with both data sets. Joint 3D modelling of regional gravity and magnetic data combined with published crustal thickness models derived from broadband seismic tomography studies were used to create a 3D model of the central and southeastern sections of the BC, as well as the southern part of the northern lobe. Eight downhole logs with more than 730 000 new density and magnetic susceptibility measurements from the RLS were combined with existing data to determine values for Bushveld Complex lithologies that were used in the model. The 3D model has a complex geometry with thick continuous RLS in most of the western lobe, thinner RLS in the south-eastern lobe, but a disrupted RLS in the eastern lobe. Large domes of Transvaal dolomite or thicker granites and granophyre in the eastern lobe interrupt the continuity of the RLS. The western and eastern lobes are therefore broadly connected, with major disruptions largely in the eastern lobe. However, they are not separate intrusions, but represent a single magma chamber affected by pre-existing and syn-magmatic updoming. The model includes the whole thickness of the crust and requires dense material at the crust mantle boundary. Thus, for the first time, I have imaged the remnants of magma staging chambers. The chambers, constrained by the extent of the diffuse crust-mantle transition as determined from teleseismic data, underlie the whole Bushveld Complex, but is thickest under the northern, south-eastern and western parts of the complex. I propose feeders that correlate with the chambers in the northern lobe near the large gravity high near Polokwane and in the south-eastern lobe.Item Management of a manganese resource, Postmasburg manganese field(2018) Perold, JacquesThe primary objective of this research report is to qualify and quantify risks and benefits that may derive from the use of resistivity data when managing PMF manganese resources. To achieve this goal a 3D geological resource model of the project area were constructed using available geological and geochemical data. A second geoelectric resource model were constructed using the same data applied in the construction of the geological model and available resistivity data over the study area. Errors made (Mc Carthy, 2003) were identified by comparing differences in geological interpretation, resultant estimated stripping ratios and mineral resource estimates. For comparative purposes both models were adjusted by limiting their extent to an equivalent 3D modelling space. Vast differences resulted from the two modelling regimes employed. These differences relate to: The shape, position and orientation of the dolomite floor and associated pinnacles; Areas of mineralization and differentiation of areas with ferruginous and manganiferous alteration for the geoelectric model; Inability to delineate the ferruginous zone of alteration as a separate domain in the geological model, due to insufficient geological and chemical data; The shape, position and orientation of overlying quartzite; and The shape, position and orientation of the unaltered shale. The financial risks of not conducting resistivity surveys, when modelling manganese resources associated with the PMF, impact both exploration expenditure and profitability. The study estimated that, as the geological environment is challenging, exploration expenditure will increase by approximately 46.8% if resistivity surveys are not conducted prior to drilling. The increased expenditure is a direct consequence of inaccurate placing of boreholes, the large number of boreholes required to be drilled and the intensive sampling and analytical regimes needed. Over estimation of manganese resource reduce stripping ratios and resulted in the over estimation of gross profit by as much as 1.55 times for the geological model. This is clearly demonstrated by estimated differences in gross profit for lumpy ore of ZARm 408.640 for the geological and ZARm 263.571 for the geoelectric model resources. It is clear that, due to the complex depositional environment of the manganese deposits of the Western Belt of the Postmasburg Manganese Field, exploration regimes based on traditional drilling and sampling are limited, costly and produce results that are potentially very misleading. The addition of resistivity data clearly demonstrated vast changes in geological interpretation, resulting in substantial differences in mineral resource estimation and subsequent profitability.Item A proposition for how musical competencies could benefit 3D character animators when synchronising performances to pre-recorded music using Khumba as a case study(2017) Jacobs, Carelize JohaniEven though a significant amount of research has been conducted over the years on film music and animation, these two fields of academic study mostly developed independently from each other. Little attention has been given to these two fields in terms of how they are deployed together, particularly after the ‘Golden Age’ of Hollywood filmmaking. This study, from an animation perspective, contributes to this need for research with an investigation and eventual proposition that will elucidate and advance the integration and contemporary deployment practices and processes of music and character animation. The aim of the study was to identify and suggest the ideal musical competency set a character animator would benefit from and, to propose an approach for notation in which these competencies are used to digitally animate characters moving to the beat of pre-recorded music for a 3D animation feature-length film. A qualitative research approach was followed and the research methodology consisted of a historical analysis, studying current practices and the analysis of a case study. The South African 3D computer-animated feature film, Khumba (2013), produced by Triggerfish Animation Studios, was used as the case study. Reasons for its suitability were twofold: Firstly because the researcher could easily access the animators (which was essential) and secondly, because the film had the musical scenes required to conduct the research. The focus was on the musical scenes in the film. The integration of animation and music in a scene was analysed, allowing the researcher to show how Khumba animators could have benefited from the suggested musical competencies and from using the proposed method when animating musical scenes. A universally agreed approach for notation in animating-to-music doesn’t exist. However, a method known as the bar sheet was used by earlier animators, requiring them to have a basic knowledge and understanding of music. This study proposes the reintroduction of an adapted version of the original bar sheet, digitised for assimilation with contemporary technology. A plug-in for Autodesk Maya was also proposed as an output of the research. Ultimately, this research has the potential to lead to a heightened proficiency of character animators when animating musical scenes in 3D feature-length films. In addition, the research could prompt a universally agreed approach for notation which combines traditional and new methods and techniques. The adoption of this approach could also lead to changes in the working practices of film making teams and the work flow within production pipelines.