D. Phil. / The Kalahari Manganese Deposit (KMD) is the largest of five erosional relics of the Hotazel Formation that are located near Kuruman in the Northern Cape Province of South Africa. Manganese ores are exploited from the lowermost of three manganiferous beds that are interbedded with banded iron-formation (BIF) and hematite lutite, that together constitute the Hotazel Formation. Two major ore types have been delineated previously, viz. low grade braunite lutite of the Mamatwan-type, and high grade oxidic ores of the Wessels-type, with the latter spatially restricted to the northern KMD. Genesis of the ores was temporally distinct, with the Mamatwan-type ore considered as a sedimentary-diagenetic precursor to the hydrothermally altered Wessels-type ore. Drill core samples from the Nchwaning-Gloria area of the northern KMD were analysed, with the aim to better characterise ore genesis, with emphasis on ore alteration. A second part of the study aimed at the application of mineralogical and geochemical information to aspects of ore smelting for the production of Mn alloy for use in the steel industry. Methods employed were drill core logging, X-ray diffraction (XRD), petrography, electron probe microanalysis (EPMA), major and trace element (including REE) analysis (employing artificial neural networks for evaluation of elemental trends), and stable isotope (C and O) analysis. Significant effort was invested in method development for quantitative mineralogical modal analysis using Rietveld refinement of XRD data. The study shows that a number of ore types can be differentiated in the northern KMD on the basis of mineral assemblage, grade, texture and geochemical characteristics. The ores are broadly classified into least altered (LA), partially altered (PA) and advanced altered (AA) types. The LA ores are low grade (<40 wt%Mn) Mn lutites, with dolomite-group carbonate a significant component in addition to braunite. Serpentine is a ubiquitous trace mineral, and boron is a characteristic trace element hosted predominantly by braunite in these ores. Ores of the PA type comprise either braunite-hausmannite-calcite or hausmannite-calcite assemblages, are fine to coarse grained, and display intermediate Mn grades (40-45 wt%Mn). They exhibit a transitional trace element signature. Advanced altered ores may be classified into five different types, based on mineral assemblages that contain hausmannite and/or braunite as significant minerals. Carbonates occur predominantly in the form of calcite, present in minor to trace proportions. Textures vary from fine to very coarse grained, and high Mn grades (typically >45 wt%Mn), are recorded. Trace elements of significance include Zn, associated with hausmannite, B, associated with massive braunite and a number of trace minerals, and P, typically present in trace quantities of apatite. In terms of ore genesis, mineralogical, geochemical and geological considerations suggest that Mn (and Fe) originated from submarine hydrothermal vents, from which it travelled in hydrothermal plumes, prior to rapid deposition ~2.2 Ga ago. Diagenesis followed soon after deposition, through redox reactions involving organic matter and higher oxides of Mn to produce the braunite-carbonate assemblage primarily observed in LA ores. The carbonate:oxide ratio and nature of the carbonates varied slightly depending on fluctuations in organic matter flux to the sediment, as well as marine bicarbonate concentrations. Metamorphism, in relation to diagenesis and metasomatism, is poorly understood, but is perceived to have resulted in serpentine formation, as observed in LA and PA ores.

A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2016 / Since the latter part of the 20th century to the present, we have seen growing concerns about the potential collapse of socio-ecological systems due to climate change. On the other hand, palaeoenvironmentalists, archaeologists and anthropologists consistently point to evidence of how Homo-sapiens have survived within climate variability underpinned by an embodied/embedded relationship to their environments. Archaeological data shows how indigenous groups such as the Bushman have inhabited landscape features such as caves for longer than 10 000 years and thus survived through periods of climate variability. Another well researched element of Bushman life is their ritual practices. Given the low supply of livelihood resources within the contexts where such communities have survived, this study hypothesised a possible relationship between Bushman ritual practices and their long-term resilience when faced with variability. Using the Holocene habitation of the Wonderwerk Cave as the main case study, this study explored the relationship between people, place and ritual. Furthermore, the study applied phenomenology as the primary data collection method. The resultant first-person experience guided the researcher in engaging with secondary data from archaeology and ethnography. The study found that Bushman ritual practices such as trance constituted a critical adaptation tool in response to perpetually variable environments. Through such practices and their related tools such as art, space and myth, such communities managed to sustain a synchronised dialogue with place thus facilitating for ongoing dissolution of maladaptive behaviour. Another key finding is that our inability to change constitutes a key characteristic of our species today as we have been seduced into the trap of our deep psychic longing for existential continuity. The study argues for an architecture for resilience whose primary role would be to facilitate higher fluidity in our embeddedness to place and allowing for faster and trauma-free transitioning in synchronicity to our changing environments. In conclusion, the study finds that our own contemporary climate change has implications far beyond the techno-scientific understanding which has prevailed so far and is instead calling to be understood as an existential phenomenon to be primarily resolved through relevant/responsive ritual practices to facilitate our own transitioning and continued resilience. / MT2017

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015 / Three new methods for determining the structural index and source distance for magnetic field data are presented. These methods require only the calculation of the first and second order analytic signal amplitudes of the total field and are applicable to both profile and gridded data. The three methods are first tested on synthetic data and then on two real datasets to test for applicability and repeatability. It was found that each method had different strengths and weaknesses and thus one method cannot be favoured over the others. Cooper (2014) describes how to calculate the distance to source over both profile and gridded data given a user defined structural index. Often however, particularly in the case of real data, the structural index is not known or varies over the surveyed area. These three new methods however do not require any user input since the structural index is calculated thus making them more applicable to regions of unknown geology. It was found that the first of the three new methods, the multi-distance inversion method, was best used as an edge-detection filter, since the use of higher order derivatives resulted in increased noise levels in the distance to source calculation. The third of these new methods, the unconstrained inversion method, discussed in Chapter 7, not only solves for the structural index but also determines the depth of the source. In that particular case, the structural index is used as a rejection filter, whereby, depth solutions associated with structural index values outside of the expected range are deemed to be invalid. Unlike the third new method, the first two methods require the distance to source to be calculated via the approach described by Cooper (2014) (which requires the user to define the structural index), the results of which are later rescaled by the calculated structural index to yield what is termed a rescaled distance to source. All three of the new methods are fully automatic and require no user control. The techniques were first tested on both profile and gridded theoretical data over sources with known structural index values. All of the methods were able to estimate the structural index of each of the particular sources and give depth estimates that varied from the true depth by less than 20 percent (with deeper sources being more inaccurate). Noise was also added to the theoretical data in an attempt to assess how the methods can be expected to perform with real data. It was found that when applied to noisy data, these methods performed equally well to slightly worse, than when the method developed by Cooper (2014) was used. As a real world case study these three new methods were tested on aeromagnetic data collected over the Kuruman Military Area, Northern Cape, South Africa. Regional deformations as well as later intrusive dykes and cross cutting faults were imaged by the chosen depth determination procedures. The dolerite dykes in the area were found to occur between 20 to 60 m deep. While the sand cover was estimated to be between 30 to 40 m thick. Overall, the techniques yield distance to source estimates that differ by less than 15 m, over sources, to the results obtained by using the source distance method (Cooper, 2014). To test for repeatability a second aeromagnetic dataset, collected over a dyke swarm within the Bushveld Complex, South Africa was considered. Again comparable (less than 15 m over sources) depth estimates were made between the unconstrained and constrained inversions. Since the distance to source estimates produced by these new unconstrained inversion methods are comparable to those produced by constrained inversion (Cooper, 2014) the project can be deemed successful.

No description available.

The subject of BIF genesis, particularly their environmental conditions and ocean chemistry at the time of deposition and their evolution through time, has been a subject of much contentiousness, generating a wealth of proposed genetic models and constant refinements thereof over the years. The prevailing paradigm within the various schools of thought, is the widespread and generally agreed upon depositional and diagenetic model(s) which advocate for BIF deposition under anoxic marine conditions. According to the prevailing models, the primary depositional environment would have involved a seawater column whereby soluble Fe²⁺ expelled by hydrothermal activity mixed with free O₂ from the shallow photic zone produced by eukaryotes, forming a high valence iron oxy-hydroxide precursor such as FeOOH or Fe(OH)₃. An alternative biological mechanism producing similar ferric precursors would have been in the form of photo-ferrotrophy, whereby oxidation of ferrous iron to the ferric form took place in the absence of biological O₂ production. Irrespective of the exact mode of primary iron precipitation (which remains contentious to date), the precipitated ferric oxy-hydroxide precursor would have reacted with co-precipitated organic matter, thus acting as a suitable electron acceptor for organic carbon remineralisation through Dissimilatory Iron Reduction (DIR), as also observed in many modern anoxic diagenetic environments. DIR-dominated diagenetic models imply a predominantly diagenetic influence in BIF mineralogy and genesis, and use as key evidence the low δ¹³C values relative to the seawater bicarbonate value of ~0 ‰, which is also thought to have been the dissolved bicarbonate isotope composition in the early Precambrian oceans. The carbon for diagenetic carbonate formation would thus have been sourced through a combination of two end-member sources: pore-fluid bicarbonate at ~0 ‰ and particulate organic carbon at circa -28 ‰, resulting in the intermediate δ¹³C values observed in BIFs today. This study targets 65 drillcore samples of the upper Kuruman and Griquatown BIF from the lower Transvaal Supergroup in the Hotazel area, Northern Cape, South Africa, and sets out to explore key aspects in BIF carbonate petrography and geochemistry that are pertinent to current debates surrounding their interpretation with regard to primary versus diagenetic processes. The focus here rests on applications of carbonate (mainly siderite and ankerite) petrography, mineral chemistry, bulk and mineral-specific carbon isotopes and speciation analyses, with a view to obtaining valuable new insights into BIF carbonates as potential records of ocean chemistry for their bulk carbonate-carbon isotope signature. Evaluation of the present results is done in light of pre-existing, widely accepted diagenetic models against a proposed water-column model for the origin of the carbonate species in BIF. The latter utilises a combination of geochemical attributes of the studied carbonates, including the conspicuous Mn enrichment and stratigraphic variability in Mn/Fe ratio of the Griquatown BIF recorded solely in the carbonate fraction of the rocks. Additionally, the carbon isotope signatures of the Griquatown BIF samples are brought into the discussion and provide insights into the potential causes and mechanisms that may have controlled these signatures in a diagenetic versus primary sedimentary environment. Ultimately, implications of the combined observations, findings and arguments presented in this thesis are presented and discussed with particular respect to the redox evolution and carbon cycle of the ocean system prior to the Great Oxidation Event (GOE). A crucial conclusion reached is that, by contrast to previously-proposed models, diagenesis cannot singularly be the major contributing factor in BIF genesis at least with respect to the carbonate fraction in BIF, as it does not readily explain the carbon isotope and mineral-chemical signatures of carbonates in the Griquatown and uppermost Kuruman BIFs. It is proposed instead that these signatures may well record water-column processes of carbon, manganese and iron cycling, and that carbonate formation in the water column and its subsequent transfer to the precursor BIF sediment constitutes a faithful record of such processes. Corollary to that interpretation is the suggestion that the evidently increasing Mn abundance in the carbonate fraction of the Griquatown BIF up-section would point to a chemically evolving depositional basin with time, from being mainly ferruginous as expressed by Mn-poor BIFs in the lower stratigraphic sections (i.e. Kuruman BF) to more manganiferous as recorded in the upper Griquatown BIF, culminating in the deposition of the abnormally enriched in Mn Hotazel BIF at the stratigraphic top of the Transvaal Supergroup. The Paleoproterozoic ocean must therefore have been characterised by long-term active cycling of organic carbon in the water column in the form of an ancient biological pump, albeit with Fe(III) and subsequently Mn(III,IV) oxy-hydroxides being the key electron acceptors within the water column. The highly reproducible stratigraphic isotope profiles for bulk δ¹³C from similar sections further afield over distances up to 20 km, further corroborate unabatedly that bulk carbonate carbon isotope signatures record water column carbon cycling processes rather than widely-proposed anaerobic diagenetic processes.

Text in English with abstracts in English, Afrikaans and Tswana with keywords in English and Tswana / Displacement in the South African context is a complex and diverse phenomenon which is under-researched, particularly from the point of view of post-resettlement stress. The Meetse-a-tala community from Groenwater, Northern Cape, was resettled in 1964 and returned in 1999 to their ancestral land after a 25 year struggle to do so. The community anticipated that the land would present all the natural resources they had in 1964, but unfortunately, when they returned, the outlook seemed a lot different. / Verskuiwing in die Suid-Afrikaanse konteks is ‘n diverse en komplekse verskynsel wat nog nie voldoende nagevors is, veral vanuit die oogpunt van post-hervestigingsstres nie. Die Meetse-a-tala-gemeenskap van Groenwater in Noord-Kaap is in 1964 hervestig en het in 1999 teruggekeer na die land van hul voorouers na ‘n 25 jaarlange stryd om dit te bewerkstellig. Die gemeenskap het verwag dat die gebied weer al die natuurlike hulpbronne sou aanbied wat hulle in 1964 gehad het, maar ongelukkig, met hul terugkeer, het die vooruitsigte heel anders gelyk. / Tiragalo ya go fudusiwa ka dikgoka mo bokaong jwa Aforikaborwa e tlhagisa marara a a farologaneng ka ntlha ya dipatlisiso tse di lekanyeditsweng malebana le kgatelelo ya maikutlo e e amanang le morago ga go fudusiwa. Baagi ba Meetse-a-tala go tswa kwa Groenwater, kwa Kapabokone, ba itemogetse tiragalo ya go fudusiwa ka 1964 mme morago ga go kgaratlha dingwaga tse 25 go boela kwa lefatsheng la badimo ba bona, ba boetse ka 1999. Baagi ba ne ba solofetse gore lefatshe le tlaa ba neela ditlamelo tsotlhe tsa tlholego tse ba neng ba na natso fa ba tsamaya ka 1964, mme ka bomadimabe, e rile fa ba bowa, ba fitlhela le lebega le farologane thata. / Anthropology and Archaeology / M.A. (Anthropology)