Bibliography: leaves 116-125. / The accuracy of the experimental (Canil, 1994; T-Canil) and the empirical (Ryan et al., 1996; T-Ryan) calibrations of the Ni geothermometer has been evaluated on two suites of geochemically and geothermobarometrically well characterised mantle xenoliths from Matsoku and Jagersfontein by comparison to the more commonly used conventional geothermometers. The two published calibrations of the Ni geothermometer are in agreement to within ±500C in the temperature range of ~900°C to 1200°C. Outside this temperature range, the two calibrations differ by between 75 and 150°C. The importance of the Ni geothermometer in diamond exploration and the studies of the mantle makes the resolution of this discrepancy very important. In addition to issues of calibration, errors in the determination of trace levels of Ni abundances in garnets may affect the accuracy of the Ni geothermometer. A 'reliable' Ni in garnet dataset was, therefore, required to minimise errors associated with Ni compositions used in temperature determination by Ni geothermometry. Thus, Ni compositions of garnets determined by PIXE, LA-ICP-MS and SIMS were compared to select the most 'reliable' dataset. Four matrix-matched secondary garnet standards were developed for the cross-checking and testing of the accuracy of data. The standards were developed by multi-method analyses, which included PIXE (using both the GeoPIXE and GUPIX software programmes for data reduction), LA-ICP-MS and solution ICP-MS. PIXE and LA-ICP-MS data were found to agree to within their 2σ errors of, respectively, 2 to 10% and 4 to 12% for a concentration range of ~15 to 112 ppm Ni. However, PIXE analyses were found to be superior in terms of smaller beam width, allowing several repeat analyses, and analysis of small and altered garnets thereby producing a relatively larger dataset.

Includes bibliographical references. / Hout Bay is situated on the Atlantic seaboard of the Cape Peninsula, in the Western Cape Province of South Africa approximately 17 km southwest of Cape Town. Hout Bay is a southward opening bay that hosts a fishing harbour and coastal residential town. This study was initiated to map the marine geology of Hout Bay and to quantify and explain the sediment dynamics of the area. This is important as Hout Bay has the only substantial accumulation of Quaternary sediments on the Atlantic Seaboard of the Cape Peninsula. The Hout Bay study area was saturated with the latest in cutting-edge geophysical techniques to collect detailed and comprehensive bathymetric, sidescan sonar, magnetic, seismic and beach profiling data. Collectively these data can be used to map offshore geological units as well as infer how Hout Bay has responded to the varying changes in sea-level throughout the Quaternary and allow for the reconstruction of the geological evolution of the Hout Bay seafloor.

Includes bibliographical references. / The migration of granitic melt is the main mechanism that facilitates upward movement of heat and mass, and the chemical differentiation of the continental crust. Whereas the processes of melt segregation and emplacement are relatively well understood, melt ascent mechanisms are more speculative. Specific outstanding questions include the structure of melt conduits, the driving forces of melt ascent, and the timescales involved. The Central Zone of the Damara Belt presents a snapshot of melt migration through subsolidus, mid-crustal rocks. Outcrops selected for detailed investigation are representative of a variety of mestasedimentary rock types and strain environments, and all contain pervasive and interconnected leucosome networks representative of melt movement through, and emplacement into these rocks.

Includes bibliographical references (leaves 132-141). / The Maningoza Suite is a set of Mesozoic igneous sub-volcanic to volcanic complexes situated in the Mahajanga sedimentary and volcanic basin in central-west Madagascar. The Maningoza Suite is exposed in an area roughly 50 x 80 km and consists of the Ambereny, Ambohitrosy, Ankibobozaka, Berevo, Fonjay and Maningoza Complexes. The Maningoza Complex also consists of the Ambolodia, Antanetilava and Sambao Formations.

This study deals with the West Rand Group (formally the Lower Division of the Witwatersrand System) sediments within an area of approximately 500 km east of Heidelberg. The aim of the study was to interpret from the stratigraphy, lithology, petrology and sedimentary structures, the type of processes which were involved in the deposition of the arenaceous units of the West Rand Group, the current dispersal pattern and the probable, equivalent modern day depositional environment. The extent of diagenesis and metamorphism was investigated by using two white mica techniques. The chemistry of the shales was related to its mineralogy and a detailed study of the geochemical profile below the West Rand/Central Rand unconformity was undertaken. The West Rand Group east of Heidelberg is made up of a thick (3400 m) succession of alternating arenaceous and argillaceous units. It has traditionally been subdivided into three Subgroups - the Hospital Hill, Government and Jeppestown. Each Subgroup is divided into three formations on the basis of laterally persistent markers. Facies analysis has indicated that deposition occurred in the following environments in the different Formations: (1) the first shale horizon of the Orange Grove Quartzite Formation marks a change from "high" energy-wave dominated to lower energy - tide dominated conditions. The basal conglomerates and overlying trough crossbedded facies are interpreted as either platform beach or inlet deposits while ebb tidal deltas and local storm deposits characterise the rest of the arenaceous succession (2) the shales and thin sublitharenites of the Park- Town Shale Formation were formed by suspension deposition of mud alternating with periodic sand influxes while the banded iron formations and magnetite rich zones probably represent distal shelf muds. (3) the 'sago'-textured units of the Brixton Formation were deposited by storm ebb surge currents in conjunction with tidal currents (4) at the base of the Promise Quartzite Formation offshore (sub- tidal shelf) marine conditions prevailed. Nearshore sequences and finally a braided stream setting of the Platte type is interpreted for the rest of the succession (5) the poor outcrop of 'tillite' in the Coronation Shale Formation made it impossible to delineate the facies associated with the till (6) the immature subgreywackes of the Witpoortjie Formation below the Government Reef represent subtidal shelf and inshore tidal flat deposits. The Government Reef marker represents an ancient beach deposit with onshore migrating sandbars and ripples moving in response to shoaling waves. The Blue Grit marker is interpreted as either a fossil submarine rockfall or a cannon and fan valley deposit (7) the shales of the Jeppestown Subgroup represent proximal shelf deposits while the sandstones formed as a response to tidal, shelf and possibly fluvial processes. The Weber crystallinity index indicates that the mineral assemblage (white mica, chlorite and quartz) are low grade. The West Rand Group's Hb(rel) value of 150 corresponds to an approximate temperatures of 290°C. The study areas baric constraints are similar to the conditions for the Hercynian metamorphism in the eastern Alps. The relative amounts of clay mineral present in a sample was calculated from its bulk chemistry. Chlorite, illite and muscovite (in that order) are the major clay phases present. The trace element abundance indicates that the source rocks for the West Rand Group in the study area are similar in petrology to the source rocks of the Fig Tree sediments. The trace elements - Sr, Ni, Rb, ca, Zn, Cr - can be used to discriminate the shales of the West Rand, Central Rand and Fig Tree Groups. The Jeppestown shale immediately below the Main Conglarerate has a geochemical profile that has traits of a palaeosol which has subsequently been modified by diagenesis and the percolation of ground waters. Two models are proposed for the deposition of the Hospital Hill Subgroup and the Government Subgroup by integrating the writer's detailed facies analysis approach with the work done by previous workers in other outcrop areas.

This thesis documents a microseismicity study in the interior of South Africa. The study area is centred on Leeu Gamka in the Western Cape province, a tectonically stable intraplate setting and is therefore expected to be seismically quiet. The International Seismological Centre (ISC) catalogue reported localised anomalous seismicity in the region between 2007 and 2013 with local magnitudes up to 4.5. The short apparent duration and time history of this anomalous reported seismicity is likely a reporting artefact. An array of 23 geophones was deployed for three months (March - June) in 2015, covering an area of 60 km - 65 km centred on the zone of anomalous seismicity. Using this array, I identified a total of 106 earthquakes over this period, with almost all events clustering in a surprisingly small area (75% of the epicentres fall within a one square kilometre block). Double-difference relocation resolved the hypocentres onto a structure with an apparent NW - SE orientation, consistent with large-scale fabric that can be recognised in satellite imagery. The focal mechanisms display strike-slip faulting with the fault plane likely in a NW - SE orientation, consistent with the distribution of the earthquakes. The velocity model was tested by varying the thickness of the Karoo supergroup to investigate the sensitivity of the depths of the earthquakes. An average hypocentral depth of approximately 6 km was calculated for the earthquakes, assuming a depth to the base of the Karoo of 5km. This places the earthquakes just below the base of the Karoo in the Cape Supergroup. The magnitudes of the earthquakes recorded range from -1.5<ML<0.4, with a magnitude of completeness of -0.8, and follow a Gutenberg-Richter distribution with the b-value range of 1.23 - 2.07 calculated within a 90 % confidence range. The presence of such a structure has implications for shale gas exploration in that wastewater pumping in an area with active faulting could trigger larger and more frequent earthquakes, as seen in case studies in the central states of America, in particular, Oklahoma.

Includes bibliographical references. / Ten Gough Island primary magma compositions were calculated for use in constrained forward modelling. The primary magma compositions were calculated by the addition of 14-28% clinopyroxene and equilibrium olivine, in equal proportions, back into the primitive lava compositions in 1 % increments until an Mg# of 69 was reached. Constrained forward modelling methods were used in determining the chemical and mineralogical nature of the mantle source region as well as the required melting parameters required in producing the Gough Island suite of lavas. The models indicate that the full compositional range, as well as the crossing REE patterns at Dy, can be produced through ~5-8% equilibrium melting of a mantle source region composed of garnet lherzolite or ~30-50% melting of a garnet pyroxenite source.

Includes bibliographical references (leaves 185-193). / Small scale diver-assisted diamond mining has taken place since 1990 in the shallow marin (&lt;30 m water depth) portions of Mining Licence 45 (Elizabeth Bay) between Halifax Island and Elizabeth Bay along the southwestern coast of Namibia. These operations in the northern part off the coast of the Sperrgebiet have produced almost 400,000 carats over a period of 17 years. Although sparse records remain from the early days, sufficient data from various sources were collected, collated and summarised to make meaningful observations. From historic and current diamond diving records, 4 submarine areas which have yielded high returns were described in terms of their geomorphology, sedimentology and diamond occurrence. Using detailed geophysical survey data (Sidescan Sonar and Multi-beam Bathymetry), the deposition of diamonds at these sites were modelled in GIS-based reconstructions. The diamond size frequency distribution (SFO) of the Shallow Marine (0 to -30 m) deposits in the study area is similar to the proximal aeolian deposit mined on land at Elizabeth Bay and the deeper Midwater (-30 to -70 m depth) deposits situated southwest of the study area.

Includes bibliography. / The Kaapvaal Craton is one of the best preserved of all Archean cratons. It is partially covered by the supracrustal sequences of the Witwatersrand, Ventersdorp and Transvaal Basin (and correlated Griqualand West Basin), which span almost a billion years (~3.1 to 2.2 Ga). This thesis describes and interprets eight newly available seismic reflection profiles, acquired by the vibroseis method to 6 seconds TWT, and totaling ~720 km in length. New stratigraphic and structural features are identified across three main regions: the Kaapvaal Craton's western margin, the northern margin or Bushveld lines (flanking the Thabazimbi-Murchison Lineament and across the western extremity of the Bushveld Igneous Complex) and the Kaapvaal Craton interior. The seismic data was interpreted using Charisma seismic interpretation software, Geoframe version 3.6 (developed by Geoquest, Schlumberger) on a UNIX, SUN workstation.

South Africa is an energy intensive economy which primarily relies on the burning of fossil fuel such as coal. The South African coal energy sector accounts for approximately 420 million metric tonnes of carbon dioxide emitted per annum. With present alarming concerns with regards to the ever-increasing atmospheric carbon dioxide concentrations resulting in global warming and climate change, several mitigation strategies have to be implemented. A majority of Carbon Capture and Storage (CCS) technologies require monitoring from potential leakages, making the process expensive. However, a benign technology exists to permanently store away anthropogenic CO₂ with products obtained instantaneously. This CCS technology is known as Mineral Carbonation. The fundamental procedure is a reaction between (magnesium - calcium - iron) silicates and CO₂ to form carbonates. The products of from the reaction require no monitoring and the fear of leakage of CO₂ is eliminated. Moreover, the carbonates from this technology are useful in the road, agriculture and building industries. The CO₂ storage capacity in mineral carbonation exceeds other CCS techniques. The South African mineral industry annually produce immense tonnages of ultramafic mine tailings. Due to the generally fine nature of the tailings, no further cost would be incurred in grinding the material. The platinum group metal (PGM), nickel and copper companies are examples of industries that produce massive tonnages of which could serve as potential feedstock for the purposes of mineral carbonation. Recent studies have shown that, the potential feedstock could sequester close of 70% of the annual CO₂ produced at Secunda, South Africa. A mineralogical investigation into the mineral carbonation potential of mine tailings was conducted using samples from seven mining companies. Four of the mining operations considered (Impala, Rustenburg, Amandelbult and Mogalakwena) are PGM operations mining the Merensky, Upper Group 2 (UG-2) and Platreef. Nkomati was another operation selected for the study, with samples collected from the Main Mineralised Zone (MMZ) and Chromititic Peridotite Mineralized Zone (PCMZ). Tailings material from the dormant O'okiep operation was the seventh, chosen for the study. To determine the suitability of these tailings for mineral carbonation, the particle size, surface area and mineral for each individual operation was accounted using Malvern, BET analysis, XRF, QXRD and QEMSCAN respectively. The overall fine-grained nature of the mine tailings was manifested in the particle size distribution results were sizes ranged from d(0.5) = 33.67 (Nkomati) to d(0.5) = 231.45 (Impala). The range in surface area was 1.45 m²/g (Amandelbult) to 5.89 m²/g (Nkomati). A theoretical carbonation capacity ranking scheme was developed where the seven mining companies selected for this study were graded based on their suitability for mineral carbonation. Three distinct factors made up the classification criteria of the ranking scheme. The first was the carbonation capacity. This was determined by the mineralogy, the Rco2 value and the tonnage of mine waste produced annually. The second major factor was the reactivity (ignoring kinetics) of the tailings. In this case, the particle size distribution and surface area of the respective mine tailings were considered. Thirdly, the distance from the CO₂ (Secunda) source was taken into account as the cost of transporting CO₂ to the mineral carbonation facility should be weighed up. In using these principles, Nkomati was unquestionably ranked first while O'okiep was rated last priority among the seven operations. The motive behind was to improve upon the theoretical carbonation capacity ranking scheme and in turn examining a variety of South African mine tailings for the purposes of detailed mineral carbonation studies in South Africa.