The petrology of the Sutherland Commonage olivine melilitite intrusives have been investigated using petrographic and chemical methods. The occurrence consists of a ring dyke which surrounds a centrally located sill complex. The rock of the ring dyke is a typical melilitite which consists of olivine in a groundmass of melilite, clinopyroxene, opaque spinel, nepheline and perovskite. The sill complex is a multiple intrusion and is comprised of a lower green melilitite and an overlying (and younger) grey melilitite. The green melilitite is deuterically altered and the original mineralogy is destroyed to a large extent. The grey melilitite contains autoliths of the green and is a fairly typical monticellitic melilitite in which phenocrysts of olivine are set in a groundmass of melilite, monticellite, opaque spine!, nepheline and perovskite. Microprobe analyses of clinopyroxenes indicate that they are aluminous titanian diopsides and salites which exhibit complex zonation patterns. They record magmatic conditions ranging from the intrusive stage to a final phase of magmatic evolution during which a vapour phase evolved after the majority of the groundmass minerals had crystallised. The chemistry of olivine phenocrysts suggests that the parent magma to the Commonage intrusives accumulated in a temperature-zoned reservoir at the base of the lithosphere. Large, unzoned olivine phenocrysts crystallised in this chamber. Subsequent rupture of the chamber and ascent of magma led to supercooling and the crystallisation of abundant, strongly zoned phenocrysts of smaller size. Olivine crystallisation continued until the magma reached crustal levels. It is inferred from the chemistry of chromites and magnetites that the magma in the ring dyke was more evolved than those in the sill complex and that very oxidising conditions prevailed in the grey melilitite during the crystallisation of magnetite in this intrusive type. The high fO₂ may have resulted from the degassing of CO₂ after intrusion. Major and trace elements have been analysed for in eleven whole rock samples and the ⁸⁷Sr/⁸⁶Sr ratio was determined for seven of the same samples. The results of the geochemical study suggest that the Commonage melilitites were derived by the melting of a recently metasomatised region of the asthenosphere, probably under the influence of an ocean-island-type hotspot situated in the lower mantle.

<p>The reservoir quality (RQ) of well E-BA1 was characterized using thin sections and core samples in a petrographic study. Well E-BA1 is situated in the Bredasdorp Basin, which forms part of the Outeniqua Basin situated in the Southern Afircan offshore region. Rifting as a result of the break up of Gondwanaland formed the Outeniqua Basin. The Bredasorp Basin is characterized by half-graben structures comprised of Upper Jurassic, Lower Cretaceous and Cenozoic rift to drift strata. The current research within the thesis has indicated that well E-BA1 is one of moderate to good quality having a gas-condensate component.</p>

A Thesis Submitted to the Faculty of Science, University of the Witwatersrand , Johannesburg for the Degree of Doctor of Philosophy / The Phalaborwa Complex, northeastern Transvaal, South Africa, consists of the main body of clinopyroxenites and subordinate phoscorite, carbonatite and syenite which is surrounded by numerous pipe-like bodies of syenitic compositions and rare clinopyroxenites. Clinopyroxenites of the main complex are characterized by cumulus textures formed by separation and accumulation of coprecipitating clinopyroxene, apatite and phlogopite. Potassium feldspar is an intercumulus phase in feldspathic pyroxenite. "Inch-scale" layering of clinopyroxene, apatite and phlogopite formed as in situ cumulus layering near the outer contact of the complex early in the cooling of the magma. Breccias of monomineralic assemblages such as glimmerite and massive pyroxenite reflect breaking up of early formed rocks by magmatic currents. Clinopyroxenes from clinopyroxenites are characterized by Fe/(Fe+Mg) = 0.07-0.29, low T i 02 (0.00-0.25%), A 120 3 (0.00-1.63%), N a 20 (0.00-1.06%), and Cr, and high Wo component and Sr. Micas from pyroxenites have Fe/(Fe+Mg) = 0.12-0.28, low T i 02 (0.17-1.73%) and have reverse and normal pleochroism and increasing A1 with increasing Fe/(Fe+Mg). Mineral compositions among feldspathic, massive and micaceous pyroxenites overlap; no zonation of the complex from outer contact inward is discernible with respect to the Fe and Mg content. However, phlogopites in "inch-scale" layering have low Fe/(Fe+Mg) of 0.12 and have reverse pleochroism due to F e 3+ entry into the Al-deficient tetrahedral site. Micas from phoscorite and carbonatites have reverse pleochroism, Fe/(Fe+Mg) = 0.05-0.58, low T i 02 (0.00-0.84%) and decreasing A1 with increasing Fe/(Fe+Mg). Olivines range from F o79 to F o91 and have very low Ni content (<0.06% N i O ) . Olivines interpreted as xenocrysts have Fo 84 to F o 8 7 . One of the olivine xenocrysts has an NiO content of 0.29%. Minerals from carbonatites have initial 87S r / 86Sr ratios of 0.70393-0.70623 and 0.71022 and minerals from clinopyroxenites have values of 0.71152-0.71242. Smallscale inhomogeneities exist within samples. Postcrystallization processes can account for variations within samples, but cannot account for variations within a rock type or for raising initial 87S r / 86Sr ratios of pyroxene from 0.7039 to 0.7115. Magmas forming pyroxenites and some carbonatites were generated in a high Rb/Sr mantle from isotopically distinct sources. Hence, liquid immiscibility and differentiation are not viable mechanisms for relating these rocks to one another. Mixing of magmas and assimilation of crust may account for isotopic variations within a rock type. U-Pb dating of uranothorianite and baddeleyite from phoscorite and carbonatite yields an age of 2047+11/-8 m.y. Rb-Sr dating of phlogopites gives widely disparate apparent ages. Nine phlogopites yield an isochron of 2012 + 19 m.y. One sample of phlogopite gave ages of 1661-2360 m.y. in nine different determinations. Older micas may be present in the Phalaborwa complex. Based on the two methods, a best age of the Phalaborwa complex is 2030 + 18 m.y. Two of the syenite pipes, Kgopoeloe and Spitskop, show different levels of emplacement. Kgopoeloe is highly brecciated from a fluid derived from the syenite. Spitskop contains minor breccia and represents multiple injection of syenite. At Spitskop, inward crystallization of the second syenite forms a ring syenite and central syenite; both syenites have cumulus enrichment of minerals. Feldspathic pyroxenite of the Guide Copper Mine is cogenetic with the pyroxenites of the main complex and contains clinopyroxenes with oscillatory zoning. Fluctuations in f02 may be attributed to formation of an immiscible sulphide liquid. Multiple intrusion of the Phalaborwa Complex is proposed. Initial injection of potassic, probably ultrabasic, liquid formed the pyroxenites. A second intrusion of low-silica, carbonate-rich magma formed phoscorite and banded carbonatite. A third intrusion of carbonatite liquid formed the transgressive carbonatite. Magmatic, cumulus processes dominated the formation of the main complex. The syenites of Kgopoeloe and Spitskop are not cogenetic with rocks of the main complex. / AC2017

The volcanic and sedimentary Nsuze Group constitutes the lower part of the / Thesis (M.Sc.-Geology)-University of KwaZulu-Natal, Pietermaritzburg, 1984.

<p>The reservoir quality (RQ) of well E-BA1 was characterized using thin sections and core samples in a petrographic study. Well E-BA1 is situated in the Bredasdorp Basin, which forms part of the Outeniqua Basin situated in the Southern Afircan offshore region. Rifting as a result of the break up of Gondwanaland formed the Outeniqua Basin. The Bredasorp Basin is characterized by half-graben structures comprised of Upper Jurassic, Lower Cretaceous and Cenozoic rift to drift strata. The current research within the thesis has indicated that well E-BA1 is one of moderate to good quality having a gas-condensate component.</p>

M.Sc. (Geology) / The south-easternmost Kaapvaal Craton is composed of scattered inliers of Archaean basement granitoid-greenstone terrane exposed through Phanerozoic cover successions. In addition, erosional remnants of the supracrustal Mesoarchaean Pongola Supergroup unconformably overlay this granitoid-greenstone terrane in the same inliers. Into this crust a variety of Precambrian intrusions occur. These are comprised of SE-, ENE- and NE-trending dolerite dykes. Also, the Hlagothi Complex intrudes into Pongola strata in the Nkandla region, particularly the quartzites of the basal Mantonga Formation. The whole area, including Phanerozoic strata, has in turn been intruded by Jurassic sills and dykes related to the Karoo Large Igneous Province. All the rocks of the Archaean inliers, with the exception of the Jurassic sills and dykes have been subjected to greenschist facies metamorphism and deformation, with petrographic, Ar-Ar geochronologic and palaeomagnetic studies attesting to this. This metamorphism and deformation is associated with the Mesoproterozoic orogeny from the nearby Namaqua-Natal Mobile Belt located to the south. This orogeny has a decreasing influence with distance from the cratonic margin, and is highly variable from locality to locality. However, it is generally upper greenschist facies up to a metamorphic isograd 50 km from the craton margin. Overprints directions seen within the palaeomagnetic data confirm directions associated with the post-Pongola granitoids across the region and the Namaqua-Natal Mobile Belt. The dolerite dykes consist of several trends and generations. Up to five different generations within the three Precambrian trends have potentially been recognised. SEtrending dykes represent the oldest dyke swarm in the area, being cross-cut by all the other dyke trends. These dykes consist of two possible generations with similar basaltic to basaltic andesite geochemistry. They provide evidence of a geochemically enriched or contaminated magma having been emplaced into the craton. This is similar to SE-trending dolerite dyke swarms across the Barberton-Badplaas region to the north from literature. In northern KwaZulu-Natal the SE-trending dolerite dyke swarms have been geochronologically, geochemically and paleomagnetically linked to either ca. 2.95 or ca. 2.87 Ga magmatic events across the Kaapvaal Craton. The 2866 ± 2 Ma Hlagothi Complex is composed of a series of layered sills intruding into Nkandla sub-basin quartzites of the Pongola Supergroup. The sills consist of meta-peridotite, pyroxenite and gabbro. At least two distinct pulses of magmatism have been recognised in the sills from their geochemistry. The distinct high-MgO units are compositionally different from the older Dominion Group and Nsuze Group volcanic rocks, as well as younger Ventersdorp volcanic rocks. This resurgence of high-MgO magmatism is similar to komatiitic lithologies seen in the Barberton Greenstone Belt. It is indicative of a more primitive magma source, such as one derived from a mantle plume. A mantle plume would also account for the Hlagothi Complex and the widespread distribution of magmatic events of possible temporal and spatial similarity across the craton. Examples include the layered Thole Complex, gabbroic phases of the ca. 2990 to 2870 Ma Usushwana Complex, and the 2874 ± 2 Ma SE-trending dykes of northern KwaZulu-Natal already described above and dated herein. A generation of NE-trending dolerite dykes in northern KwaZulu-Natal can also be palaeomagnetically linked to this event with either a primary or overprint direction. Flood basalts seen within the upper Witwatersrand and Pongola Supergroups (i.e., Crown, Bird, Tobolsk and Gabela lavas) may also be related. This large, voluminous extent of magmatism allows us to provide evidence for a new Large Igneous Province on the Kaapvaal Craton during the Mesoarchaean. This new Large Igneous Province would encompass all of the above mentioned geological units. It is possible that it could be generated by a shortlived transient mantle plume(s), in several distinct pulses. This plume would also explain the development of unconformities within the Mozaan Group. This is reasoned through thermal uplift from the plume leading to erosion of the underlying strata, culminating in the eruption of flood basalts coeval to the Hlagothi Complex. Marine incursion and sediment deposition would occur during thermal subsidence from the plume into the Witwatersrand-Mozaan basin. This magmatic event also assists in resolving the apparent polar wander path for the Kaapvaal Craton during the Meso- to Neoarchaean. Between existing poles established for the older ca. 2.95 Ga Nsuze event, to poles established for the younger ca. 2.65 Ga Ventersdorp event, a new magnetic component for this ca. 2.87 Ga magmatic event can be shown. This new component has a virtual geographic pole of 23.4° N, 53.4° E and a dp and dm of 8.2° and 11.8° for the Hlagothi Complex, with a similar magnetic direction seen in one generation of NE-trending dolerite dykes in the region. This new ca. 2870 Ma addition to the magmatic barcode of the Kaapvaal Craton allows for comparisons to be made to other coeval magmatic units on cratons from around the world. Specific examples include the Millindinna Complex and the Zebra Hills dykes on the Pilbara Craton. Precise age dating and palaeomagnetism on these magmatic units is needed to confirm a temporal and spatial link between all the events. If substantiated, this link would assist in further validating the existence of the Vaalbara supercraton during the Mesoarchaean. After the Hlagothi Complex event, different pulses of magma can be seen associated with the Neoarchaean Ventersdorp event. A generation of NE-trending dolerite dykes in the region was dated herein at 2652 ± 11 Ma. In addition, a primary Ventersdorp virtual geographic pole established in Lubnina et al. (2010) from ENE-trending dolerite dykes was confirmed in this study. This ENE-trending dolerite dyke has a virtual geographic pole of 31.7° S, 13.6° E and a dp and dm of 7.0° and 7.2°. This date and virtual geographic poles from NE- and ENE-trending dolerite dyke swarms in northern KwaZulu-Natal match up with NE- and E-trending palaeostress fields seen in the Neoarchaean Ventersdorp and proto- Transvaal volcanics by Olsson et al. (2010). Both generations of dolerite dykes also demonstrate variable geochemistry. The NE-trending dolerite dyke swarm is tholeiitic, and the ENE dolerite dyke swarm is calc-alkaline. In addition, some of the tholeiitic NE-trending dolerite dykes have a similar magnetic component to NE-trending dolerite dykes much further to the north in the Black Hills area according to Lubnina et al. (2010). This magnetic component is also similar to the Mazowe dolerite dyke swarm on the Zimbabwe Craton. The NE-trending dolerite dykes in the Black Hills area differ geochemically from those in northern KwaZulu-Natal though, but are also of ca. 1.90 Ga age. The Mazowe dolerite dyke swarm was linked to the dyke swarm of the Black Hills dyke swarm through palaeomagnetic studies. The Mazowe dolerite dyke swarm however is geochemically similar to the NE-trending dolerite dykes of northern KwaZulu-Natal, creating greater complexity in the relationship between the three dyke swarms. It is clear from the complex array of dolerite dyke swarms and other intrusions into these Archaean inliers of northern KwaZulu-Natal, that much more work on the dykes within the south-easternmost Kaapvaal Craton needs to be done. This will resolve these complex patterns and outstanding issues with regard to their palaeo-tectonic framework.

Magister Scientiae - MSc / The reservoir quality (RQ) of well E-BA1 was characterized using thin sections and core samples in a petrographic study. Well E-BA1 is situated in the Bredasdorp Basin, which forms part of the Outeniqua Basin situated in the Southern Afircan offshore region. Rifting as a result of the break up of Gondwanaland formed the Outeniqua Basin. The Bredasorp Basin is characterized by half-graben structures comprised of Upper Jurassic, Lower Cretaceous and Cenozoic rift to drift strata. The current research within the thesis has indicated that well E-BA1 is one of moderate to good quality having a gas-condensate component. / South Africa

M.Sc. / This dissertation deals with meteorites, but from a few different perspectives. As of 2000, there are 49 known meteorites that have been recovered from South Africa, including the new Merweville chondrite, which is first described and classified here. This represents only about 1.5% of worldwide falls and finds. Perhaps because of the relatively small number of specimens, and a possible resulting drop in interest amongst the scientific community, research on extant South African meteorites has declined in recent years. In this study, new results are presented for two South African meteorites, the Malvern howardite, and the newly recovered Merweville chondrite. In addition, South African public knowledge and awareness of meteorites and planetary sciences is discussed, and remedial recommendations are made. The Malvern howardite is a rare type of polymictbreccia. New petrographic, mineralogical and geochemical studies of clasts reveal an abundance of impact-melt clasts, with lesser amounts of cataclastic, granoblastic and metal and sulphide-rich clasts. The matrix of Malvern is dominated by comminuted pyroxene, very likely derived from mechanical degradation of pre-existing, pyroxene-richimpact-meltclasts. Chondritic clasts, including carbonaceous chondrites, have been reported in similar howardites (e.g. Washougal, Jodzie and Kapoeta); such clasts were searched for, but not found in our specimens of Malvern. To investigate the social impact of meteorite studies, a survey of Grade 11 and 12 pupils and first year university students in South Africa was undertaken to determine their level of literacy, interest and awareness of meteorites and planetary sciences. Students in Johannesburg and Cape Town were chosen to represent different societal sectors, including school students from disadvantaged and advantaged communities. The results indicate that learners with poor results in awareness and literacy are still very keen on the subject. The advantaged learners outperformed their disadvantaged colleagues in most categories, proving that the discrepancy between them is still a factor and should be dealt with, but only 20% of all students asked have visited a museum before. Based on these results, it is recommended that much more emphasis be put on science and technology in South African schools. Taking learners to science and natural history museums or associated institutions are also very important in generating interest.

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.

D.Phil. / This study which describes rocks of the Upper Critical Zone of the Bushveld Complex is subdivided into three parts. The main rock type of the Upper Critical Zone, the noriteanorthosite, is the subject of the first part. Inclusions in chromite and plagioclase were studied. The inclusions' in chromite were observed at different stages of their formation. The chromite crystals usually overgrow plagioclase, pyroxene and hydrous minerals (biotite, amphibole and clinozoisite) trapping them at grain boundaries or triple junctions of chromite host grains. With 'continuous growth of the host minerals the inclusion starts changing its shape from elongated to circular and the hydrous mineral proportion of the inclusion increases. Simultaneously amphibole changes its composition from pargasitic to tremolitic...