>Magister Scientiae - MSc / With the latest advancements in the Pletmos Basin it is imperative to understand and study how sandstone reservoirs are affected by clay minerals. Clay minerals are an influential component in sandstone reservoirs worldwide and thus have an impact on the reservoir quality and petrophysical properties. The present research was aimed at assessing the effects of clay minerals on the petrophysical properties of sandstone reservoirs from the Offshore Pletmos Basin. This was done by integrating geological (wireline logs and core analysis), geochemical (XRD and pore water chemistry) and petrographical (QEMSCAN and thin section petrography) analysis to highlight the effects of clay minerals on the intrinsic properties (porosity, permeability and fluid saturation) on reservoirs encountered within the two wells (Ga- Q1 and Ga – S1). The results highlight pervasive quartz cementation as well as the presence of clay minerals: Glauconite (Illite group), Kaolinite (Kaolinite group), Clinochlore (Chlorite group) as the dominant clay minerals and Calcite as the dominant cement in both well Ga – Q1 and well Ga – S1. The most abundant clay mineral in both wells is Glauconite. This clay mineral had a more profound effect on the petrophysical parameters compared to the other clay minerals. The clay minerals occur as pore–filling Kaolinite and pore–bridging Glauconite and pore–lining Clinochlore. As a result, the clay minerals affected the pore connectivity (permeability) more than the pore spaces (porosity). This is confirmed by the petrophysical analysis where both wells have extremely low permeability and good porosity values. The study concludes that the presence of Glauconite, Kaolinite, Clinochlore and Calcite in both wells (Ga-Q1 and Ga-S1) had an adverse effect on the permeability more compared to the porosity in sandstone reservoirs. Due to the high volume of clay and high clay mineral content in well Ga-Q1, the petrophysical parameters were more adversely affected compared to well Ga-S1. As a result, we see better petrophysical properties (porosity and permeability) in the sandstone reservoir from well Ga-S1 due to intense bioturbation. The reservoir quality of well Ga-S1 is much better compared to well Ga – Q1 because water saturation averages at 42% and gas saturation averages at 58%, has decent porosity averages at 12% but low permeability ranges of 0, 1 – 4mD. / 2021-09-30

Thesis(Ph.D.(Physics)) -- University of Limpopo, 2020 / Surface properties of pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS) and sphalerite (ZnS) most thermodynamically stable surfaces have been studied using first priniciples density functional theory. The most stable surfaces showed the highest surface exposure as it covered a higher percentage of the surface area on morphologies. The interaction of water with such sulphide surfaces was also investigated; the structures of sulphide minerals surfaces were changed in the presence H2O molecules. The surfaces of FeS2 and ZnS relax most while those of CuFeS2 and PbS surfaces change slightly in the presence of H2O molecules. The results on the effect of chain length of DTPs and DTCs on the enthalpies of adsorption on pyrite, galena, chalcopyrite and sphalerite have shown that an increase in chain length of the DTPs resulted in an increase in the enthalpies of adsorption trend for pyrite, galena and sphalerite. This is an important observation since the ligand is the same in all cases and therefore the effect is due to the role of the alkyl group Moreover, we noted a decrease of enthalpies of adsorption with an increase of DTCs chain lengths on pyrite, galena, chalcopyrite and sphalerite. The effect of the branching of the hydrocarbon chain length of the dithiocarbamates on the enthalpy of adsorption of pyrite was investigated. The results show that the configuration of the alkyl chain length of the same carbon number has an influence on the enthalpy of adsorption. Furthermore, the results indicate that there was minimal enthalpy of adsorption when DeDTP was dosed to galena, chalcopyrite and sphalerite minerals as compared to DeDTC and ethyl xanthate. On the other hand, the enthalpies of adsorption of DeDTP on pyrite were very high which represented a greater exothermic reaction than for any of the DeDTC and ethyl xanthate. The bond distance between thiol collector and the surface is consistent with the corresponding calculated adsorption energies. The Mulliken population of S-Fe/S-Pb/S-Zn bond for the adsorption of eX on CuFeS2 surface are high compared to PbS and ZnS surfaces, which indicated that there is a strong covalent bond between S and Fe atoms as compared to S-Pb and Pb-Zn bonds. Such observations are consistent with results of other thiol collectors. It was seen that the Mulliken atomic charges populations of CuFeS2, PbS and ZnS surface layers are different before and after DTPs adsorption. The charges of Fe atom reduce, which indicates that the Zn and Pb atoms become more positive and the Fe atom becomes more negative. In addition, there are changes in the charges of S atoms in ZnS and PbS surface layers before and after H2O absorption, suggesting that the presence of water would affect the adsorption of thiol collector. The densities of states (DOS) of the thiol collectors on surfaces of sulphide minerals have shown a strong hybridisation between the S 3p-orbital HOMO, metals (Fe, Pb, Zn) 3d-orbital for pyrite and chalcopyrite, 6p-orbital for galena and (3d and 4s)-orbitals for sphalerite. The collector S 3p-orbital reduces to zero states on the surfaces of Fe, Pb and Zn atoms. The Fe-S bond population for DeDTP is lower than that of DispDTP and DbDTP in pyrite, respectively. For chalcopyrite the DeDTP Fe-S population is higher than both DispDTP and DbDTP: similar trends were observed for Pb-S and Zn-S, however, the Pb-S bonding was less covalent as compared to the Fe S in chalcopyrite. The DTPs Fe-S bond population is generally higher in chalcopyrite than in pyrite. Mulliken charges analysis indicated that the DTPs S atoms lost charges and the metals gained with a decreasing DTPs chain length for pyrite: a similar trend was observed for chalcopyrite. The DTPs gained electrons from galena and sphalerite surface. For DTCs pyrite and chalcopyrite surface Fe atoms gain more electrons in the presence of DeDTP than other DTPs, while galena and sphalerite lost most electrons in the presence of DbDTC than other DTCs. As for xanthate, the Mulliken bond charges indicated that the S atoms and the metals lost charges, suggesting that some charges reside at the internuclear region between the metals and sulphurs (M– S). These show that electron charges are collector and mineral dependent; collector would be an electron acceptor or donor depending on the mineral makeup. A comparison of the computational results, isothermal titration calorimetry (ITC) and microfloatation experiments for the interaction of DeDTP, DeDTC and eX with pyrite and galena was made. The calculated adsorption energies between thiol collectors and mineral surfaces were always more exothermic than the experimentally determined ones. In computational calulations, water adsorption was found to reduce the reactivity of Fe and Pb atom for the interaction with thiol collectors and bring the adsorption energies closer to the magnitude of the experimental values. FeS2 (100) surface heat of adsorption depict similar trends to experimental recoveries from microfloation for DeDTP, DeDTC and eX, while FeS2 (111) heats of adsorptions for DeDTP and DeDTC are consistent with ITC experimental results. Lastly, calculated DeDTP and DeDTC adsorptions on the PbS (100) are also consistent with experimental recoveries. / National Research Foundation (NRF), South African Minerals of Metal Institution (SAMMRI) and University of Limpopo (UL)

>Magister Scientiae - MSc / There has been increasing interest in finding alternative sources for Rare Earth Elements (REEs) due to their application in green energy and Coal Fly Ash (CFA) has been found to be a viable potential source. Thus investigations on the feasibility of recovering REEs from CFA and the possibility of optimizing the current recovery techniques have become popular. The main focus in the investigations has been to use equipment and products that are environmentally sustainable and economically efficient. In addition, studies have shown that there is a relationship between the particle size of CFA and the REE concentration, which can potentially increase the recovery of REEs. However, there have been inconsistencies in the findings of this relationship.

Bibliography: pages 150-158. / Gahnite (ZnAl₂O₄) is commonly associated with sulphide mineralization in metamorphosed massive sulphide deposits, and also occurs in marbles, pegmatites and quartz veins. Its formation has been attributed to the breakdown of Zn-staurolite or desulphidation of sphalerite during metamorphism. The stability of zinc-rich spinels under a wide range of metamorphic conditions in a variety of lithologies results in its persistence in rocks where many other prograde, high temperature minerals and sulphides have been altered. Thfs has resulted in various investigations into its use in exploration and potential for determining metamorphic parameters. With the interest in finding new ore bodies and in determining the metamorphic history and mineralogy in Namaqualand, some gahnite-bearing localities have been investigated in this study.

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Yes / Sida requested the Helpdesk to present a ‘snapshot’ and analysis of the problem of conflict minerals in the Great Lakes region, and particularly of the Democratic Republic of Congo (DRC). In anticipation of instructions in the forthcoming country/results strategy for the DRC, Sida will use the report in order to identify possible Swedish efforts in the field. Sida requested that report should be presented with both a perspective on the Great Lakes region in general, as well as a more detailed analysis of the situation in DRC in a regional perspective.

Concerns about beef production are growing among consumers, questioning the use of antibiotics, hormones, and metaphylactic treatments, as well as its environmental footprint. Therefore, beef production systems need to be more efficient to increase productivity while using less resources to become sustainable and reduce environmental impact. There is a need to develop and apply non-pharmaceutical alternatives to improve health, feed efficiency and performance of beef cattle. We investigated four different targeted strategies to enhance performance of beef cattle: 1) The effect of an injectable multi-mineral complex supplementation for grazing beef cows on overall mineral status, fertility, and subsequent offspring performance. Two doses of the trace mineral injection increased in pregnancy rate after artificial insemination, with a greater impact on cows with poor body condition score; 2) Inclusion of a yeast-derived product combining live yeast (probiotics) and cell wall components (prebiotics), on performance and physiological responses of beef steers during backgrounding and finishing phases. Including a yeast-derived product into a finishing diet containing monensin did not improve performance, physiological responses, and carcass quality of feedlot cattle. Nonetheless, inclusion of the yeast derived product as a substitute of monensin during the backgrounding and finishing phases decreased feed intake without affecting growth, with an overall improvement in feed efficiency; 3) Use of phytotherapy (condensed tannins) to reduce protozoa parasites load and prevent coccidiosis in peripartum beef heifers and their newborn calves. Daily supplementation of condensed tannins reduced coccidia load in heifers and newborn calves, although this reduction was transient; and 4) following the smart farming approach, validate the use of an automated scale system for grazing or feedlot beef cattle, which was able to accurately measures body weight in grazing and feedlot systems for growing and mature beef cattle while reducing cattle handling, without disrupting feeding behavior, decreasing the probability of animal lesions, accidents and optimizing labor. / Doctor of Philosophy / Diet diversification is a response of a growing economy, growing population, and urbanization, which increases the demand of meat products, especially beef, in substitution of staple foods. However, concerns around beef production and its impact on the environment are becoming more relevant for consumers. The need to produce more with less resources requires a sustainable intensification process. Specifically, beef cattle production systems are less efficient when compared to poultry or swine in terms of time and amount of feed required. Beef production systems need to focus on environmental and socially conscious strategies to satisfy the demand, increase animal health, productivity, and profitability. One approach is based on nutritional strategies and applied technologies to enhance productivity, efficiency, welfare, and health. In this dissertation we present three different strategies to improve efficiency of beef production systems: 1) using injectable trace minerals supplementation to ensure adequate mineral nutrition in grazing cows, improving their pregnancy rate to artificial insemination, particularly when cows are in poor body condition; 2) use of yeast as natural additives to successfully substitute antibiotics as growth promotants in feedlot diets with an improvement in feed efficiency; 3) use of secondary plant compounds, such as tannins, to substitute prophylactic antibiotic utilization for coccidiosis in cows and newborn calves. We demonstrate three successful strategies that can improve health, feed efficiency and reproductive performance of beef cattle, all of which are important to achieve greater productivity and profitability in beef production systems.

<p> A method is presented for the determination of trace quantities of the rare earth elements and yttrium in calcareous minerals by X-ray fluorescence analysis. Initial chemical concentration of the rare earths is accomplished by scavenging their insoluble hydroxides on a ferric hydroxide precipitate and serves the further purpose of elimination of matrix absorption effects which dampen sensitivity when the raw minerals are analysed.</p> <p> Triplicate analyses are given for La, Ce, Sm and Y in a calcite-fluorite-apatite skarn rock and for each of the three minerals of this rock. Apatite and calcite are enriched in all the rare earths investigated relative to the whole rock, while fluorite shows a relative depletion. The apatite is enriched in the rare earths relative to the calcite. Peak height ratios of Nd, Eu, Er, Lu, Gd+Ho and Dy+Tm in each of the separated minerals to the whole rock show the same trends as the quantitative data and also indicate that apatite and fluorite show a stronger affinity for the lanthanides of low atomic number than for those of higher atomic number. The abundances of the rare earths in the apatite show the same dependence on ionic radius as has been noted by other workers. The whole rock and each of the minerals which it contains are enriched in all the rare earths relative to chondrites.</p> <p> The rare earths have preferentially entered the lattices of those minerals which provide a stronger rare earth-anion bond.</p> / Thesis / Bachelor of Science (BSc)