A study of the geology of the Vaalbank and Lady Frere areas in the Karoo Basin of South Africa using gravity, magnetic and gamma-ray spectrometry data: implications of groundwater potential

The Vaalbank and Lady Frere areas belong to the Elliot, Molteno and Burgersdorp Formations, that are part of the sedimentary succession of the Beaufort Group in the Karoo Basin of South Africa. There is Quaternary alluvium covering the mudstone, sandstone and shale rocks of the Beaufort Group. Dolerite and gabbro sills of the Karoo age have intruded the whole area. A number of investigations were carried out for the study namely field observations, petrographic, X-ray diffraction, airborne gamma-ray spectrometry, aeromagnetic and gravity analyses. Twenty four rock samples were collected in the field from fresh outcrops of the Karoo dolerites, Burgersdorp and Molteno formations. The measured densities and porosities show that the Karoo dolerite suite has the highest average dry density of 2.771 g/cm3 and the lowest average porosity of 3%. The Burgersdorp Formation has an intermediate average density of 2.458 g/cm3 and an intermediate average porosity of 5.4%. The Molteno Formation has the lowest average density of 2.190 g/cm3 and the highest average porosity of 14.5%. Petrographic and geochemical investigations were carried on 19 rocks samples collected in the field to determine the mineralogy character using microscopic and XRD analyses. Both petrographic and X-ray diffraction analyses revealed that the sandstones of the study area are composed of quartz as their primary mineral and feldspars as the secondary mineral. The dolerite consists of euhedral structured minerals such as magnetite, pyroxene, plagioclase and amphibole. The gamma ray maps show high spectrometric values are associated with the Burgersdorp Formation, alluvium cover and dolerite dykes. The low spectrometric values are associated with dolerite sills and ring complexes. The boundaries of the sill/ring complexes are clearly delineated by the K/U ratio and ternary maps. The magnetic maps show ring like patterns of magnetic high anomalies that are due to the sills/ring complexes whilst the numerous, narrow, linear magnetic highs are due to faults and dolerite dyke swarms. The majority of the dykes trend in a NW-SE direction and a few dykes are in a NE-SE direction. The magnetic power spectrum indicates four depths of the magnetic sources at average depths of 0.13 km, 1.60 km, 2.83 km and 12.40 km. The magnetic depth iii slices maps show that both the circular/ring like and linear anomalies extend from shallow to deeper depth of 12.4 km. The gravity map is dominated by a long wavelength gravity anomaly that increases from about -120 mGals in the northwestern corner of the study area to -110 mGals in the southeastern corner of the study area. Results from 2½D gravity modelling show that this long wavelength anomaly is due to a horizontal Moho at a depth of 47 km in the study area, which shallows outside the study area near the coast. Superimposed on it are short wavelength gravity anomalies due to low density sediments and high density dolerite intrusions. The simple 2½D models generated from five profiles traversing the study area reveal that the sediments of the Karoo Supergroup extend from the surface down to a depth 5 km below sea level attaining a maximum thickness of about 6½ km. These sediments are dykes, sills and ring complexes. The dykes and sills/ring complexes identified from gamma ray spectrometry, magnetic and gravity data results are likely to be associated with fractures, joints, cracks and fissures in the host rocks, which form preferential pathways for groundwater transmission. Hence, they could be suitable targets for groundwater

Crustal structure beneath southern Africa and its implications for the formation and evolution of the Kaapvaal and Zimbabwe cratons,

Abstract. The formation of Archean crust appears to involve processes unique to early earth history. Initial results from receiver function analysis of crustal structure beneath 81 broadband stations deployed across southern Africa reveal significant differences in the nature of the crust and the crust-mantle boundary between Archean and post-Archean geologic terranes. With the notable exception of the collisional Limpopo belt, where the crust is thick and the Moho complex, the crust beneath undisturbed Archean craton is typically thin (∼ 35-40 km), unlayered, and characterized by a strong velocity contrast across a relatively sharp Moho. This crustal structure contrasts markedly with that beneath post-Archean terranes and beneath Archean regions affected by large-scale Proterozoic events (the Bushveld complex and the Okwa/Magondi belts), where the crust tends to be relatively thick (∼ 45-50 km) and the Moho is complex

Efficiency in PrEP Delivery: Estimating the Annual Costs of Oral PrEP in Zimbabwe.

Although oral PrEP is highly effective at preventing HIV acquisition, optimizing continuation among beneficiaries is challenging in many settings. We estimated the costs of delivering oral PrEP to populations at risk of HIV in seven clinics in Zimbabwe. Full annual economic costs of oral PrEP initiations and continuation visits were estimated from the providers' perspective for a six-clinic NGO network and one government SGBV clinic in Zimbabwe (January-December 2018). Disaggregating costs of full initiation and incremental follow-up visits enabled modeling of the impact of duration of continuation on the cost per person-year ($pPY) on PrEP. 4677 people initiated oral PrEP, averaging 2.7 follow-up visits per person. Average cost per person initiated was$238 ($183-$302 across the NGO clinics; $86 in the government facility). The full cost per initiation visit, including central and direct costs, was$178, and the incremental cost per follow-up visit, capturing only additional resources used directly in the follow up visits, was $22. The average duration of continuation was 3.0 months, generating an average$pPY of $943, ranging from$839 among adolescent girls and young women to $1219 in men. Oral PrEP delivery costs varied substantially by scale of initiations and by duration of continuation and type of clinic. Extending the average oral PrEP continuation from 2.7 to 5 visits (about 6 months) would greatly improve service efficiency, cutting the$pPY by more than half

Heterocyclic Cyclohexanone Curcumin Analogues Inhibit Growth of Ovarian Cancer Cells, in-vitro

Background: Ovarian cancer is the most lethal gynaecological cancer in women. Nearly a quarter of a million women are newly diagnosed globally, with up to 140,200 lives lost annually. The high mortality is attributed to vague symptomatology and lack of reliable markers in the early stages of cancer. There also exist challenges of resistance to currently available therapies such as carboplatin and paclitaxel owing to gross heterogeneity of the ovarian tumours. This study examined the efficacy of second generation heterocyclic cyclohexanone analogues of curcumin in ovarian cancer models. Methods: SKOV-3 and OVCAR-3 cells were used to model ovarian cancer. Various concentrations of the 14 analogues were used to treat the cells for 72 h, and IC50 curves were established using the SRB assay and Graphpad Prism analysis. Further studies were conducted using the two most potent compounds, namely RL112 and RL117. Flow cytometry was performed to determine their effect on cell cycle and apoptosis. The effect of treatment on the expression of key proteins was also determined using western blotting at 24, 48 and 72 h time points. The ability to inhibit migration was determined through a scratch assay. Results: RL112 and RL117 had the highest potency. In SKOV-3 cells, the respective IC50 were 0.52 and 0.97 µM, while in OVCAR-3 they were 0.64 and 0.99 µM. A time- and concentration- dependant, cell-specific effect was observed following the time course. Treatment with RL112 and RL117 caused S- and G2/M-phase increases of between 1 and 186% in SKOV-3 cells, and the effect lasted up to 72 h. No cell-cycle effect was detected in OVCAR-3 cells. In addition to the treatment-induced cell cycle effects, the morphological outlook of both cell types was indicative of apoptosis in both cell lines, and this was confirmed via flow cytometry showing time and concentration-dependent, statistically-significant increases in proportion of apoptotic cells. Western blot results showed reduced expression of the proteins AKT, phosphorylated AKT, NF-κB, ERK and phosphorylated ERK in RL112 treated SKOV-3 cells. Highest inhibition of AKT activity was at 72 h (48%), while that of NF-κB was at 24 h (72%). Inhibition of ERK activity was greatest at 24 h (68%). RL112 also inhibited migration of SKOV-3 cell in a concentration-dependent manner. Conclusions: The results have shown that the heterocyclic cyclohexanone analogues RL112 and RL117 are plausible lead compounds. Cytotoxicity to SKOV-3 and OVCAR-3 cells, both of which are resistant to cisplatin, was demonstrated. The mechanisms of action were shown to be potentially via multiple pathways, namely AKT, ERK and NF-κB, by reducing total and phosphorylated protein expression, which resulted in cell cycle arrest and apoptosis, as well as inhibiting the cells’ migratory capacity

Heterocyclic Cyclohexanone Curcumin Analogues Inhibit Growth of Ovarian Cancer Cells, in-vitro

Background: Ovarian cancer is the most lethal gynaecological cancer in women. Nearly a quarter of a million women are newly diagnosed globally, with up to 140,200 lives lost annually. The high mortality is attributed to vague symptomatology and lack of reliable markers in the early stages of cancer. There also exist challenges of resistance to currently available therapies such as carboplatin and paclitaxel owing to gross heterogeneity of the ovarian tumours. This study examined the efficacy of second generation heterocyclic cyclohexanone analogues of curcumin in ovarian cancer models. Methods: SKOV-3 and OVCAR-3 cells were used to model ovarian cancer. Various concentrations of the 14 analogues were used to treat the cells for 72 h, and IC50 curves were established using the SRB assay and Graphpad Prism analysis. Further studies were conducted using the two most potent compounds, namely RL112 and RL117. Flow cytometry was performed to determine their effect on cell cycle and apoptosis. The effect of treatment on the expression of key proteins was also determined using western blotting at 24, 48 and 72 h time points. The ability to inhibit migration was determined through a scratch assay. Results: RL112 and RL117 had the highest potency. In SKOV-3 cells, the respective IC50 were 0.52 and 0.97 µM, while in OVCAR-3 they were 0.64 and 0.99 µM. A time- and concentration- dependant, cell-specific effect was observed following the time course. Treatment with RL112 and RL117 caused S- and G2/M-phase increases of between 1 and 186% in SKOV-3 cells, and the effect lasted up to 72 h. No cell-cycle effect was detected in OVCAR-3 cells. In addition to the treatment-induced cell cycle effects, the morphological outlook of both cell types was indicative of apoptosis in both cell lines, and this was confirmed via flow cytometry showing time and concentration-dependent, statistically-significant increases in proportion of apoptotic cells. Western blot results showed reduced expression of the proteins AKT, phosphorylated AKT, NF-κB, ERK and phosphorylated ERK in RL112 treated SKOV-3 cells. Highest inhibition of AKT activity was at 72 h (48%), while that of NF-κB was at 24 h (72%). Inhibition of ERK activity was greatest at 24 h (68%). RL112 also inhibited migration of SKOV-3 cell in a concentration-dependent manner. Conclusions: The results have shown that the heterocyclic cyclohexanone analogues RL112 and RL117 are plausible lead compounds. Cytotoxicity to SKOV-3 and OVCAR-3 cells, both of which are resistant to cisplatin, was demonstrated. The mechanisms of action were shown to be potentially via multiple pathways, namely AKT, ERK and NF-κB, by reducing total and phosphorylated protein expression, which resulted in cell cycle arrest and apoptosis, as well as inhibiting the cells’ migratory capacity

Geology (Fundamental Earth Science A/B): GLG 111

Geology (Fundamental Earth Science A/B): GLG 111, BSc main examinatin June 2011

Geology (Economic Geology, Geophysics): GLG 511

Geology (Economic Geology, Geophysics): GLG 511, BSc (Hons) examination June 2011

Modal composition and tectonic provenance of the sandstones of Ecca Group, Karoo Supergroup in the Eastern Cape Province, South Africa

Petrography of the sandstones of Ecca Group, Karoo Supergroup in the Eastern Cape Province of South Africa have been investigated on composition, provenance and influence of weathering conditions. Petrographic studies based on quantitative analysis of the detrital minerals revealed that the sandstones are composed mostly of quartz, feldspar and lithic fragments of metamorphic and sedimentary rocks. The sandstones have an average framework composition of 24.3% quartz, 19.3% feldspar, 26.1% rock fragments, and 81.33% of the quartz grains are monocrystalline. These sandstones are generally very fine to fine grained, moderate to well sorted, and subangular to subrounded in shape. In addition, they are compositionally immature and can be classified as feldspathic wacke and lithic wacke. The provenance characteristics suggest the influence of plutonic and metamorphic terrains (meta-magmatic arc) as the main source rock with minor debris derived from recycled sedimentary rocks. The latter revealed that the compositional immaturity of the sandstones is a result of weathering or recycling and short transport distance. The weathering diagrams and semi-quantitative weathering index indicate that the Ecca sandstones are mostly from a plutonic source area, with climatic conditions ranging from arid to humid. The detrital modal compositions of these sandstones are related to back arc to island and continental margin arc. These results, therefore, support previous studies that infer foreland basin setting for the Karoo Basin