Masters Degrees (Geology)

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The assessment of groundwater quality in rural communities : two case studies from KwaZulu-Natal.
(1998) Sherman, Heidi Michelle.
The health and life expectancy of populations in developing countries is largely determined by the availability of good quality drinking water. Boreholes and springs generally provide water of better microbiological and physical quality than surface water sources, however, they may cause health and aesthetic problems due to chemical constituents dissolved out of the host rock. As part of a pilot study to assess the health-related quality of community water supplies, samples were taken from two Quaternary catchment areas in KwaZulu-Natal. The Umkomazi catchment area is located inland from Amanzimtoti, while the Umfolozi catchment area is located north-east of Ulundi. The geology in these areas is significantly different. The Umkomazi area is predominantly underlain by basement rocks of the Natal Structural and Metamorphic Province, while the Umfolozi area is underlain by sedimentary rocks of the Karoo Supergroup. Geographical information systems (GIS) were used to examine the influence of lithology, rainfall and landuse activities on groundwater quality. Major ion analysis of groundwater samples from the Umkomazi area revealed a linear relationship between borehole and spring concentrations. Dwyka Tillite was found to produce water with the highest concentrations of major ions, while Karoo dolerite produced water with the lowest concentrations of major ions. Samples from basement rocks and Natal Group contained intermediate concentrations of major ions. In the Umfolozi area Karoo dolerite samples showed the lowest concentrations of major ions, while the Vryheid Formation and Dwyka Tillite produced the highest borehole and spring concentrations, respectively. High salinity levels in sedimentary rocks may be due to marine influence during deposition. Piper diagrams show relative enrichment of major cations and anions and Stiff diagrams showed characteristic patterns. Fluoride is associated with siliceous basement rocks and related to calcium concentrations through the solubility of calcium fluoride. The trace metals, manganese, iron and zinc were found to cause significant aesthetic problems and possibly health problems in sensitive individuals. These constituents are derived from weathering of bedrock and possibly from the corrosion of metal pipes. There is an inverse relationship between mean annual rainfall (MAR) and electrical conductivity (EC), except near the coast where windblown salinity increases with rainfall. Nitrate, ammonium and E. Coli contamination are linked to landuse activities such as occurrence of human and animal excreta near the water source and the proximity of pit latrines. It is recommended that rural communities be educated about the nature and importance of groundwater quality.
Assessment of the permeability of Vryheid formation sediments.
(1994) Venter, Bernardus Jacobus.; Jermy, Colin A.
Permeability is that physical property of a porous medium that controls the flow of fluids through that medium. The flow of methane and water may be induced by the excavation of a mine opening in methane-bearing strata. Methane flow into a mine opening constitutes one of the biggest hazards in the coal mining industry. It is poisonous to humans and can ignite at concentrations as low as 5 % per volume and create explosions in the presence of coal dust from mining. If the flow of methane and/or water into the mine opening becomes blocked by an impervious layer, excessive pressures may develop, particularly in the roof strata of the mined seam, which can lead to roof falls. In order to characterize the flow of methane and water into and around the openings in a mine, that was plagued by roof falls suspected of being the result of excessive fluid pressure build-up, a large scale laboratory investigation of the permeability of the roof sediments of the working coal seam in the area was undertaken. The permeability was measured under atmospheric conditions by means of a modified Ohle permeameter, and under triaxial conditions with the aid of a modified Hoek cell. The permeability of the sediments towards methane and water was measured. Nitrogen was used as a control because it is much less reactive than methane towards the sediments used in this project. It was found that the permeability decreases with increasing gas pressure, in the case of gas being the permeating fluid, and increased with increasing water pressure, in the case of water being the permeating fluid. In some instances anomalous plots of permeability versus reciprocal mean gas pressure were obtained. These were attributed to the effects of methane adsorption or the Klinkenberg effect, and a possible method to determine which of the two processes is dominant is discussed. To characterize the flow in the roof strata of the coal seam being mined, the permeability was correlated to fades type. The different fades types were numbered from 1 to 14 with increasing grain size for ease of correlation. Due to the variable nature of the sediments, even in a fades type, no single permeability could be obtained for a fades type. Instead permeability ranges were obtained for each fades type. The definition of the lower and upper limits for each range were found to be dependant on the number of tests done on samples for that fades type. Nonetheless a relationship of increasing permeability with increasing grain size was found in the coarser grained fades (facies type 8 and higher). For the fIner grained fades types the permeability was found to decrease with increase in grain size. A graph could be constructed for use in predicting possible hazardous zones by identifying the fades type and then reading the permeability range that can be expected off the graph. Due to the variable nature of the sediments, the graph is, at this time, only applicable to the areas where the samples were obtained. A permeability prediction graph for all localities would be an ideal but is beyond the scope of this project. Such a graph, and the methods discussed have a wide range of applications in the coal mining and methane gas exploitation industries.
The bathymetry, sedimentology and seismic stratigraphy of Lake Sibaya- Northern KwaZulu-Natal.
(1998) Miller, Warwick Richard.; Mason, Tom R.; Watkeys, Michael Keith.
The morphology of Lake Sibaya is a product of an ancient fluvial system that drained a coastal landscape dominated by aeolian processes. The sedimentary processes within the lake are driven by wind generated currents. The dominant sedimentary process is one of lake segmentation, whereby prograding bedforms isolate the lake into smaller water bodies. The prograding bedforms include cuspate forelands and sand spits. The size and mobility of these bedforms is a function of sediment availability and current regime. The bathymetry of Lake Sibaya is discussed, with emphasis on geomorphic features derived from the ancient aeolian landscape as well as features related to modern sedimentary processes. The presence of underwater knickpoints and terraces indicate that lake level fluctuations have been common in Lake Sibaya. It is during lake highstands that large volumes of sand are eroded from aeolian dunes which surround the lake and made available for shoreline progradation. Ancient dune topography is preserved to depths of 20 m below water-level within the lake. Surface sediment distribution maps were compiled from 515 grab samples and thirteen core samples. Fine grained, well sorted, coarse skewed quartz sand comprises the majority of the surface area of the lake floor. Gyttja is the other dominant sediment type and accumulates in palaeovalleys and depressions on the lake floor. Sediment distribution in Lake Sibaya is discussed in terms of modern lacustrine processes as well as inherited sedimentary characteristics. The stratigraphy of the sediments underlying Lake Sibaya was investigated using a Uni-Boom seismic profiling system. Seismic profiles were compiled by identifying acoustically reflective surfaces that show regional development. Thirteen seismic overlays were prepared, and are illustrated as west - east and north - south seismic profiles. Five sequences ranging in age from late Cretaceous to Holocene were identified from the seismic profiles, and are described in terms of sequence stratigraphic principles. The seismic sequences were interpreted within a lithostratigraphic framework and are presented as a series of idealised geological sections. Thirteen sediment cores were collected from the Lake Sibaya area in order to ascertain the accuracy of the stratigraphic interpretation of the seismic records, to investigate reflective horizons identified from seismic records and to collect dateable material. Interpretation of the sediment cores reveals that a proto Lake Sibaya existed on drowned dune topography, during the period ± 43500 BP to ± 25500 BP prior to the Last Glacial Maximum. During the early to mid Holocene the Lake Sibaya site was occupied by a saline lagoon which underwent isolation from the sea ± 5030 BP. Since the mid-Holocene the lake has evolved to totally freshwater conditions and has undergone little sedimentation. The geological evolution of the Lake Sibaya area is discussed in terms of the geometry of the identified seismic sequences, the sedimentary characteristics of these sequences and the radiocarbon dates provided from the sediment cores. Palaeo-environmental conditions during the accumulation of the sedimentary sequences is discussed where fossil remains permit.
Catchment hydrological modelling using ArcSWAT : a study of the Ingula pumped storage scheme (IPSS) catchments, South Africa.
(2017) Ngubane, Zesizwe.; Demlie, Molla Bekele.
Abstract available in PDF file.
Characterisation of geotechnical, geochemical and metallurgical properties for mine-to-mill optimisation at Sandsloot open pit platinum mine, South Africa
(2008) Walker, Shonagh.
Sandsloot open pit mine extracts platinum, copper and nickel from the Platreef orebody in the Northern Limb of the Bushveld Complex. At present, it is the world's largest open pit platinum mine, but it is one of the smaller of six pits to be mined in this area by Potgietersrust Platinums Limited (PPRust). As mining progresses and the mine operations expand, sound knowledge of the subsurface ground, the orebody properties and their performance in the processing plant is imperative. An accurately characterised orebody, in terms of its geotechnical, geochemical and metallurgical properties, will facilitate the development of appropriate and cost effective mining practices and processing plant design. It will improve the prediction and performance of materials in each of the steps involved in converting the orebody rock mass into a concentrate /marketable product, which ultimately leads to mine-to-mill optimisation. This dissertation has focused on the geotechnical and metallurgical strength properties of the Platreef orebody at Sandsloot; the geochemical properties of the various lithologies and defined for each orebody rock type the associations and correlations within and between these properties. The petrography of the orebody material was studied to identify and classify the rock types. A rigorous testing programme was conducted and an extensive database of petrographic, geotechnical, geochemical and metallurgical information was assembled. The corresponding results within and across the different studies were grouped together and statistical analysis and interrogation of the data sets were performed. The research identified diverse rock types with contrasting physical properties in the Sandsloot open pit orebody. For each of the rock types the distinguishing characteristics and the variations in properties were identified. Significant differences and relationships between rock types for each property were assessed for predictability in mining. Statistical associations and correlations between the properties of each study were defined and models for predicting strength and rock type were developed.
Characterisation of groundwater and surface water interaction in the eThekwini Metropolitan District, KwaZulu-Natal, South Africa.
(2021) Mtshali, Sphindile.; Demlie, Molla Bekele.
Abstract available in PDF.
A combined sedimentological-mineralogical study of sediment-hosted gold and uranium mineralization at Denny Dalton, Pongola Supergroup, South Africa.
(2009) Hicks, Nigel.; Hofmann, Axel.
The ~2.98 - 2.87 Ga Pongola Supergroup in South Africa is subdivided into the lower volcano-sedimentary Nsuze Group, and the upper sedimentary Mozaan Group, the latter comprising a several kilometres thick succession of fluvial to shallow marine sandstones and shales. Thin beds of gold and uranium-bearing conglomerates are locally present in the Mandeva Formation near the base of the Mozaan Group and have been mined at Denny Dalton in northern KwaZulu-Natal. The style of mineralization strongly resembles that of the Witwatersrand goldfields, however appears to be of low grade and limited tonnage. The ~1 m thick basal conglomerate, the “Mozaan Contact Reef” (MCR, herein referred to as CG 1), at Denny Dalton hosts erratic gold and uranium mineralization. The conglomerate is laterally discontinuous and occupies east-northeast trending scour channels. Polymict, matrix-supported conglomerates are common, while clast-supported conglomerates are rare. Well rounded, pebble to cobble-sized clasts of vein quartz and chert are hosted in a sandy matrix of quartz, pyrite and sericite. Where mineralized, the CG 1 hosts abundant rounded pyrite grains, interpreted as detrital in origin, with subordinate U-bearing minerals, such as brannerite and uraniferous leucoxene. Rounded detrital pyrite occurs in three phases, compact, porous and radial. Gold forms inclusions within massive pyrite grains, which are concentrated in shoots associated with the basal parts of the channel scours. SEM-EDX results, as well as the high reflectivity of the gold show a high Ag content, indicative of a primary origin for the gold within the pyrite grains. Uranium within CG 1 is hosted primarily as secondary inclusions of uranium within black chert pebbles within the basal cobble-sized regions of the conglomerate. Geochemical comparison of the chert pebbles at Denny Dalton with similar chert from the Nondweni Greenstone Belt indicates that the uranium is secondary in origin as no U anomalies occur in the Nondweni chert. Geochemical and SEM analysis of the uppermost conglomerate (CG 4) indicate the presence of uraninite and coffinite within the uppermost horizon as both fillings of voids within, and coatings on, detrital pyrite grains. Palaeocurrent data indicate a likely source terrain for the detrital material to the west of the inlier. This orientation, as well as differing mineralogical and sedimentological aspects between the Mandeva Formation and the correlative Sinqeni Formation within the main Pongola basin, indicate a separate and more proximal provenance for the auriferous conglomerates of the White Umfolozi Inlier. The Mandeva Formation is a fluvial to shallow marine sequence that has been affected by cyclic sea-level changes. The basal conglomerates of the Denny Dalton Member were deposited in a proximal braided alluvial plain environment. The conglomerates fine upwards into trough cross-bedded quartz arenites which appear to have been deposited as shallow marine sands in a shoreface environment. They are overlain with a sharp contact by a laterally extensive unit of polymictic conglomerate which represents a transgressive ravinement surface within the wave zone and marks the onset of a major marine transgression into the Pongola basin. The conglomerate is overlain by massive grits and coarse-grained quartz arenite. This unit is overlain with a sharp and locally sheared contact by shales and subordinate banded iron formation which can be traced into other parts of the Pongola basin and indicates continued rapid transgression onto large parts of the Kaapvaal Craton with deeper marine, sub-storm wave base sediments being deposited in quiet-water environments on a sediment-starved shelf. The heavy mineral assemblage as well as bulk geochemical data is consistent with a granitoid-greenstone source terrain for the conglomerates and sandstones. The geochemical composition of chert pebbles from the CG 1 is similar to the composition of cherts present in the Nondweni Greenstone Belt that is situated ~30 km west of the White Umfolozi Inlier. Multiple sulphur isotope (ä34S, ä33S) values for detrital pyrite from the MCR are consistent with an origin from mantle-like rocks, such as hydrothermal sulphide-quartz veins in a granitoid-greenstone setting. Palaeocurrent, mineralogical and geochemical data all point to a likely granitoid-greenstone provenance to the west of the White Umfolozi Inlier.
Conventional hydrogeological, hydrochemical and environmental isotope study of the Sandspruit River Catchment, Berg River Basin, South Africa.
(2012) Naicker, Sivashni.; Demlie, Molla Bekele.
The Sandspruit River catchment, found within the heart of the Swartland region is infamous for wheat and wine production. Variable groundwater quality and low productivity is encountered within the folded and fractured Malmesbury Group aquifer, whilst the most productive and better quality groundwater is found within the Table Mountain Group sandstone. The Sandspruit catchment (a tributary of the Berg River) represents a drainage system, whereby saline groundwater with TDS up to 10870 mg/l, and EC up to 2140 mS/m has been documented. The catchment belongs to the winter rainfall region with precipitation seldom exceeding 400mm/yr, as such, groundwater recharge occurs predominantly from May to August. Recharge estimation using the catchment water-balance method, chloride mass balance method, and qualified guesses produced recharge rates between 8-70 mm/yr. To understand the origin, occurrence and dynamics of the saline groundwater, a coupled analysis of major ion hydrochemistry and environmental isotopes (δ¹⁸O, δ²H and ³H) data supported by conventional hydrogeological information has been undertaken. Research data were collected in three seasonal field sampling campaigns within the study catchment. These spatial and multi-temporal hydrochemical and environmental isotope data provided insight into the origin, mechanisms and spatial evolution of the groundwater salinity. These data also illustrate that the saline groundwater within the catchment can be attributed to the combined effects of evaporation, salt dissolution, and groundwater mixing. The geology together with the local and regional faults control the chemistry of the groundwater, whereby relatively fresh groundwater can be observed in certain direct recharge areas. The salinity of the groundwater tends to vary seasonally and evolves in the direction of groundwater flow. The stable isotope signatures further indicate two possible mechanisms of recharge; namely, (1) a slow diffuse type modern recharge through a relatively low permeability material as explained by heavy isotope signal and (2) a relatively quick recharge prior to evaporation from a distant high altitude source as explained by the relatively depleted isotopic signal and sub-modern to old tritium values. A conceptual hydrogeological model based on the hydrogeological, hydrochemical, and environmental isotope data was developed for the Sandspruit catchment. This model, together with statistical and groundwater quality analysis has lead to the development of a proposed local optimized monitoring scheme for the catchment.
Defining the spectral characteristics of rocks within the Mambulu Complex, Natal Belt, South Africa.
(2012) Hoosen, Zayd Goolam.; McCourt, Stephen.; Ahmed, Fethi B.
Field and laboratory spectroscopy are sub-fields of remote sensing, where the radiometric data of materials are individually measured either where the materials occur in situ or in a controlled laboratory environment. Both applications require the use of a spectroradiometer to record this reflected electromagnetic radiation. The spectral properties of rocks from the Mambulu Complex in the Natal Belt have not been studied previously. Four dominant rock types, namely, massif-type anorthosite, leuco-gabbro, pyroxenite and magnetitite were sampled from the Mambulu Complex and their spectral reflectances measured. Absorption features were determined after continuum removal was applied to the spectra. Anorthosite showed absorption features at 480-490, 592, 603, 608, 627-726, 765, 1410, 1905-1955, 2200, 2250 and 2330nm. For leuco-gabbro absorption features were observed at 481, 950-1010, 1407, 1917, 2206, 2252, and 2300-2340nm. Magnetitite displayed absorption features at 414, 460-515, 620-715, 982, 1380-1480, 1800, 1905-1930 and 2145-2330nm. For medium-grained pyroxenite absorption features were present at 410-420, 483, 680, 977-993, 1410-1415, 1800, 1920, 2205, 2250, 2307, 2400 and 2430nm. Coarse-grained pyroxenite showed absorption features at 460-727, 979, 1000, 1401, 1422, 1800, 1913, 1930, 2203, 2258, 2321, 2388 and 2421nm. ANOVAs and Bonferroni tests were applied to the spectral data to calculate significant spectral differences and between which pairs of rocks these significant differences occurred. Results showed that there were significant spectral differences between all the rock types of the Mambulu Complex. The variability of spectral characteristics within rock species was attributed to the difference in composition of fresh and weathered surfaces; and the significant spectral differences between rock samples can be attributed primarily to differences in mineral composition.
Foraminiferal distribution in unconsolidated sediment associated with a marginal coral reef in South Africa.
(2015) Hayman, Stephanie Vivien.; Schleyer, Michael H.; Mackay, Christine Fiona.
Abstract available in pdf file.
The genesis of the quartz-sericite schists of the Toggekry Formation, Nondweni Greenstone Belt, South Africa.
(2013) Jele, Nkosinathi Luvuno.; Watkeys, Michael Keith.
The aim of this study was to investigate the origin of sulphide-bearing quartz sericite-schists of the Toggekry Formation in the Archaean Nondweni greenstone belt (NGB) in the SE Kaapvaal craton, and to compare them with similar units in the Barberton greenstone belt (BGB). Geochemical studies reveal that the quartz-sericite schists had a rhyolite protolith. These rocks were subjected to two major deformation phases. D1 involved thrusting and stacking of the greenstone stratigraphy while D2 formed the large syncline structure of the greenstone belt. Within the study area, the F2 buckling mechanism seems to have been tangential longitudinal strain. Peak metamorphism occurred after D2 at 3230 Ma when the Mvunyana granodiorite intruded. The extensive alteration of the schists is interpreted as being partially due to the deformation and metamorphism but mainly because of the position of the schists in the contact metamorphic aureole of the Mvunyana granodiorite. The tholeiitic and calc-alkaline signatures of both the mafic and felsic rocks of the Toggekry Formation indicate that they formed in a back-arc setting. The enrichment in LREE relative to HREE that the rocks display is characteristic of crustal contamination and/or subduction zone magmas, enriched mantle source or small degrees of melting. The positive Pb anomalies and negative Nb-Ta are characteristic of subduction zone processes and indicate crustal involvement in the magma process. Epsilon Hf data suggests derivation either from a depleted mantle source with contamination by older continental crust or from a depleted mantle at an earlier age followed by re-melting. The Toggekry Formation has an age of 3.54 Ga and is indistinguishable in age to the Theespruit Complex of BGB. Both sequences are lithologically similar and interpreted as forming in backarc settings. However significant geochemical differences indicate that they formed in coeval but separate basins. Four models are proposed to account for this. The peak metamorphic event at ca. 3.2 Ga in both areas is considered to reflect an accretionary event during the formation of the Kaapvaal craton.
A geochemical study of the Theta Reef of the Frankfort Mining Complex in the Sabie-Pilgrim's Rest Goldfield South Africa.
(2015) Metz, Alexander Richard.; McCourt, Stephen.; Elburg, Marlina Augusta.
For over a century the Sabie-Pilgrim’s Rest Goldfield has been one of the most important gold producers in South Africa. The epigenetic gold deposits are situated at the eastern escarpment of the Eastern Transvaal Drakensberg, approximately 60 km away from the eastern rim of the Bushveld Igneous Complex. The Theta and Bevets Reef of the Frankfort Mining Complex occur within the Neoarchean dolomite of the Malmani Subgroup and the Paleoproterozoic Pretoria Group, respectively, of the Transvaal Supergroup. While the Theta Reef is situated in the dolomites of the Eccles Formation of the Malmani Subgroup, the Bevets Reef is situated at the contact between a conglomerate, also called the Bevets Conglomerate and the shales of the Rooihoogte Formation of the Pretoria Group, therefore providing two different environments for the ore mineralisation. The ore-bearing reefs are represented by quartz-carbonate veins. The ore minerals are pyrite, arsenopyrite, chalcopyrite and minor amounts of minerals of the tetrahedrite-tennantite series. The reefs were emplaced along thrust faults developed parallel to bedding which dips at 4-7° west towards the Bushveld Complex. The thrusts are attributed to forces related to the emplacement of the intrusion. Stable isotope geochemistry revealed that isotopes within a single mineral phase and between two phases are not in isotopic equilibrium. This suggests an episodic mineralisation of the ore-bearing quartz vein. Oxygen and carbon isotopic compositions of 10.9 – 13.8 (fluid) and -4.1 - -2.8 ‰ (calcite), respectively, indicate that the ore forming fluids are most likely of igneous origin and interacted with the rocks of the Transvaal Supergroup. Sulphur isotopic compositions of -1 – 2.3 ‰ (sulphides) show that fluids and metals seem to have originated from the Bushveld Complex. Trace element analysis of ore samples from the most northern section of the Theta Reef shows that the gold content within pyrite is generally low. The common trace elements are Cu, As, Ag Sb, Au, Pb and Bi, occurring as minerals or mineral inclusions of the tetrahedrite-tennantite series. Gold occurs as invisible solid solution and/or as Au-As and/or Au-Sb compound in arsenic rich sulphide minerals and occasionally in association with silver as electrum. The research shows that the intrusion of the Bushveld Complex played a major role in the formation of the gold deposits in the Sabie-Pilgrim’s Rest area being responsible for the mineralizing hydrothermal fluids, the ore metals, the heat budget for the hydrothermal cell and the forces that created the thrust faults that acted as pathways for the circulation of the mineralizing fluids. The circa 2.055Ga age of the Bushveld Complex also provides a maximum age for the Au-mineralization.
A geological and hydrogeological study of the Shu Shu thermal springs, KwaZulu-Natal.
(2013) Gravelet-Blondin, Kent Royson.; Watkeys, Michael Keith.; Demlie, Molla Bekele.
The Shu Shu thermal springs are located in central KwaZulu-Natal in South Africa at an altitude of 250m above mean sea level at the bottom of the Tugela Valley. They have been investigated in an attempt to ascertain whether or not they possibly share a common origin with fifteen other springs which are located in a north-northwestern trending, 1000km long zone within the eastern interior of the country. They have also been studied to establish if they potentially represent a viable and sustainable geothermal energy resource that may be developed in the future. Isotope ratios confirm that the thermal springs are meteoric in origin, and are likely recharged within a 130km long band located to the west toward the Great South African Escarpment. These waters then descend vertically to a depth of approximately 1827m – 2153m, at which point the fractures along which they move close due to escarpment-associated confining pressure. It is a reduction in this self-same confining pressure along the coastal plain, which occurs due to the continual removal of overburden, which forces the thermal water to migrate toward the east along ever-more opening fractures. Due to a slightly elevated geothermal gradient of 3.1°C / 100m at depth, this groundwater reaches a temperature of approximately 75°C – 85°C as it traverses toward the Shu Shu thermal springs over a time period of > 61 years (at present). The geochemical signature of the Shu Shu thermal waters is derived through leaching from the basement rocks through which they pass, with elevated concentrations of Na, K, Ca, Mg, Fe, Al, Si, F, Sr and SO₄ detected. Once below the floor of the Tugela Valley, at a depth of approximately 990m, the thermal groundwater commences its ascent, likely along the west-southwest – east-northeast orientated thrusts and associated fractures of the Tugela Terrane of the Natal Metamorphic Province. However, the thermal waters abut against those brittle structures trending north-northwest – south-southeast, which are perpendicular to the axis of least principle compressive stress, and so are ultimately forced to rise within the Shu Shu thermal springs. Prior to surfacing, the temperatures of these waters drop to approximately 67°C as a result of natural, conductive cooling processes. However intermixing with shallow, cold groundwater, which is discernible through geochemical and isotopic variations, and atmospheric impacts, further cool the thermal waters to a surfacing temperature of approximately 50°C. Nevertheless, a binary cycle geothermal energy power plant remains a possibility. Although thermal efficiency and volume flow rate values are favourable, heat transfer values are low and require further investigation through exploratory drilling. Nevertheless, the establishment of a 400kW power plant, should it occur, will typically be sufficient to service 625 rural homes.
The geology and geochemistry of the Rooi Rand Dyke Swarm.
(1996) Meth, Deanna Lorrine.; Watkeys, Michael Keith.
The Jurassic Rooi Rand dolerite dyke swarm was emplaced sub-parallel to the Lebombo Monocline during the initial stages of Gondwana breakup. The dykes extend northwards from the southern Lebombo region in northern KwaZulu-Natal, into central Swaziland, spanning a distance of approximately 200 kilometres with a width between 10 and 22 kilometres. Detailed mapping of a 600m-Iong section on the Pongolo River, established at least eleven phases of intrusion. Each dyke age was systematically sampled and analysed for whole-rock major, trace and rare earth element composition, as well as mineral chemistry. Selected samples were analysed for stable isotopes. In addition to notable intra-dyke chemical variations, there is also a high degree of inter-dyke mineralogical and geochemical variation, each dyke age bearing distinct geochemical characteristics. The apparent geochemical trend is not one of simple fractionation with time. Dyke chemistries are closely linked to magma genesis and magma volumes with time. Evolution of the magmas may be described in terms of varying degrees of partial melting and fractional crystallization, with a small degree of crustal contamination. Major, trace and rare earth element data indicate a lithospheric mantle source for the majority of dyke phases, and an asthenospheric source for only two of the eleven ages. Contrary to this, isotopic data (oxygen and radiogenic) indicate an enriched asthenospheric source for all the dolerites. This suggests that all ages may have originally been derived from the asthenosphere, with the majority of ages being intruded into the lithospheric mantle to later undergo partial melting and fractional crystallization, with some contamination. Previous studies assumed an asthenospheric source with depleted MORB-like rare earth element profiles to be representative for the majority of Rooi Rand dolerites. The Rooi Rand dolerites appear to display a geochemical link with the southern Sabie River Basalt Formation, as well as the Lebombo rhyolites. Magmatic evolution of the dykes was intimately linked to the initial rifting processes of lithospheric stretching and asthenospheric upwelling, which in this case concluded in a classic failed rift situation.
The geology and geochemistry of the volcanic rocks of the Pongola sequence in southern Swaziland.
(1993) Mabuza, Mbongeni Henry.; Wilson, Allan H.
The ~3.0 Ga Pongola Sequence, comprising a lower dominantly volcanic Nsuze Group and an upper largely sedimentary Mozaan Group, crops out in the Mahlangatsha and Kubuta areas of southern Swaziland. The Nsuze Group consists of basaltic, andesitic, dacitic and rhyolitic rocks with intercalations of ferruginous shale and pyrophyllitic schists. The Mozaan Group comprises quartzites, ferruginous shales, basalts and minor amounts of andalusite and sericitic schists. In the study area in southern Swaziland the Pongola Sequence is represented by a northerly striking lens of metavolcanic basaltic rocks extending southwards to the Ngwavuma River valley. These lavas comprise basalts, basaltic andesites and very minor rhyolites that are amygdaloidal and vesicular in places. Hunter (1952) tentatively correlated these metabasaltic rocks with the Nsuze Group but the geochemistry indicates that an upper Mozaan correlation is more likely. In the study area four stages of deformation have been deduced: a cleavage development (D1); low angle thrusting and bedding-parallel thrust faulting (D2); normal/oblique slip faulting (D3) and fracturing/jointing (D4). There has been duplication of strata by thrusting and normal faulting. Absence of marker beds prevents the determination of the degree of duplication. It is clear from the geochemical analysis that there are two broad groups of data from the suite, one from the Sigwe Hills in the north and the other from south of the Ngwavuma River. The samples from south of the Ngwavuma River are enriched in TiO2, AI2O3, CaO, Cr, Zr and Nb compared to the samples from Sigwe Hills. These volcanic rocks are tholeiitic in nature and indicate a within plate continental setting.
The geology and rock mass quality of the Cenozoic Kalahari Group, Nchwaning Mine Northern Cape.
(2002) Puchner, Richard A.; Watkeys, Michael Keith.; Jermy, Colin A.; Maud, Rodney.
With the extension of the Nchwaning Mine shaft complex in the Northern Cape Province, various geological and geotechnical complications needed to be identified in order to ensure correct use of tunnelling methods and support techniques. An understanding of the geological history of the area and the resulting geotechnical nature was important in defining the rock mass quality ahead of shaft development. A total of 12 geotechnical boreholes were drilled, and an additional 18 old boreholes revisited to accurately detennine the stratigraphy, geological structure and associated weathering effects. Various soils and rock testing helped quantify the materials encountered. Sands of the Gordonia Fonnation form the surface cover of this area, and together with the weathered calcrete, calc-arenite, conglomerate and clay, they form part of the Cenozoic Kalahari Group. The 30m thick basal unit of red clay is common throughout this region. This silty clay material is problematic in that it is expansive and hygroscopic. The clay unit rests unconformably on folded, faulted and highly weathered shale of the Proterozoic Lucknow and Mapedi Formations of the Olifantshoek Supergroup. Unconformably below this sequence lies the manganiferous ore deposits of the Hotazel Member, which is contained within the Voelwater Formation of the Griqualand West Supergroup. For the development of the decline shaft through the Gordonia Formation a box cut was excavated to a depth of 25m. The anticipated poor geotechnical conditions for a further 125m below the Gordonia sands called for high quality permanent tunnel support in the upper weathered horizons. Barton's Q-analysis was adopted as a recognized tunnelling quality index to predict and quantify the rock mass characteristics ahead of the shaft. The highly variable and generally low Q-values from borehole core analysis indicated that precast tunnel lining be used for 800m (at 11.5°) through the entire weathered Cenozoic sequence and into the weathered shales immediately below the Red Clay.
The geology and tectonic setting of the Shashe-Foley-Tonota area (Central Motloutse Complex), NE Botswana.
(2013) Moseki, Molatlhegi Larty Lostman.; McCourt, Stephen.
The well-developed NE-SW structural grain of the Shashe, Foley and Tonota (SFT) region is used to separate it from the NW-SE trending structures that characterise the Matsitama belt and adjacent area previously described as the Shashe belt. The study area is divided into 4 domains showing different geometrical and geological characteristics. Domain 2 (Shashe Dam shear zone) and Domain 3 lie to the NW and SE of the metasedimentary belt (Domain1). Domain 4 (the Gulushabe shear zone) is to the NE of the metasedimentary rocks. The rocks are characterised by NNE to ENE striking foliation present in both the the metasedimentary belt (supracrustal rocks) and the granitoid rocks. The metasedimentary rocks are deformed into large map scale NE to ENE trending folds structures (the Foley synform and the Gulushabe antiform) that deform bedding (So) and foliation (S1). The deformation involved NW-SE or NNW-SSE horizontal compression and is explained by two main episodes of NE-ENE coaxial (F1/F2) folding followed by a younger phase (F3) that produced NNE trending folds. The effect of F3 folding is reflected in stereographic plots of poles to bedding and foliation in Domains 1and Domain 2 which indicate folds plunging to the NNE. The foliation and the shape of deformed pebbles in the pebbly-quartzite is a product of oblate strain (flattening) in response to NW or NNW horizontal compression. This pebble elongation is considered to reflect the end result of F1 and F2 folding produced by oblate strain. Likewise, the shape of the K-feldspar megacrysts in the megacrystic granite gneiss in Domain 2 can be attributed to flattening (pure shear) rather than simple shear. The kinematics of the deformation features recognized are not compatible with the accretion-linked models proposed by previous workers for the SW margin of the Zimbabwe craton. Field based intrusive relationship studies indicate the granitoid gneisses were derived from igneous protoliths. Neoarchaean U-Pb zircon ages obtained confirm the order of granitoid emplacement obtained from field based studies. The ages obtained are 2724±48 Ma (Tonota biotite gneiss), 2698.9±9.2Ma (tonalite gneiss), 2647±24 Ma (megacrystic granite gneiss) and 2631.5±4 Ma (pink granite). Granitoid magmatism occurred between about 2724 Ma (biotite gneiss) and 2631 Ma (pink granite), a duration of ~ 94 Ma. The foliation (S1) in the tonalitic gneiss (2699 Ma) and the megacrystic gneiss (2647 Ma) predate intrusion of the pink gneissic granite (2631 Ma). Since S1 in the granitoid rocks is equated with S2 in the metasedimentary sequence, deformation fabrics in both the metasedimentary sequence and granitoid rocks predate 2631 Ma. The U-Pb ages obtained in this study, together with previous U-Pb zircon ages for granitoids from adjacent parts of the Motloutse Complex, the Limpopo belt and the Mosetse Complex indicate a geotectonic link between the terranes during the interval 2.6-2.7 Ga Domain 3 fabric is parallel to large scale ENE-WSW trending ductile dextral strike-slip shear zones (Regional D4 structures) that define the northern boundary to the Central Zone of the Limpopo belt but no kinematic indicators were found in the domain to confirm the shear sense. Structural evidence (this study) indicates thrust sense shearing characterises the SW vergent Gulushabe shear zone (Domain 4) which forms the boundary between the SFT area and the SE margin of the Tati greenstone belt. The Gulubashe shear zone dips N to NE thus deviating from the regional scale WNW/SSE trending system of thrust sense ductile shear zones which dips SW. The Gulushabe shear zone has the geometry of a back-thrust in an overall NE vergent system. The last deformation event is marked by widespread development of NE trending minor shear zones. The minor shear zones were not found in the pink granite gneiss implying that they are older than 2631 Ma. The development of these minor ductile shear zone is constrained between 2647 Ma and 2630 Ma. The structural history of the rocks and the kinematics of the deformation features recognised are given in table 3.1. Stable isotope analysis has shown that carbonate rocks (dolomites and calc-silicates) from the SFT region have high positive ð13C values (4.8 to 14.2‰). Such elevated ð13C values suggest a Palaeoproterozoic (2.4-2.1) age. However in the SFT area the regional foliation (S2) present in the granitoid gneisses and metasedimentary rocks is older than 2631 Ma indicating that despite the high ð13C values, the metacarbonate rocks are Neoarchaean in age.
The geology of the Ngoye granite gneiss formation.
(1985) Scogings, Andrew John.
The Ngoye Granite Gneiss Formation is located in the Natal sector of the Proterozoic Namaqua-Natal Mobile Belt, about 10 km southwest of Empangeni. It forms a prominent east-west trending elongate whalebacked massif some 30 km in length, within amphibolitic gneisses and schists of the Tugela Group. A suite of twelve different, gneissic granitoids has been-recognised within the Ngoye Formation on the basis of field relationships, mineralogy and supportive geochemistry. They range in composition from peraluminous syenite to peralkaline granite. Peraluminous varieties are typically muscovite and garnet-bearing whereas metaluminous granites in the formation contain olivegreen biotite and/or hornblende and sphene. Riebeckite, aegerine and yellow-brown biotite, with accessory fluorite and zircon are characteristic of the peralkaline granites. Geochemically, the samples analysed display a range in SiO₂ from 63,79 - 78,47∞, are extremely depleted in CaO and MgO, while being enriched in Na₂O and K₂O. Depletion of CaO relative to alkalis is shown by an alkali-lime index of only 36, suggestive of an alkalic character. The agpaitic index (A. I. = mole Na₂O + K₂O/AL₂O₃) of the peralkaline samples ranges between 1,02 and 1,16; which classifies them as granites of comenditic affinity. Various chemical classification schemes have been tested and evaluated, of which the RI - R2 multicationic diagram provides results most similar to modally-derived terminology. Accordingly, the Ngoye granitoids are shown to range from minor syenites and alkali granites to predominant monzo - and syeno-granites. Trace element data indicate that the peralkaline granites are enriched in Nb, Zr and Zn relative to the other, non-peralkaline, granites in the formation. In addition, radioactive, magnetite-bearing quartz-rich rocks associated with the peralkaline granites, have extremely enhanced contents of Nb, Zr, Y, Zn, U, Th and to a lesser extent Sn and W. Peraluminous and near-peraluminous granites have the highst Rb/Sr and Rb/Ba ratios of all samples analysed, as well as enhanced Sn, U and Th contents while Zr is notably depleted. Small, muscovite-rich pods associated with muscovite-bearing granites are highly enriched in Sn. The application of certain discriminants based on modal and geochemical parameters has shown the Ngoye Formation to comprise typical "A" - type granites. "A" - type granites are characteristically intruded as ring complexes into anorogenic or post-orogenic tectonic settings in attenuated or epiorogenically-domed continental crust. Comparison of the Ngoye Formation wi th the well-known "younger granite" complexes of Nigeria and Saudi Arabia reveals marked similarities. The inference is therefore that the Ngoye Formation represents a metamorphosed "postorogenic" granite complex with most of the hallmarks of "A" type or "within-plate" magmatism. Four phases of deformation (D₁ to D₄) are recognised within the area mapped. Evidence of D₁ deformation is rare, but rootless folds within the transposed layering in the amphibolitic country rocks reflect the intensity of this prograde metamorphic event, M₁, during which upper amphibolite grades were achieved. Field evidence shows that the Ngoye granites were intruded after the D₁ event and prior to D₂. This latter event caused widespread folding about east-west F₂ axes, with the development of a pervasive S₂ planar fabric within the antiformally folded Ngoye Formation. S₂ is locally developed in the amphibolitic country rocks. The D₂ event culminated in the development of northward-directed overthrusting and retrogressive ,M₂, metamorphism of mylonitic thrust planes. Lateral shearing characterizes D₃, with development of macroscopic mylonites and mesoscopic conjugate shear zones. This was in response to a sinistral sense of movement, as indicated by prominent sub-horizontal extension lineations (L₃) and microscopic asymmetric augen structures. D₄ is deduced from stereograms and is indicated as cross-folding of F₃ fold axes.
Geotechnical characterization and slope stability analyses of the Town Bush Valley, Pietermaritzburg, South Africa.
(2018) Singh, Keval.; Hingston, Egerton Daniel Christian.; Demlie, Molla Bekele.
The construction of settlements over zones of instability is increasing the impact of disasters across the world both in developed and developing nations. Many areas in the greater Pietermaritzburg region in South Africa, such as the Town Bush Valley, are prone to slope instability due to the terrain morphology and high intensity rainfall. This study has investigated the geotechnical conditions at the Town Bush Valley, in Pietermaritzburg. A geotechnical characterization of the Town Bush Valley has been undertaken in order to understand the geotechnical conditions prevailing on site. Furthermore, two critical slopes were selected for slope stability analyses to investigate the conditions under which failure would occur. The method of analyses chosen was the Morgenstern and Price method using the Rocscience, SLIDE software. The analyses involved a deterministic approach and a probabilistic approach. In the deterministic approach, all the input variables were considered as constant values. In the case of the probabilistic approach, the effective shear strength parameters were chosen as the random variables in order to account for their uncertainty. Prior to the analyses, sensitivity analysis was conducted in order to see the effect of the effective shear strength parameters, c´ and φ´, on the factor of safety. Various scenarios, including groundwater conditions and surcharge load, were considered during the analyses. Results from the site characterization show that the site is characterized by heterogeneous talus material, which is underlain at depth by shales of the Pietermaritzburg Formation and sandstones of the Vryheid Formation. Particle size analysis, Atterberg Limits Determination and consolidated-drained triaxial tests were undertaken on the talus material. The slope stability analyses show that the probabilistic approach presents a better insight into the assessment of the slope than a deterministic approach in accounting for the uncertainty in the geotechnical parameters. The random behaviour of the geotechnical parameters was quantified through various probabilistic functions. The various functions derived during probabilistic slope stability analyses, allowed for an assessment of the reliability of the data sets. Keywords/Phrases: Deterministic slope stability analysis; Phreatic surface; Probabilistic slope stability analysis; Random variables; Town Bush Valley
Hydrochemical characterisation of Northern KwaZulu-Natal historic coal mining districts, Northeastern South Africa.
(2018) Mduduma, Hlumela.; Demlie, Molla Bekele.
This M.Sc. dissertation reports the results of a hydrogeochemical study undertaken on historical coal mining districts of northern KwaZulu-Natal (KZN) Province, South Africa. The research catchment covers an area of about 12945 km2, located in the head waters of the Tugela River Basin or the uThukela Water Management Area (WMA). The main aim of the study was to assess the effectiveness of the rehabilitation undertaken by the South African Government on the various defunct/abandoned historical coal mines in northern KZN in improving surface water and groundwater quality in the region. Characterisation of surface water and groundwater water in terms of their interconnection, flow and hydrochemistry were undertaken. Primary (original data) and secondary data and information were collected, collated and analysed to understand the hydrogeochemical conditions of the region. The original data collected through a series of field campaigns within the study area, were complimented with secondary data from the Department of Water Affairs and Sanitation (DWS) monitoring programme, the KZN Groundwater Recourse Information Project (GRIP), the National Groundwater Archives (NGA) and borehole logs, hydrochemical and borehole yield data from various reports. The results of the study reveal that since the beginning of groundwater monitoring in 2010, the groundwater has been characterised by circumneutral waters. Time series EC, SO42- and Fe2+ data reveal no incongruities apart from a few episodes of elevated concentrations. Surface water hydrochemical analyses revealed peaks in EC coupled with low pH at varied sampling points which are presumed to be impacts from Acid Mine Drainage (AMD). Time series saturation states of groundwater with respect to calcite and dolomite indicate that groundwater remains oversaturated with respect to these minerals but under saturated with respect to gypsum as a result of carbonate AMD neutralization reactions. Trace metal data reveal no anomalous concentrations both in surface water and groundwater samples as a result of the circumneutral hydrogeochemical conditions. Major ion hydrochemical data show two main groundwater hydrochemical facies in the study area, namely most upstream boreholes are characterized by Na-Ca-HCO3-SO4 and most downstream boreholes are characterised by Ca-Mg-HCO3-SO4 hydrochemical water types. All surface water and groundwater samples have δD and δ18O isotopic values that plot on or below the Local and Global Meteoric Water Lines, indicating recharge from meteoric source with some evaporation mainly within the rehabilitated mine dumps. The detectible tritium signal in the shallow aquifers reflect recent active recharge taking place.

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