D.Phil. (Geology) / Please refer to full text to view abstract

D.Phil. (Geology) / The tectonic evolution of the "western margin" of the Witwatersrand Basin is examined and indications are that it has undergone a long and complex history. In order to examine the nature of Witwatersrand-age structures, structures in both pre- and post-Witwatersrand sequences are also examined. Rocks of the ±3074 Ma Dominion Group were subjected to a tectono-metamorphic event prior to the deposition of Witwatersrand strata on an angular unconformity. An oligomictic conglomerate is sporadically developed at the base of the Witwatersrand Supergroup. PreVentersdorp structures in Witwatersrand strata are developed in two distinct trends, north-south and northeast-southwest. The relationship between the two directions of folds and thrust faults are best explained within a regional, sinistral transpressive shear couple; the north-south faults are sinistral strike-slip faults and the northeast-southwest trending folds and thrust faults are secondary structures associated with the strikeslip faults. The implications of this model are that Witwatersrand sedimentation was probably controlled by lateral movements on north-south trending faults and not by thrust faults in a foreland system as suggested by the most recent models of Witwatersrand basin development. Post-Witwatersrand deformation is complex. Southeastward verging, pre-Ventersdorp, thrust faults were reactivated as normal faults during Platberg times and the resultant half-grabens were infilled by conglomerates of the Kameeldoorns Formation. Later deformational events include eastward verging post-Ventersdorp thrust faults and post-Transvaal normal and strike-slip faults. It can be demonstrated that the majority of this later fault movements took place along pre-existing fault planes and therefore tectonic inversion is a fundamental process in the evolution of the Witwatersrand Basin. Clearly therefore, the present distribution of Witwatersrand strata does not reflect the original basin geometry, it is the result of several periods of basin inversion and no basin margins can be defined.

M.Sc. (Geography) / Severe Aeolian deposition of windblown dust from mine tailings storage facilities (TSFs) is a common phenomenon on the Witwatersrand, especially during the spring windy season. For communities around tailings storage facilities, this poses health and environmental challenges. This dissertation estimates the risk of adverse health effects resulting from human exposure to hazardous elements in particulate matter (sub 20 μm diameter) for selected tailings storage facilities: East Rand Gold and Uranium Company (ERGO); East Rand Proprietary Mine (ERPM); Crown Gold Recoveries (CGR) and Durban Roodepoort Deep (DRD). Samples of surface material from these TSFs were analysed for heavy metal content using the ICP-MS method. Other than the expected gold, five heavy metals (arsenic, cadmium, chromium, lead and uranium) exhibited enrichments in the tailings material significantly above average (greater than a factor of 2) crustal composition. These elements were selected for comprehensive risk assessment through airborne exposure routes. The mean ambient particulate concentration in air of 540 μg m-3 (used in the risk calculations) was based on a conservative worst-case exposure scenario. U.S. Environmental Protection Agency (US EPA) risk assessment methods were used to determine the inhalation and ingestion hazard quotient and hazard indices for adults and children. The sum of the hazard indices was below the non-cancer benchmark (hazard indices 1.0) considered to be acceptable for a lifetime exposure. The risk cancer included the excess life cancer risk for the inhalation and the ingestion risk. The total risk for both exposures was within the range of 1 in 1 000 000 to 100 in 1 000 000 - taken as “acceptable risk” by the U.S. Environmental Protection Agency for adults and children.

This thesis presents the application of the state-of-the-art processing, interpretation and modeling to the 3D reflection seismic data that were acquired between 1988 and 2003 across the West Rand and West Wits line goldfields of the Archean Witwatersrand Basin. The re-processing of the old 3D seismic data using new imaging techniques, such as 3D Kirchhoff prestack time migration (KPSTM), has led to better imaging of the ore body, structures (faults and dikes), and steeply dipping stratigraphy. Detailed interpretations of the highly auriferous Ventersdorp Contact Reef (VCR) using advanced complex seismic trace and horizon - based seismic attributes, have led to discoveries of ore blocks (~ 1 km long and ~ 250 m wide) that are bound by multi-fault segments of the first-order scale Bank and West Rand faults, leading to an increase of the resource portfolio and potentially, the quantity of the reserves. In particular, the edge detection attributes have resolved faults with throws as small as 10 m and complex structural architectures such as intersecting and cross-cutting faults, and fault bifurcations which are difficult to detect using conventional techniques (e.g., amplitude, dip and azimuth). Potential conduits, such as faults and dikes for migration of water and methane into underground workings were also mapped using edge detection attributes. These results have the potential to play into safe mine planning. The interpretation of the merged 3D seismic datasets, integrated with underground maps, boreholes, absolute and relative geochronological data, has added to our understanding of the gross structural architecture and Neoarchaean tectonic evolution of the goldfields. On a first-order scale (400 m - 2.5 km) the data resolved: (1) the northerly-trending disharmonic Libanon Anticline with a wavelength of 8 km and amplitude of 2 km, which was formed during deformation in the Umzawami Event (ca 2.73 Ga); and (2) the north-northeast trending, west-dipping (65°–70°W) listric West Rand and Bank faults, which were formed during a major extensional event, herein termed the Hlukana- Platberg Event (2.70-2.64). On a second-order scale (25 m - 400 m) the datasets resolved: (1) the Tandeka and Jabulani thrusts 1.5 km below the West Rand and Bank faults in the depth interval of 6-8 km; and (2) a series of drag synclines and rollover anticlines in the immediate footwall and hangingwall of the West Rand and Bank faults. Further to this, the seismic sections across the goldfields provided evidence that the first- and second-order scale faults, thrust and folds were dissected, eroded and overlain by the Transvaal Supergroup above an angular unconformity. The oldest approximate age for the Transvaal Supergroup is given as 2.58 Ga, thus constraining the age of the faults, thrust and folds to the Neoarchaean or pre- 2.58 Ga.

Gold mining in the Witwatersrand Basin of South Africa has resulted in soil contamination due to the lack of sufficient environmental management plans for the tailings dumps and remnant footprints. Tailings reclamation as a strategy of reducing pollution in the Central Rand, for instance, has resulted in contamination of water systems by acid mine drainage (AMD). After removal of the tailings dumps, remnant material is left over on the tailings footprints and these contain significant amounts of pollutants that were initially in the tailings. Heavy rainfall during summer dissolves primary minerals and later in the dry season, secondary minerals are precipitated as efflorescent crusts on and nearby tailings dumps as well as footprints due to high evaporation. The efflorescent crusts can redissolve when it rains and form acidic, metal and sulphate-rich solutions due to their soluble characteristics. This study aimed to characterise tailings footprints in areas targeted for human settlements and office spaces to assess their potential to release left over toxic elements such arsenic (As), lead (Pb), copper (Cu) and zinc (Zn). The approach to the study involved characterisation of oxidised and unoxidised tailings material and secondary precipitates on both tailings dumps and footprints. This involved determining the mineralogical composition using Powder X-ray Diffraction (PXRD). Dissolution and leaching studies were also conducted on the material followed by determination of constituent elements using inductively coupled plasma optical emission spectroscopy (ICP-OES) and sulphates using ion chromatography (IC). The leaching solutions used included rainwater; dilute sulphuric acid at pH of 3.0 (a common leachate in such acidic soils); as well as plant exudates such as oxalic and citric acids. The leachate solutions were used to correlate the mineralogical composition of secondary precipitates and tailings footprints. Potential implications on humans following any accidental ingestion of the tailings or contaminated soils were assessed using gastric juices. The ecological risk factors and risk index together with the model to evaluate daily intake and different pathways to humans were used to assess the toxicity caused by exposure to contaminants in the materials. The experimental work was augmented by computer simulations based on geochemical modelling (using the PHREEQC geochemical modelling code) to determine the speciation of elements (and thus their potential lability and bioavailability), dissolution and formation of secondary mineral precipitates in the tailings dumps and footprints. The findings of the PXRD study showed that the mineralogy of the tailings and footprints was dominated by quartz (SiO2) and some minor minerals such as pyrite (FeS2), pyrophyllite (Al2Si4O10(OH)2), chlorite (Mg,Fe)3(Si,Al)4O10), mica (K(Mg,Fe)3 AlSi3O10(F,OH)2) while that of secondary precipitates was dominated by jarosite (KFe3+ 3(OH)6 (SO4)2), goethite (FeOOH), melanterite (FeSO4.7H2O) and gypsum (CaSO4.2H2O). Minerals obtained for the secondary precipitates were corroborated by geochemical modelling. Leaching results using rainwater with pH ranges from 3.5 to 3.9 showed that trace elements are released very slowly from tailings dumps and footprints and in small concentrations during rainy seasons as follows: As (1.5 mg/L-4.5 mg/L), Pb (3.5 mg/L-5.5 mg/L), Cu (4 mg/L-4.8 mg/L) and Zn (23 mg/L-44 mg/L). The release and mobility of Cu, Pb, Zn and As occurs quite markedly when secondary precipitates dissolve, making the immediate impacted environment unfavourable for plant growth and any habits in the vicinity. This was substantiated by simulated dissolutions and assessment of the resulting elemental speciation that pointed to the elements being distributed in bioavailable forms, implying potential uptake by plants (such as vegetables that may be cultivated on such impacted soils). The model was used to evaluate the daily intake and different exposure pathways and the results showed that children may daily intake 48.4 mg kg-1 day-1 and adults‟ 32.8 mg kg-1 day-1 . After 5 years (1825 days) of exposure more harm may be experienced and findings shows that kids are the most victims on these contaminated sites compared to adults. Both children and adults may absorb low levels of these toxic elements daily and after long time of exposure it may cause disease like cancer in their body which may lead to death. Pathways may be through inhalation and accidentally ingesting tailings soil that contain toxic elements. Drawing from the above findings, it will be important that tailings footprints that have been earmarked as land for development (residential or office space) be thoroughly assessed for potential release of toxic elements and high levels of acidity. Further reclamation aimed at reducing these hazards can then be implemented. / College of Agriculture and Environmental Sciences / M. Sc. (Environmental Science)

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In recent years acid mine drainage (AMD) has become the focus on many mine sites throughout the world. The Witwatersrand gold mines have been the main focus of AMD in South Africa due to their extensive impact on especially groundwater resources. The Witwatersrand Basin is a regional geological feature containing the world-famous auriferous conglomerate horizons. It is divided into sub-basins and the East Rand Basin is one of them. Due to the regional scale of the East Rand Basin AMD issues, a systems approach is required to provide a useful tool to understand the pollution source term and fate and transport dynamics and to aid in environmental decision making and to evaluate the geochemical impact of mitigation measures and evaluate future scenarios. The numeric geochemical models, using a systems perspective, show that the mine waste facilities, specifically the tailings dams are significant contamination point sources in the East Rand Basin, specifically for acidity (low pH), SO4, Fe, Mn, U, Ni, Co, Al and Zn. When the AMD solution enters the soil beneath the tailings, ferrous and SO4 concentrations remain elevated, while Mn, U, Ni and Co and perhaps other metals are adsorbed. After ~50 years the pollution plume starts to break through the base of the soil profile and the concentration of the adsorbed metals increase in the discharging solution as the adsorption capacity of the soil becomes saturated. The pollution pulse then starts to migrate to the shallow groundwater where contamination of this resource occurs. Toe seepage from the tailings either first reacts with carbonate, where acidity is neutralised to a degree and some metals precipitated from solution, where after it reaches the surface water drainage, such as the Blesbokspruit, where it is diluted. Some evaporation can occur, but evaporation only leads to concentration of acidity and dissolved constituents, thereby effectively worsening the AMD solution quality. The mixing models have shown that the dilution factor is sufficient to mitigate much of the AMD, although seasonal variability in precipitation and evapotranspiration is expected to have some influence on the mixing ratio and some variability in the initial solution will also be reflected in variation in surface water quality. From a sustainability perspective, a basic cost benefit analysis shows that the costs for the operating mine and society in general is lower when mitigation measures are employed during operation. For a theoretical mine in the ERB with an operating life of 100 years, the cost of operational mitigation measures is ~R 31 billion. This value is 4% of turnover and 19% of profits over the time period. Post closure remediation costs are ~R 67 billion. This value is 8% of turnover and 41% of profit over the time period. Although the initial capital investment in mitigation measures is substantial, although some measures will be implemented during operation, it is a smaller percentage of profits than eventual post-closure mitigation. / AFRIKAANSE OPSOMMING: In die laaste paar jaar het suur mynwater loging (SML) die fokus geword by baie myn areas regoor die wêreld. Die Witwatersrand goud myne het die hoof fokus van SML in Suid Afrika geword as gevolg van die groot impak wat Witwatersrand SML op veral grondwater bronne het. Die Witwatersrand Kom is ‘n regionale geologiese struktuur wat die wêreld beroemde goud-draende konglomeraat horisonne bevat. Die Witwatersrand Kom word onderverdeel in sub-komme, waarvan die Oos- Rand Kom een is. As gevolg van die regionale skaal van die Oos-Rand Kom SML probleem sal ‘n sistemiese benadering ‘n bruikbare middel wees om besoedelingsbron migrasie en eindpunt dinamika te verstaan asook om omgewingsbesluitneming en die geochemiese impakte en mitigerings metodieke asook toekoms senarios te evalueer. Die numeriese geochemiese modelle, wat vanuit ‘n sitemiese oogpunt beskou is, wys dat die myn afval fasiliteite, veral die slikdamme in die Oos-Rand Kom, beduidende kontaminasie puntbronne is van veral suur inhoud, SO4, Fe, Mn, U, Ni, Co, Al and Zn. Wanneer die SML oplossing die grond onder die slikdamme binnedring, bly Fe2+ en SO4 konsentrasies hoog, terwyl Mn, U, Ni en Co asook ander metale geadsorbeer word. Na ~50 jaar begin die besoedelingsoplossingspluim deur die basis van die grond profile breek. Die konsentrasie van die geadsorbeerde metale neem dan toe in die oplossing wat deur die grondprofiel beweeg het soos wat die adsorpsie kapasiteit van die grond versadig word. Die besoedelingspuls begin dan stadig na die vlak grondwater akwifeer migreer waar dit dan besoedeling van die grondwater versoorsaak. Water wat van die slikdam basis sypel reageer eers met karbonaat, waar suur tot so ‘n mate geneutraliseer word, dat sommige metale uit die oplossing neerslaan, waarna dit die oppervlak water lope, soos die Blesbokspruit, beryk en verdun word. Verdamping van die SML oplossing kan plaasvind, maar verdamping veroorsaak die konsentrasie van suur en opgeloste stowwe, wat die SML probleem dus kan vererger. Meng modelle het gewys dat die verdunning faktor genoegsaam is om baie van die SML te mitigeer, alhoewel seisoenale fluktuasies in reënval en verdampings syfers kan verwag word om ‘n mate van invoed op die meng verhouding tussen die SML oplossing en oppervlak water te hê wat dan in die oppervlak water kwaliteit gereflekteer sal word. Vanuit ‘n volhoubaarheidsperspektief is ‘n basiese koste voordeels analise gedoen. Hierdie analise het gewys dat die koste van ‘n operasionele myn en die samelewening as geheel laer is wanneer mitigasie metodieke tydens operasie toegepas word. Vir ‘n teoretiese myn in die Oos-Rand Kom met ‘n operasionele lewe van 100 jaar, is die operasionele mitigeringsmetodieke koste ~R31 miljard. Hierdie waarde is 4% van die myn omset en 19% van winste oor die tyds periode. Na operasionele remdiasie kostes is ~R67 miljard. Hierdie syfer is 8% van omset en 41% van winste oor die tydperk. Alhoewel die inisiële kapitaal uitleg van mitigasie metodes groot is, alhoewel sekere metodes eers tydens operasie implimenteer sal word, is die uitleg ‘n kleiner persentasie van winste as wanneer remediasie na operasie implimenteer word.

M.Sc. / Please refer to full text to view abstract

The approximately 2.9 Ga old Witwatersrand Basin of South Africa hosts different types of pyrite grains. The pyrite grains are hosted in different quartz pebble conglomerate reefs including the Ventersdorp Contact Reef (VCR). The various reefs are accessible from numerous goldfields. Regardless of years of studying the various types of pyrite grains from the VCR, there is still a disagreement as to their origins. Numerous pyrite grains of different types, shapes, and textures have been identified in the VCR of the Kloof Gold Mine. The origin of the different types of pyrite grains have been attributed to various mechanisms. Consequently, different depositional models were suggested for the mineralisation of the pyrite grains. Nevertheless, the style of mineralisation and origin of the different types of pyrite grains require further work especially for the VCR. This study determined whether a single or multiple processes were responsible for the formation of the different pyrite grains. The different types of pyrite grains including the rounded porous, rounded massive and angular massive grains were identified using a reflected light microscopy, scanning electron microscopy, and Röntec energy-dispersive x-ray spectroscopy. The above techniques were used to describe the shapes, sizes, and textures of the different types of pyrite grains in order to classify and group the pyrite grains for further investigation by chemical analysis. Identification and description of minerals associated with pyrite were conducted to determine the environment and conditions under which pyrite grains were formed. Genetic structures were identified in order to resolve whether the pyrite grains were transported or crystallised in situ. Different types of inclusions hosted in pyrite grains were identified and described to determine the nature of pyrite grains. Rounded zircon grains were identified in rounded massive pyrite grains, and the appearance the rounded zircon grains might suggest that the rounded massive pyrite grains formed later after the deposition of the Witwatersrand basin sediments. A particle induced x-ray emission, an electron microprobe, and a laser ablation inductively coupled plasma mass spectrometry were used to carry out chemical analysis of the major, minor and trace elements of the different pyrite grains. The chemical analyses were conducted to investigate and determine the chemical signatures and the composition of the different types of the pyrite grains to determine their processes of formation. Compositional zonation patterns and overgrowths of the pyrite grains were identified in order to determine whether the pyrite grains were formed through multiple mechanisms. The compositional zonation patterns were observed in the rounded porous pyrite grains. The zonations suggest multiple stages of growth processes resulting in most porous parts of the pyrite being enclosed by nearly pure pyrite. The rounded pyrite grains are generally containing high concentrations of Ni and Co as opposed to angular pyrite grains. The Ni/Co ration is low in the angular pyrite grains, but high in the rounded grains. The high Ni/Co ratio in rounded grains may be related to low-temperature sedimentary processes, whereas the low Ni/Co ratio in angular pyrite grains may indicate hydrothermal source. The differences between rounded and angular pyrite grains can be interpreted as a result of different genetic history, and origin from different sources. Thus the different pyrite grains formed under different chemical and atmospheric conditions, and by different depositional mechanisms. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geology / unrestricted

The Wonderfontein Cave is located within the Witwatersrand Basin (Gauteng province, South Africa) and is associated with the river banks of the Wonderfontein Spruit. This cave system has for many years been subjected to the influx of polluted mine water. Since subterranean environments remain poorly studied, it is unknown what the effect of this might be on the associated ecosystem. Furthermore, water that enters the Wonderfontein Cave poses a severe health threat as it drains into the underlying aquifer, which is abstracted for human and animal use. The general aim of this study was to determine the extent of metal pollution (enrichment), as well as to study the toxicity hazard potential of the soils and sediments associated with the Wonderfontein Cave. The objectives of this study were to (1) quantify the extent of anthropogenic metal pollution of water, soils and sediments associated with the Wonderfontein Cave (2) and assessing the toxicity hazard potential of these substrates; (3) determining whether nematode taxa and C. gariepinus individuals represent isolated communities and a population within the Wonderfontein Cave, respectively; (4) measuring the effect of mining-associated pollutants on the soil and sediment health of the Wonderfontein Cave by making use of nematodes to serve as bioindicators; (5) evaluating and comparing biomarker responses to metal bioaccumulation in C. gariepinus populations associated with the Wonderfontein Cave and epigean (surface) environments and lastly (6) comparing the results of the above identified assessments over both a temporal and spatial scale. Sampling was undertaken during April (1st sampling interval) and September (2nd sampling interval) 2013, which respectively represented the end of the high and low flow periods. Also, sampling of the subterranean (Wonderfontein Cave) and associated surface (Wonderfontein Spruit) environments were undertaken. The findings of this study suggested that especially the sediments associated with the Wonderfontein Cave have been subjected to severe nickel, copper, zinc, cobalt, aluminium, cadmium, lead and uranium enrichment. Also, the concentrations of many of the studied metals exceeded the respective water, soil and sediment environmental quality guidelines. Thus, also taking into consideration that most of the sediments were classified as being toxic, a severe threat is posed to the health of the associated biota. Although 60 nematode genera were identified from soil and sediments samples collected from the respective sampling sites associated with the Wonderfontein Cave and Spruit, it was concluded that most of these genera were likely only temporary residents of the subterranean environment. Even though plant-parasitic and nonparasitic nematodes were present, most of the collected soil and sediment samples were dominated by bacterivores (non-parasitic nematodes). Zero genetic divergence was recorded between the C. gariepinus populations associated with the Wonderfontein Cave and Stoffels Dam (Wonderfontein Spruit). However, significant temporal and spatial variation was observed in some bioaccumulated metals and biomarker responses within and between the respective C. gariepinus populations. Furthermore, the metal bioaccumulation levels present in both these fish populations pose a substantial threat to human health and are thus not fit for consumption. Also, no significant fish condition differences were observed between the C. gariepinus populations associated with the Wonderfontein Cave and Spruit. This study served as an initiative to create awareness and promote the conservation of Africa’s karst landscapes. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The Wonderfontein Cave is located within the Witwatersrand Basin (Gauteng province, South Africa) and is associated with the river banks of the Wonderfontein Spruit. This cave system has for many years been subjected to the influx of polluted mine water. Since subterranean environments remain poorly studied, it is unknown what the effect of this might be on the associated ecosystem. Furthermore, water that enters the Wonderfontein Cave poses a severe health threat as it drains into the underlying aquifer, which is abstracted for human and animal use. The general aim of this study was to determine the extent of metal pollution (enrichment), as well as to study the toxicity hazard potential of the soils and sediments associated with the Wonderfontein Cave. The objectives of this study were to (1) quantify the extent of anthropogenic metal pollution of water, soils and sediments associated with the Wonderfontein Cave (2) and assessing the toxicity hazard potential of these substrates; (3) determining whether nematode taxa and C. gariepinus individuals represent isolated communities and a population within the Wonderfontein Cave, respectively; (4) measuring the effect of mining-associated pollutants on the soil and sediment health of the Wonderfontein Cave by making use of nematodes to serve as bioindicators; (5) evaluating and comparing biomarker responses to metal bioaccumulation in C. gariepinus populations associated with the Wonderfontein Cave and epigean (surface) environments and lastly (6) comparing the results of the above identified assessments over both a temporal and spatial scale. Sampling was undertaken during April (1st sampling interval) and September (2nd sampling interval) 2013, which respectively represented the end of the high and low flow periods. Also, sampling of the subterranean (Wonderfontein Cave) and associated surface (Wonderfontein Spruit) environments were undertaken. The findings of this study suggested that especially the sediments associated with the Wonderfontein Cave have been subjected to severe nickel, copper, zinc, cobalt, aluminium, cadmium, lead and uranium enrichment. Also, the concentrations of many of the studied metals exceeded the respective water, soil and sediment environmental quality guidelines. Thus, also taking into consideration that most of the sediments were classified as being toxic, a severe threat is posed to the health of the associated biota. Although 60 nematode genera were identified from soil and sediments samples collected from the respective sampling sites associated with the Wonderfontein Cave and Spruit, it was concluded that most of these genera were likely only temporary residents of the subterranean environment. Even though plant-parasitic and nonparasitic nematodes were present, most of the collected soil and sediment samples were dominated by bacterivores (non-parasitic nematodes). Zero genetic divergence was recorded between the C. gariepinus populations associated with the Wonderfontein Cave and Stoffels Dam (Wonderfontein Spruit). However, significant temporal and spatial variation was observed in some bioaccumulated metals and biomarker responses within and between the respective C. gariepinus populations. Furthermore, the metal bioaccumulation levels present in both these fish populations pose a substantial threat to human health and are thus not fit for consumption. Also, no significant fish condition differences were observed between the C. gariepinus populations associated with the Wonderfontein Cave and Spruit. This study served as an initiative to create awareness and promote the conservation of Africa’s karst landscapes. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015