Masters Degrees (Geology)

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Open Access
The allanite deposits on Vrede, Gordonia District, Cape Province
(University of the Free State, 1961-11) Hugo, Petrus Jacobus; De Villiers, J. E.; Kent, L
Allanite deposits of an unusual nature occur in two types of granulite on the farm. Vrede, portion of Cnydas West, Gordonia District, Cape Province. The granulites belong to the Archaean complex which is also represented by schists and gneisses. These rocks, which are described in detail, have been correlated with the Kaaien Series of the Kheis System. The ore bodies are characterised by their distinct banding and the close -connection between their distribution and the regional structure of the metamorphic rocks. Allanite occurs with tourmaline, apatite, zircon and monazite in bands ranging from one-sixteenth to two inches in thickness, parallel to the foliation of the granulites. The mineralisation, probably hydatopneumatolytic in nature, started with the introduction of zircon, monazite and tourmaline, after which apatite, allanite, magnetite and quartz followed in that order. The optic axial angle of the allanite is 2V=60° or more. A high magnesian variety, however, has a positive sign with 2V=40°. The range in refractive indices is: no~=1.732 - 1.757 n f3 = 1. 7 4 7 1. 7 68 n~ = 1.759 1.779 This variation is probably due to differences in chemical composition. The three analyses of allanite given have been recalculated on the basis of 13 (O, OH, F) atoms to the unit cell and the formulae obtained conform closely to the formula X₂ Y₃ Z₃ (O, OH, F) 13 developed by Machatschki. Chip sampling was done on all the deposits and the samples were radiometrically assayed against a standard uranium-thorium sample. The average values obtained are Allanite is, therefore, a prescribed material in terms of the Atomic Energy Act. The other ore minerals are all normal in their properties. A crystallising pegmatite is believed to have been the source of the mineralising, solutions giving rise to these deposits. This pegmatite and those of the surrounding area are related to a younger granitic intrusion, probably the acid granite intruded into parts of Bushmanland. The deposits opened up by 1960 occur intermittently over a total area of approximately 600 feet by 200 feet, but their extent in depth has still to be proved. Only the main deposit may perhaps be workable; if the allanite bands there extend to a depth of 200 feet, the ore reserve will be of the order of 1500 tons, assuming that the ore contains roughly 10 percent allanite.
Open Access
Assessment of potential toxic influence of uranium trial mining in the Karoo uranium province
(University of the Free State, 2003) Scholtz, Nicolaas; Loock, J. C.
An assessment of uranium trial mining on four mining sites in the Karoo Uranium Province, South Africa revealed localised above-background values for U, Mo, Pb, Cu, As and Fe in surface - and ground water, soils, sediment and crops. Inadequate remedial action on cessation of mining activities in 1980 led to the presence of uranium ore in stockpiles, open pits, mining shafts, mining equipment and waste dumps within featured areas. Heavy metal contamination is suppressed by the lack of run–off and the dry climate experienced within the mining areas. However, the heavy metal content in surface water and sediment within the open pits on Rietkuil and Mooifontein is especially high. These values pose a risk for human ingestion and may cause cancer in the long term or renal damage over the short term. These pits are easily accessed, lack a fence and are used for a drinking medium by fauna and as a growth medium for flora. The easily accessed Cameron Shaft on Ryst Kuil is a matter of concern due to the possible presence of the radioactive inert gas, radon. Farm owners were unaware of the possible toxic effects of uranium and coherent heavy metals. This led to previous usage of mine water for crop irrigation, the moving and feeding of livestock as well as wildlife amongst uranium ore stockpiles, swimming in water-filled open pits and using crushed uranium ore for gravel road maintenance and construction. The presence of uranium ore in stockpiles and the coherent effects on the water, soils, sediment, fauna and flora and possibly man, prioritises the remediation and rehabilitation of the of uranium trial mining sites within the Karoo Uranium Province.
Open Access
Basin analysis of the Kalahari Manganese Basin
(University of the Free State, 2015-12-01) Van der Merwe, Sarel Johannes; Van der Merwe, S. W.; Van der Westhuizen, W. A.
Abstract not available
Open Access
Chemical and isotopic variations in plagioclase from the Upper and Main Zones, Northern Limb, Bushveld Complex
(University of the Free State, 2016-01) Mangwegape, Mpho; Roelofse, F.
The in-situ major element, trace element, and Sr-isotopic compositions of plagioclase in the broadly gabbroic cumulates from the Upper and Main Zones of the Northern Limb of the Bushveld Complex, as obtained from the Bellevue (BV-1) and Moordkopje (MO-1) drill cores have been determined by means of electron microprobe and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results show the existence of inter and intra-crystal initial 87Sr/86Sr disequilibrium of coexisting plagioclase, a phenomenon which has received rather rudimentary attention not only in the Bushveld Complex, but in other layered intrusions as well. This disequilibrium is particularly striking in samples from the Lower Main Zone, an interval which also records a lack of differentiation, as exemplified by the An% of plagioclase. In the rest of the stratigraphy, up to the top of the Rustenburg Layered Suite, there is less, if any, inter and intra-crystal initial 87Sr/86Sr disequilibrium of plagioclase coupled to more prominent differentiation trends. These results are in support of a model for the petrogenesis of this part of the Bushveld Complex, which involves the Lower Main Zone forming through the repeated intrusion of crystal mushes derived from a deeper seated, sub-compartmentalized staging chamber, into the Bushveld main magma chamber, with fractionation processes being key in the formation of the Upper Main and Upper Zones. Based on the initial 87Sr/86Sr composition of plagioclase, the Northern Limb of the Bushveld Complex can also be divided into a putative integration and differentiation stages, similar to the Western Limb of the Bushveld Complex. The integration stage in the Western Limb included the Lower, Critical, and Lower Main Zones, whereas the differentiation stage included the Upper Main and Upper Zones. The integration stage in this study incorporates the lower reaches of the Lower Main Zone, with the rest of the stratigraphy up to the top of the Upper Zone covering the differentiation stage. Furthermore, the Lower Main Zone of the Northern Limb of the Bushveld Complex has very consistent concentrations of most trace elements investigated, and these concentrations tend to increase upwards into the Upper Main and Upper Zones. This also suggests repeated intrusion for the Lower Main Zone with differentiation processes dominating in the upper parts of the Rustenburg Layered Suite.
Open Access
The content and behaviour of natural radionuclides in basement-hosted groundwater from Vaalputs, Namaqualand, South Africa
(University of the Free State, 2012-01) Pretorius, Huibrecht Catharina Florina; Tredoux, M.; Andreoli, M. A. G.; Vermeulen, D.
English: Vaalputs, the South African radioactive waste disposal facility, is currently licensed to dispose only low and intermediate level radioactive waste. The repository has been disposing radioactive waste since 1986; however, up until May 2011 no long-lived uranium containing waste has been delivered to Vaalputs. The Nuclear Energy Corporation of South Africa (Necsa) has foreseen this disposal and so ordered this study to establish a baseline for the behaviour of naturally occurring radionuclides from the uranium and thorium decay chains in the groundwater of Vaalputs. This baseline will be used to monitor the groundwater below Vaalputs for possible anthropogenic additions to the environmental radioactivity. This baseline was established by studying a unique dataset of 25 years of analysis of activities of man-made and naturally occurring radionuclides as well as cation and anion concentrations in the groundwater at Vaalputs. This database is the result of annual monitoring of the groundwater from a confined set of boreholes on and around the facility as part of the regulatory requirements of radioactive disposal. The analytical results of radionuclides in groundwater from 13 annually and 3 quarterly sampled boreholes have been evaluated during this study. Cation and anion concentrations were measured respectively by inductively coupled plasma optical emission spectrometry and ion chromatography. In routine analyses the activities of the long-lived radionuclides 238U and 232Th were measured by instrumental neutron activation analysis, while the short-lived radionuclide 226Ra was detected by γ-ray spectrometry. The overall radioactivity hazard from total α and β radiation levels were measured by gas flow proportional counting. On occasion groundwater samples have been analysed by α-spectrometry to determine the activities of α-emitting radionuclides from the decay chains of 238U, 235U and 232Th. These analytical results have been integrated in order to evaluate trends in activities of radionuclides, the relative contributions of individual radionuclides to total radiation levels and how these are influenced by groundwater conditions. 238U levels show a natural anomaly in the near-field of the disposal site, attributed to basement rocks anomalously enriched in uranium located close to the disposal trenches. This should be taken into consideration when monitoring the groundwater for possible additions of uranium. One set of duplicate samples from 2009 has been analysed by alpha spectrometry, determining an average activity ratio of 234U/238U in the groundwater of Vaalputs as 4.1. This average ratio has been used in the rest of the study for comparison of the contribution of 234U to total α radiation with the contribution of the other α-emitting radionuclides. However, it is suggested that a more extensive experiment should be carried out to determine a statistically representative activity ratio for the different areas at Vaalputs. High levels of 226Ra, unsupported by 238U, have been found in groundwater from certain boreholes, mostly boreholes lying closely together on the western side of the property. This groundwater also yielded low activity ratios for 234U/238U, lower pH and stronger oxidizing conditions than that of the rest of the area. The distinct host of Namaqualand rocks with the absence of overlaying sedimentary rocks has been suggested as the key to the different geochemical conditions of the groundwater of these boreholes. 232Th and its daughter radionuclides yielded levels far below the guideline of 1 Bq.l-1 given by the World Health Organisation, as is expected from the known low mobility of thorium. A peak in total α radiation levels was seen in 2000 in the near-field area. Assessing the cumulative contributions of the various radionuclides it was very clear that the greatest factor in producing α radiation is 234U. However, no data is available for the levels of 234U in 2000. It is suggested that future occurrences of elevated total α radiation levels should be investigated either by performing alpha spectrometry on a duplicate sample or on a sample collected as soon as possible after the original sampling. Analysis of total β radiation levels were found to be unreliable up to 2005, and since the analysis of β-emitting radionuclides was not part of the scope of this study, no conclusions with regard to the contributors to total β radiation could be made. It is suggested that the elevation of total β radiation levels of specific beta-emitting radionuclides, especially 40K, should be determined.
Open Access
The development and application of key profit drivers in mineral resource management
(University of the Free State, 2002-02) Van Niekerk, Gerhardus Johannes; Van der Westhuizen, W. A.; Boer, R. H.
Every mining operation is constantly seeking for new ways to manage a broad range of business variables. Managers across the production chain find themselves torn between the initiatives to reduce costs, balancing throughput and asset utilisation improvements, maintaining product quality, and other similar performance indicators. This they do in their respective areas of responsibility, measuring against their set targets. Herein lies the dilemma: Which operational factors will maximise the profit of the organisation as a whole as opposed to the individual areas. And what is the impact of parameters outside their domains on their performance areas? Phalaborwa Mining Company has been no exception in this scenario. With time the same issues and operational challenges were presenting itself to the management team. The question had to be asked: Would a fundamentally new approach to viewing the business unearth anything new and useful to take this remarkable company to new heights? This study was launched to challenge the views of business and to offer answers to the above dilemma. The study has shown a remarkable degree of interlinkedness between production variables across the production chain. For instance, the mineralogy and petrology of the rock mined had strong effects in the milling, flotation and even smelting processes, and the status of the metal market price conditions offered exciting options to operational managers, provided the relationships are understood. Using an integrated model the magnitude and nature of interrelationships between the drivers of performance are explained. As a result it could provide the capability to "play off' costs against benefits for operating decisions. For example: How long should one keep the open pit mine operational and should it be decommissioned at the same or at a different time as the downstream units? The integrated nature of the business model clearly showed that to reach optimal performance for the whole company, decision-makers across the production chain need to plan collaboratively. It was evident that the powerful modelling approach will loose its effectiveness if the organisational thinking is not changed to a collective one. The model therefore, could only be effective if it is embedded into the planning and monitoring business cycles.
Open Access
Die geologie in die omgewing van Britstown
(University of the Free State, 1977) Lemmer, William Murray
Afrikaans: 'n Stratigrafiese kolom is met behulp van geologiese kartering en profiele vir die gebied opgestel. Die twee eenhede van die Ventersdorpgroep kan gekorreleer word met die eenhede in die Bothaville-omgewing. Die nuwe standaard onderverdeling van die Karoosupergroep wat in die gebied gebruik is, verskil van die ou indeling. Paleogeomorfologiese gegewens en primêre strukture toon dat die Dwyka-ysplate in 'n suid-suidoostelike rigting beweeg het. Verskillende afsettingsomgewings soos diep mariene, onderste wegstrand, boonste wegstrand, strandfase, delta-top en kontinentale fluviale omgewings kan in die veld vir die Ecca- en Beaufortgroepe onderskei wrod. Primêre strukture, petrografiese en paleontologiese gegewens dui op 'n diep mariene, beperkte afsettingskom vir die Prins Albertformasie. Die Whitehill- en Tierbergformasies is onder soortgelyke toestande afgeset. Die water het vlakker geword en deltas wat die begin van die Beaufortsedimentasie aandui, het vanuit die suidweste gemigreer. Kontinentale fluviale sedimente is op die sikliese deltaïese sedimente afgeset. Die kontak tussen die Ecca- en Beaufortgroepe is graderend en vir praktiese doeleindes is die basis van die eerste deurlopende sandsteenlaag aan die bokant van die Eccagroep konsekwent as 'n herkenbare en karteerbare eenheid in die veld as kontak geneem. 'n Enkele kimberliet wat nie vantevore beskryf is nie, is gevind. Die verspreiding van kalkreet word beheer deur die topografie en kom net op ou Afrika-oppervlakke voor.
Open Access
An evaluation of the coal bed methane potential of the Mid-Zambezi and North Eastern Kalahari Karoo basins
(University of the Free State, 2017) Potgieter, Johannes Hermanus Jacobus; Van der Westhuizen, W. A.; Nel, L.
With the growing energy demand worldwide it is very important to identify any new fossil fuel resources for future use. Coal remains the most widely used fossil fuel for electricity generation in Southern Africa but over the past two decades gas has been seen as a possible supplement and ultimate replacement for the coal. A lack of world class conventional gas accumulations in Southern Africa, unconventional gas deposits, hosted in the Karoo Supergroup, have been investigated as an alternative gas source. The primary unconventional resource focused on in north-eastern Botswana and north-western Zimbabwe to date has been coal bed methane (CBM), a natural gas generated during the coalification process and stored within internal coal structures. A major limiting factor for a regional investigation into the CBM resource potential is the lack of exploration information specifically focused on gas rather than coal. The gas saturation state of coal has a notable impact on the measureable gas content value as well as the production potential within an area. One of the assumptions of previous semi-regional assessments was that the coal is fully saturated, which has not been the case from dedicated gas exploration campaigns in the region. As part of this evaluation the coal ranks, obtained from historic borehole data over the study area, were compared to the laboratory measured maximum sorptive capacities to determine the theoretical gas content of the coal. Investigations of two regional analogous coal fields showed that the coals are unlikely to be fully saturated and for a resource evaluation based on coal rank it is imperative to use a range of saturations for the final data inputs. Schlumberger’s GeoX software was used for a probabilistic resource calculation using Monte Carlo simulations with ten thousand iterations. The resource estimation results showed a wide distribution of probable values. Even with a resource value of 22Tcf, the major basins in Canada and the US have significantly higher resource densities than that of the Study Area indicating a lower prospectivity for CBM.
Open Access
Field relationships and petro-chemical investigation of mafic sills and dykes in the vicinity of the Uitkoms complex, Mpumalanga South Africa
(University of the Free State, 2011-05) Pecher, Marie-Luise; Gauert, Ch.; Borg, G.
Numerous mafic sills and dykes intruded into the Lower Transvaal sediments and the Archaean Basement in the vicinity of the Uitkomst Complex, which is assumed to be a satellite intrusion of the Bushveld Complex. Investigations on mafic sill intrusions near the Eastern Bushveld Complex described sills of pre-, syn- and post-Bushveld age and assigned the syn-Bushveld sills to the corresponding marginal rocks of the Bushveld Complex. Purpose of the presented combined diploma thesis was to map the mafic sills and dykes in the vicinity of the Uitkomst Complex as basis for a petrographical and geochemical characterization. The geological mapping as well as the petrographic description distinguishes three groups of mafic intrusive rocks: microgabbro sills, gabbronorite sills and gabbronoritic basement dykes. The group of elongated microgabbro sills shows a widespread spatial as well as stratigraphic distribution within the study area, whereas the gabbronorite sills form huge sill bodies within a main stratigraphic position between the Upper Timeball Hill Shale and the Klapperkop Quartzite. The gabbronoritic basement dykes intruded into the Archaean granite gneiss and represent the oldest of the investigated mafic rocks. Evaluation of the obtained geochemical data from about 160 samples verifies the classification into the three main groups. Based on incompatible element contents and element ratios different magma derivations are interpreted for the gabbronoritic sills, basement dykes and microgabbro sills. The basement dykes and gabbronorites sills are derived from a primitive partial melt, whereas the microgabbro sills show an evolved magma composition. Additional contamination with crustal material also changed the magma composition of each group as reflected by changing Ti/Zr ratios within the groups. The gabbronorite sills and basement dykes are probably contaminated with SiO2-rich material from quartzites and granite gneiss (highest SiO2 and Zr values), whereas the microgabbro sills show possible contaminations with dolomitic material (highest variation in CaO contents).The comparison to Bushveld related marginal rocks shows a similar composition of the gabbronorite sills and basement dykes to the B1 quenched textured micropyroxenites, whereas the microgabbro sills indicate little correlation with the composition of one of the Bushveld marginal rocks (B1 to B3). Furthermore the microgabbro sills are nearly conformable in composition of selected trace elements with the Basal Gabbro chilled margins at Uitkomst and Slaaihoek, which is supported by a possible palaeomagnetic age relationship in some extent. The geochemical fingerprints of the investigated sills and dykes compared to the Uitkomst Complex have identified no direct correlation between them and show only low contents of exploration relevant elements for microgabbro sills, gabbronorite sills as well as basement dykes.
Open Access
Geochemical and mineralogical investigation of the Merensky Reef and its noritic hangingwall at Two Rivers Platinum Mine and Eerste Geluk, Eastern Bushveld, with special reference to the PGE distribution and cryptic variation of the mineral chemistry
(University of the Free State, 2014-12) Beukes, Jarlen Jocelyn; Gauert, C. D. K.
This research study focuses on the unusual occurrence of noritic lenses (termed “brown sugar norite” by mine geologists), within the pyroxenite of the Merensky Reef as well as its hanging wall at Two Rivers Platinum Mine, situated on the southern sector of the eastern limb of the Bushveld Complex. The primary purpose of this study is to determine the origin of these noritic lenses (hereafter referred to as BSN) and their influence on PGE distribution within the Merensky Reef. This study will also attempt to characterise the cumulate rocks associated with the Merensky Reef unit through geochemistry and mineralogy. Furthermore, a comparison with similar rock types of different genetic facies types of the same stratigraphy north of the Steelpoort fault at Eerste Geluk will be performed. The BSN is a fine-grained mela-gabbronorite and only occurs where the upper chromite stringer of the Merensky Reef unit is present. Orthopyroxene is the dominant cumulate phase in both the BSN and pyroxenite of the MR followed by interstitial plagioclase. Clinopyroxene occurs mostly as an exsolved lamellae phase within orthopyroxene and as intermittent rims around orthopyroxene. This can be attributed to exsolution of the Ca end member during decrease in temperature and compositional change of the melt during cooling. Some of the chromite crystals present in the pyroxenite are well-rounded possibly indicating magmatic erosion. Textural features of minerals from the different rock types such as plagioclase inclusions within orthopyroxenes as well as triple junctions of orthopyroxene crystals suggest disequilibrium and recrystallization of mineral phases respectively. The dominant mineral phases control most of the chemical composition of the rocks in accordance with their mineral proportions as they concentrate most of the lithophile elements. The main difference between the Merensky reef at Two Rivers Platinum and the Merensky reef north of the area at the farm Eerste Geluk is the absence of brown sugar norite at the latter. Also, the minerals of the Eerste Geluk Merensky lithologies display a higher degree of alteration or deformation and a higher concentration of hydrous minerals. Eerste Geluk is situated proximal to the Steelpoort fault which suggests that the rocks in the area were affected by faulting and late hydrothermal fluids which resulted in the alteration of minerals. Strontium isotope analyses of five representative samples of the Merensky interval at TRP yielded 87Sr/86Sr ratios typical of Critical Zone magma. Though both the pyroxenite and BSN have 87Sr/86Sr ratios representative of Critical Zone magma, the BSN has a lower ratio relative to pyroxenite. This suggests that it formed from a more primitive magma. Whole rock MgO content is higher in the BSN, ranging between 24-28 wt. % compared to the 21-23 wt. % MgO found within the surrounding Merensky reef pyroxenite. This provides some evidence suggesting that the BSN formed from a more primitive magma. EPMA results show cryptic vertical variation of En content, Al2O3, TiO2 and MnO in orthopyroxene and An content variation in plagioclase. This indicates fractionation and replenishment of magma. Base metal sulphides and associated PGMs occur disseminated throughout the Merensky pyroxenite interval. The PGMs analysed by EPMA are relatively enriched in Pt but are poor in Pd and Rh. These findings are consistent with the ICP-MS study done on the base metal sulphides. Textural features such as zonation of these PGMs suggest the action of late stage magmatic processes. The occurrence of the BSN has not influenced the content of the PGE mineralisation. It contains relatively little if any base metal sulphides and PGMs. It is therefore suggested that the BMS and PGM saturation was not affected during crystallization of BSN. With regards to emplacement, it is suggested that the BSN formed prior to the MR and that a magmatic erosion caused by the injection of the new MR magma may have disturbed the previously formed BSN layer. It thus resulted in isolated lenses of relict and primitive BSN. The BSN is not laterally consistent in the TRP area and may be attributed to this phenomena. The absence of BSN in other mines of the Bushveld may be due to this reason, or the occurrence of the BSN has been overlooked due to its similarities to MR pyroxenite.
Open Access
The geochemistry of the dykes in the Carletonville Goldfield
(University of the Free State, 2009-11) Litthauer, Alida; Van der Westhuizen, W. A.; Tredoux, M.
Numerous dykes traverse the Witwatersrand Supergroup rocks in the Carletonville Goldfield. The aim of this study was to investigate a classification system for the dykes. Samples were obtained from Tau Tona and Mponeng mines as well as from AngloGold Ashanti’s field office. The mineralogical investigation revealed that most dykes, with the exception of the Brazil dyke, are altered. The most abundant minerals are chlorite, actinolite, epidote, quartz and albitised and/or saussuritised feldspar, corresponding to a greenschist metamorphic facies mineral composition. Veins are commonly filled with quartz, calcite, epidote and chlorite, with sulphides and Fe oxides occurring occasionally. However, mineralogical heterogeneity as a result of different degrees of alteration, were found between samples from the same dyke. This heterogeneity may be an important consideration where rock engineering is concerned as it could cause different sections of the same dyke to have different physical properties Geochemical separation of the dykes into different groups was achieved by means of Bowen’s (1984) TiO2 v Zr and Zr/P v P/Ti plots as well as Linton’s (1992) discriminant plot. These same plots were employed in order to classify the dykes according to geochemical data taken from literature for four igneous events, namely, the Ventersdorp Supergroup, Transvaal Supergroup, Bushveld Igneous Complex and Karoo Supergroup, as well as geochemical data for dykes from the East Rand Proprietary Mine. Rare Earth Element patterns from the dykes were compared to literature data for the above-named igneous events in order to obtain a better classification.
Open Access
Die geologie van die gebied Poortjie 3022B in die distrikte Britstown, Carnarvon, Prieska en Victoria-Wes, Noord-Kaapland
(University of the Free State, 1977) Van der Westhuizen, Willem Andries
Die geologiese geskiedenis van die gebied was kompleks en word gekenmerk deur verskeie diskordansies en klinodiskondansies asook vulkanisme, vervorming, metamorfose en vergletsering. Die oudste gesteentetipe is die Welgevondengraniet, 'n horst, wat as vloer beskou word. In die noordoostelike hoek van die gebied dagsoom dolomiet; kalksteen en gestreepte ysterformasie van die Sisteem Transvaal. Wes van die Doornberglineament dagsoom gesteentes bestaande uit arkoose, lawa, kalksteen en gestreepte ysterformasie wat vroeër as 'n gedeelte van die Serie Marydale beskou was, maar wat nou die Soetvleiformasie genoem word, en wat 'n ouderdom vergelykbaar met die Transvaalgesteentes het. Die geochemie van die Soetvleilawas dui 'n tholeiïetiese basaltiese samestelling aan. Die lae van die Sisteem Transvaal knyp uit teen die Welgevondengraniet en gevolglik kan die Welgevondengraniet as ‘n gedeelt e van die westelike grens van die Transvaalkom beskou word, of dit kan in hoog in die. Transvaalkom wees met 'n laterale variasie in die litologie wes van die hoog af. Wes van die Welgevondengraniet is daar 'n dik opeenvolging van metapelitiese gesteentes bestaande uit kwartsiete, gneise en amfiboliete wat met die Matsap/Kheis gekorreleer word. Die graad van metamorfose is egter eerder vergelykbaar met dié van die Namakwalandse Mobiele Gordel as met die Kheis- of Matsapdomein verder noord. Die gesteentes het drie hoofperiodes van vervorming ondergaan waarvan die eerste twee isoklinaal ko-aksiaal was, met ‘n noord-noordwestelike strekking, gevolg deur 'n periode van oopplooiing loodreg op die b-plooias van die eerste twee periodes van vervorming. Hierdie laaste periode van plooiing het koepel-en-kom strukture tot gevolg gehad. Die gesteentes wes van die Doornberglineament was aan verskeie temperatuur- en druktoestande blootgestel en gevolglik kan twee isograde deur die gebied getrek word. Daar is 'n toename in graad van metamorfose van oos na wes en die metamorfe gebiede bestaan uit baie laegraadse-, laegraadse- en 'n medium- tot hoëgraadse area. Na die tydperke waartydens vervorming en metamorfose plaasgevind het, het 'n glasiale periode begin waartydens die Serie Dwyka afgeset is. Uit die voorkoms van halietkristalle in die Étage Bo-Dwykaskalies kan afgelei word dat die afsetting van dié Serie onder vlakwatertoestande plaasgevind het en nie in 'n relatief diep see soos aanvanklik vermoed is nie. Na die afsetting van die Karoosuksessie het doleriet, en nog later, kimberliet die Karoogesteentes binnegedring. Die Karoogesteentes word grootliks deur resente materiaal soos kalkreet, sand en grond bedek. Ondergrondse water is geassosieer met verskuiwings en lineêre strukture en goeie lewerings kom voor. Geormorfologies bestaan die gebied uit groot vlaktes met inselberge. Die vernaamste erosiesiklusse was die Afrika- en na—Afrikasiklusse.
Open Access
Die geologie van die serie Stormberg in die sisteem Karoo, suid van Bethlehem, O.V.S.
(University of the Free State, 1964-08) Kingsley, Charles Seymour; Van Biljon, W. J.
Afrikaans: 'n Gebied tussen Bethlehem en Fouriesburg, waarin alle etages van die Etage Bo-Beaufort tot die Etage Drakensberg verteenwoordig is, is gekarteer asook die veldgegewens opgeteken. Oor geskikte roetes in die gebied is monsters geneem waarop verskillende petrografiese ondersoeke gedoen is. Vanaf swaarmineraalstudies kon gevolgtrekkings gemaak word omtrent oorspronggebied en afsettingstoestande van die Serie Stormberg. Korrelgrootte en -verspreiding is in die sandstene deur sifanalise bepaal. 'n Vergelykende studie is met behulp van die mikroskoop op die sandstene sowel as op die dolerietindringings en lawavloeiings uitgevoer. Uit die resultate kon in hooftrekke die volgende afleidings gemaak word: Die oorsprongrotse van die sedimente moes hoofsaaklik vanaf granitiese stollingsgesteentes wat êrens na die suidooste geleë was afkomstig gewees het. Die afsetting van die sedimente moes in landelike meergebiede geskied het. Die Moltenolae se afsetting moes relatief vinnig onder nat toestande plaasgevind het, terwyl die Eooilae en Holkranssandsteen onder 'n geleidelike droeër-wordende klimaat gevorm is. Die laaste stadiums van afsetting van die Holkranssandsteen het gelyktydig met die eerste lawavloeiings plaasgevind. Laastens was die dolerietgange in hierdie gebied moontlik ook die toevoerkanale vir die basaltiese Drakensberglawa.
Open Access
The geology of an area west of Welkom, O.F.S.: (degree blocks 2825 A and B and 2826 A)
(University of the Free State, 1980-10) Behounek, Norbert Josef; Grobler, N. J.
Rocks present in the mapped area range from Early Precambrian (Easement granite) to the most recent deposits of aeolian sands, alluvium, gravel and calcrete. Outcrops of Ventersdorp rocks are scarce and widely scattered. Nevertheless, agglomerates and felsic lavas of the Makwas'sie Quartz Porphyry Formation, fanglomerates, .quartzites, volcanic breccias, tuff, mafic massive la.vas and pillow lavas of the Rietgat Formation, quartzites of the Bothaville Formation and plateau lavas of the Allanridge Formation could be distinguished and studied. The latter were all grouped together in accordance with the lithostratigraphic classification of Winter (1976), because of the proximity to his type area. Overlying the Ventersdorp Supergroup are shales and/or tillite of the Karoo Sequence. Bore holes drilled to the east (outside) of the mapped area proved that Dwyka glacial deposits are preserved in pre-Karoo valleys and/or valleys excavated through ice movement. Here, the Dwyka Formation consists of tillite, varved shales and a glacio-fluvial unit, viz. the sandstone-siltstone-shale unito In the western sector of the mapped area. Ventersdorp rocks are directly overlain by black, micaceous shales of the Ecca Group (Prince Albert Formation). The V/hitehill .Formation is probably not present as one continuous layer over the whole of the mapped area, and only occurs in a few isolated pockets. As a result the Prince Albert Formation is in most cases overlain by grey shales of the Tierberg Formation which grades from shales and mudstones (marine deposits) upwards into rhythmic layers of grey shales and sandstones (deltaic deposits). The transitional zone between the Ecca Group (Tierberg Formation) and the overlying Beaufort Group is exposed on the farm Basberg 416. The Beaufort Group in this area shows the typical features of a fluvial deposit, viz. coarse-grained channel-axis facies which laterally grade into finer-grained and thin-bedded hannelmarginal facies and levee mudstone deposits. The latter sediments were most probably deposited on the flood plain of a braided rivero Intrusive rocks consist of post-Karoo dolerites (sills and dykes) and the kimberiite intrusions at Rovic Diamond Mines. Nodular and laminated calcrete deposits are the most abundant calcrete deposits in the area under investigation, Aeolian sands cover large tracts of this area and occurmaiicly as aeolian sheet deposits but also as dunes of variable magnitude. The Vaal River Gravels and the alluvial sands and silts of the Yet and Sand Rivers are the most significant alluvial deposits present in the mapped area. Pans of variable shaper, and sizes have originated through the erosion of paleo river channels by subsequent wind action.
Open Access
Hydrogeochemical determination of the salt load from copper mine waste in the Bushveld igneous complex
(University of the Free State, 2008-11-28) Moukodi, Georges Pascal; Usher, Brent H.
This dissertation characterised geochemically waste from a copper mine in the Bushveld Igneous Complex, coupled with hydrochemical interpretations. In the first part of the dissertation, the methods involved in the quantification and qualification of mine acidic drainage were discussed. This included paste and rinse pH, Acid and Base potentials, net neutralisation potentials and neutralisation potential ratio. These methods form what is known as Acid-Base Accounting, (ABA). In the second part of this dissertation, the sampling methods and representativeness of the samples were discussed. All these methods are scientifically justifiable as they are in agreement with methods used internationally. In the third and most important part of this dissertation, results where discussed and proven to correlate with visual estimates from the field. In sulphides-containing waste material, Acid Mine Drainage (AMD) is produced due to the ingress of oxygen and water mainly from rainfall, and thus subsequent oxidation of sulphide-bearing minerals with the help of bacteria. However, in the presence of sufficient neutralisation potential, alkaline drainage is favoured as carbonated minerals (mainly dolomite and calcite) buffer the acidity. For this study, copper sulphide is recovered from foskorite ore imbedded with carbonatite which helped at the non acidification of the mine site. In the dissertation, the geochemical software PHREEQC was used and it confirmed that many silicates and alumino-silicates minerals are dissolved in the groundwater. This is an important finding as the presence of silica is an indication that substantial amount of acidity could have been released. This also constitutes reasonable evidence for the fact that chalcocite and covellite which are the main sulphides of copper mined on site can be considered as “weak” sulphides unlike pyrite which can be more severe to the environment. The software PHREEQC also confirmed that dolomite and calcite control the pH of the water, thus only fairly alkaline values in the range of pH 8 to pH 9.5 are expected on site. With visual investigations, it has been noticed that natural vegetation is taking place around the site even on the most hostile tailings like the magnetite. This is a very important aspect as positive outcome is expected for the fauna after mine closure. The following serve as recommendations: - The neutralisation processes release sulphate into the groundwater, and it is recommended that tracer tests methods be conducted to estimate the travelling time of the salts. - It is also recommended that the mine speed up the re-vegetation process as many animals cross the Kruger National Park to feed themselves within the mine. - It is recommended that more regular monitoring on boreholes be conducted as many dataless. Also it is suggested that anomalous boreholes be investigated, geochemically logged and re-sampled to verify or determine likely origins and interactions. - For further research, standard values of salt loads should be implemented so as to compare acceptable values with abnormal values. - The study of ABA using static tests should always be coupled with the humidity cells methods. While the former provides with the probability of acid formation, the latter provides with the reaction rates. - Additional studies should be conducted exclusively outside the mine to corroborate with the results from inside the mine.
Open Access
Hydrogeological exploration and characterisation of the aquifers found in Middelburg, Eastern Cape, for town water supply
(University of the Free State, 2014-06) Grobler, Reuben John; Vermeulen, D.
English: The Karoo town of Middelburg in the Eastern Cape Province is solely dependent on groundwater for water supply, as no large surface water bodies are present in the town’s vicinity. Previously (1987) water supply from existing municipal production boreholes was adequate to supply the town, but town growth has now resulted in a water supply shortage. The shallow aquifer with alluvial character currently used as sole source is under severe stress and water levels are declining steadily. Piping water from the Orange-Fish River scheme was considered, but this option was shown to be very expensive (±R180 million). Instead, regional and deep groundwater potential was investigated. Deep exploration borehole drilling to around 300 mbgl was used as discussed in Woodford et al. (2002). A detailed GRIP hydrocensus and groundwater sampling was conducted across the study area. A total of 1695 geosites were surveyed. Of 414 boreholes sampled, the water quality of 16% were good, 45% were marginal, 30% were poor and 9% were dangerous. Six sub-catchments were delineated based on hydrogeological principles and groundwater potential. For each sub-catchment a minimum groundwater balance was calculated, based on a 95% assurance level. The Glen, Dunblane, Karmel and Grootfontein sub-catchments were targeted for groundwater exploration based on their favourable groundwater balances. Geophysical surveys comprised magnetic, electromagnetic and electrical resistivity profiling to determine the orientation of dolerite intrusions. Drilling targets were mainly deep fracturing associated with dolerite ring structures and dyke intrusions. The 18 new boreholes drilled using rotary air-percussion and water-hammer drilling techniques delivered an accumulated airlift yield in excess of 187 ℓ/s with the deepest strike at 236 mbgl. Aquifer tests were conducted and aquifer parameters were calculated using the constant discharge test data and applying the Cooper-Jacob-, FC- and derivative-equations. A total of 26 pumping tests were performed on selected new and existing boreholes. An accumulated sustainable yield was calculated to be approximately 80 ℓ/s. Detail analytical water balances were calculated for the sub-catchments to estimate the amount of groundwater available in each one. Different recharge and abstraction methods were used and compared through analytical balance scenarios. A higher confidence conservative scenario using the saturated volume fluctuation recharge method and a water level-transmissivity based abstraction estimate per sub-catchment showed abstraction:recharge ratios of: The Glen, 15% (33 ℓ/s); Karmel, 32% (20 ℓ/s); Middelburg Municipal, 447% (-100 ℓ/s); Dunblane, 93% (4 ℓ/s); Lusernvlei, 104% (-1 ℓ/s) and Grootfontein compartment, 94% (2 ℓ/s). The chloride mass balance recharge provided even higher values of recharge in the order of 6.7% of MAP for mountainous sub-catchments like The Glen and Karmel, which is in line with Vandoolaeghe’s (1979) mountainous catchment recharge. Numerical modelling was performed to determine whether the estimated recharge-based volumes available and abstraction thereof is feasible given hydraulic parameters. A good (R2 = 0.94) snapshot data calibration was obtained, but history matching (transient calibration) was required to get correlation in hydraulic head trends using time series municipal abstraction. The Present day numerical scenario even with inclusion of the new production boreholes in The Glen showed more favourable balances that the analytical balances: The Glen, 41% (40 ℓ/s); Karmel, 17% (45 ℓ/s); Middelburg Municipal, 184% (-47 ℓ/s); Dunblane, 65% (29 ℓ/s); Lusernvlei, 104% (-1 ℓ/s) and Grootfontein compartment, 48% (36 ℓ/s). The 2 – 5 years of water level information from the new monitoring network developed are also not as negative as expected, however longer groundwater level fluctuation data is required to make conclusive statements. There was also a drought from 1997 – 2002/2003. Current municipal abstraction is sustainable, but should be more spatially distributed. The shallow Middelburg aquifer has excellent hydrogeological properties, except for aquifer thickness. Production boreholes were historically developed in too close proximity to each other, resulting in the local aquifer being stressed beyond its capacity. The key during new groundwater resource development is a wider borehole distribution and monitoring network and the exploration and development of deeper boreholes associated with fracturing within and adjacent to dolerite ring structures. Results predict a connection between the shallow and deep aquifers. The optimised use of shallow aquifers, combined with monitoring and the use of newly developed deep regional boreholes will ensure a more sustainable groundwater supply to Middelburg. Opportunities for artificial recharge are also seen in the Middelburg study area.
Open Access
Investigation into alternative wheat aphid control strategies for emerging farmers
(University of the Free State, 2011) Richter, Johannes Mattheus; Prinsloo, G. J.; Van der Linde, T. C. de K.
In the Qwa-Qwa and Thaba N’chu regions of the Free State Province, South Africa, resource limited farmers that produce wheat are mainly situated in temporary crop environments. They are drastically affected by crop losses that occur during years of serious Russian wheat aphid (Diuraphis noxia) (Kurdjumov) and oat aphid (Rhopalosiphum padi) (Linnaeus) infestations. Therefore the main objective of this study was to identify simple alternate control methods to be used by small-scale farmers for the control of these aphids. The focus was on minimizing the numbers of the immigrating individuals. That must happen before they arrive in the crop habitat and decrease the possibility of the pest population reaching damaging levels when the crop is still in its susceptible phase for insect damage. Plant derived semiochemicals, which could modify insect behaviour, were considered as an option to be used since this could be extracted from plants, and were demonstrated to be successful in other countries. These semiochemicals are also known to attract natural enemies of these insects. It was therefore decided to test two types of extracts (an aqueous and a light mineral oil) which could be easily prepared from four plant species, namely Wild wormwood Artemisia afra (Jacq. ex Willd.), Big thorn apple Datura stramonium (Linnaeus), Khaki bush Tagetes minuta (Linnaeus) and Wild garlic Tulbachia violacea (Harv.). The plants were chosen due to their availability in the wheat production regions and their possible insect repelling properties known from other species in the same genera. The behavioural response of alate aphids D. noxia and R. padi and two parasitoids, Aphelinus hordei (Kurdjumov) and Diaeretiella rapae (McIntosh) to these extracts was tested in olfactometer trials in the laboratory. The aphid D. noxia showed the highest repellence to the aqueous extract of A. afra and the oil extract of T. violacea. Aphid R. padi was also best repelled by the aqueous extract of A. afra and the oil extract of D. stramonium. The parasitoid A. hordei was strongly attracted to the aqueous extracts of A. afra and T. minuta. Diaeretiella rapae on the other hand, was also highly attracted to the aqueous extract of T. minuta, but T. violacea oil extract had a very strong effect on the parasitoid and would be recommended to farmers. Artemisia afra and T. violacea are perennials and available as green material for extraction purposes in the winter when wheat is planted. The other two plants are annuals and not available in winter. The A. afra aqueous extract will repel both aphid species when sprayed early in the wheat growing season when wheat is still small and aphids are flying into the wheat. This extract will also attract A. hordei and this could enhance the biological control of D. noxia. The T. violacea oil extract could also be used to repel D. noxia. It could also be used to attract the parasitoid D. rapae later in the season and enhance the biological control of both aphid species. Thus there are potential alternate simple aphid control methods available for small-scale farmers. These methods should be refined and farmers trained to use them effectively.
Open Access
An investigation of microscopic phases in the Bon Accord Ni-oxide body, Barberton region, South Africa
(University of the Free State, 2012) Wildau, Antje; Tredoux, Marian
Abstract not available
Open Access
Investigation of the possibility of platinum-group element clusters in magmatic systems, using synthetic sulphide melts
(University of the Free State, 2014-01-28) Kennedy, Bianca; Tredoux, M.; Steyl, G.
The behaviour of platinum-group elements (PGE: Ir, Os, Rh, Ru, Pd and Pt) on a nano level may be the key to the enrichment of PGE in mafic ore bodies, like the Bushveld complex. Temperature controlled sulphide melts were used to investigate possible PGE-rich nano phases or clusters, in a magmatic environment, and the influence these structures may have on PGE enrichment. The sulphide portion of a natural Cu-Ni-S ± PGE system was mimicked experimentally. Sulphides are of the first minerals to form in a magmatic system and more likely to carry PGE-clusters. Samples were prepared using the dry powder silica tube technique. The starting powders consisted of a base mixture of an S, Cu and Fe. These were doped with variable concentration of PGE (either Pt or Pd or Ru) and chalcogene ligand (As). The samples were cooled at different rates to monitor the influence of environmental changes (time, chemistry, kinematic- and thermodynamic) on possible cluster formation. A variety of primary and secondary nano structures (<100nm) were measured in the synthetic samples, using semi-quantitative scanning Auger microscopy (SAM). The size, morphology and composition of the nano entities were a function of the PGE-system (chemistry) and allowed cooling time. The structures formed irrelevant of the PGE concentration. Several of the identified nano structures were re-classified as potential PGE-clusters. These structures fall within the size range of clusters (10-100nm) and were a good indication whether clusters could form. Although no conclusive clusters were measured evidence from time of flight secondary ion mass spectrometry (TOF-SIMS) analysis supported the notion that the PGE can form PGE-ligand agglomerations of 10-100nm. Scans showed irregular distribution of PGE-ligand ion bundles in compatible and incompatible phases. The PGE-ligand bundles were conclusive evidence that potential clusters can stay preserved in a system with changes in environment. If this interpretation is correct, it might indicate that a physical enrichment process is at work during the early stages of crystallization in a magmatic environment. However clustering is only one of several mechanisms that may contribute to PGE enrichment of Bushveld-type deposits
Open Access
An investigation of the trace element compositions of gold from Zimbabwe and South Africa: implications for tracing the source of archeological gold artefacts
(University of the Free State, 2011-03) Netshitungulwana, Robert; Tredoux, Marian; Jacobson, Leon
The early black farmers who settled in southern Africa were involved in trading and metal technology. The history of mining for metals like iron, copper, tin and gold in southern Africa spans at least the past 2000 years. The main aim of the research was to test the viability of using gold chemistry to compare the composition of gold ores in South Africa and Zimbabwe with those of the archaeological gold artefacts from Thulamela, Mapungubwe and Great Zimbabwe. Samples from the Archaean greenstone belts in South Africa and Zimbabwe, as well as samples from ores associated with the Witwatersrand Supergroup, were used in the study. Trace element signatures were determined by laser ablation inductively coupled plasma mass speetrometry (LA-ICP-MS), a technique whereby low concentrations (down to low ppb levels) can be detected. In addition, Ag concentrations (wt %) were determined using a scanning electron microprobe, so that Ag could be used as an internal standard during the LA-ICP-MS runs to give semi-quantitative data. The most commonly occurring isotopes in gold, namely, 56Fe, 59Co, 60Ni 63CU, 66zn, 75As, 1880S, 105pd, 195pt, 202Hg, 107.109Ag, and 204, 206,207,208Pb and 209Bi, were used to construct the signatures, using their intensities in the mass spectra in counts per second (cps). Isotopic ratios were used to compare the gold ores with each other. The results show some variations in the signatures of gold from the greenstone belts and the Witwatersrand Basin. The 107Ag and 202Hg concentrations in gold from the Witwatersrand Basin are high compared to the greenstone belts. These differences have implications for the various models of gold deposition in these environments, pointing to different geochemical histories. Multivariate correspondence analysis plots for the major gold deposits show the wide group of the Barberton samples with little or no distinctive characteristics, compared to the Zimbabwean gold samples. The Witwatersrand gold plotted differently to the Barberton Greenstone Belt but closely related to the Zimbabwean greenstone belts. The ratio plot of 56Fe/107 Ag versus 202HglI07 Ag shows that archaelogical gold artefacts differ completely from the natural gold, indicating that the gold could not merely have been cold-worked, as has been suggested. This suggests that gold from anyone archaeological site could not be related to any particular or even regional source. This could be associated with the possibility of mixing of gold from multiple sources, recycling, contamination in melting and trade in items.