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Item 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, LAllanite 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.Item Open Access Aspects of the hydrogeochemistry of the Karoo sequence in the Great Fish River basin, Eastern Cape Province, with special reference to the groundwater quality(University of the Free State, 1978-12) Tordiffe, Eric Arthur Wolferstan; Botha, B. J. V.The aim of the study was to examine some of the major aspects responsible for the chemical quality of the groundwater in the Great Fish River Basin and its influence on the irrigation water. Approximately 18 000 ha of land are at present irrigated from several weirs down the river. The section of the Great Fish River Basin under discussion comprises an area of approximately 25 000 km² located between longitudes 25°E to 27°E and latitudes 31° 15'S to 33° 15'S. This area is divided into the following geomorphologic provinces: The Marginal Region (lower than 760m), the Great Escarpment (750 - 1070m), the Headbas (1070 - 1370m) and the Interior Plateau (higher than 1370m). Each of these provinces play an important part in controlling the movement and the chemical quality of groundwater in the area. Most of the annual precipitation (350 - 450 mm) occurs between February and March when evapotranspiration is at its highest. Runoff from the entire basin amounts to only 3 percent of the annual precipitation. The rest of the water either evaporates immediately because of the semi-arid climatic conditions, or is temporarily stored in the soil before it is lost to the atmosphere by means of evapotranspiration. It is also pointed out that apart from periods of extreme precipitation, the monthly evapotranspiration always exceeds the monthly precipitation. Such semi-arid climatic conditions, as well as the nature of the soils in the area prohibit a fast infiltration of meteoric water and it is therefore doubted whether as much as 5 percent of the annual precipitation over reaches the groundwater table. The area under discussion is underlain by sedimentary rocks of the Karoo Sequence beginning with the glacial deposits of the Dwyka Tillite Formation (680 m) at the bottom, followed by the marine deposits of the Ecca Group (2 340 m), the transitional deposits of the Koonap Formation (980 m) and the fluvial deposits of the Beaufort Group (4 540 m). Because the Koonap Formation represents the transition between the marine (deltaic) deposits of the Ecca Group and the fluvial deposits of the Beaufort Group, it is regarded as a separate formation not belonging to either group. The Beaufort Group on account of the environment in which the sediments were deposited, is subdivided into the Adelaide Subgroup (reducing environment) and the Tarkastad Subgroup (oxidizing environment). Red mudstone is regarded as indicative of an oxidizing environment and is present only in patches in the Middleton Formation, which forms the lower part of the Adelaide Subgroup. No red mudstone is present in the Balfour Formation, which forms the top half of this subgroup, but becomes very prominent in the Katberg and Burgersdorp Formations of the Tarkastad Subgroup. The Balfour Formation, on lithologic grounds, is subdivided into the Oudeberg Sandstone Member (180 m), The Daggaboersnek member (1 200 m), the Barberskrans Sandstone Member (190 mA) and the Elandsberg Member (320 m). It is suggested that the arenaccous units of the Beaufort Group, i.e. the Oudeberg Sandstone Member, the Barberskans Sandstone Member and the Katberg Formation represent periods of major tectonic activity in the provenance which was located to the south-east. During such activity vast amounts of coarse-grained material were transported and deposited at a relatively fast rate. Owing to the semi-arid climatic conditions, which prevail in the area, the soils tend to be rather alkaline with a high clay content and the poor development of an A-horizon. Calcrete or caliche occurs at or near the surface of most of the soils. Dolorite has intruded the sedimentary strata as concordant and conical sills, as well as near-vertical dykes. The dykes in the south of the area have an orientation of approximately 290°, coinciding with the Cape Fold Belt, whilst farther north, a prominent northerly trend with a weaker easterly trend is observed. In the extreme north, where the sedimentary strata is at its thickest, an almost random orientation is present. Various types of dolerite are encountered in the area and of particular interest is the occurrence of quartz dolorite which has intruded a sill of normal dolorite near Speelmanskop. This leucocratic body is probably the result of magmatic differentiation lower down in the cust, whilst limited differentiation whithin the body itself, both from floor to roof and in an "up-dip" direction, must have occurred. The intrusion of the dolerite is of particular importace because of the fracture zones it causes in the adjacent sedimentary rocks. Such zones are normally open to circulating groundwater. Where the dolerite itself is not fractured it may act as an impervious barrier when crossing the regional flow path of the groundwater. In such cases groundwater compartments are developed. Weathering of the provenance and of the various rock-types in the area, diagenetic processes which proceeded the deposition of the sediments in the Karoo Basin and the adsorption and ion exchange during the interaction of the surface and groundwater with the surrounding rocks, are considered to be the main geochemical factors responsible for the changes in the chemical quality of the groundwater in the area. During the chemical weathering of the rock-forming minerals cations such as Na+, K+, Mg++ are released to solution in the groundwater, whilst compounds such as SiO2O3 regroup to form residual clay minerals such as montmorillonite. Weathering of the sedimentary rocks is, however, limited because of the fact that the primary minerals which constitute such rocks have already withstood at least one cycle of weathering in the provenance. In areas where leaching is vigorous, K+ is, however, removed from illite in the mudstone with the result that this clay mineral adopts swelling features similar to montmorillonite, thus causing the rock to crumble. Dolerite in turn, because of its igneous origin, is more prone to chemical weathering. As a result of compaction the porosity and permeability of the sediments in the Karoo Basin was reduced to extremely low values. The chemistry of the interstitial waters was also altered by this process because of the diagenetic alteration of montmorillonite to illite during which K+ is removed from the water, whilst SiO2, H2O, Na+, Ca++, Mg++ and Fe++ are added to the water. During the compaction process, C1- was accumulated in the remaining water in the lower strata as result of ultra-filtration as the formation water was squeezed through clay-rich mudstone layers. Because of its small ionic radius and high electrical charge, Ca++ is adsorbed by the clay minerals in the mudrock of the area to a far greater extent than any of the other cations present. The maximum concentration of adsorbed Ca++ is observed in the Oudeberg Sandstone Member, which suggests that this unit represents a geochemical marker. A gradual increase in the CEC of the mudrock from the lower strata to this unit is furthermore observed. Sodium concentrations increase toward the south of the study area, therefore suggesting an influence of the palaeomarine environment on the adsorbed cations. Groundwater in the Great Fish River Basin is restricted mainly to joints in the sedimentary rocks and to fracture zones caused by the intrusion of dolerite. The water levels in most of the bore-holes therefore represent a pressure or piezometric surface rather than an actual water table. Such levels, however, regionally represent a surface which closely resembles the surface topography, whilst the flow of groundwater is down the regional slope and the rivers act as effluent drainage canals for the groundwater. Although the groundwater is recharged in the higher lying areas by circulating meteoric water, there appears to be no direct relationship between the seasonal precipitation and the groundwater levels. As far as the origin of the major ions in the groundwater is concerned, the cations are derived mainly from the weathering of primary rock-forming minerals, whilst the anions accumulate from non-lithologic sources. Generally, the groundwater in the areas of recharge, i.e. the higher lying areas, has a pronounced Ca++ and HCO-3-character, whilst in the stagnant low-lying areas Na+ and C1- are the predominant ions. In between the two extremes, groundwater with a prominent Mg++ and SC=4-character is encountered. This trend corresponds well with the normal metamorphism of natural waters and appears to be controlled largely by the topography of the area. Groundwater with a distinctly high Na+ and C1- -concentration also has a high salinity concentration. The pH in turn is highest in the areas of high Ca++ and HCO-3-concentrations and lowest in the areas of high Na+ and C1- -concentrations. All the water of the area is, however, oversaturated in relation to CaCO3 and, where conditions are suitable, calcrete is precipitated. Chloride is the dominant anion in the lower strata of the Karoo Sequence and is attributed mainly to the retention of this ion during the migration of the formation waters through the argillaceous material. High salinities, as a result of high Na+ and C1- -concentrations, prevail in the groundwater up to the Daggaboersnek Member. From the Barberskrans Sandstone Member upward, the concentration of these ions decrease sharply. The cation percentages in the groundwater of the upper strata, however very considerably, thus indicating the influence of chemical weathering. There is more SO=4 in the groundwater of the lower strata, which was deposited under reducing conditions, than in the upper strata, which was deposited under oxidizing conditions. This is attributed to the formation of pyrite under reducing conditions, which can later oxidize to release SO=4 to the water. During the periods of extreme precipitation a considerable amount of meteoric water infiltrates down to the groundwater level, dissolving precipitated salts on its way down. This naturally causes an increase in the salinity of the groundwater and is a result of an increase in Na+ and C1-. Seepage water in the Great Fish River contains Na+ as the main cation and increases gradually in concentration farther downstream. To the north of Cradock HCO-3 is the dominant anion but it decreases rapidly farther downstream, with a concurrent sharp increase in the C1- -concentration. The increase in the Na= and C1- -concentration coincides with an increase in the total salt load farther downstream. A similar trend is observed in the change in groundwater quality down the Great Fish River. This is conclusive proof of the influence of groundwater on the seepage water in the river. The groundwater compartments caused by dolerite intrusions also have a marked influence on the quality of the seepage water. During a single irrigation lead from Grassridge Dam the initial irrigation water reaching the consecutive weirs along the river possessed an extremely high salinity load as a result of the solution of precipitated salts in the river bed as well as the flushing of saline water from stagnant pools. The duration of the saline head increased at each consecutive weir downstream. Such conditions present a serious threat to the irrigable land along the Great Fish River and therefore measures will have to be taken to either prevent such contamination of the irrigation water or to limit the application of such contaminated water by allowing the saline head to pass the various weirs.Item 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.Item 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 availableItem 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.Item Open Access Composition and evolution of the proterozoic Vioolsdrif batholith (including the Orange River group), Northern Cape province, South Africa(University of the Free State, 2011-12) Minnaar, Hendrik; Schoch, A. E.English: The Vioolsdrif Suite and Orange River Group represent genetically related calcalkaline plutonic and volcano-sedimentary assemblages of Palaeoproterozoic age formed during the Orange River orogeny. Together they occupy the largest part of the Richtersveld Subprovince – a unique tectono-stratigraphic terrane. Radiometric data indicate the period of formation roughly between 2.0-1.73 Ga. The subprovince has been vastly eroded and isolated from its original tectonic environment by subsequent tectonic processes, leaving a relatively small portion of its original extent for investigation. Previous studies have dealt with limited parts of the subprovince and although informal subdivisions of the Orange River Group and Vioolsdrif Suite are generally in use, some correlations and further subdivisions remained controversial. This study has two main aims, viz., to propose formal subdivisions of the two units and to investigate the magmatic processes and original tectonic environment of their formation. Geochemical evidence is presented here to support the proposed subdivisions, which were previously based entirely on field evidence. The subdivisions largely follow that of previous studies. The Orange River Group is subdivided into the Haib and De Hoop Subgroups. Geochemical evidence show that these two subgroups differ in the magmatic processes that led to their formation. The Haib Subgroup shows a genetic gradational relationship with the Vuurdood Subsuite, which is regarded as remnants of the primary magmas. The De Hoop Subgroup does not display this relationship with the Vuurdood Subsuite. The Vioolsdrif Suite is subdivided into the Vuurdood, Goodhouse and Ramansdrif Subsuites. Mafic-ultramafic bodies of the Vuurdood Subsuite are regarded as remnants of the primary magmas. This is based on multi-element variation diagram patterns and comparison to source magmas in modern island arcs (MORB). Previous studies have also shown that initial isotope ratios for the Vuurdood Subsuite are similar to those of the Goodhouse Subsuite and Orange River Group, relating them to a similar source. Dark mineral cumulate material are contained in the mafic-ultramafic bodies. The Goodhouse Subsuite is subdivided into the Khoromus Tonalite, Blockwerf Migmatite, Xaminxaip River Granodiorite, Gaarseep Granodiorite and Hoogoor Granite. The Khoromus Tonalite is identified as the oldest unit within the subsuite based on contact relationships as well as radiometric data, which continuously render older ages for the Khoromus Tonalite compared to the other units within the subsuite. Certain field and petrological observations in this unit may be interpreted as products of magma mixing processes. The Blockwerf Migmatite is distinguished from the other units by its migmatitic character and anomalous La/Yb ratios. The unit is identified as a possible remnant volcanic centre. The Xaminxaip River Granodiorite is interpreted as a subvolcanic unit and is characterised by the development of migmatite in places. This migmatite is attributed to metamorphic conditions which locally reached high grade in an orogenic geothermal regime. The Gaarseep Granodiorite represents the main phase of the Vioolsdrif Suite. Its compositional range includes all those represented by the other units individually from gabbro through diorite, tonalite and granodiorite to granite. Its development spans almost the entire evolutionary history of the Richtersveld Subprovince as a whole. The Hoogoor Granite is included in the Goodhouse Subsuite based on the geochemical variation patterns and available radiometric evidence. The Ramansdrif Subsuite is subdivided into the Ghaams and Sout Granites based on grain size variation and petrological evidence. The subsuite could have been formed by partial melting of the older plutonic phases of the Vioolsdrif Suite. The deformation associated with this partial melting event has not been identified. Previous studies have related the evolution of the Richtersveld Subprovince to modern subduction zone magmatism similar to that of the Andean volcanic arc. This is largely supported by the current study, however, a change in magmatic processes and the tectonic environment can be observed in the geochemical variation patterns. Multielement diagrams show patterns typical of subduction zone magmatism for both the Orange River Group and Vioolsdrif Suite. During the initial stages, primary magmas, now represented by the Vuurdood Subsuite, were derived from a depleted mantle reservoir. The first volcanic eruptions – those of the Haib Subgroup – represent fractional crystallization products off the primary magmas. With progressive development of the arc, newly formed crust was continuously recycled back into the mantle and crustal partial melting led to a change in magmatic processes with magma mixing and contamination becoming increasingly important. Tectonic discrimination diagrams suggest that the initial stages of the batholith development may be compared to a primitive continental arc, while the later stages may be be compared to a typical continental arc.Item 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.Item 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.Item Open Access Die geologie in die omgewing van Britstown(University of the Free State, 1977) Lemmer, William MurrayAfrikaans: '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.Item Open Access Dike-induced aquifer models derived from high-resolution multi-spectral satellite imagery(Nature Research, 2024) Radebe, Samkelo; Clark, MartinThe Main Karoo Basin in South Africa is a typical example of an expanding arid region dependent on groundwater resources. Dolerite dikes in the region, analogous to dolerite dikes worldwide, are known to influence subsurface groundwater flow and spatially relate to high-yielding boreholes. Here, the effect of dolerite dikes on groundwater flow is remotely assessed using the Modified Soil Adjusted Vegetation Index derived from high-resolution multi-spectral satellite imagery. From imagery collected during the wet and dry seasons of 2018 and 2021, two aquifer models relating to 505 dikes were identified; (1) barrier-controlled aquifers are induced by ~ 56% of dikes, (2) fractured aquifers are induced by ~ 35% of dikes. Surficial areas overlying aquifers are also shown to sustain vegetation growth through dry seasons. This research demonstrates the efficacy of vegetation indices to rapidly characterise dike-related aquifer models and their seasonal sustainability, critical for effective groundwater exploration and management.Item Open Access The effect of crystal-plastic deformation on isotope and trace element distribution in zircon: Combined BSE, CL, EBSD, FEG-EMPA and NanoSIMS study(Elsevier, 2016) Kovaleva, Elizaveta; Klotzli, Urs; Habler, Gerlinde; Huet, Benjamin; Guan, Yun-bin; Rhede, DieterPlastically-deformed zircon grains from granulite-facies (Ivrea-Verbano Zone, Southern Alps, Italy) and amphibolite-facies (Tauern Window, Eastern Alps, Austria) shear zones have been investigated. The main focus was on the effects of crystal-plastic deformation on the distribution of trace elements and their isotopes. Zircon grains reveal crystal-plastic deformation patterns in form of (I) gradual bending of the lattice (high density of free dislocations), (II) highly-deformed margins revealing a combination of low- and high-angle boundaries and gradual bending of the lattice, and (III) a low-angle boundary (LAB) network. Chemical and isotopic maps and profiles show that trace elements in zircon are re-distributed in all plastically-deformed domains. Changes in trace element composition along LABs are sometimes revealed by brighter CL and darker BSE signal. LABs and domains of high free-dislocation density have depletion in U, Y, Yb and enrichment in Ce, La and Nd, while Ti and P are either enriched, depleted or remain unaffected, and Hf demonstrates stability. Y and Yb are decreased in concentration across LABs, and have oscillating concentration in domains of high free-dislocation density. Our observations confirm that crystal-plastically deformed domains in zircon act as effective pathways for trace cations. The Pb isotopic system is disturbed by crystal-plastic deformation microstructures, as indicated by relative 207Pb/206Pb ages showing significant discordance in plastically-deformed zircon domains. In deformed domains, a positive correlation between dislocation density and the degree of isotopic age distortion is observed. Fractured or porous domains and domains with high density of (sub)grain boundaries are enriched in common Pb from the matrix, and thus show significantly older relative 207Pb/206Pb ages than pristine domains. In contrast, Pb loss occurs in domains with high free-dislocation density at a distance of 5-10 μm from the grain boundary, caused by out-diffusion of radiogenic Pb. This study adds to a growing database on the consequences of crystal-plastic deformation for trace elements and isotopic systems in zircon. We provide additional evidence that such deformation cannot be neglected and may have important implications for zircon geochronology and geochemistry.Item 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.Item 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.Item Open Access Geochemical and mineralogical characterization of the lithological units of the geodehoop colliery in the Witbank coalfield to fathom the source and the receptor of metals in the riet-olifants catchment, South Africa(University of the Free State, 2022) Netshitungulwana, Khashane Robert Tshishonga; Gauert, C.; Vermeulen, D.; Yibas, B.The study aims to understand the element deportment's geochemical characteristics from the source, pathway and receptor realm in the Riet-Olifants catchment (ROC) drainage system. The ROC is part of the Olifants primary catchment (OPC) area that extends over the border between South Africa and Mozambique and covers a total area of approximately 87000 km2. The ROC is the area most influenced by coal mining activities surrounding the major towns of Emalahleni (formerly Witbank) and Middleburg. The geological units of the Vryheid Formation, Ecca Group of the Karoo Supergroup dominate the area, with the Witbank coalfield being the primary resource for coal. The focus herein is directed on identifying the geochemical characteristics of the source rocks, the pathways of mobilization and transport and the receiving environment. The key to this study is to identify the mobile elements in minerals occurring in different sedimentary units of the source rock geological units, with the assessment of its contribution to the elevated metal concentrations in the receiving environment of the drainage area. The results are also tested in determining the geogenic element entry of naturally occurring source rocks from an anthropogenic source. In recent years, the area has been under regulatory verification over high pollution levels through coal mine drainage (MD). Previous studies show that although the land use of industrial and agricultural activities is also essential, the contribution to water and sediment contamination from the mining activities within the catchment is significant and yet needs to be fully understood.Item 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.Item Open Access Geochemical evolution in defunct gold mine tailings and modelling of seepage water quality: an investigation of a typical tailings storage facility in the East Rand, Johannesburg, South Africa(University of the Free State, 2022) Fourie, Petrus Johannes; Usher, B.; Hansen,R. N.The geochemical evolution in a defunct tailings dam was investigated in the East Rand Basin of the Witwatersrand. The research aimed to geochemically characterise the tailings, quantify oxygen infiltration into the tailings dam and develop a numerical geochemical model to simulate the geochemical evolution within the dam over the past 60 years. Two holes (3.4 and 6 m deep, respectively) were hand-augured into the tailings dam to geochemically characterize the tailings. Tailings samples were collected at roughly 15 cm intervals. On selected samples from the 6 m hole, the whole-rock elemental composition (using X-ray Fluorescence and a Leco Element Analyser) was performed, as well as acid-base testing, X-ray diffraction and Scanning Electron Microscope. Field measurements of pH, Electrical Conductivity (EC) and Oxidation-reduction Potential (ORP) were performed on drilled-out samples of the 3.4 m hole. The oxygen concentration in the tailings gas phase was measured to correlate the oxygen ingress with the other measured geochemical parameters and for later use in the geochemical model. Air chambers were installed in the 6 m hand-augered hole. Each air chamber comprised a perforated 7 cm high plastic container wrapped in a geotextile that is then connected with an 8 mm silicon pipe. Air collection chambers were installed at depths of 0.5 m, 1 m, 1.5 m, 2 m, 2.5 m, 3 m, 4 m, 5 m, and 6 m. Based on the oxygen concentration in the gas phase, the top of the tailings dam was subdivided into three geochemical environments, namely the Oxic Zone (0-2 m), the Transition Zone (2-4 m), and the Anoxic Zone (>4 m). The data shows that oxygen penetrates slightly deeper during the winter than in the summer months. The seasonal effect could be attributed to the higher rainfall in the summer than in winter. A conceptual model of the geochemical evolution within the tailings dam was developed. The aim was to outline the major mechanisms that influence the geochemical evolution in the dam to include them in the numerical model. Batch reactor testing was performed at three different pH's (pH ~3, pH ~5 and pH ~7) to back-calculate the effective surface area of the pyrite in a tailings sample based upon its reaction during the experiment. The experiments were performed over about 14 days. Except for the last few days, samples were collected twice a day. The sulphate production was the lowest in the pH ~3 experiment and the highest in the pH ~7 experiment. This is because pyrite oxidation by oxygen is inversely proportional to hydrogen activity. The modelled pyrite reaction rate fitted the results for all three experiments. The optimal surface area was determined at 1046.26 g/cm². A numerical geochemical model was performed to simulate the geochemical evolution within the dam over the past 60 years. The primary objective of the modelling was to improve the understanding of the mechanisms that control the geochemical reactions and dispersion of chemicals. A secondary objective of the model was to match the model results with the observations 60 years after closure.Item Open Access A geochemical study of the Middle Group chromitites, Helena mine, Bushveld complex, South Africa(University of the Free State, 2011) Kottke-Levin, Janine; Tredoux, Marian; Gauert, ChristophThe study in hand reports on compositional variations in mineral and whole-rock geochemistry of the chromitite and silicate layers occurring in the Middle Group of the eastern Bushveld Complex. Special attention is paid to the platinum-group element (PGE) content and mineralization as well as the nature of platinum-group minerals (PGM) within the MG sequence. A general progressive evolution of the MG chromitite layers can be deduced from chromite composition showing decreasing Mg# and enrichment of Fe and Al relative to Cr as well as from the decreasing whole-rock Mg#. At the LCZ/UCZ transition no marked change in mineral and whole-rock geochemistry can be observed, indicating that the MG sequence derives from a continuously progressive evolving melt. The presence of one parental magma for the formation of the MG is further substantiated by the chondrite-normalized PGE patterns of the MG chromitite layers, which resemble each other. They further resemble that of the UG2, which suggests that they derive from the same magma and a similar style of mineralisation applied. One marked reset to compositions even more primitive than the MG1 chromitite layer is present at the level of the MG4A chromitite layer, which is illustrated by a low Mg#chr, low whole-rock Mg#, low mineral and whole-rock Cr3+/(Cr3++Fe3+) ratios and increasing mineral and whole-rock Cr3+/(Cr3++Al3+) ratios and TiO2 contents. It strongly suggests the addition of hot and primitive magma at this level of the MG stratigraphy. Whole-rock geochemistry of the silicate layers is strongly governed by mutual influence of co-precipitating minerals competing for major elements like Mg, Fe, Al or Cr, and hence a statement to general trend with respect to evolution from bottom to top of the stratigraphic column of the MG sequence can’t be made. Nevertheless, a strong decrease in whole-rock Mg# and low whole-rock Al2O3 concentrations at the level of the MG4A pyroxenite is illustrated, which can be ascribed to the same event of addition of primitive magma concluded for the MG4A chromitite layer. The existence of Na-rich silicate inclusions occurring in chromite of all the MG chromitite layers most likely proves chromitite formation by mixing of primitive melt with a siliceous melt. Hence, the general process for the formation of the chromitite layers and their corresponding silicate layers in the MG seems to be mixing of a primitive (mafic-ultramafic) parental melt with siliceous roof-rock melt deriving from the granophyric Rooiberg felsites. Although Cu deriving from the base metal sulphides (BMS) seems to migrate away from the chromitite layers, local Cu enrichment in the chromitite layers to concentrations up to >6000 ppm can be observed. This excess Cu most likely derives from an external source e.g. country rocks, which could have ‘generated’ metal-loaded hydrothermal fluids. Excess S occurring in the silicate layers may result from limited, probably hydrothermal, dissolution of BMS from the respective chromitite layer below. Chromitite samples have been investigated with the mineral liberation analyzer (MLA) for their PGM. The study focused on the mineral association of the PGM, i.e. whether they occur liberated, locked or attached to gangue or the BMS, since the mineral association is important to conclude on PGE mineralization and PGM formation. The majority of the PGM occurring in the chromitite layers of the MG sequence are Pt- Rh -sulfides (26.2%), followed by laurite (25%), Pt-Pd -sulfides (24.3%) and Pt -sulfides (13.8%). The remaining 10.7% comprise PGE –sulphoarsenides and PGE- arsenides, Pt - and Pd –alloys and Pt - and Pd –tellurides. Except laurite, which is commonly locked in chromite (66%), the PGM are dominantly associated with silicate minerals, and to a lesser extend with the BMS only. According to this discrepancy in the PGM association, PGE mineralization of the MG chromitite layers most likely can’t be modelled in terms of the R-factor and therefore PGE concentration by the cluster model is favoured by the author. Alteration of the primary silicate minerals in the MG chromitite layers to amphibole, chlorite, talc, mica and quartz can be observed locally. Since the primary BMS assemblage (chalcopyrite, pyrite and pentlandite) shows losses of Fe, Cu and S, and millerite, a Ni-rich sulphide of secondary origin, occurs, the influence of hydrothermal fluids on the chromitite layers was concluded. Besides affecting the BMS, the fluid most likely also redistributed the PGE occurring in solid solution in the BMS, i.e. Pt and Pd, as especially the negative slope from Pt to Pd in the chondrite normalized PGE patterns of the MG chromitite layers suggests. Enrichment of the high-temperature PGE (HT-PGE) over the low-temperature PGE (LT-PGE) is depicted in the chondrite normalized PGE patterns of the MG chromitite and silicate layers. The fact that the HT-PGE are enriched relative to the LT-PGE in the lowermost MG chromitite layers as well as in the MG4A suggests that temperature could play a role in PGE fractionation. Temperature control on PGE fractionation has also been concluded from changing Pt/Ir ratio in dependence of the whole-rock Al2O3 content from bottom to top of the MG sequence, with increasing Al2O3 concentrations considered to point to decreasing temperature. Hence, Al-depletion, i.e. decreasing Al2O3 content, of chromite relative to Cr may result in enrichment of the HT-PGE relative to the LT-PGE. The LT-PGE are preferentially concentrated by increasing amounts of plagioclase within the chromitite layers.Item 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.Item Open Access Geological conditions and environmental impact of the Mohale Dam, Lesotho Highlands Water Project(University of the Free State, 2004) Letlatsa, Gerard Molatoli; Praekelt, Hermann J.; Van Tonder, Gerrit J.Abstract not availableItem 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 AndriesDie 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.