Scheelite, wolfram Ite and cassIterIte mIneralizat ion is hosted wIthin numerous quartz-tourmaline-feldspar-fluorite veins at Van Rooi's Vley, N.W. Cape Province . MineralizatIon and hydrothermal alteration within, and around, these veins is hIghly complex and reflects the intricate interaction of hydrotherma l activity upon a structurally deformed sequence of ProterozoIc med ium to high-grade gneisses. Four distinct stages of alteration and mineralization occurred, including a l ate 'epithermal stage'. Although the location of mineralization was strongly controlled by st ructure, the concentration of mineralizati on was controlled by physicochemical variables, of which host-rock geochemistry was particularly important . Further W/Sn mineralization occurs on a local scale, some of which is spatia lly related to minor leucogranite dykes. Leucogranite bodies are not uncommon within the region and some are enriched in Wand Sn. By comparing FIB ra tio s,W/Sn ratios, the alteration mineralogy, the ore mineralogy and the Fe-content of tourmaline, the deposits within the Van Rooi's Vley area can be placed into a 'proximal' to 'distal' classification, with respect to a common source of mineralizing hydrothermal fluids. The Van Rooi's Vley deposit, whilst affiliated to greisen-style deposits, represents a ' distal' quartz-vein lode deposit. / KMBT_363 / Adobe Acrobat 9.53 Paper Capture Plug-in

Geochemical, mineralogical and tenor variation studies were carried out on the cores from UMT040, UMT064 and UMT063, located in the Flatreef on Turfspruit, in the southern sector of the Platreef. The investigation comprised three objectives (1) to identify controls on mineralisation in the upper section of the Platreef, (2) to construct a 3D PGE tenor model, and (3) to test whether the new geological interpretation on Turfspruit correlates with the eastern and western limbs of the Bushveld Complex. The above-mentioned holes were used for geochemical analyses of major and trace elements; and UMT064 was also used for orthopyroxene microprobe analyses. For construction of the tenor model, a total of 276 drill holes were used. The distance between drill holes for geochemical studies is 145 m and 175 m respectively; and for the tenor model is approximately 100 m. The outcomes of the study have demonstrated that the upper section of the Platreef comprise at least four lithological units i.e. the topmost portion of T1, lowermost portion of T1, T2 Upper and T2 Lower that can be interpreted to have been formed by four separate pulses of magma. Considering the possibility of the T2 Lower being metamorphosed calc-silicates, this reduces the number of magma pulses to three. This is supported by the mineralogy, geochemical content and tenor variations. The T1 is made up of an orthopyroxenite (feldspathic in places), the T2 Upper comprised a pegmatoidal orthopyroxenite (also feldspathic in places) and the T2 Lower is made up of a harzburgite. High grade PGE, Ni and Cu mineralisation was found to occur within two zones in the upper section of the Platreef i.e. the T1m and T2 (Upper and Lower). Mineralisation occurs in the form of base metal sulphides such as pyrrhotite, pentlandite and chalcopyrite; and PGEs are dominated by amphoterics (PGE-arsenides, tellurides, antimonides and bismuthinides). These amphoterics are associated with base metal sulphides. The sulphides in both the T1m and T2 are interstitial. PGE minerals such as michenerite, sperrylite, hollingworthite and cooperite are present in the study area. In the T2, an increase in sulphide content and PGE grades are generally associated with the presence of the “main” chromitite stringer/ seam at the contact between a feldspathic pyroxenite (T1) and the coarse-grained to pegmatoidal pyroxenite (T2 Upper). Several other chromitites might be present above and below this contact, and it has been noted that not all of those chromitites are associated with an increase in sulphide content and higher PGE grades. PGE grades were found to be higher in T2 Upper than in T2 Lower, whereas, the base metals (particularly Ni) are generally higher in T2 Lower. In the T1m, mineralisation occurs close to the contact between the feldspathic pyroxenite and orthopyroxenite, but only the orthopyroxenite hosts the sulphides. Chromitite stringers rarely occur in the T1m. Where present, they generally occur at the top of the mineralised zone. The sulphides in both the T1m and T2 are thought to have resulted from separate and different processes. Those in the T1m are thought to have resulted from a fractional segregation process, whereas the sulphides in the T2 were thought to have been emplaced in bulk or as a mush. The 3D PGE tenor model has demonstrated that the tenor in both the T1 and T2 are higher than previously thought for the northern limb of the Bushveld Complex. Tenors in the T1 reach up to 700 ppm, whereas tenors of about 1000 ppm were recorded in the T2. These tenors are comparable to the tenors measured from the sulphide melt inclusions elsewhere in the northern limb. Tenors are the highest in the northwestern part of Turfspruit and they gradually decrease towards the southeast. Both the T1 and T2 are dominated by a tenor of about 100 ppm. In the T1, a tenor of 250 ppm is dominant in the northwestern and southeastern parts of the study area, whereas in the T2 it is only dominant in the northwestern part. Vertical variation in tenors has shown that the tenors are the highest in the topmost portion of the T1 and at the top of T2 Upper (below the T1-T2 contact). The T1 has been found to be comparable with the Merensky Reef due to the following: (a) similarities with respect to major and trace element compositions of whole rock analyses; (b) Cr/MgO ratios which are greater than 80; and (c) similarities in the pyroxene content excluding the MgO/((MgO)+FeO) ratio and CaO contents; and in the PGE tenor of the sulphides. In addition, the T1 has many of the characteristics of the model proposed by Naldrett et al (2009) for the formation of the Merensky Reef in the western Bushveld. However, the differences between the T1 and the Merensky Reef were also noted i.e. the MgO/((MgO)+FeO) ratios in this study are lower (averaging 0.71) than the Mg# reported for the Merensky Reef (Mg#78-83), the upper Critical Zone (Mg#78-84) and elsewhere in the Platreef north of Turfspruit. The CaO levels (representing the wollastonite component of the orthopyroxene) at Turfspruit are higher (>2 wt %) compared to the Merensky Cyclic Unit and other parts of the northern limb where the CaO levels are below 2 wt %. This is an indication that the pyroxene composition at Turfspruit is more evolved compared to the Merensky Reef.

The Albert Silver mine is situated on the farm Roodepoortjie, 32 kilometres north of Brorikhorstspruit in the Transvaal. The deposit forms the largest of a number of sub-parallel quartzhematite lodes accompanied by sulphide mineralization and is accompanied by an extensive alteration zone along its northern flank. / Thesis (M.Sc.)-University of Natal, Durban, 1970.

The variations in the composition, specifically the Cr20 S content and the Cr:Fe ratio, and the morphology of the Lower Group (LG) and Middle Group (MG) chromitite seams of the Critical Zone (CZ) across the western Bushveld Complex, including the Ruighoek and Brits sections, is investigated by means of whole-rock chemical data, both major and trace elements analysis, XRD and electron microprobe data. As a result ofthe paucity of exposed or developed LG1 - LG5 chromitite seams in the western Bushveld Complex, this study is confined to the investigation of the compositional variations of the LG6 to MG4 chromitite seams. In only one section, the Ruighoek section, was the entire succession of chromitite seams, from the LG1 - MG4, exposed. The silicate host rocks from the LG6 pyroxenite footwall to the collar of the CC2 drillcore (lower uCZ) in the Rustenburg section were sampled. This study reviews the compositional trends of the silicate host rocks, as the compositional variations of the chromitite seams reflect the chemical evolution of the host cumulate environment and, to a lesser degree, the composition onhe interstitial mineral phases in the chromitite seams. The compositional variations of the LG and MG chromitite seams are attributed to the compositional contrast between the replenishing magma and the resident magma. The chemical trends of the LG and MG chromitite layers and the host cumUlate rOCKS do not support the existence of two compositionalfy dissimilar magmas in the CZ, rather the cyclic layering of the CZ and the chemical variations of the chromitite seams are attributed to the mixing of primitive magma with the resident magma, both of which have essentially similar compositions. The compositional variations of the LG and MG chromitite seams along strike away from the supposed feeder site (Union section) to the distal facies (Brits section) are attributed to the advanced compositional contrast between the resident magma and the replenishing primitive magma pulses. The CZ is characterized by reversals in fractionation trends and this is attributed to the compositional evolution of the parental magma and not to the replenishment of the resident magma by influxes of grossly dissimilar magma compositions. The Cr20 S content and the Cr:Fe ratio of the MG chromitite layers increase from the Ruighoek (near proximal) section to the Brits section (distal facies). This is attributed to the advanced compositional contrasts between the resident magma and the replenishing primitive magma. In contrast, the Cr20 3 content and Cr:Fe ratios ofthe LG6 and LG8a chromitite seams decreases eastwards from the Ruighoek section. The average Cr:Fe ratio for the western Bushveld Complex is between 1.5 and\2.0, nonetheless, a progressively lower Cr:Fe ratio is noted from the LG1 chromitite up through to the MG4 chromitite seam in the Ruighoek section. tn the LG2 - LG4 chromitite interval a deviation to higher.lratios is encountered. A progressive substitution of Cr by AT and Fe in the Cr-spinel crystal lattice characterizes the chromitite succession from the LG1 seam up through the chromitite succession to MG4. The petrogeneSiS of the chromitite seams of the CZ is attributed to magma mixing and fractional crystallization of a single magma type.

M.Sc. (Geology) / Please refer to full text to view abstract

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

Text in Afrikaans / Prospektering is een van die eerste en belangrikste stappe in die mineraalontginningsproses en dit word ondersoek teen die agtergrond van die Mineraalwet 50 van 1991, wat die belangrikste "mynwette" herroep en die Suid-Afrikaanse mineraal- en mynreg in vele opsigte op 'n heel nuwe grondslag geplaas het. Die hoofdoel met hierdie proefskrif is om prospekteerregte te sistematiseer en te bepaal of dit beperkte saaklike regte daarstel. Ten aanvang word bepaal welke aktiwiteite prospektering daarstel en welke stowwe regtens as minerale kwalifiseer. Daar word gekyk na die regte waarvan prospekteerregte dee! vorm of waaruit dit afgelei word, naamlik eiendomsreg en mineraalregte. Die afskeiding van minerale van grond, die afskeiding van mineraalregte van grondeiendomsreg en die afskeiding van prospekteerregte van mineraalregte en grondeiendomsreg, asook die inhoud van en beperkings op die uitoefening van prospekteer- en mineraalregte, word ook ondersoek. Daar word veral aangetoon dat mineraalregte nie so wyd is as wat algemeen aanvaar word nie en dat dit 6f by die af skeiding van die roerende minerale tot niet gaan of uitgeput raak 6f in eiendomsreg daarop oorgaan. Prospekteerregte word meestal verleen by wyse van prospekteerkontrakte, waarvan daar verskillende verskyningsvorme bestaan en waarvan die een wat in die Registrasie van Aktes Wet 47 van 1937 omskryf word, as uitgangspunt geneem word. Aangesien die reg om te myn ook die reg om te prospekteer insluit, word die verlening van mynregte en antler verkrygings van prospekteerregte ook behandel. Alvorens gemeneregtelike prospekteerregte egter uitgeoefen mag word, meet magtiging daarvoor by die staat verkry word. Die verlening van statutere prospekteer- en mynmagtigings het by die inwerkingtreding van die Mineraalwet 50 van 1991 grondige veranderings ondergaan wat tesame met die relevante oorgangsbepalings ondersoek word ten einde die uitwerking van die wet op prospekteerregte te bepaal. Die vereistes vir en die regsaard van die verskillende regte word ondersoek ten einde 'n oorsig van prospekteerregte daar te stel en dit vlugtig met veral Australiese reg te vergelyk. Daar word tot die gevolgtrekking geraak dat blote prospekteerregte nie beperkte saaklike regte daarstel nie. / Prospecting is one of the first and most important steps in the minerals exploitation process and is examined against the background of the Minerals Act so of 1991, which repealed the most important "mining" legislation and in many ways placed the South African mining and minerals law on a completely new basis. The main purpose of this thesis is to systematise prospecting rights and to establish whether they constitute limited real rights. It is at the outset determined which activities constitute prospecting and which materials qualify in law as minerals. The rights from which prospecting rights are derived or of which they form part, namely ownership and mineral rights, are considered. The severing of minerals from land, the severing of mineral rights from landownership and the severing of prospecting rights from mineral rights and landownership, as well as the contents of and limitations on the exercising of prospecting and mineral rights, are also examined. It is in particular shown that mineral rights are not as comprehensive as is generally accepted and that they either terminate or are exhausted upon severance of the movable minerals from the land or are converted into ownership thereof. Prospecting rights are mostly granted by way of prospecting contracts, of which different varieties exist and of which the one defined in the Deeds Registries Act 47 of 1937 is taken as the starting point. Since the right to mine includes the right to prospect, mining rights and other acquisitions of prospecting rights are also considered. Before common law prospecting rights may be exercised, however, authority to do so must be obtained from the state. Upon the commencement of the Minerals Act 50 of 1991, the granting of statutory prospecting and mining authorisations underwent fundamental changes, which are examined with the relevant transitional provisions to determine the effect of the act. The requirements for and the juridical nature of the various rights are considered in order to establish an overview of prospecting rights and briefly to compare them mainly with Australian law. The conclusion is reached that mere prospecting rights do not constitute limited real rights. / Jurisprudence / LL. D.

D.Phil. / This study which describes rocks of the Upper Critical Zone of the Bushveld Complex is subdivided into three parts. The main rock type of the Upper Critical Zone, the noriteanorthosite, is the subject of the first part. Inclusions in chromite and plagioclase were studied. The inclusions' in chromite were observed at different stages of their formation. The chromite crystals usually overgrow plagioclase, pyroxene and hydrous minerals (biotite, amphibole and clinozoisite) trapping them at grain boundaries or triple junctions of chromite host grains. With 'continuous growth of the host minerals the inclusion starts changing its shape from elongated to circular and the hydrous mineral proportion of the inclusion increases. Simultaneously amphibole changes its composition from pargasitic to tremolitic...

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. 23 September, 2014, Johannesburg. / The Witwatersrand Basin has been mined for the last 125 years and is still one of the world’s largest producers of gold and has produced over 50 000 tonnes. However, uranium has also been mined as a by-product of gold from the Witwatersrand reefs, and over 150 000 tonnes have been produced. Over the past decades, the origin of this world class gold and uranium deposit has been debated and still remains controversial. Three main hypotheses were developed, and these are the placer, modified placer and hydrothermal models. In this study, the aims are: to evaluate how many generations of uranium-bearing minerals are in the Vaal Reef samples analysed from Great Noligwa, Moab Khotsong and Kopanang mines and to determine which model among the placer, modified place and hydrothermal best supports the emplacement of the uranium-bearing minerals in the reef. The Vaal Reef occurs in the lower parts of the Strathmore Formation of the Johannesburg Subgroup in the Central Rand Group of the Klerksdorp Goldfield in the Witwatersrand Supergroup. The Vaal Reef is split into three facies, namely the C, B and A Facies; the C and A Facies are the most economic facies at the three mines. The C Facies is well developed at Kopanang mine and the A Facies is well developed at both Moab Khotsong and Great Noligwa mines. Geochemical analyses revealed that the C Facies is enriched in uranium, carbon, sulphur and aluminium; this is due to the presence of uraninite, carbonaceous matter, pyrite and sheet silicate minerals, respectively. The A Facies, however, is more enriched in gold and quartz content, although high uranium, carbon and sulphur concentrations are found, they do not exceed the C Facies concentrations. Mineralogical investigations showed that uraninite, brannerite and uraniferous leucoxene are the uranium-bearing minerals present in the Vaal Reef samples. Uraninite is the main mineral and occurs firstly with detrital minerals such as pyrite, zircon and chromite in the quartz matrices; the second occurrence of uraninite is with the carbonaceous matter. Brannerite and uraniferous leucoxene are suggested to be formed from the breakdown of detrital uraninite grains interacting with Ti-rich minerals such as rutile. Unlike uraninite, brannerite and uraniferous leucoxene occur mainly in the C Facies matrix and occur as patchy or irregular-shaped minerals. The uraninite grains associated with the detrital minerals are mainly round in shape with sizes up to ~150 to 200 μm. This association with the detrital minerals suggests that uraninite was deposited together with the detrital minerals at the same time and that they were in hydraulic equilibrium with one another. Therefore, uraninite is also detrital in origin. The second generation of uraninite grains in the carbonaceous matter mainly show replacement and breakdown of uraninite by the latter, in many observations, uraninite grains are penetrated by the carbonaceous matter through cracks and are further fragmented into smaller grains. The sizes of these fragmented grains vary between 5 – 80 μm and have angular shapes, suggesting that they were first rounded and later broken down and replaced by the carbonaceous matter. A four-staged paragenetic sequence of the Vaal Reef samples was developed, and more importantly the paragenesis showed that the carbonaceous matter post-dates the deposition of uraninite. The three-dimensional microfocus X-Ray computed tomography (3D μXCT) was applied to the Vaal Reef samples and the main objectives were to visualise and analyse the uranium-bearing minerals in the Vaal Reef samples for their sizes, shapes and distribution with respect to other mineral components in the samples in 3D. The technique is currently unable to distinguish individual minerals from one another, especially when minerals have similar grey values as a result of close attenuation coefficients, mineral compositions and density. Mineral groups were identified following this similarity, include quartz and sheet silicates as one mineral group, all sulphides as another group and uranium-bearing minerals with gold as a third mineral group. The analysed uraninite with gold mineral group in the matrix, exhibited grains up to 200 μm in size which were round in shape, as observed in 2D mineralogical techniques. These observations support mineralogical observations acquired by conventional mineralogical techniques suggesting that 3D μXCT can be used to complement other mineralogical techniques in obtaining 3D information on minerals. However, 3D μXCT has limitations such as spatial resolution, partial volume effect and overlapping of mineral grey values. It is therefore, suggested that the technique not be used as an independent tool for mineral characterisation, but rather in support of the existing mineralogical techniques. The source area of the uraninite in the Vaal Reef of the Klerksdorp Goldfield is suggested to have been the hydrothermally altered Archaean basement granite bodies of the Witwatersrand Basin hinterland, from the Hartebeesfontein Dome northwest of the goldfield in particular. High UO2/ThO2 ratios, as determined by electron microprobe analyses (EMPA), support the notion that the uraninite grains are not a product of hydrothermal fluids, and furthermore high Pb contents showing that the uraninite grains are older than the age of the Witwatersrand deposition. In conclusion, the emplacement of uranium-bearing minerals in the Vaal Reef samples analysed in this study is best explained by the modified placer model.

Abstract available on PDF file. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1978.