Thesis -- Memorial University of Newfoundland. / Typescript. Also available online.

M.Sc. (Chemistry) / The determination of 17 trace elements (As. Ba. Co. Cr. Cu. Mo. Nb. Ni. Pb. Rb. Sr. Th. U. V. Y. Zn and Zr) in uranium ores by X-ray fluorescence spectrometry was investigated in this study. The determination of major elements. however. was also necessary for the calculation of mass absorption coefficients. Major elements were determined on borate melts and trace elements on powder briquettes pressed at 7 t with a binder in liquid form. Initially a method was developed for the determination of the elements of interest in unmineralised rocks The rhodium tube was used for the Group 1 elements (As. Mo. Nb. Pb, Bb, Sr. Th, U. Y and Zr) and the gold tube for the Group 2 elements [Ba, Co. Cr. Cu. Ni. V and Zn). Background and peak overlap corrections were made by means of background and interference factors. Corrections for absorption of radiation by the sample were made by means of mass absorption coefficients. which were calculated from the major element composition or obtained from the relation between the inverse of the mass absorption coefficient and the intensity of the Compton scattering peak. Due to various problems. only the latter method was suitable for uranium ores. The high uranium content in uranium ores mainly affected the Group 1 elements. Because of the high intensity of various UL lines. large overlap corrections were necessary. while only a few completely interference-free background positions were available. Consequently. the Feather and Willis method was used for determining the background intensity at the peak positions as well as for mass absorption coefficients. As a result of the presence of the UL absorption edges both primarx and secondary mass absorption coefficients had to be used for matrix corrections. Furthermore. it was observed that the background intensity in the region of the uranium lines increases with increasing uranium content of the sample instead of the expected decrease due to the increasing mass absorption coefficient. This effect was greater for the LiF(11 0) crystal than for the LiF(100) and was attributed to the scattering of uranium lines in the spectrometer chamber. especially from the crystal. A method was developed to correct the measured intensities for this scattering effect. Calibration lines of the contribution from the scattering of uranium lines to the measured intensity at the different 28 positions versus the uranium peak intensity were plotted by using samples with various uranium concentrations (<2 %) and for which the mass absorption coefficients and concentrations of the various elements were known. The precision of the method was less than 2.5 % at concentrations greater than 50 ppm. With the exception of barium. detection limits varied between 1 and 5 ppm. Accurate results were obtained over large concentration ranges for various unmineralised samples and for uranium ores. The results of the analysis of a number of Karoo uranium ores are given.

The Arizona Appraisal System is a totally integrated methodology that uses a series of interactive computer programs to translate subjective geologic opinion into a probabilistic estimate of mineral endowment. By "totally integrated methodology" is meant a unified, conceptually complete approach. This methodology comprises two main sections, each executed on a different computer system. The first section, the Geologic Decision Model, has been computerized as an interactive PLATO program. Using the PLATO system, the geologist describes probabilistically the perceived states of geologic processes and conditions. The decision model analyzes this information and computes a probability distribution for mineral occurrence. The second section, the Endowment Simulation Model (program MASTER), is run on the DEC 10 and Cyber 175 computers. Program MASTER takes the product of the Geologic Decision Model, combines it with other data, and produces a probabilistic estimate of mineral endowment for the region being evaluated. Development and testing of the Arizona Appraisal System were carried out simultaneously over a period of about three years. During this period, four geologists from government and industry were called upon four or five times over a period of about a year for a study of the uranium (U₃O₈) endowment in the San Juan Basin of northwestern New Mexico. The results produced by the system consist, for each geologist, of a probability distribution for tons of U₃O₈ endowment for (1) each partition of each stratigraphic unit, (2) each stratigraphic unit as a whole, (3) "formations" or "merged units" (groups of stratigraphic units), and (4) the San Juan Basin as a whole (all stratigraphic units). The system also calculates the average distribution across all geologists for the various merged units and for the basin as a whole. The result for the basin as a whole (in thousands of tons) is: mean 3,855, variance 4,108 x 10⁹, and 95th percentile 6,541. The author believes that his major contribution has been to design and implement a working resource estimation methodology that is flexible with respect to commodity and geographic location.

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.

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The ~2.98 - 2.87 Ga Pongola Supergroup in South Africa is subdivided into the lower volcano-sedimentary Nsuze Group, and the upper sedimentary Mozaan Group, the latter comprising a several kilometres thick succession of fluvial to shallow marine sandstones and shales. Thin beds of gold and uranium-bearing conglomerates are locally present in the Mandeva Formation near the base of the Mozaan Group and have been mined at Denny Dalton in northern KwaZulu-Natal. The style of mineralization strongly resembles that of the Witwatersrand goldfields, however appears to be of low grade and limited tonnage. The ~1 m thick basal conglomerate, the “Mozaan Contact Reef” (MCR, herein referred to as CG 1), at Denny Dalton hosts erratic gold and uranium mineralization. The conglomerate is laterally discontinuous and occupies east-northeast trending scour channels. Polymict, matrix-supported conglomerates are common, while clast-supported conglomerates are rare. Well rounded, pebble to cobble-sized clasts of vein quartz and chert are hosted in a sandy matrix of quartz, pyrite and sericite. Where mineralized, the CG 1 hosts abundant rounded pyrite grains, interpreted as detrital in origin, with subordinate U-bearing minerals, such as brannerite and uraniferous leucoxene. Rounded detrital pyrite occurs in three phases, compact, porous and radial. Gold forms inclusions within massive pyrite grains, which are concentrated in shoots associated with the basal parts of the channel scours. SEM-EDX results, as well as the high reflectivity of the gold show a high Ag content, indicative of a primary origin for the gold within the pyrite grains. Uranium within CG 1 is hosted primarily as secondary inclusions of uranium within black chert pebbles within the basal cobble-sized regions of the conglomerate. Geochemical comparison of the chert pebbles at Denny Dalton with similar chert from the Nondweni Greenstone Belt indicates that the uranium is secondary in origin as no U anomalies occur in the Nondweni chert. Geochemical and SEM analysis of the uppermost conglomerate (CG 4) indicate the presence of uraninite and coffinite within the uppermost horizon as both fillings of voids within, and coatings on, detrital pyrite grains. Palaeocurrent data indicate a likely source terrain for the detrital material to the west of the inlier. This orientation, as well as differing mineralogical and sedimentological aspects between the Mandeva Formation and the correlative Sinqeni Formation within the main Pongola basin, indicate a separate and more proximal provenance for the auriferous conglomerates of the White Umfolozi Inlier. The Mandeva Formation is a fluvial to shallow marine sequence that has been affected by cyclic sea-level changes. The basal conglomerates of the Denny Dalton Member were deposited in a proximal braided alluvial plain environment. The conglomerates fine upwards into trough cross-bedded quartz arenites which appear to have been deposited as shallow marine sands in a shoreface environment. They are overlain with a sharp contact by a laterally extensive unit of polymictic conglomerate which represents a transgressive ravinement surface within the wave zone and marks the onset of a major marine transgression into the Pongola basin. The conglomerate is overlain by massive grits and coarse-grained quartz arenite. This unit is overlain with a sharp and locally sheared contact by shales and subordinate banded iron formation which can be traced into other parts of the Pongola basin and indicates continued rapid transgression onto large parts of the Kaapvaal Craton with deeper marine, sub-storm wave base sediments being deposited in quiet-water environments on a sediment-starved shelf. The heavy mineral assemblage as well as bulk geochemical data is consistent with a granitoid-greenstone source terrain for the conglomerates and sandstones. The geochemical composition of chert pebbles from the CG 1 is similar to the composition of cherts present in the Nondweni Greenstone Belt that is situated ~30 km west of the White Umfolozi Inlier. Multiple sulphur isotope (ä34S, ä33S) values for detrital pyrite from the MCR are consistent with an origin from mantle-like rocks, such as hydrothermal sulphide-quartz veins in a granitoid-greenstone setting. Palaeocurrent, mineralogical and geochemical data all point to a likely granitoid-greenstone provenance to the west of the White Umfolozi Inlier. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.

Typescript (Photocopy) / Includes copies of 5 published papers co-authored by the author in back / Bibliography: leaves 214-230 / xi, 230, [86] leaves : ill., maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1990

Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2004. / Includes bibliographical references (leaves 32-35).