Thesis (M.Sc.(Geology))--University of Pretoria, 2007. / Abstract in English. Includes bibliographical references (leaves 208-235).

Thesis (M.Sc.(Geology))--University of Pretoria, 2003. / Summary in English. Includes bibliographical references.

Thesis (Ph.D.(Mineralogy))--University of Pretoria, 2001. / Summaries in English and Afrikaans. Includes bibliographical references.

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

Please read the abstract in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2009. / Geology / unrestricted

At the Karee Mine of the Lonplats mining company in the Bushveld Complex, South Africa, the Rooikoppies iron-rich ultramafic pegmatite (IRUP), which covers the stratigraphy from below the UG2 chromitite layer up to the Main Zone, replaces cumulus anorthosite and pyroxenite. The Rooikoppies IRUP was studied using transmitted and reflected light microscopy, X-ray fluorescence, X-ray diffraction, and electron microprobe techniques. Two visually different varieties of IRUP were observed: a) a relatively smaller grained greyish variety and b) a relatively coarser grained greenish variety. In drill core, the IRUP body was observed to be in contact with the host cumulate rocks either by means of gradual or sharp contacts. Bulk rock compositions indicate that the Rooikoppies IRUP is enriched in Fe2O3, MgO, and CaO (relative to the cumulate host rocks) while having lower concentrations of Al2O3. Chemical differences between cumulus host rocks and IRUP are accompanied by changes in mineral assemblage and mineral chemistry. Spatially related IRUP samples revealed areas with potentially more pronounced increases in iron and magnesium contents relative to the host cumulate rocks. Element ratios indicate that aluminium acted as an immobile element during the formation of the IRUP body and that the addition of iron, magnesium, and calcium, through the action of hydrothermal fluids, diluted the already existing cumulus feldspar, resulting in the low concentrations of Al2O3 in the IRUP samples. The addition of iron, magnesium, and calcium also resulted in the crystallization of large proportions of clinopyroxene and olivine, and resulted in changes in the mineral assemblage and mineral chemistry, relative to the host cumulate rocks. The Rooikoppies IRUP body can be classified as a silicate rich variety (Viljoen and Scoon, 1985), consisting of clinopyroxene, olivine, plagioclase, secondary magnetite and ilmenite. It is suggested that the formation of the Rooikoppies IRUP is not due to a single event, but rather that the IRUP body formed through multiple replacement events, resulting in a network of chemically different zones within one large IRUP body. / Dissertation (MSc)--University of Pretoria, 2009. / Geology / unrestricted

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2007. / Geology / MSc / Unrestricted

>Magister Scientiae - MSc / The Platreef is known for its complexity and its heterogeneous lithologies, coupled with an unpredictable PGE and BMS mineralisation. The motivation behind this study was to aid mining geologists in targeting mineralisation irrespective of the farm. It is known that the Platreef generally overlies different footwall lithologies at individual farms. Thus, the aims of this study were firstly to investigate the potential of chemostratigraphy by delineating indices indicative of distinctive lithological layers. These indices were then tied to the second aim; which were to use geochemical vectoring, which is process-based, to target the PGEs at two different farms. This study included three drillcores: from the farms Sandsloot (SS339) and Tweefontein (TN754 and TN200). The footwall units at Tweefontein are shales of the Duitschland Formation and the Penge banded iron formation; and at Sandsloot it is the Malmani Subgroup dolomites. Samples included 121 quarter cores, used for petrographical and geochemical studies. The elemental rock composition was determined by XRF and ICP-OES analyses. The approach also included statistical and mass balance methods to understand the geological and geochemical controlling processes. Initially, the Platreef package at both farms was petrographically divided into three main layers: pyroxenite, and two distinctive feldspathic pyroxenites (FP-I and FP-II). However, the pyroxenites were also further separated as P-I and P-II, because of a higher notable difference in the degree of alteration within P-I. Progressive degrees of metasomatism were further observed in the lithologies, e.g. within the Platreef package, where feldspathisation was potentially the main metasomatic process. Many geochemical plots (corroborated by the petrographical and mass balance results) illustrated that the feldspathisation were linked to an increase in the content of Al₂O₃ and CaO, and coupled with a decrease in content of Fe₂O₃ and MgO. Together with other geochemical trends, geochemically distinct units of the Platreef package could be discriminated with a metasomatism index (MI; CaO + 10Na₂O / CaO + 10Na₂O + Fe₂O₃ + MgO). The ensuing MI is lowest for the P-II pyroxenite and shows a progressive increase through FP-I, P-I to the highest values in FP-II. Geochemical layering were also observed in the calcsilicates and hornfels; e.g. a progressive decrease in the content of Fe₂O₃, Al₂O₃, Ce, Co, Cu, Ni, Zn, Zr, Au, Pd and Pt from the hornfels subunits H-I, H-II to H-III and an increase in of SiO₂, Fe₂O₃, TiO₂, SO₃, Co, Cu, Ni, Rb, V and Zn content from CS-I, CS-II to CS-III. Correlating the pyroxenites and feldspathic pyroxenites spatially from one drillcore to another were hindered, hence, chemostratigraphy were not completed. In terms of vectoring, it was essential to establish a possible link between the metasomatism index and the nature and style of the PGE and/or BMS mineralisation. The Hornfels subunit H-I and calcsilicate subunit CS-III were the main carriers of BMS and PGE. The Platreef package were more complicated: P-I (low PGE, low BMS); P-II (low PGE, high BMS); FP-II (high PGE, low BMS); and FP-I (high PGE, high BMS). Element indices (e.g. Cu+Ni and Co+Zn) were developed to define a consistent gradient indicative of these ore subunits. A validation process to assess the metasomatism index (MI), base metal indices and PGE distribution within the individual drillcores (TN754, TN200 and SS339) were then undertaken. The results were that the MI ranges were similar in all drillcores, and discriminated the subunits of the Platreef package, gabbronorites and even the calcsilicates. The base metal ratios (e.g. Ni/Co and Cu/Co) were indicative of the PGE rich zones. Trends of the base metal ratios reflected a strong positive relationship with the MI within the Platreef package and the calcsilicates. However, the opposite trend is observed with the hornfels. In conclusion, the MI could potentially be a strong vector of high PGE and BMS mineralisation. It is also possible to discriminate lithologies within the Platreef package with the MI. However, it should be noted that the limitation of this study is that the results are based on three drillcores. The Platreef is heterogeneous at individual farms and extremely diverse across the northern limb. Therefore, future research could be undertaken to validate these findings, by using a bigger drillcore database. / National Research Foundation

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 1985. / Geology / unrestricted

A sequence of 3250 m of the Rustenburg Layered Suite and its associated mineralization south of Potgietersrus was investigated. Four episodes of faulting have deformed the area. This resulted in very early differentiates, not seen elsewhere in the Bushveld Complex, to outcrop together with economic concentrations of the best metallurgical grade chromite presently being mined in the Republic. The Mg:Fe:Ca ratio of theCa-poor pyroxenes varies from 89,5:8,8:1,6 in the lower zone to 44,2:52,3:3,37 in the upper zone. The latter composition demarcates the Fe-rich end of the two pyroxene limit. Textural evidence implies that there is a peritectic reaction between the ironrich Ca-poor pyroxene and the melt and that this may account for the termination of the two pyroxene field. A significantly higher mean Ko~~~F~p; for the study area (0,822) than for the other sectors of the Bushveld Complex (0,782) suggests that the pyroxenes of similar composition crystallized at higher temperatures in the Potgietersrus limb. Examination of the Al :Si ratio in Ca-rich pyroxenes from a variety of magmatic environments confirms that this variable can be used to monitor relative changes in the a ~~~t. Chemical data of the Ca-rich pyroxenes suggest that this phase define~ an Fe enrichment - Ca depletion trend during differentiation uhlike that for most other tholeiitic intrusions. The V205 content of the main magnetitite layer and the cr203 and the Cr/Fe2++Fe3+ values in the upper and lower chromitite layers in the study area are the highest encountered in the Bushveld Complex. Textural evidence in these layers show that they have been up-graded to dense monomineralic layers by postcumulus sintering. Calculated intensive parameters for the Potgietersrus magma suggest that it crystallized over a temperature interval from 1276°C in the lower zone to 1022°C in the basal portion of the upper zone. Oxygen fugacity conditions for the lower zone ranged from 10-6,21 to 10-4,98 atm whereas lower values of 1o-11 to 1o-9 atm were operative in the upper zone. The study area contains abundant concentrations of sulfides at several levels in the sequence. The separation of the sulfide liquid is related in most cases to new influxes of metal-rich magma and mixing with the residual magma in the chamber. Several definite sulfide facies occur in the layered sequence. Sulfur isotope investigations indicate that all the sulfur in the study area is mantle derived and that the isotopic composition of the sulfur was controlled by the prevailing fo2, which in turn controlled the partitioning of S02 and HzS between sulfide melt and magma. / Thesis (PhD)--University of Pretoria, 1983. / gm2014 / Materials Science and Metallurgical Engineering / Unrestricted