published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

M.Sc. (Geology) / Refer to full text for abstract

The thesis takes the form of a collection of publications and patents concerning gold extraction which were presented over a period of 18 years while employed at the Anglo American Research Laboratories.

M.Sc. / Please refer to full text to view abstract

A series of impedance-mismatch experiments with aluminum-gold targets has been performed. These experiments are used to probe the equation of state (EOS) of gold at high pressure. By measuring the shock breakout time from the target rear surface, the shock trajectory is determined and found to be in good agreement with equation of state predictions. In addition, temperatures derived from temporally resolved luminescence measurements of the shocked target rear surface are compared with two different equation of state theoretical models. Our results indicate that whereas the SESAME (from Los Alamos National Laboratory) EOS seems to overestimate the shock temperature, the equation of state of gold which incoporated both the solid and liquid phases gives much closer agreement with observations. The measurements of gold at a shock pressure of ~ 6 Mbar and temperature of ~ 17500 K also represent the first study of gold under shock melting. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

M.Sc. / This study focuses on the mineralogical variability of the A1, A5 and UE1A Elsburg reefs, obtained at Rand Uranium’s underground mining areas. A total of 133 reef samples, consisting of the Elsburg UE1A, A1 and A5-reefs have been obtained from Cooke 2 and 3 (two of the three Rand Uranium Mines) using the conventional chip sampling method. One of the challenges faced by Rand Uranium Gold Mines in the Cooke section area is the difficulty in differentiating between the various reef types by means of their macroscopic characteristics (colour, pebble types/sizes/shapes, sorting, matrix type, visible sulphide mineralization etc.). This difficulty led to this study which is aimed at utilizing mineral liberation analyzer (MLA)-based automated mineralogy to distinguish between the various reefs and to assess the mineralogical variation within the A1, A5 and UE1A-reefs. The mineralization in this area is hosted by the upper Central Rand Group of the Witwatersrand Supergroup. The main orebodies that are exploited at the mines occur within the Gemsbokfontein Member of the Elsburg Formation. These orebodies have been deformed into an east-west trending anticline at Cooke 3. The present study also attempts to prove or disprove the equivalence of the UE1A-reef on the western limb of the anticline to the A1 or A5-reefs on the eastern limb of the anticline on the basis of mineralogy. Representative splits of the samples were subjected to mineralogical abundance quantification as possible through quantitative MLA-based modal abundance protocols such as XMOD. A standard file on the various mineralogical phases encountered, was created on the 600F MLA and complemented by quantitative XRD (X-ray diffraction) data. Mineral abundances were quantified by MLA, based on integrated backscatter electron (BSE) images and energy dispersive spectrometry (EDS) analyses. Thirty one minerals have been detected using the MLA and they include phases such as quartz, pyrophyllite, chlorite, brannerite, gold, monazite and pyrite as well as minor unknown minerals. Only a few of the minerals are relatively more abundant within the reefs while the majority occurs in very low abundance. Albite, chlorite, muscovite, pyrite, pyrophyllite, quartz, uraninite and zircon are relatively more abundant than the rest of the minerals.