M.Sc. / The gold mining industry in South Africa is exposed to various legal issues due to the nature of its operations. Furthermore, there has been a renewed focus on environmental management in South Africa over the past decade, as well as an international focus on sustainable development. Environmental management in the gold mining industry must incorporate sustainable development, as well as the ‘cradle to grave’ concept. The gold mining industry has to ensure that its activities are compliant with environmental legislation and best practice requirements, as the increase in environmental awareness and legislated principles has escalated gold mines’ exposure to demands for the remediation and reparations of pollution and environmental degradation. No single document exists that provides the gold mining industry with detail on the environmental legislation and best practice requirements that gold mines are able to refer to in order ensure effective environmental management. Furthermore, there is no implementation plan for gold mines to implement in order to achieve compliance with environmental legislation and best practice requirements. This study has presented such a document, as it has provided the reader with detail concerning the responsibilities of the regulatory authorities, the current and new legislation, best practices, codes of practices, and offences and liabilities that gold mines will become exposed to should they not adhere to environmental legislative requirements. This detail has been used to compile an implementation programme (Chapter 4), which when implemented will ensure environmental compliance for the gold mining industry in South Africa. This mini-dissertation has thus provided the gold mining industry with an overview from which to work in order to become legally compliant with issues pertaining to environmental management in South Africa.

M.Sc. / The dimeric structure of Lawesson’s reagent, (RPS2)2 (R = 4–MeOC6H4), or its ferrocenyl analogue (R = ferrocenyl, Fc) leads to symmetrical cleavage through nucleophillic attack by alcohols to form dithiophosphonic acids, which can be readily deprotonated by ammonia to form the corresponding ammonium salts, which can be further reacted with transition-metal halides to form new metal complexes. Among the phosphor-1,1-dithiolates as a generic class of compounds, the dithiophosphates, [S2P(OR)2]-, have been most intensely studied and the dithiophosphonates [S2PR(OR’)]-, the subject of the present study, to a far lesser extent. In this study, a large variety of new dithiophosphonate salts were synthesized from diverse alcohol functionalities derived from cholesterol, estrone, estradiol, pentaerythritol, ethandiol, hydroquinone, resorcinol, glucose and ribose. The salts were oxidized with iodine to yield various S-S oxidative products, of which two X-ray crystal structures of such compounds, the ethandiol and pentaerythritol derivatives, were obtained and they were subjected to further investigation by cyclic voltammetry due to the ferrocenyl-rich functionalities they contain. The reaction of these [S2PR(OR’)]- type salts with a number of gold(I) and palladium(II) precursors, yielded a variety of new complexes. The compounds containing multiple alcohol (hydroxy) sites have been reacted with gold(I) and palladium(II) starting materials ClAu(tht) and PdCl2(PPh3)2, respectively and also with other gold(I) variants, including the mono- and dinuclear phosphines ClAuPPh3, Au2Cl2dppe and Au2Cl2dppa. A new X-ray single crystal structure of a gold(I) complex could be obtained as a decomposition product. New products have been characterized through a combination of solution 1H and 31P NMR, EIS mass spectrometry, IR, elemental analysis, electro-chemistry and single crystal X-ray crystallographic studies.

M.Tech. / The study presented, investigated the acid leaching behavior of calcines emanating from conventional roasting and microwave assisted roasting of sulphide ores. The aim was to investigate a possible change in the mineral composition of the calcine produced and to investigate the leaching behavior of the calcine produced by conventional and microwave assisted roasting. Two sulphide concentrates were received, pyrite concentrate from OTJIHASE concentrator and sphalerite concentrate from ZINCOR. The mineralogical study was done using the XRD (PANalytical X-PertPro X-Ray diffractometer) to determine the mineral composition of the concentrate and the head grade of each concentrate was determined with an Atomic Absorption Spectrometry (AAS) machine for copper, iron and zinc. The concentrates were wet screened at 500, 355, 212, 150, 106 and 75 μm screens for size distribution and for the purpose of the study it was required that 80% of concentrate should pass the 75 μm screen since after roasting, the calcine obtained were to be acid leached. Conventional roasting was carried out at temperatures of 500oC, 700oC, 850oC and 1000oC at durations of 5min, 10min, 20min, 30min, 1hour and 2hours, while microwave assisted roasting carried out at powers of 200W, 400W, 600W, 800W and time intervals of 3s, 10s, 30s, 30min and 1hour

Au(I) catalysis has recently emerged as a powerful tool for the realization of a broad range of organic transformations. Despite this rapid development, attaining selectivity and maintaining catalyst stability remain significant challenges. Rational ligand design, such as the employment of NHC or TA ligands, has been used to confront these issues. This thesis focuses on the use of Au(I) catalysts bearing these ligands for the selective hydroalkynylation of enol ethers. By employing a TA-Au stabilized catalyst, [(OAr)3PAu(TA-H)]OTf, the intermolecular hydroalkynylation of enol ethers, a substrate that is well-known to promote decomposition of the gold cation, was efficiently achieved. As an expansion of this reaction, the NHC-Au catalyst, IPrAuNTf2, was utilized in a multicomponent system to promote the tandem hydroalkynylation of enol ethers formed in-situ via the cycloisomerization of alkynols. Further exploration of this tandem reaction revealed that IPrAuNTf2 catalyzes a cascade ring-expansion of the alkynylated heterocycles to form oxepines. The mechanistic and synthetic insight obtained from these developed reactions has the potential to be applied towards future studies in gold catalysis.

This work describes, for the first time, the electrochemical and electrocatalytic properties of self-assembled layers of single-walled carbon nanotubes (SWCNTs) intergrated with selected organo-iron complexes and Cysteamine (Cys) forming a base on gold electrodes. The organo-iron complexes selected for this study were octa(hydroxyethylthio)phthalocyaninatoiron(II) (FeOHETPc), tetraaminophthalocyninatoiron(II) (FeTAPc), tetraaminophthalocyninatocobalt(II) (CoTAPc), ferrocene monocarboxylic acid (FMCA), ferrocene dicarboxylic acid (FDCA) or a mixture of SWCNT and FMCA or FDCA. The successful fabrication of these electrodes were established using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), square wave voltammetry (SWV) and chronoamperometry (CA) The Au-Cys-SWCNT-FeOHETPc electrode exhibited strong dependence on the reaction of the head groups and the pH of the working electrolytes. The high electron transfer capability of the Au-Cys-SWCNT-FeOHETPc electrode over other electrodes as the Au-Cys-SWCNT or the Au-Cys-FeOHETPc or the Au-FeOHETPc suggests that SWCNT greatly improves the electronic communication between FeOHETPc and the bare gold electrode. The electron transfer rate constant (kapp) of Au-Cys-SWCNT-FeOHETPc in pH 4.8 conditions (~1.7 x 10-2 cm s-1) over that of the electrode obtained from SWCNT integrated with tetraaminophthalocyninatocobalt(II) (Au-Cys-SWCNT-CoTAPc) (5.1 x 10-3 cm s-1) is attributed to the possible effect of both the central metal on the phthalocyanine core and subsituents on the peripheral positions of the phthalocyanine rings. This work clearly proved that the aligned SWCNTs arrays exhibit much faster electron transfer kinetics to redox-active species in solutions compared to the randomly dispersed (drop-dried) SWCNTs. The advantageous electron transfer properties of the aligned Au-Cys-SWCNT-FeOHETPc electrode, coupled with its ease of fabrication and electrochemical stability, could be found useful in electrochemical sensing and catalysis. Thiocyanate ion was used as an analytical probe to examine the electrocatalytic properties of these modified gold electrodes. This work shows that SWCNT-FeOHETPc hybrid exhibits excellent sensitivity towards the detection of thiocyanate compared to electrodes containing SWCNT or FeTAPc or FeOHETPc only, indicating the ability of the SWCNTs to function as effective conductive nanowires for the detection of this important analyte. The electrochemical response of the FeOHETPc based electrodes was greater than their FeTAPc-based electrode counterparts, indicative of the impact of peripheral substituents on the phthalocyanine core towards electrocatalytic behaviour of these types of hybrids. Nevertheless, the exchange of the central metal as seen with the case of CoTAPc (see chapter 3), provide useful comparative electrochemical activity of this complexes versus FeTAPc with the same chemical environment with an indication of iron being the best as metal centre. FMCA or FDCA were covalently attached to the base Cysteamine monolayer to form the Au-Cys-FMCA and Au-Cys-FDCA, respectively. The same covalent attachment strategy was used to form the mixed SWCNTs and ferrocene-terminated layers (i.e., Au-Cys-SWCNT/FMCA and Au-Cys-SWCNT/FDCA). The impact of neighbouring SWCNTs on the electron transfer dynamics of the ferrocene molecular assemblies in acidic medium (0.5 M H2SO4) and in a solution (pH 7.2) of an outer-sphere redox probe ([Fe(CN)6]4-/ [Fe(CN) 6]3-) was explored. The electron transfer rate constants in both solution media essentially decrease as Au-Cys-FMCA > Au-Cys-SWCNT/FDCA > Au-Cys-FDCA > Au-Cys-SWCNT/FMCA. This trend has been interpreted in terms of several factors such as the locations of the ferrocene species in a range of environments with a range of potentials, the proximity /interactions of the ferrocenes with one another, and electrostatic interaction or repulsion existing between the negatively-charged redox probe and the modified electrodes. Square wave voltammetry was used to examine the catalytic behaviour of the electrodes. Au-Cys-SWCNT/FDCA proved to be the best electrode, possibly due to the repulsive interactions between the negatively charged SCN- and high number of surface –COOH species at the SWCNT/FDCA. This novel study has provided some useful insights as to how CNTs co-assembled with ferrocene-terminated thiols could impact on the heterogeneous electron transfer kinetics as well as the electrocatalytic detection of the self-assembled ferrocene layers. / Thesis (PhD)--University of Pretoria, 2010. / Chemistry / unrestricted

No description available.

Lateritisation is associated with tropical climates and geomorphic conditions of peneplanation where hydromorphic processes of weathering predominate. Laterites are products of relative (residual) and absolute(chemical) accumulation after leaching of mobile constituents. Their major element chemistry is controlled by the aluminous character of bedrock and drainage. Bauxitisation is characterised by residual gibbsite neoformation and lateritisation, by both residual accumulation and hydromorphic precipitation of goethite controlled by the redox front at the water table. The laterite forms part of a weathering profile that is underlain by saprock, saprolite, the mottled zone and overlain by a soil horizon. The secondary gold in laterites has its source invariably with mineralised bedrock. The distribution of secondary gold is controlled by mechanical eluviation and hydromorphic processes governed by organic, thiosulphate and chloride complexing. The precipitation of secondary gold is controlled by pH conditions, stability of the complexing agent and ferrolysis. Gold-bearing laterites are Cainozoic in age and are best developed on stable Archean and Proterozoic cratons that have suffered epeirogenesis since lateritisation. Mechanical eluviation increases in influence at the expense of hydromorphic processes as a positive function of topographic slope and degradation rate. Gradients greater than 10⁰ are not conducive for lateritisation, with latosols forming instead. High vertical degradation rates may lead to the development of stone lines. In the Western Australian case, post-laterite aridification has controlled the redistribution of secondary gold at levels marked by stabilisation of the receding palaeowater table. Mineable reserves of lateritic ore are located at Boddington, Westonia and Gibson toward the south-west of the Yilgarn Block. A significant controlling variable appears to be the concentration of chloride in the regolith. Based on the Boddington model, the laterite concentrates the following elements from bedrock gold lodes: i) Mo, Sb, W, Hg, Bi and Au as mobile constituents. ii) As and Pb as immobile constituents. Geochemical sampling of ferruginous lag after bedrock and laterite has provided dispersed anomalies that are easily identifiable. "Chalcophile corridors" up to 150 km in length are defined broadly by As and Sb but contain more discrete anomalies of Bi, Mo, Ag, Sn, W, Se or Au, in the Yilgarn Block. The nature of the weathered bedrock, the tabular distribution of secondary gold ore deposition and the infrastructural environment lends the lateritic regolith to low cost, open-cut mining. The western Australian lateritic-gold model perhaps can be adapted and modified for use elsewhere in the world.

Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.

It has been established that porphyry copper/copper-gold deposits have formed from I Ma to 2 Ga ago. Generally, they are related to the Mesozoic-Cenozoic interval with few reported occurrences from the Palaeozoic or Precambrian. A reason cited is the erosion of these deposits which are often related to convergent plate margins and orogenic belts. Observations of the alteration and mineralisation within and around porphyry copper/copper-gold systems have been included in numerous idealised models. These alteration and mineralisation patterns are dependent on the phases of intrusion, the tectonic setting and rock type, depth of emplacement and relationship to coeval volcanics, physiochemical conditions operative within and surrounding the intrusive and many other mechanical and geochemical conditions. Island arc and cratonic arc/margin deposits are generally considered to be richer in gold than their molybdenum-rich, intra-cratonic counterparts. Metal zonation may occur around these copper/copper-gold deposits, e.g. copper in the core moving out to silver, lead, zinc and gold. This zonation is not always present and gold may occur in the core, intermediate or distal zones. Examples of gold-rich porphyry deposits from British Columbia, Chile and the SW Pacific Island regions suggest gold is closely associated with the potassic-rich zones. Generally these gold-rich zones have greater than 2% magnetite and a high oxygen fugacity is considered to be an important control for gold deposition. High Cl contents within the magma are necessary for gold mobility within the host intrusive centres. Beyond this zone HS₂ becomes an important transporting ligand. Exploration for porphyry copper-gold deposits includes an integrated geological, geophysical and geochemical approach. Petrographic work through to Landsat imagery may be used to determine the chemical conditions of the system, ore association, favourable structural zones and alteration patterns, in order to focus exploration activities.

The development of an open pit mine at the Endeavour 42 (E42) epithermal gold deposit, situated in the Junee-Narromine Volcanic Belt of the Ordovician Macquarie Arc, central New South Wales, has provided a 3D view of the structurally controlled deposit which was hitherto not available due to the paucity of outcrop in the region. Outcropping geological relationships present a complicated history of overprinting structural deformation and vein events, including the spatial characterization of the gold-mineralizing system. Host rocks consisting of interbedded sedimentary and resedimented volcaniclastic facies, trachyandesite and porphyritic andesite lavas and intrusions (coherent and autoclastic facies), intruded by a large diorite sill, were initially tilted and faulted, followed by the emplacement of multiple dyke phases along faults. Economic gold mineralization at E42 is restricted to faults, fault-hosted breccias, and veins, and was deposited over a period spanning two distinct structural regimes. Early gold-bearing veins are steeply dipping and interpreted as forming coevally along two sets of faults and dykes within a tensional stress regime. High grade fault-hosted, hydrothermally cemented breccia intervals are included temporally with early gold-bearing veins based on comparable mineralogy and steep, fault parallel orientations. Crosscutting the early steep gold-bearing vein sets are two populations of coeval inclined gold-bearing veins, dipping moderately to the southwest and northwest, respectively, which formed in a compressional stress regime with tension directed subvertically. The E42 epithermal deposit likely developed in the period of overall crustal extension, ca. 443-433 Ma, following Phase 1 of the Late Ordovician – Early Silurian Benambran Orogeny. The generation of permeability, styles of fracture propagation, and the reactivation of pre-existing planes of weakness in the rock package are key factors in the development and current geometry of the E42 gold deposit. High grade veins and faults are commonly flanked by sericite-quartz ± carbonate alteration haloes, which exhibit consistent geochemical patterns for metals and pathfinder elements, both laterally away from structures, and vertically within the deposit. Au, Ag, As, Hg, Sb, Tl, Cu, Pb, and Zn, all display increasing concentrations towards high-grade structures, as well as higher up in the epithermal system, with varying dispersion haloes. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate