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1
Van, Tonder Erika. "The effect of ore blends on the mineral processing of platinum ores." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10982.
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Includes abstract.Includes bibliographical references (leaves 96-101).
This thesis investigates the effect of ore blends on milling and flotation performance. Anglo Platinum's Waterval UG2 concentrator in Rustenburg processes ore from various shafts.
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Hassan, Maisson Mohamed Zeinelabieden. "Identification of platinum ores via trace element signatures." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10672.
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This project studies the natural variation in the elemental composition of processed platinum ore from different extraction locations in South Africa in order to assess whether this provides sufficient information for the elemental fingerprinting" of the material.
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Murahwi, Charley Zvinaiye. "The geology of the Unki platinum-base metal deposit, Selukwe subchamber, great dyke, Zimbabwe." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005574.
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This thesis focuses on platinu'm group element (PGE) mineralization in the Unki Section of the Selukwe Subchamber of the Great Dyke (Zimbabwe), and is based on drill hole intersections and underground and surface exposures of the Main Sulphide Zone (MSZ) which hosts significant concentrations of PGE. The petrological and geochemical data presented are part of a broader study currently underway and the present are restricted to the 2m section of the PGE-rich MSZ encountered in drill hole MR126. The PGE-rich MSZ at Unki is unique in having a shear, locally referred to as the Footwall Shear, developed at or close to its base . It is however, similar to the other PGE occurrences on the Great Dyke (MSZ) in having its hanging-wall restricted to within 1m of the websterite/bronzitite contact. Slight axial tilting to t he west is indicated by steeper dips on the eastern flank. The sulphide concentration wit hin the MSZ can be used as a rough guide to the PGE-rich zone, but is not sufficiently precise to be used in stope control. The visual identification of the potentially mineable zone remains a problem that is unlikely to be solved. Based on petrological evidence, the bulk of the sulphides with which the PGE are associated, are cumulus in status. This provides unequivocal evidence for an orthomagmatic origin of the MSZ. The dominant platinum group mineral (PGM) phase is the Arsenide/Sperrylite group which is most commonly found at the contact zones between base metal sulphides (BMS) and gangue. The PGM range up to 90 ~m in length. Geochemical evidence from the analyses of cumulate orthopyroxenes through the 2m PGE-rich MSZ interval at Unki reveals a trend of arked Fe enrichment upwards which corresponds to an enrichment in sulphide. This indicates that precipitation of sulphide was caused by fractionation with lowering of temperature in the magma. The Fe enrichment is followed by a reversal in Mg# of orthopyroxene which corresponds to the decrease in sulphide content, suggest i ng that the termination of the PGE-rich MSZ was due to an increase in temperature associated with an influx of new magma. Coupled with these magmatic events are a complex interplay of chemical and physical processes occurring at a critical stage in the overall fractionation of the Great Dyke magma chamber. The overall persistence and continuity of t he PGE zone as observed in the Unki area is consistent with the inferred orthomagmatic origin of the mineralization
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Kloppers, Lourens Marthinus. "Froth flotation of a Merensky platinum bearing ore with various THIOL collectors and their mixtures." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2481.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.The Bushveld igneous complex in northern South Africa has the largest deposit of platinum group elements (PGE) in the world. In trace amounts, these are closely associated with base metal sulphides (BMS). Froth flotation is used to beneficiate these PGE ores. The process constitutes a bulk sulphide recovery. Improvement of recovery of the BMS is required to maximise the recovery of PGEs. The performance of the froth flotation process is largely dependent on the chemical additives used and these chemicals have been extensively studied. Mixtures of collectors are widely used in the flotation of sulphide and platinum group mineral (PGM) ores. A range of performance benefits for the use of mixtures over pure collectors have been observed on many systems. These include improved valuable metal grades and recoveries, lower reagent dosage requirements, improved rates of flotation and enhanced recovery of coarse particles. Improvements observed with mixtures of chemical reagent have been attributed to synergism; defined as the interaction of two or more agents to produce a combined effect greater than the sum of their individual effects. Synergism is highly desired in froth flotation. For this study, mixtures of thiol collectors were used in batch froth flotation tests in an attempt to identify synergism between the different collectors on flotation performance of a typical platinum ore from the Merensky reef. Flotation performance was evaluated in terms of grades and recoveries of copper and nickel, and the rate of metal flotation. Single thiol collectors of xanthate (SIBX), a dithiocarbamate (DTC) and a dithiophosphate (DTP) were evaluated to determine the effect of functional group on flotation performance. SIBX was then used in mixtures with both DTC and DTP at various molar ratios to establish whether synergism occurs between these collectors on this particular platinum ore. Molar ratios of 90:10, 80:20, 70:30 60:40 and 50:50 were considered with SIBX being the major component. Further tests were conducted with the addition of a carboxymethyl cellulose depressant to the collector mixtures.
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Chaponda, Brian. "Effect of operating variables on IsaMill™ performance using platinum bearing ores." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/17950.
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Includes bibliographic references.Comminution involves crushing and grinding operations. The grinding operations use the traditional tumbling mills and stirred mills to reduce the ore to the required fineness. This thesis intends to investigate the influence of design and operating variables on the IsaMillTM specific energy and product size, when grinding UG2 platinum-bearing ore. The main objectives of this work were to study the effects of operating variables on specific energy consumption and product fineness, and to investigate IsaMillTM scale-up protocol. The experimental studies were conducted using the M4 IsaMillTM on a laboratory scale and the M10 000 IsaMillTM on an industrial scale.
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Vermaak, Matthys Karel Gerhardus. "Fundamentals of the flotation behaviour of palladium bismuth tellirudes." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-10132005-105623.
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Manyeruke, Tawanda Darlington. "The petrography and geochemistry of the Platreef on the farm Townlands near Potgietersrus, northern Bushveld Complex." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-04282005-110052/.
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Matsau, Eunice Nthabiseng. "Determination of platinum, palladium, rhodium and gold in platiniferous ores using ICP-MS and microwave dissolution." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53354.
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Thesis (MSc)--Stellenbosch University, 2003.ENGLISH ABSTRACT: The determination of the platinum group metals (PGMs), platinum, palladium, rhodium, iridium, ruthenium and osmium, remains a problem for the low-grade ore samples, and the analysis of these samples in a routine laboratory relies entirely on the fire assay technique. The use of large sample masses to overcome sub-sampling errors has been the greatest advantage of this technique. The increased economic value of PGMs and recent developments in instrumentation such as inductively coupled plasma-mass spectrometry (ICP-MS) which is capable of trace element detection as low as part per billion (Ppb) levels, have led to a search for complementary methods to ensure the accuracy of fire assay results. This work investigates the feasibility of direct dissolution of ore samples using microwave-assisted dissolution followed by ICP-MS as the measurement technique. Due to the limited sample mass that can be used, a thorough consideration had to be given to sampling errors and analytical errors to assess the overall precision achievable. Most PGM-bearing minerals occur as sulphides and these are highly resistant to acid dissolution. It was found that roasting the Merensky type samples in air, prior to dissolution gives quantitative recoveries for platinum. Recoveries up to 100% were obtained for platinum, palladium, rhodium and gold for a Merensky flotation concentrate with excellent precision (about 4%) except for gold which had poorer precision (16%). However, ore samples presented a problem due to their lower PGM content and smaller sample masses being used. Precision for all elements improved significantly (from about 20% to about 8%), with the use of l g-sample aliquot compared to that ofO.25 g-sample. Acid dissolution, even after roasting proved to be insufficient for the UG-2 chromitite samples. When roasting was followed with reduction under hydrogen flame the solubility of the UG-2 flotation concentrate improved remarkably. The recoveries obtained were approximately 95 ± 5% for platinum, 99 ± 5% palladium, 104 ± 12% gold and 102 ± 5% for rhodium with good precision (comparable to that of Merensky concentrate). The accuracy and precision of the results depended very much on the sample mass and air-flow in the furnace during the roasting procedure. For this method to be used successfully, the air flow is very critical, and should lead to a better furnace design which can rotate the crucibles to enable an even flow of air over all the samples during roasting.
AFRIKAANSE OPSOMMING: Die bepaling van platinumgroep metale (PGM'e), platinum, palladium, rhodium, iridium, ruthenium en osmium is 'n voortdurende probleem vir die lae-graad erts monsters. Die analise van hierdie monsters in 'n roetine laboratorium is geheel afhanklik van die klassieke "fire assay"-tegnieke. Die groot voordeel van hierdie tegniek is die voorkoming van monsternemingsfoute deur die gebruik van groter monster massas. Die ekonomiese waarde van PGM'e saam met die onlangse ontwikkeling van instrumentasie soos die induktief-gekoppelde plasma-massaspektrometrie (IGP-MS) wat in staat is om spoorelemente in konsentrasies so laag soos dele per biljoen (ppb) te meet, het daartoe gelei na soeke vir komplementêre metodes om die akkuraatheid van klassieke "fire assay" -tegnieke te verseker. Hierdie werk ondersoek die waarskynlikheid van direkte oplossing van ertsmonsters deur gebruik te maak van mikrogolf-ondersteunde oplossing gevolg deur IGP-MS as opmetingstegniek. As gevolg van die beperkte monster massa wat gebruik kan word, moes deeglike oorweging gegee word aan monsternemingsfoute en analitiese foute, om die oorkoepelende presiesheid te bepaal. Meeste PGM-draende minerale bestaan in die vorm van sulfiede en bied groot weerstand teen oplossing in 'n suur. Die gloei van Merensky-tipe monsters in lug voor oplossing gee kwantitatiewe herwinning van platinum Herwinning tot 100% is behaal vir platinum, palladium, rhodium en goud vir 'n Merensky-flotasie-konsentraat met uitstekende akkuraatheid (4%) behalwe vir goud met 'n swak (16%) akkuraatheid. Die erts monsters was problematies as gevolg van die laer PGM inhoud en kleiner monstermassas wat gebruik is. Presiesheid vir al die elemente het beduidend verbeter (van 20% tot 8%) met die gebruik van 1 g- monster massas vergelyk met 0.25 g-monsters. Ten spyte van die gloei van die monster is suur oplossing onvoldoende vir die UG-2 chromatiet-houdende monsters. Wanneer die monster gegloei is onder 'n waterstof vlam (reduksie) het die oplossbaarheid van UG-2 flotasie-konsentraat aansienlik verbeter. Die herwinbaarheid wat behaal is, is 95 +/- 5% vir platinum, 99 +/- 5% vir palladium, 104 +/- 12% vir goud en 102 +/- 5% rhodium met goeie relatiewe presiesheid vergeleke met Merensky-konsentrate. Die akkuraatheid en presiesheid van resultate hang meerendeels af van monster massa en lugvloei in die oond gedurende gloei. Die lugvloei is krities vir die sukses van hierdie metode en sal moet lei tot beter oond ontwerp wat kroesies kan roteer en 'n gelyke vloei van lug oor die monsters gedurende verbranding toelaat.
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Monama, Nkwe Oscar. "Electronic structure studies of pallandium sulphide (PdS) and platinum (pt) ternaries." Thesis, University of Limpopo (Turfloop Campus), 2008. http://hdl.handle.net/10386/762.
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Thesis (M.Sc. (Physics)) --University of Limpopo, 2008We present first principles structural, electronic and optical properties investigation of PdS, which are carried out using density functional theory under plane wave pseudopotential method within the local density approximation. We used ultrasoft- pseudopotentials to carry out our calculations. Calculated lattice parameters of the system show excellent agreement with the experimental values. The lattice parameters were observed to decrease linearly with increasing pressure. The density of states and optical properties of PdS have been computed under hydrostatic pressure. The actual size of the band gap remains constant with increasing pressure, whilst the peaks just below and above the Fermi energy moves to the left and to the right respectively. We also investigated the effect of compositional variation on our reflectance by calculating the reflectivity of Pd4-xPtxS4 and Pd4-xNixS4. Since we have different positions for the same concentration, we used the heats of formation to determine the most stable structures and these structures were used to study the effect of compositional variation on our reflectance spectrum. We studied the equation of state (EOS), structure under hydrostatic pressure, and deduced the bulk modulus. It is important to study these properties under such extreme conditions of pressure and temperature as they tend to occur below the earth's surface. Investigation of stability and mechanical properties of binary and ternary compounds from PtS to PdS have been carried out, were the presence of the miscibility gap is still uncertain. We investigate stability of these compounds by studying the heats of formation, elasticity and electronic properties. Our results show no miscibility gap but continuum solid solution between these compounds. A shift of the Fermi energy towards the conduction band is observed at a 50% concentration of Pd and Pt. All the information obtained on PdS is intended to assist in fitting interatomic potentials to enable studies of systems with many atoms.
10
Knight, Robert. "The primary magmatic concentration and secondary remobilisation of platinum-group elements in Ni-Cu sulphide ores." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/65680/.
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The PGE mineralisation in the Fazenda Mirabela ultramafic-mafic and Jinchuan ultramafic intrusions has been characterised by determining the platinum-group mineralogy of each complex and the concentration of PGE in solid solution in the base metal sulphides (BMS). The Mirabela intrusion is largely unaltered and hosts two PGE occurrences from which 128 Au- and Ag-bearing minerals and 716 PGM have been identified; predominantly Pt-Pd-Ni tellurides in the Santa Rita sulphide ore deposit and to a lesser extent in the underlying sulphur-poor dunite. A localised Pd-Cu±Pb alloy assemblage is identified in the dunite in the central zone of the intrusion. The PGM assemblages at the edges of the intrusion are relatively As-rich containing sperrylite (PtAs2); arsenic may have been introduced through crustal assimilation. Two orebodies (#1 and #24) have been studied from the Jinchuan intrusion which has undergone extensive greenschist facies alteration. A total of 64 Au- and Ag-bearing minerals and semimetal alloys, and 93 PGM have been identified including michenerite (PdTeBi), froodite (PdBi2), members of the hollingworthite-irarsite-platarsite solid solution series ([RhIrPt]AsS), sperrylite and maslovite (Pt[BiTe]2) in decreasing order of abundance. The PGM vary across these two orebodies as a result of sulphide fractionation, with the Ni/MSSrich orebody #1 hosting early crystallising sulpharsenides and As-bearing PGM whereas the relatively Cu/ISS-rich orebody #24 hosts more Pd-bearing PGM with Pd partitioning into the Cu-rich sulphide liquid during MSS crystallisation. These studies show that Bi- and Te-bearing PGM ([PtPdNi]Te2, PdBi2, PdBiTe) may exsolve from the BMS during sub-solidus cooling after these elements have partitioned into the BMS at high temperatures whereas As-bearing PGM (PtAs2, [RhIrPt]AsS) and sulpharsenides (gersdorffite-cobaltite [NiAsS-CoAsS]) may crystallise early directly from an As-bearing immiscible sulphide melt. In the Mirabela intrusion, the IPGE and Rh have partitioned into MSS, from which pentlandite, pyrrhotite and pyrite have exsolved. Osmium and Ir preferentially partitioned into pyrite (with Co) whereas Ru and Rh partitioned equally between pentlandite and pyrite. In the Jinchuan intrusion, Ir, Rh and Pt have preferentially partitioned into early crystallising sulpharsenides (from which [RhIrPt]AsS PGM exsolve) depleting MSS in these elements. Palladium is identified in pentlandite in both complexes studied and may have diffused from ISS/chalcopyrite or partitioned into MSS at an earlier magmatic stage. Platinum does not usually partition into BMS (excluding sulpharsenides) and instead forms PGM. However, Pt does partition into pentlandite in the Mirabela sulphur-poor dunite where semimetal concentrations are very low and Pt-bearing PGM form only in low quantities, if at all. Minor localised serpentinisation of the Mirabela intrusion does not remobilise the PGE with the primary magmatic distribution of PGE and PGM preserved; the latter are predominantly associated with interstitial BMS and occur in sulphide stringers shown to be of magmatic origin. Pervasive greenschist facies hydrothermal alteration at Jinchuan altered and oxidised the BMS during a process of sulphur loss, resulting in the formation of secondary magnetite and the liberation of Pd, Bi and Te which coalesce to form secondary froodite and michenerite in situ at the edges of these replacement oxides; however, the PGE are not extensively remobilised. Both complexes show that the semimetal content of the ore-forming magma is critical in controlling the distribution of PGE into BMS and/or PGM.
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Manyeruke, Tawanda Darlington. "Compositional and lithological variation of the Platreef on the farm Nonnenwerth, northern lobe of the Bushveld Complex implications for the origin of platinum-group elements (PGE) mineralization /." Thesis, Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01192009-164657/.
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Zilibokwe, Nosibulelo Julie. "Characterization of the distribution of platinum group elements in sulphide ores within the Merensky Reef at Modikwa and Two Rivers Platinum Mines, Eastern Bushveld Complex, South Africa." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/7938.
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The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
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Solomon, Nomonde. "Effect of HPGR on platinum bearing ores and the flotation response as compared to the conventional ball mill." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11277.
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Includes abstract.Includes bibliographical references.
This thesis focuses on the application of the high pressure grinding rolls (HPGR) on platinum bearing ores Merensky, UG2 and Platreef. Conventional tumbling mills such as the ball mill that are typically applied on these ore types are highly energy intensive with a small percentage of the input energy being used for actual breakage. Rapidly increasing energy costs have contributed to the rising interest of the HPGR in the platinum industry, particularly in plants processing UG2 and Platreef ores. Therefore, this thesis seeks to determine if the HPGR can be used as an alternative to the ball mill. Key aspects of interest are throughput, energy efficiency, PGE grade and recovery and PGM liberation.
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Dzingai, Theophilus C. "A Process Mineralogical Study on the effect of Alteration on the Flotation of Great Dyke Platinum Group Element (PGE) Ores." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29628.
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Ores from the same deposit may exhibit extensive variability in their mineralogy and texture. The ability to quantify this variability linked to metallurgical performance is one of the primary goals of process mineralogy and geometallurgy. Ultimately this information can be used to inform decisions around all core activities of mining and processing. This study focusses on identifying the key mineralogical differences between three Great Dyke platinum group element (PGE) ores in Zimbabwe. These ores are known to be characterized by extensive oxidation and alteration resulting in numerous metallurgical challenges in recovering the PGE. The behaviour of three different ores sampled along the strike of the Great Dyke is compared, focusing on mineralogical composition, rheological characteristics and batch flotation performance. The contribution of the differences in mineralogy (bulk mineralogy, base metal sulfide (BMS) liberation and association, and naturally floating gangue) to processing challenges and potential opportunities to manage these was considered. It was noted that slight differences in mineralogy, particularly BMS liberation and association, yielded notable differences in copper, nickel, platinum and palladium recoveries. The most oxidized ore was found to have lower recoveries due to the oxidation of the BMS, though a deeper understanding of the oxidation and flotation behaviour of PGEs (and platinum group minerals - PGMs) is still necessary. Through the mineralogical analysis of the batch flotation concentrates it was observed that more finely disseminated and yet locked (unliberated) talc resulted in higher amounts of naturally floating gangue (NFG). The effect of 3 polymeric carboxymethyl cellulose (CMC) depressants, differing in degree of substitution, was also evaluated in terms of their ability to depress the naturally floating gangue and mitigate any rheological complexities that may be associated with these ores, through the electrostatic repulsion of the negatively charged carboxylate groups. There was no significant advantage of one depressant over the others in the batch flotation tests or in the rheology tests. The more oxidized ore was found to contain relatively low amounts of phyllosilicate minerals and, therefore, no rheological problem was present that would have required a chemical solution. There were no noticeable differences in the rheology of the slurries of the 3 ores. This was likely to be due to the dampening or buffering effect of the high proportion of minerals that do not contribute to rheological complexity. Changing of depressant type also had no effect in this case possibly due to the same reasons. In addition to this, the region after which the rheological complexity of all 3 ore types begins to increase exponentially is from 30-35 vol.% solids concentration (60-65 wt.% for an ore with a specific gravity of 3.3). It is therefore advisable for Great Dyke operations not to exceed these solids concentrations as this would exacerbate the processing challenges associated with rheological complexity. The use of such solids concentrations during flotation is however unlikely though this may be the case in other parts of the processing circuit, e.g. comminution, and should thus be noted. The decoupling of the terms referring to alteration (that is oxidation and hydrolysis/hydration) is also presented in this study together with the effects of these different types of alteration on the processing of PGE ores. Oxidation affects the valuable minerals and thus flotation recoveries whilst hydrolysis/hydration acts on the gangue minerals and therefore mainly affects concentrate grade. The more oxidized ore sample in this study had undergone the oxidation type of alteration, rather than hydrolysis/hydration and the processing challenge associated with it lies not in the gangue but with the valuable minerals. Finally, it was shown that investigating an ore’s characteristics solely on mineralogy may not necessarily give a full prediction of the ore’s response but the linking of the mineralogical characterization with metallurgical test work gives a more holistic view.
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Farré, de Pablo Júlia. "Genesis and evolution of chromitites in ophiolite complexes from a mineralogical perspective." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673632.
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The finding of a suite of unusual minerals associated to ophiolitic chromitites questions traditional model for the formation of these rocks. These findings include minerals typically considered indicators of ultra-high pressure and super-reducing conditions (i.e., diamond). Several authors proposed new genetic models for ophiolitic chromitites which involved their formation and/or evolution in the deep mantle (>410 km), opening an intense debate that is still active. This Ph.D. thesis contributes to this debate by studying four examples of ophiolitic chromitites from different geodynamic settings (fore-arc, back-arc, and supra-subduction mantle interacted with mantle plume) in order to evaluate the origin of these “exotic” minerals in ophiolitic chromitites and their possible meaning into the evolutionary history of these enigmatic rocks.
The studied examples of chromitites formed in fore-arc settings include chromitite veins from Havana-Matanzas ophiolite (Cuba) and chromitite pods from Loma Las Cabirmas hill in Loma Caribe peridotite (Dominican Republic). The chromitites from Havana-Matanzas are characterized by abundant platinum-group mineral (PGM) inclusions and by being associated with orthopyroxenite in ophiolitic mantle section. Chromite studies reveal that the chromitites and orthopyroxenites formed coetaneously from Si- and Mg-rich andesitic melts with boninitic affinity originated in the fore-arc mantle of an intra-oceanic arc. The melts infiltrated the pre-existing harzburgite, dissolving olivine while precipitating orthopyroxene and chromite. The abundance of PGM is interpreted to result from the “collector” effect of chromite during the chromitite formation, which was enhanced due to the small volume of chromitites formed.
The Loma Las Cabirmas chromitites display unusually high platinum-group elements (PGE) contents and hydrothermal PGE mineralizations. The study of these chromitites suggests that hydrothermal fluids infiltrated the chromitites during serpentinization of the rocks and gave place to the in situ alteration of magmatic PGM in the chromitites and the precipitation of hydrothermal Pt-rich mineralization in uvarovite- and chromian clinochlore-filled fractures, within the thermal range of 350–150 ºC. Therefore, the PGE bulk geochemistry and mineralogy of these chromitites was largely impacted by post-magmatic processes.
Microdiamonds were found in situ in ophiolitic chromitites from Tehuitzingo serpentinite (Mexico), interpreted as an ophiolitic mantle section formed in a back-arc geodynamic setting. Micrometric diamonds were located within healed fractures crosscutting the chromite grains. These diamonds were associated with amorphous C bearing O-species and with a low-pressure and low-temperature mineral assemblage. Thermodynamic calculations show that the chromite from the healed fractures recrystallized at 670–510 ºC. Consequently, the diamonds are inferred to be metastable and form from C undersaturated CO2–H2O–CH4 fluids infiltrating the chromitite during serpentinization processes. The diamond formed due to the super-reducing conditions achieved within the sealed inclusions. The formation of microdiamonds in (ultra)reduced low-pressure and low-temperature environments during serpentinization challenges the idea that diamond in ophiolitic rocks constitutes an unequivocal indicator of ultra-high pressure conditions.
Chromitites from the northern and central part of the Loma Caribe peridotitic belt (Dominican Republic) were studied as an example of chromitites hosted in an ophiolite with geochemical fingerprints of deep-seated plume activity. These chromitites display unusual compositions, different from other ophiolitic chromitites. Instead, the analyzed chromite grains exhibit major and trace element composition that overlaps the field of komatiitic chromite. Moreover, the composition of parental melts of these chromitites is similar to plume derived products of the Dominican Republic. Therefore, I inferred that these chromitites formed in the lithospheric mantle after parental melts derived from an enriched peridotite source influenced by the Caribbean mantle plume.
Altogether, my results show the importance of differentiating features resulting from magmatic primary processes from those resulting from alteration processes. Only then it will be possible to reconstruct the genetic story and evolution of the chromitites and propose accurate models.En els darrers anys s’han trobat una sèrie de minerals considerats “exòtics” en cromitites ofiolítiques que han fet replantejar a la comunitat científica internacional els models de formació d’aquestes roques. Aquests minerals inusuals són sovint considerats indicadors de condicions d’ultra-alta pressió i súper reductores (i.e. diamant), de manera que els models proposats a partir d’aquestes troballes inclouen un origen i/o una evolució de les cromitites a nivells profunds mantèl·lics (>410 km), contraposant-se a la formació en el mantell litosfèric proposada pels models tradicionals. Aquesta tesi doctoral estudia quatre exemples de cromitites ofiolítiques que pertanyen a diferents contexts geodinàmics amb l’objectiu d’identificar minerals o trets inusuals en les cromitites i/o en les seves roques associades per tal d’avaluar-ne el seu origen i el seu possible significar en el marge de la historia evolutiva d’aquestes roques. Els casos estudiats són: (1) les venes de cromitita de l’ofiolita d’Habana-Matanzas (Cuba), pertanyents a un context de avant-arc; (2) els pods de cromitites de Loma Las Cabrimas (peridotita de Loma Caribe, República Dominicana), també pertanyents a un context d’avant-arc i caracteritzades per les seves mineralitzacions hidrotermals de baixa temperatura de Pt; (3) les cromitites de la serpentina de Tehuitzingo (Mèxic), interpretada com una secció mantèl·lica ofiolítica formada en un context de rere-arc; per últim, (4) les cromitites del nord i del centre del cinturó peridotític de Loma Caribe (República Dominicana), que constitueixen un exemple de cromitites encaixades en una ofiolita amb evidències geoquímiques d’activitat de ploma mantèl·lica. En conjunt, els resultats demostren la importància de diferenciar els efectes de processos magmàtics primaris d’aquells derivats de processos d’alteració per tal de fer una interpretació correcta de la història evolutiva d’aquestes roques.
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Scoon, Roger N. "Discordant bodies of postcumulis, ultramafic rock in the upper critical zone of the Bushveld complex : iron-rich ultramafic pegmatite bodies at Amandelbult and the Driekop platiniferous ultramafic pipe." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1004912.
Full textAbstract:
From the abstract: In the layered sequence of the Bushveld Complex a number of distinct, but possibly genetically related groups of transgressive, postcumulus, ultramafic and mafic rock are recognised. The main part of this thesis investigates a suite of postcumulus rocks for which the name iron-rich ultramafic pegmatite is proposed. The majority of iron-rich ultramafic pegmatite bodies examined are from the upper critical zone of the layered sequence at Rustenburg Platinum Mines Amandelbult Section, in the northern sector of the western Bushveld Complex. Field relationships imply that the iron-rich ultramafic pegmatites should be considered as an integral feature of the layered sequence, even though they transgress the cumulates. Consequently, this thesis also includes a study of the cumulate sequence at Amandelbult. A second group of postcumulus, ultramafic rocks which is investigated comprises latiniferous ultramafic pipes; the Driekop pipe has been selected as a case study. This thesis is presented in four sections, namely, an introduction and verview, and studies on the Driekop pipe, the cumulate sequence at mandelbult and the iron-rich ultramafic pegmatite suite. A new classification scheme of discordant bodies of postcumulus, ultramafic rock in he Bushveld Complex is proposed (see also Viljoen & Scoon, in press). In he scheme presented here, two main varieties of postcumulus, ultramafic rock re recognised, namely, non-platiniferous magnesian dunites and iron-rich ltramafic pegmatites.
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Phillips, David. "Mineralogy and petrology of the Townlands iron-rich ultramafic pegmatite." Thesis, Rhodes University, 1985. http://hdl.handle.net/10962/d1007617.
Full textAbstract:
The Townlands iron-rich ultramafic pegmatite is a relatively large pipelike body situated in the western corner of Rustenburg Section, Rustenburg Platinum Mines. It is characterised by a strong negative magnetic signature and transgresses the noritic layered sequence of the upper critical zone of the Bushveld Complex. The layered rocks are downwarped in the vicinity of the pipe and are in sharp contact with the pegmatitic material. The pegmatite varies in composition between dunite and wehrlite, with the marginal zones being more wehrlitic in composition. Olivine (Fo₃₀ - Fo₅₂) and clinopyroxene (Wo₄₅En₃₀Fs₂₅ - Wo₄₅En₃₇Fs₁₈) are the dominant constituents and accessory phases include ilmenite, Ti -magnetite, apatite, amphiboles, chlorite-group minerals, biotite, ilvaite and a host of unusual ore minerals. The Fe-Ti oxides exhibit exsolution textures typically found in slowly cooled igneous rocks and temperatures of formati on are consi dered to be in excess of 800°C. The UG2 chromitite leader layers intersected by borehole TLP.l are enriched in Fe and Ti and exhibit compositions intermediate between chromite and Ti-magnetite. The ore mineral assemblage includes a primary sulphide assemblage consisting of troilite, chalcopyrite, cubanite and pentlandite, and an array of unusual phases formed by late-stage secondary processes. The unusual sulphides mooihoekite and haycockite, that occur in certain parts of the pegmatite, are considered to have formed by partial replacement of the primary assemblage and a possible paragenetic sequence is discussed. Mineral compositions and whole rock geochemical data are consistent with an origin for the pegmatite by crystallization from a fractionated melt. It is suggested that intercumulus fluids, trapped during the crystallization of the noritic layered sequence, accumulated in an area of structural weakness, in response to an increasing overburden pressure and/or tectonic activity. Evidence is also presented that indicates that the Townlands pegmatite may consist of at least two separate, but adjoining pegmatite bodies.KMBT_363
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Penberthy, Catharina Johanna. "The effect of mineralogical variation in the UG2 chromitite on recovery of platinum-group elements." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-11282005-113358/.
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Carroll, Sandy. "The viability of the Kaplats Platinum group element deposit." Access, 2006. http://upetd.up.ac.za/thesis/available/etd-07102008-080330/.
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Mwase, James Malumbo. "Hydrometallurgical extraction of platinum group metals from a low-grade ore concentrate." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8966.
Full textAbstract:
Includes bibliographical references (leaves 143-153).The aim of this study is to investigate the economic and technical feasibility of processing platinum group metals (PGMs) and base metals (BMs) from a low-grade ore concentrate produced in the concentrator plant at Lonmin Pic. The PGMs of particular interest are platinum, palladium, ruthenium and rhodium, while the BMs of interest are copper and nickel. The ore concentrate, as a by-product, represents only 5 % of the total PGM value but as much as 70 % of the total tonnage of material processed in the concentrator plant. Further upgrading this material is not considered a viable route. However, even this low PGM content in the concentrate material accumulates to appreciable value on an annual basis motivating the need to develop alternative methods of extracting value from it. Initial estimates indicate that extraction levels of at least 50 % of the PGMs and 50 % of the BMs would need to be achieved, using low cost hydrometallurgical processes, to make the venture economically viable. These methods would exclude treatment via the smelter and pressure leaching: which are costly. energy intensive and result in leaching of large quantities of non-valuable elements. Previous studies revealed that organic acids had the potential to economically extract the PGMs under alkaline conditions, and BMs under acidic conditions, from various ores and concentrate materials. A literature survey confirmed that certain organic acids can be used to leach metals from ores and concentrates via chemical complexation. It further revealed that other chemical agents. namely cyanide, thiosulphate and bisulphide, were similarly capable of strongly complexing PGMs under various conditions of pH and temperature. The survey also revealed industrially established methods for extracting BMs from low-grade ores and concentrates. Based on this material, this study experimentally evaluated these options with the intent to propose a flowsheet to treat the concentrate material. This was conducted in two phases of experimental work.
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Barra-Pantoja, Luis Fernando. "A Re-Os Study of Sulfides from the Bagdad Porphyry Cu-Mo Deposit, Northern Arizona, USA." Thesis, The University of Arizona, 2001. http://hdl.handle.net/10150/249252.
Full textAbstract:
Use of Re-Os systematics in sulfides from the Bagdad porphyry Cu-Mo deposit provide information on the timing of mineralization and the source of the ore -forming elements. Analyzed samples of pyrite, chalcopyrite and molybdenite mainly from the quartz monzonite and porphyritic quartz monzonite units are characterized by a moderate to strong potassic alteration (secondary biotite and K- feldspar). Rhenium concentrations in molybdenite are between 330 and 730 ppm. Two molybdenite samples from the quartz monzonite and porphyritic quartz monzonite provide a Re-Os isotope age of 71.7 ± 0.3 Ma. A third sample from a molybdenite vein in Precambrian rocks yields an age of 75.8 ± 0.4 Ma. These molybdenite ages support previous suggestions of two mineralization episodes in the Bagdad deposit. An early event at 76 Ma and a later episode at 72 Ma. Pyrite Os and Re concentrations range between 0.008-0.016 and 3.9-6.8 ppb, respectively. Chalcopyrite contains a wide range of Os (6 to 91 ppt) and Re (1.7 to 69 ppb) concentrations and variable ¹⁸⁷Os/¹⁸⁸Os ratios that range between 0.13 to 22.27. This variability in the chalcopyrite data may be attributed to different copper sources, one of them the Proterozoic volcanic massive sulfides in the district, or to alteration and remobilization of Re and Os. Analyses from two pyrite samples yield an eight point isochron with an age of 77 ± 15 Ma and an initial ¹⁸⁷Os/¹⁸⁸Os ratio of 2.12. This pyrite Re-Os isochron age is in good agreement with the molybdenite ages. We interpret the highly radiogenic initial 1870s/188Os as an indication that the source of Os and, by inference, the ore-forming elements for the Bagdad deposit, was mainly the crust. This conclusion agrees with previous Pb and Nd isotope studies and supports the notion that a significant part of the metals and magmas have a crustal source.
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Tremblay, Christian. "Les éléments du groupe du Platine dans le dyke de Méquillon ceinture de Cape-Smith, Nouveau-Québec /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1990. http://theses.uqac.ca.
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De, Beer Francis. "The characterisation of a two stage flotation circuit treating a complex platinum and chromite ore." Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/16119.
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Bibliography: pages [144]-152.The methodology was developed to characterise the complex MF2 circuit at Impala Platinum Ltd. The circuit was divided into individual units and each unit was evaluated over a period of time. The performance of each unit in terms of platinum, palladium, rhodium and chromite recoveries was determined by sampling around the unit. The changes in ore floatability characteristics were monitored by carrying out batch flotation tests on samples taken from the feed to each unit. The mixing in the units was characterised by performing residence time distribution studies on the units. The batch flotation results were modelled using a distributed rate approach. The model yielded parameters which were associated with three floatability classes, viz. a fast floating, a medium floating and, a slow floating class and a class for valuable minerals which did not float. The model was not able to discriminate between mineralogical and particle size effects on flotation rates. This would be an important prospect of a future investigation. The rate constants associated with each floatability fraction obtained from the batch flotation together with residence time distribution results were used in association with the actual recoveries from each unit. These factors were used to simulate the performance of the circuit. The same model was used for all the units and the differences in cell design as indicated by hydrodynamics, aeration rate, etc. were accounted for in the· mixing parameters and flotation rates. This procedure to simulate plant performance was successfully applied to three different circuits thus confirming its validity. The difference in the three simulated circuits was in the cleaning stages. Among other things, the simulation shows that the best ·platinum, palladium and rhodium recoveries could be obtained if the greatest cleaning capacity was situated in the secondary stage of the circuit. Although the changes in the circuit configuration could be simulated to establish the effect on the platinum, palladium and rhodium recoveries, the chromite recovery could not be simulated. This is due to the fact that chromite is mainly floated by entrainment which is not incorporated into the model. Since the chromite recovery is crucial for the design of optimum cleaning circuits in the flotation of UG-2 ore, research needs to be done to quantify the entrainment phenomenon.
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Viljoen, Willemien. "Phase relations in the system Cu-Fe-Ni-S and their application to the slow cooling of PGE matte." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-10132005-100921/.
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Mbandezi, Mxolisi Louis. "Finite element simulations of shear aggregation as a mechanism to form platinum group elements (PGEs) in dyke-like ore bodies." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1018249.
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This research describes a two-dimensional modelling effort of heat and mass transport in simplified intrusive models of sills and their feeder dykes. These simplified models resembled a complex intrusive system such as the Great Dyke of Zimbabwe. This study investigated the impact of variable geometry to transport processes in two ways. First the time evolution of heat and mass transport during cooling was investigated. Then emphasis was placed on the application of convective scavenging as a mechanism that leads to the formation of minerals of economic interest, in particular the Platinum Group Elements (PGEs). The Navier-Stokes equations employed generated regions of high shear within the magma where we expected enhanced collisions between the immiscible sulphide liquid particles and PGEs. These collisions scavenge PGEs from the primary melt, aggregate and concentrate it to form PGEs enrichment in zero shear zones. The PGEs scavenge; concentrate and 'glue' in zero shear zones in the early history of convection because of viscosity and dispersive pressure (Bagnold effect). The effect of increasing the geometry size enhances scavenging, creates bigger zero shear zones with dilute concentrate of PGEs but you get high shear near the roots of the dyke/sill where the concentration will not be dilute. The time evolution calculations show that increasing the size of the magma chamber results in stronger initial convection currents for large magma models than for small ones. However, convection takes, approximately the same time to cease for both models. The research concludes that the time evolution for convective heat transfer is dependent on the viscosity rather than on geometry size. However, conductive heat transfer to the e-folding temperature was almost six times as long for the large model (M4) than the small one (M2). Variable viscosity as a physical property was applied to models 2 and 4 only. Video animations that simulate the cooling process for these models are enclosed in a CD at the back of this thesis. These simulations provide information with regard to the emplacement history and distribution of PGEs ore bodies. This will assist the reserve estimation and the location of economic minerals.
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Mainza, Aubrey Njema. "Contribution to the understanding of the three-product cyclone on the classification of a dual density platinum ore." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5513.
Full textAbstract:
Includes bibliographical references (p. [234]-246).The detrimental effects exhibited by the conventional hydrocyclone in classifying ores that contain different density components motivated the AMIRA P9 project to look into modifications to the conventional hydrocyclone that can improve separation by component density. In this project a cyclone termed the three-product cyclone has been developed and tested. The three-product cyclone is a modification of the conventional hydrocyclone with an additional vortex finder termed the inner vortex finder inserted concentric to the existing one, termed the outer vortex finder, resulting in three products from the same hydrocyclone. The three-product cyclone produces a finer overflow stream, an intermediate overflow stream comprising fine high density particles and medium sized light particles, and a coarse underflow stream. The work presented in this thesis involved designing an overflow arrangement which allowed interchangeable inner vortex finders to be tested, and a special rig for industrial scale experiments using a 600mm diameter hydrocyclone.
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Steyn, Johannes Jakobus. "Developing a framework for the design of the milling and rougher circuits for a platinum-bearing UG2 ore." Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12868.
Full textAbstract:
Includes bibliographical references.In the western limb of the Bushveld Igneous Complex, platinum is mined predominantly from two reefs – Merensky and UG2. Most of the platinum group minerals (PGM’s) in Merensky ore are associated with base metal sulphides (BMS), and thus Merensky concentrators will usually resemble simple BMS circuits. However, the mineralogy of UG2 ore is more complicated, and thus UG2 circuits are also more complex. The UG2 reef is a chromitite layer in the critical zone of the Bushveld Igneous Complex, which results in high chromite content. Chromite causes significant complications in the downstream smelter process, and therefore chromite constraints are imposed on UG2 concentrators. A further aspect complicating the treatment of UG2 ore is that PGM’s are not only associated with BMS, but ultra-fine PGM’s are also locked in gangue minerals. This affects the milling and flotation characteristics of the circuits, as it is not possible to efficiently target the liberation and recovery of relatively large BMS and ultra-fine PGM’s in the same circuit. As a result UG2 circuits have evolved to deal with these issues in a number of ways. This thesis focuses on the design of milling and flotation circuits to optimise the recovery of coarse BMS (with associated PGM’s) and ultra-fine PGM’s contained in associated siliceous gangue minerals. In order to achieve this, UG2 circuits usually feature more than one milling and flotation stage.
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Du, Pisani Petro. "The financial benefit of using borehole radar to delineate mining blocks in underground platinum mines." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-02092009-141519/.
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Andrews, Lesley. "Base metal losses to furnace slag during processing of platinum-bearing concentrates." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01222009-172643/.
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Bandyayera, Daniel. "Formation des latérites nickélifères et mode de distribution des éléments du groupe du platine dans les profils latéritiques du complexe de Musongati, Burundi /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1997. http://theses.uqac.ca.
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Ramonotsi, Mpho. "Characterisation of the effect of alteration on the PPM platinum ore and evaluation of selected strategies to improve metallurgical performance." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11275.
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The aim of this study is in two parts; the first part focuses on mineralogical quantification of the extent of weathering at PPM by profiling the flotation behaviour and host rock density with spatial depth.
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Michaud, Michael Julien. "The geology, petrology, geochemistry and platinum-group element-gold-copper-nickel ore assemblage of the Roby Zone, Lac des Iles mafic-ultramafic Complex, northwestern Ontario." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0027/MQ52068.pdf.
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Manono, Malibongwe Shadrach. "An investigation into the effect of ionic strength of plant water on valuable mineral and gangue recovery of a platinum bearing ore from the Merensky reef." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/11985.
Full textAbstract:
Includes synopsis.Includes bibliographical references.
Higher solids and water recoveries were obtained at higher ionic strength. The increase in the ionic strength in the absence of any depressant caused an increase in Cu and Ni recovery.
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Junge, Malte [Verfasser]. "The fate of platinum-group elements during weathering processes : with a special focus on the pristine and weathered Platreef ore at the Mogalakwena Mine in the Bushveld Complex / Malte Junge." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/1137165731/34.
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Maharaj, Lakesh. "Optimal design of a secondary milling circuit for treating chromite-rich UG-2 platinum ores." Thesis, 2011. http://hdl.handle.net/10413/5092.
Full textAbstract:
Extraction of platinum group elements (PGE) is a major source of revenue in South Africa and the reserves represent about 75 per cent of world reserves. Most of the remaining Platinum Group Mineral (PGM) reserves are located in the UG-2 chromitite layer of the Bushveld Igneous Complex. Platinum concentrators experience significant losses of PGE in their
secondary milling circuits due to insufficient liberation of platinum-bearing particles. The chromium oxide (Cr2O3) content in UG-2 concentrates is typically 3%, which results in operational problems in the downstream smelting process. Ways of improving the design of the secondary milling circuit were investigated, with the purpose of improving PGE recovery and
reducing Cr2O3 entrainment in the subsequent flotation stage.
Batch-scale laboratory and pilot plant tests were carried out to investigate the optimal design of a secondary milling circuit configuration. The optimal design consisted of a conventional hydrocyclone to de-slime the feed, followed by gravity separation with a spiral concentrator circuit to separate the ore into lights (silicates-rich) and heavies (chromite-rich) fractions.
Separate milling of the light and heavy fractions made it possible to grind the silicate-rich fraction finer and to avoid over-grinding of the chromite. The total milling energy was redistributed between the silicates and chromite ball mills with 88% of the energy input to the silicates mill and 12% to the chromite mill thus reducing chromite over-grinding. The effects on the recovery of PGE, and the entrainment of Cr2O3 were measured in combined batch rougher flotation tests. The results indicated a 2% improvement in the secondary rougher flotation PGE recovery for the densifier underflow sample as compared to the standard MF-2 circuit, and most significantly the Cr2O3 entrainment was reduced by over 30% overall.
Attritioning of the chromite-rich heavies fraction and ball milling of the silicates-rich lights fraction resulted in a 52% reduction of Cr2O3 in the rougher flotation concentrate and a 0.4% increase in PGE recovery (0.4%) as compared to the standard circuit. The improved reduction in chromite entrainment may be attributed to the lower fines generation with attritioning (52.8%- 106μm) as compared to ball milling with a 12% energy input (83.6% -106μm). Over 50% of the chromite minerals remained in the +106μm of the attritioned heavies product as compared with 21% for the ball milled spiral heavies stream. This accounted for a significant proportion of the overall chromite reduction in the flotation concentrate and supported the motivation for the inclusion of a separate grinding circuit for the chromite and silicate particles. Pilot plant testwork on a VHG (very high grade) spiral concentrator circuit followed by laboratory milling and rougher flotation tests confirmed the above conclusions. A 3.7% improvement in PGE recovery was noted with a 32% Cr2O3 reduction in the secondary rougher flotation concentrate as compared to the standard circuit. The statistical reliability of the laboratory and pilot plant data were quantified at various stages of the testwork due to the heterogeneous nature of the feed material and representative sampling. The repeat analyses on selected flotation tests for the high grade ore revealed that the
variances were below 0.5%, 4%, and 7% for the head grades, PGE and Cr2O3 recoveries respectively. The flotation results for the standard and significantly improved milling circuits had variances in the 4E recoveries for the low grade ore and pilot plant ore of below 5.5% and 1% respectively. Low variances (<1%) in the Cr2O3 recoveries were noted for the low grade and pilot plant ores. A preliminary cost estimate was undertaken based on the pilot plant data to determine what value the proposed circuit could add for an additional 3.7% PGE recovery. An additional revenue of approximately R50 000 per day could result based upon the platinum mineral recovery only. The other precious metals, i.e. palladium and rhodium were neglected and would further increase the overall revenue. The minimum payback period for the estimated capital investment would be approximately 4 years. This confirmed the benefit of this improved
secondary milling circuit design as a viable option. A closed-circuit operation of the silicates mill should offer more significant benefits compared to the open circuit option; however, this was not considered in the current testwork. This project has confirmed the benefit of separate ball milling and the use of a spiral concentrator as an effective gravity separation device in the secondary milling circuit for a chromite-rich (>50%) UG-2 platinum ore.Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.
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Brogan, Paul Louis. "The measurement of the viability of PGM-mining projects in a competitive market." Thesis, 2016. http://hdl.handle.net/10539/20976.
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Moodley, Taswald Llewelyn. "The development of an experimental technique for UG-2 ore flotation." Thesis, 2013. http://hdl.handle.net/10413/11216.
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Production of platinum and associated metals is a major source of revenue for South Africa. Significant losses occur in the concentrating stage (10 to 15 per cent) and this research is focused on optimising platinum flotation. Research begins by conducting laboratory batch flotation tests. However, subsequent pilot-plant tests often produce different results. It is believed these differences arise from the artificial nature of laboratory techniques. This project was focused on improving flotation techniques in the laboratory.
The largest source of platinum in South Africa is the UG2 reef and two samples of this ore were used for testing: ‘good’ and ‘bad’ ore. These had different characteristics with regards to the recovery of PGMs and the presence of talc. The latter is an unwanted floatable mineral, which must be depressed to prevent excessive recovery.
The conventional laboratory test procedure makes use of batch tests in various sizes of flotation cells. The procedure was made more realistic, by using four stages of flotation, rather than just two, to mimic a typical platinum flotation plant. The use of four stages made it possible to separate the fast-floating and slow-floating stages and to control froth conditions accordingly. Attention was also given to the fact that in laboratory tests, water is often added to the ‘cleaner’ stage of flotation, to make up the level. Experiments showed that this dilution, which does not take place in practice, had a significant impact on overall efficiency.
A method of measuring frother concentration was developed and used to determine the realistic level of frother in cleaning tests. Tests at these levels of frother concentration showed that significant improvements could be made to plant performance, by making use of a thickener to reduce the frother concentration in the cleaning stages.
The improved test procedure was used on both good and bad ores, and the effect of regrinding was also tested. A combined solids recovery of 2 % over both cleaners was targeted for all test work. At this recovery, the regrinding of the bad ore increased the PGM recovery from 67 to 76 per cent at the cost of an additional 8 g/t depressant.
An investigation of the effect of frother concentration in the cleaning stage, using good ore, demonstrated that that rejection of chromite could be improved significantly by reducing frother concentration. The tests mimicked the use of a thickener to separate some of the water with a high concentration of frother. Tests conducted on the good ore showed that use of two thickeners, as opposed to none, reduced the Cr2O3 content of the final concentrate from 4.2 to 3.2 per cent for the equivalent concentrate mass and PGM recovery. The depressant requirement was also reduced from 67 to 55 g/t. These tests provided insight on how to improve performance on a platinum flotation plant, particularly when floating the bad ore.
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"MLA-based mineralogical investigation of PGE mineralisation at Lonmin's Akanani Platinum Group Metal Project, Northern Limb of the Bushveld Complex." Thesis, 2012. http://hdl.handle.net/10210/5069.
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Fitzhenry, Clifford. "The mineralogy, petrology and PGE geochemistry of the UG2 cyclic unit at Lebowa Platinum mine (ATOK), North-Eastern Bushveld complex." Thesis, 2008. http://hdl.handle.net/10413/1046.
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Makgoale, Dineo Mokganyetji. "Effects of mill rotational speed on the batch grinding kinetics of a UG2 platinum ore." Diss., 2019. http://hdl.handle.net/10500/26498.
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In this study, the effect of speed was investigated on the breakage rate of UG2
platinum ore in a batch mill of 5 dm3 and 175 mm internal diameter. One size fraction
method was carried out to perform the experiment. Five mono-sized fractions in the
range of 1.180 mm to 0.212 mm separated by √2 series interval were prepared. The
fractions were milled at different grinding times (0.5, 2, 4, 15 and 30 min) and three
fractions of mill critical speed were considered (20%, 30%, and 40%). The target of
critical speed below 50% was due to the need of lower energy consumption in milling
processes. The selection and breakage function parameters were determined and
compared for fractions of critical speed.
First the grinding kinetics of the ore was determined and it was found that the
material breaks in non-first order manner. Thereafter, effective mean rate of
breakage was determined. It was found that the rate of breakage increased with
increase of mill speed and optimum speed was not reached in the range of chosen
mill speed fractions. Again the rate of breakage was plotted as a function of particle
size, the optimum size was 0.8 mm when milling at 30% critical speed. As for 20% and
30% optimum size was not reached. The selection function parameters estimated at
30% critical speed were 𝑎0 = 0.04 min−1
, 𝛼 = 1.36, 𝜇 = 0.9 mm, and Λ = 3. Breakage
function parameters were determined and was noticed that the material UG2
platinum ore is non-normalised, i.e. Φ value was changing from 0.25 to 0.90
depending on feed size and mill speed. The parameters 𝛽 and 𝛾 were constant at 7.3
and 1.17 respectively.College of Science, Engineering and Technology
M. Tech. (Chemical Engineering)
41
Smith, Albertus Johannes Basson. "The geometallurgical characterization of the Merensky Reef at Bafokeng Rasimone Platinum Mine, South Africa." Thesis, 2014. http://hdl.handle.net/10210/12358.
Full text
42
Vermaak, M. K. G. (Matthys Karel Gerhardus). "Fundamentals of the flotation behaviour of palladium bismuth tellurides." Thesis, 2005. http://hdl.handle.net/2263/28676.
Full textAbstract:
Previous mineralogical investigations (QemSCAN) performed on all effluent flotation streams of Mimosa mine (Zimbabwe) indicated the presence of appreciable amounts of platinum group minerals (PGMs), which are not recovered. Most, generally in excess of 70%, of the liberated PGMs in these streams belonged to the Pt-Pd-Bi-Te class in all the samples investigated. In the first part of this work, electrochemical investigations, electrochemically-controlled contact angle measurements and Raman spectroscopy have been employed to investigate the interaction of ethyl xanthate with Pd-Bi-Te and PtAs2. Impedance measurements showed lower capacitance values in solutions containing KEX indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction, hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. The result of this investigation has shown dixanthogen to be present on both the minerals (PtAs2 and Pd-Bi-Te) when the surfaces are anodically polarized. Chemisorbed xanthate could be identified within 120 seconds yielding a hydrophobic surface as indicated by electrochemically-controlled contact angle measurements. Maximum contact angles of 63o were measured in the case Pd-Bi-Te. As a result the mineral surface is expected to be hydrophobic and a lack of collector interaction with the mineral is not the reason for low PGM recoveries experienced. Secondly, the flotation recovery of synthetically prepared Pd-Bi-Te was compared with that of chalcopyrite (a typical fast-floating mineral) and pyrrhotite (a typical slow-floating mineral), with microflotation tests. These indicated Pd-Bi-Te to be a fast-floater with flotation rates exceeding that of chalcopyrite. Predicted flotation rate constants (from the Ralston model) were significantly lower for small particles (with diameters similar to those lost to the effluent streams) compared with those of particle with intermediate sizes. This supports the suggestion that losses to effluent streams are caused by particle size effects.Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2006.
Materials Science and Metallurgical Engineering
unrestricted
43
Manyeruke, Tawanda Darlington. "The petrography and geochemistry of the Platreef on the farm Townlands, near Potgietersrus, northern Bushveld Complex." Diss., 2004. http://hdl.handle.net/2263/24178.
Full textAbstract:
The Platreef is a platinum group element (PGE) and base metal enriched mafic/ultramafic layer situated along the base of the northern (Potgietersrus) limb of the Bushveld Complex. It represents an important resource of PGE which is only in its early stages of exploitation. The present study contains a detailed petrographic and geochemical investigation of a borehole core drilled on the farm Townlands. At this locality, the Platreef rests on metasedimentary rocks of the Silverton Formation of the Transvaal Supergroup, and is comprised of three medium grained units of gabbronorite/feldspathic pyroxenite that are separated by hornfels interlayers. I refer to the three platiniferous layers as the Lower, Middle and Upper Platreef. The Middle Platreef is the main mineralized layer, with total PGE contents up to 4 ppm. The Lower and Upper Platreefs are less well mineralized (up to 1.5 ppm). Trace element and S-isotope data show compositional breaks between the different platiniferous layers suggesting that they represent distinct sill-like intrusions. The study also reveals a reversed differentiation trend of more primitive rocks towards the top of the succession. For example, pyroxene shows an increase in Cr2 O3 with height couples with a decrease in TiO2 . Olivine from the Upper Platreef has Fo contents between 80-83 (averaging Fo81) and those from the Middle Platreef have Fo from 78-83 (averaging Fo79 ). The Upper and Lower Platreefs have d 34S values averaging 80/00 while the Middle Platreef has d 34S values averaging 4 0 /00. All three Platreef layers have elevated d 34S values, indicating addition of 34S-enriched crustal sulphur. The model of contamination is supported by elevated K, Ca, Zr and Y contents in the Platreef relative to Critical Zone rocks from elsewhere in the Bushveld Complex, and by high Zr/Y ratios. Well defined correlations between concentrations of the individual PGE, and between the PGE and S suggest that the concentration of the PGE was controlled by segregating sulphide melt. Alteration of the rocks, possibly due to infiltration by fluids derived from the floor rocks, caused localized redistribution of Cu and, to a lesser degree, the PGE. A model is proposed whereby the Platreef magma assimilated calcsilicate and hornfels from the country rocks. The hornfels and calcsilicate of the Silverton Formation that forms the floor rocks to the Platreef on the farm Townlands constitute a possible source of the crystal sulphur. Release of S from the floor rocks caused S-supersaturation in the magma, followed by segregation of an immiscible sulphide melt. The sulphide melt scavenged the PGE from the silicate magma. The sulphides and the xenoliths were entrained by successive, metal-undepleted magma flows, causing high metal tenors in the sulphides and undepleted Ni contents in associated olivineDissertation (MSc)--University of Pretoria, 2006.
Geology
unrestricted
44
Viljoen, Willemien. "Phase relations in the system Cu-Fe-Ni-S and their application to the slow cooling of PGE matte." Thesis, 2002. http://hdl.handle.net/2263/28674.
Full text
45
Penberthy, Catharina Johanna. "The effect of mineralogical variation in the UG2 chromitite on recovery of platinum-group elements." Thesis, 2002. http://hdl.handle.net/2263/29887.
Full textAbstract:
Platinum-group elements (pGEs) are recovered from UG2 chromitite by milling and flotation. The mechanisms involved during beneficiation of this type of ore are still poorly understood, partly because of its complex nature. Image-analysis techniques were used to characterise the mineralogy ofUG2 chromitite from diverse geological environments, as well as the milling and flotation products derived from each of these ores. Postmagmatic alteration ofUG2 chromitite has a profound effect on the mineralogy, chemistry and recovery characteristics of the UG2 chromitite. Relatively unaltered UG2 chromitite consists predominantly of chromite and primary silicates, mostly bronzite and plagioclase with minor phlogopite, and small amounts of secondary silicates such as talc and chlorite. Trace quantities of base-metal sulphides, predominantly pentlandite, pyrrhotite and chalcopyrite ± pyrite, generally occur at chromite-silicate grain boundaries. PGEs are present both as discrete PGE minerals, and, to a lesser extent, sub-microscopically in other phases, mostly palladium and rhodium in pentlandite. The PGE mineral assemblage is characterised by sulphide minerals, mostly braggite, cooperite, nickeloan malanite and laurite, and is closely associated with the base¬metal sulphides. Recovery of PGE minerals is strongly dependent on the degree of liberation, with liberated PGE minerals and PGE minerals associated with liberated base-metal sulphides, the fastest-floating particles. PGE minerals report to flotation tailings predominantly as fine-grained inclusions in coarse silicate particles. In places, the footwall rocks have been replaced by iron-rich ultrabasic pegmatoid. As a result of interaction with Fe- and Ti-rich fluids, the chromite grains in the UG2 chromitite have been enlarged due to sintering, and the PGE mineral assemblage replaced by one consisting predominantly of laurite, Pt-Fe alloy and other non¬sulphide PGE minerals. The non-sulphide PGE mineral grains appear to be slower ¬floating than sulphide PGE minerals. Low temperature hydrothermal alteration appears to have caused relatively widespread alteration of the UG2 chromitite in some areas, resulting in corrosion and redistribution of sulphide minerals, as well as the replacement of primary magmatic silicates by secondary silicates such as pumpellyite, epidote, prehnite, albite, talc, chlorite and quartz. Ore from such areas are characterised by a base-metal sulphide assemblage consisting predominantly of millerite, chalcopyrite, and pyrite. Base¬metal sulphide and PGE minerals occur in fine-grained intergrowths with silicates, resulting in poor liberation. In the samples investigated, composite particles were often faster-floating than expected, at least partly due to the presence of naturally floatable talc. The effect of faulting on the mineralogy of the UG2 chromitite probably depends on distance from the fault zone, and possibly also timing of faulting, and can cause cataclasis of the ore. Where cataclasis occurred, broken mineral grains are cemented by secondary, hydrous silicates. Liberation of base-metal sulphides and PGE minerals are poor, and recoveries consequently very low. It was demonstrated that reasonable estimates of total PGE+Au recovery can be made from the mineralogical characteristics ofUG2 chromitite ore. Based on the mineralogy of ore from a specific area, provision can be made for appropriate adjustments to metallurgical flowsheets.Thesis (PhD)--University of Pretoria, 2006.
Geology
Unrestricted
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Nashwa, Velaphi Moses. "The flotation of high talc-containing ore from the Great Dyke of Zimbabwe." Diss., 2008. http://upetd.up.ac.za/thesis/available/etd-09042008-160536.
Full text
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Mohloki, Lefu Justinus. "Ore reserves generation at variable development and stoping rates for a UG2 Bushveld Complex platinum reef conventional mining layout." Thesis, 2010. http://hdl.handle.net/10539/8301.
Full textAbstract:
Ore reserves generation at a rate lower than the depletion or mining rate will lead to a shortage of
places to be mined usually referred to as ‘lack of flexibility’.
The purpose of the research was to critically evaluate one major capital project that was about to
be implemented with a view to establish if there exists a balance between depletion and
replacement of ore reserves in that particular project. The project was planned to deliver 100 000
tonnes per month.
Numerical modelling was carried out in Mine2-4D and Earthworks Production Scheduler, EPS,
the results, of which, were imported into Microsoft Excel for further analysis.
The analysis revealed that:-
1 Planned production level (100 000 tonnes per month) cannot be achieved at the planned
development rates.
2 Production levels above 33 000 tonnes per month (15m/month face advance) takes the
system out of balance.
3 Optimal Production equals 33 000 tonnes per month achieved in 4 years and maintained
over 9 years.
Project flexibility should be assessed before any project can be approved, and monitored
throughout the life of the project.
48
Mbandezi, Mxolisi Louis. "Finite element simulations of shear aggregation as a mechanism to form platinum group elements (PGEs) in dyke-like ore bodies." Thesis, 2001. http://eprints.ru.ac.za/2322/1/MBANDEZI-MSc-TR02-65.pdf.
Full textAbstract:
This research describes a two-dimensional modelling effort of heat and mass transport in simplified intrusive models of sills and their feeder dykes. These simplified models
resembled a complex intrusive system such as the Great Dyke of Zimbabwe. This study investigated the impact of variable geometry to transport processes in two ways. First the
time evolution of heat and mass transport during cooling was investigated. Then emphasis was placed on the application of convective scavenging as a mechanism that leads to the formation of minerals of economic interest, in particular the Platinum Group Elements (PGEs). The Navier-Stokes equations employed generated regions of high shear within the magma where we expected enhanced collisions between the immiscible sulphide liquid particles and PGEs. These collisions scavenge PGEs from the primary melt, aggregate and concentrate it to form PGEs enrichment in zero shear zones. The PGEs scavenge; concentrate and glue in zero shear zones in the early history of of
viscosity and dispersive pressure (Bagnold effect). The effect of increasing the geometry size enhances scavenging, creates bigger zero shear zones with dilute concentrate of PGEs but you get high shear near the roots of the dyke/sill where the concentration will not be dilute. The time evolution calculations show that increasing the size of the magma chamber results in stronger initial convection currents for large magma models than for small ones.
However, convection takes, approximately the same time to cease for both models. The research concludes that the time evolution for convective heat transfer is dependent on the
viscosity rather than on geometry size. However, conductive heat transfer to the e-folding temperature was almost six times as long for the large model (M4) than the small one (M2).Variable viscosity as a physical property was applied to models 2 and 4 only. Video animations that simulate the cooling process for these models are enclosed in a CD at the
back of this thesis. These simulations provide information with regard to the emplacement history and distribution of PGEs ore bodies. This will assist the reserve estimation and the location of economic minerals.
49
Makamba, Tapiwa. "Evaluation of financial performance of South African gold, platinum, coal and iron ore mining companies for the period 2012 – 2016." Thesis, 2018. https://hdl.handle.net/10539/26591.
Full textAbstract:
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in partial fulfilment of the requirements for the Degree of Master of Science in Engineering.South Africa hosts vast mineral resources that it has a great global comparative advantage in terms of mineral resources endowment. The mining industry continues to be a key contributor to the country’s economy. However, since the end of the 2008 global economic crisis, the industry has faced multiple global and local economic and operational challenges that together threaten the survival and sustainability of the industry. This study investigated the effects these challenges had on the financial performance and health of the South African mining industry for the period 2012 to 2016. The research focussed on the performance of platinum, gold, coal and iron ore mining companies listed on the Johannesburg Stock Exchange. To determine the companies’ financial performance, financial ratios were used to measure the profitability, liquidity, solvency, activity and market performance of the companies. Validation of the findings of ratio analysis was done using the Altman Z”-score analysis model that also classified the companies’ financial health over the period. As commodity price is a key driver of mining companies’ value, a Pearson coefficient correlation analysis was done to determine the influence commodity price had on the performance of the mining companies during the period. The study found that the overall financial performance and health of mining companies was declining over the course of the analysis period. Profitability was low for all commodity sectors except iron ore, liquidity was good for the platinum and iron ore sectors but poor for the gold and coal sectors. All commodity sectors had good activity ratios but, had poor solvency and market ratios except the iron ore sector. Only the iron ore mining sector performed well in all the ratio categories. Declining commodity prices for most commodities, increasing operating costs, declining productivity were found to be the main factors that affected the performance of mining companies. In addition, the impact on the mining sector of government and policy uncertainty such as the Mining charter, resulted in wholesale decline in the value of mining stocks as investor confidence waned. The Altman Z”-score analysis showed that most analysed companies were in a safe zone, but a few were in a distress zone during the analysis period. Because mining Page | companies are price takers, it is important that they improve on their efficiencies to remain viable and sustainable against a constrained economic and operational challenges.
E.R. 2019
50
Loidl, Gernot C. "The Elura Orebody: a multidisciplinary study investigating geochemical mineralogical & geometallurgical ore characteristics." Thesis, 2012. http://hdl.handle.net/2440/82375.
Full textAbstract:
The Elura Zn-Pb-Ag deposit 43km NNW of Cobar, NSW, contained a pre-mining resource of 50.7 Mt at 8.8 wt% Zn, 5.6 wt% Pb, 107 g/t Ag and 0.2 wt% Cu. Sediment-hosted ore within a turbiditic sequence is strongly structural controlled. It is sheet-like with several elongated, subvertical massive zoned sulphide bodies with central pyrrhotitic cores surrounded by pyrite ore which is enclosed by semi-massive and breccia-stringer mineralisation. This study showed pronounced grain sizes, texture, mineral composition and trace element geochemistry heterogeneity. The pyrite-pyrrhotite-galena-sphalerite ore has minor marcasite, chalcopyrite and arsenopyrite and trace tetrahedrite (±freibergite), native silver and magnetite. Enrichment trends towards the surface and peripheral pyrite-dominated ore zones are in Ag, As, Tl, Hg, Sb, Sn, Mo and Au. The first Re-Os whole rock massive sulphide isochron age is 378±15 Ma. Initial ϒOs of ~170 is either caused by juvenile continental crust of the Lachlan Fold Belt as metal source or by a contribution of primitive mantle Os. Zinc isotope compositions of sphalerite (δ⁶⁶ZnJMC 0.220- 0.450‰) suggest effectively leached average continental crust as the source for metals, chlorite thermometry showed temperatures at 314-343°C, high Cu concentrations coincide with light Zn isotopes that define two major zones of fluid influx and the isocon method showed host lithology replacement was negligible during ore genesis. Sulphides formed in sites of increased dilation and fracture-induced permeability during prolonged periods of fracturing and fluid pulses. Decreasing fluid pressure and adiabatic cooling initiated precipitation of sulphides. No evidence for fluid mixing was identified. Initially, lower parts of the orebody formed in dilational zones in sandstone-rich sequences along a transpressional fault corridor. Major fracturing then caused the formation of upper main lode and upgrading of the lower main lode ore zones. Changing fluid temperatures, internal refinement via dissolution-reprecipitation and temporal fluid composition change created vertical mineralogical and geochemical ore zonation. The orebody was modified during post-depositional compression during continued basin inversion resulting in sulphide remobilisation, upgrading and amplified ore zonation. Zinc and, in particular, Pb recovery rates significantly fluctuated since production began in1983. Fluctuating recovery rates resulted from grain size variability and subsequent poor particle liberation during grinding. Silver recoveries rarely exceeded 50%. Poor Ag recoveries were due to fine-grained argentian tetrahedrite, common associations with gangue phases and alteration of tetrahedrite. High concentrations of Bi were encountered recently in lead concentrate. A galenamatildite solid solution contains Bi (max. 5,645ppm). High Bi is limited to the lower most main lode ore zone. Geometallurgical ore characterisation via QEMSCAN® was undertaken to predict mineral processing characteristics of ore sourced from parts of the same stope. On the stope scale there are significant variations in flotation characteristics from different parts of the stope which enables prediction of recoveries, concentrate qualities and mill throughput. Theoretical recovery calculations suggest that ore from the western part will have10% lower recovery. Theoretical and long-term average recoveries are similar for Zn but not for Pb. Theoretical data may over- estimate recovery because sample preparation may liberate more particles than plant grinding. An overview of mineralogy and trace elements allows geometallurgical ore characterisation on the stope scale to better predict mill performance. Investigation of geometallurgical ore characteristics and penalty element concentrations are recommended on a stope-by-stope basis within life-of-mine planning.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2012