Dissertations / Theses: 'Gold bearing'

1

Seitkan, Ainur. "Environmental mineralogy of gold recovery from refractory gold-arsenic-bearing Bakyrchik concentrates." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273373.

Full text

Abstract:

Arsenic contamination of groundwater associated with mining operations is a widespread problem across the globe. The release of arsenic (As) into the environment occurs naturally by oxidation of exposed sulfide minerals. In the case of gold ores, the mining and beneficiation may also produce As-bearing wastes and this can accelerate the natural mechanisms of As mobilization. The Bakyrchik is the largest gold deposit in Kazakhstan and one of the largest in the world. Gold (Au) is dispersed in pyrite and arsenopyrite in the form of microscopic inclusions. Despite the fact that only 10% of gold ore has been mined to date, it has left behind a dangerous As-containing legacy. Speciation of As has been determined for samples from Bakyrchik to understand the post-processing environment and the mobility of arsenic in the mining-influenced area. As(III) and As(V) have been detected in water samples using HPLC-ICP-MS. The variability of As species across the narrow pH and Eh range indicates that biogeochemical processes can play a role in the speciation of As in water at the study site. In order to understand processes controlling As mobilization in water, the solid phase speciation of As in Bakyrchik sediments, soil, and metallurgical processing products has been investigated using XRD and EPMA. This revealed arsenopyrite, As-bearing pyrite, and their alteration products containing up to 25% As, iron oxides and oxyhydroxides (with up to 2.5% As), haidingerite, and calcium arsenate in studied samples. Sequential extraction demonstrated that in soil and sediment samples As is associated mainly with Al and amorphous Fe oxyhydroxides. Results suggest that the main mechanisms controlling As mobility in Bakyrchik are dilution with regional waters, adsorption onto iron and aluminium oxyhydroxides, and co-precipitation of dissolved As with alteration products of sulfide minerals. Assessment of As bioaccessibility through inhalation demonstrates its strong dependence on the mineralogy rather than on total As content of the solid samples. Calculated cancer and non-cancer risks of inhalation exposure imply that all samples are highly hazardous for human health. With the depletion of the oxide lode ore deposits, gold extraction is moving towards the mining of technologically difficult ores, such as those found at Bakyrchik. A new method of Au recovery from double refractory Au-As-bearing concentrates has been developed, allowing recovery of 97% of Au, and the conversion of up to 95% As into iron-arsenic alloy. Fe-As alloy can contain up to 40% As, and do not require further solidification/stabilisation prior to disposal. The method has been published as a patent with the Patent Office of the Republic of Kazakhstan. Quantitative phase composition of the Fe-As alloy, has been determined by EPMA, QEMSCAN, X-ray and neutron diffraction. Toxicity and solubility of Fe-As alloy in aqueous solutions have been characterised. High-temperature structural behaviour of Fe-As alloy and Fe$_{2}$As in inert atmosphere has been determined by $\textit{in situ}$ synchrotron XRD. Results of the study support the development of the new method as an efficient alternative for processing double refractory Au-As-bearing concentrates.

APA, Harvard, Vancouver, ISO, and other styles

2

Miller, D. M. "Biooxidation of a gold bearing arsenopyrite/pyrite concentrate." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/18299.

Full text

Abstract:

The objectives of this project have been to characterise the biooxidation of an auriferous pyrite/arsenopyrite flotation concentrate, and to interpret laboratory batch and continuous pilot plant data in the light of the logistic model. Furthermore, the possibility of predicting continuous biooxidation plant performance from batch data was considered. The batch testing was carried out on five narrowly sized fractions of Fairview concentrate, as well as on the bulk concentrate. Extents of removal of iron, arsenic and sulphide-sulphur were described by the logistic equation and values of the kinetic parameters obtained. Maximum rates of removal of these components, predicted by the logistic parameters, correlated well with experimentally determined rates of removal obtained from the linear portions of the fractional removal versus time curves. Bibliography: pages 93-98.

APA, Harvard, Vancouver, ISO, and other styles

3

Müller, Ruben S. Ramon. "Homogeneous gold catalysts : development of applications for gold(I) catalysts bearing N-heterocyclic carbene ligands." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2531.

Full text

Abstract:

Recently established as an excellent activator for π-systems, efforts made in gold chemistry have increased enormously, resulting in a new ‘Gold Rush’ in chemistry. This thesis is a small contribution to it. There are two main aspects dominating the following chapters: gold catalysts bearing N-heterocyclic carbenes (NHCs) as supporting ligand, and H₂O assisted catalysis. The initial motivation for the presented work was to specifically demonstrate the potential of [(NHC)AuCl] as suitable catalysts for both known and new organic transformations and to establish these commercially available catalysts in gold chemistry, a field currently dominated by phosphine bearing gold complexes. Water mediated catalysis became the next repeatingly occurring aspect of this thesis by pursuing this initial aim and finding water as a useful solvent or agent, respectively. Various useful applications for gold-NHC complexes are presented, starting with the Meyer-Schuster rearrangement of propargylic alcohols as a continuation of the work realized with propargylic acetates by the Nolan group in early investigations on gold catalysts. Next, a study on alkyne hydration is presented with focus on low catalysts loadings to establish gold catalysts as a powerful choice for such a highly relevant reaction. The catalytic system is then advantageously adapted to a silver-free variation, still active at low catalyst loadings and with further mechanistic insight. Inspired by gold activation of alkynes, a gap of reactivity in gold catalysis is closed by a successful demonstration of nitrile hydration, a functionality previously thought to be inert towards gold activation. In this context, formation and role of dinuclear hydroxy-bridged gold complexes is investigated highlighting these complexes as a possible resting state of gold complexes in the presence of water. Next, the formation of furanones via alkoxylation/lactonization of propargylic propiolates is presented, an observation initially made when exploring the scope of the Meyer-Schuster rearrangement. The dissertation finally closes with the gold-catalyzed formation of amides, this time however achieved from aldoximes reacting via dehydration/hydration mechanism.

APA, Harvard, Vancouver, ISO, and other styles

4

Sanchez-Corrales, Victor Manuel. "Electrochemical leaching of gold-bearing arsenopyrite in alkaline cyanide solutions." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184952.

Full text

Abstract:

Rest potential measurements, cyclic voltammetry, linear sweep voltammetry and constant potential coulometry were used to determine the electrochemical response of arsenopyrite in the absence and in the presence of cyanide and to determine its dissolution chemistry. Surface oxidation of arsenopyrite is proposed to proceed by a two-step reaction sequence. FeOOH, H₂AsO₃⁻, and Sᵒ, are produced in the initial step. Oxidation of Sᵒ to SO₄²⁻, and H₂AsO₃⁻ to HAsO₄²⁻ account for the second step. Coulometric results confirmed that 14 electrons are involved in the overall reaction. The implications of these results on the cyanidation of arsenical gold-bearing concentrates were also investigated. The response of four different concentrates to various cyanidation techniques was examined. Alkaline pressure oxidation in 1 M NaOH, at 200°C and under 500 psi of oxygen overpressure followed by conventional cyanidation resulted in 81% gold extraction from a concentrate that yielded only 2% gold extraction after direct cyanidation.

APA, Harvard, Vancouver, ISO, and other styles

5

Mujdrica, Stefan. "Gold-bearing volcanic breccia complexes related to carboniferous-permian magmatism, North Queensland, Australia." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005577.

Full text

Abstract:

Gold-bearing volcanic breccia complexes are the major sources of gold in the Tasman Fold Belt System in north Queensland. The Tasman Fold Belt System represents the site of continental accretion as a series of island-arcs and intra-arc basins with accompanying thick sedimentation, volcanism, plutonism, tectonism and mineralisation. In north Queensland, the fold belt system comprises the Hodgkinson-Broken River Fold Belt, Thomson Fold Belt, New England Fold Belt and the Georgetown Inlier. The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusivesof the transitional tectonic stage of the fold belt system. The formation and subsequent gold mineralisation of volcanic breccia complexes are related to Permo-Carboniferous magmatism within the Thomson Fold Belt and Georgetown Inlier. The two most important producing areas are at Mount Leyshon and Kidston mines, which are high tonnage, low-grade gold deposits. The Mount Leyshon breccia complex was emplaced along the contact between CambroOrdovician metasedimentary and metavolcanic rocks, and Ordovician-Devonian I-type granitoids of the Lolworth-Ravenswood Block. The Kidston breccia complex is located on a major lithological contact between the Early to Middle Proterozoic . Einasleigh Metamorphics and the Silurian-Devonian Oak River Granodiorite. The principal hosts to the gold mineralisation at the Mount Leyshon and Kidston deposits, are breccia pipes associated with several episodes of porphyry intrusives. The goldbearing magmatic-hydrothermal and phreatomagmatic breccias post-date the development of a porphyry-type protore. The magmatic-hydrothermal breccias were initially emplaced without the involvement of meteoric-hydrothermal fluids, within a closed system. Later magma impulses reached higher levels in the cooled upper magma chamber, where meteoric water invaded the fracture system. This produced an explosive emplacement of phreatomagmatic breccias, as seen at Mount Leyshon. Widespread sericitisation and pyrite mineralisation are common, with cavity fill, disseminated and fracturelveincontrolled gold and base metal sulphides. The Kidston and Mount Leyshon breccia complexes have hydrothermal alteration and mineralisation characteristics of the 'Lowell-Guilbert Model'. However, the argillic zone is generally not well defined. The gold travelled as chloride complexes with the hydrothermal fluids before being deposited into cavities and fractures of the breccias. Later stage epithermal deposits formed at the top of the breccia complexes that were dominantly quartz-adularia-sericite-type. The erosion, collapse and further intrusion of later porphyry phases allowed the upper parts of the breccia complexes to mix with the lower hydrothermal systems. Exploration for gold-related volcanic breccia complexes is directed at identifying hydrothermal alteration. This is followed by detailed ground studies including geological, mineralogical, petrological and geochemical work, with the idea of constructing a 'model' that can be tested with subsequent subsurface work (e.g. drilling). Geomorphology, remote sensing, geochemistry, geophysics, petrology, isotopes and fluid inclusions are recommended exploration techniques for the search of gold-bearing volcanic breccia complexes. Spectral remote sensing has especially become an important tool for the detection of hydrothermal alteration. Clay and iron minerals of the altered rock, within the breccia complexes, have distinctive spectral characteristics that can be recognisable in multispectral images from the Landsat thematic mapper. The best combination of bands, when using TM remote sensing for hydrothermally altered rock, are 3/5/7 or 4/5/7. The breccia complexes have exploration signatures represented as topographic highs, emplaced within major structural weaknesses, associated I-type granitic batholiths, early potassic alteration with overprint of sericitic alteration, and an associated radiometric high and magnetic low. The exploration for gold-bearing volcanic breccia complex deposits cannot be disregarded, because of the numerous occurrences that are now the major gold producers in north Queensland.

APA, Harvard, Vancouver, ISO, and other styles

6

Drossou, Marianna. "The kinetics of the bioleaching of a refractory gold-bearing pyrite concentrate." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/23206.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Jobson, David Hamilton. "Genesis of the gold-bearing breccia bodies at the Lebong Tandai Mine, Sumatra." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241251.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Norman, Philippa Fernandes. "An Investigation into the bacterial leaching of a gold-bearing pyrite/arsenopyrite ore." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/21903.

Full text

Abstract:

Bibliography : pages 157-173.
The main aim of this study was to develop an economically viable bacterial leaching process for a gold-containing pyrite/arsenopyrite ore. The effect of various parameters on, and the mechanism of, bacterial leaching were investigated. Initially milled run-of-mine ore was examined. Batch tests and a continuous bacterial leach were carried out. Bacterial leaching was successful and 91-93% gold dissolution was attained in four days. The process was not economically feasible when compared to the standard flotation-roasting process.

APA, Harvard, Vancouver, ISO, and other styles

9

Jahoda, R. "Geology, and genesis of auriferous hydromagmatic breccias and related deposits in northwestern Spain." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383648.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Vlassopoulos, Dimitrios. "Some experimental studies bearing on the solubility and speciation of gold in natural waters." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61767.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Chapman, J. T. "The batch and continuous bacterial leaching kinetics of a refractory gold-bearing pyrite concentrate." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/17706.

Full text

Abstract:

Bibliography: pages 125-136.
The recent focus on bacterial leaching as a preoxidation step in the treatment of refractory gold bearing sulphide ores and concentrates, has created the need for kinetic models to adequately describe bacterial leaching reactor performance. This work is a kinetic study of the bacterial leaching of a refractory gold bearing, pyrite concentrate. The study includes the presentation of two mechanistically based, the shrinking particle and propagating pore (Hansford and Drossou, 1986), batch reactor kinetic models. These models are derived for single stage continuous reactor description. In addition, the empirical logistic growth model (Pinches et al., 1987) is presented for both batch and continuous reactor description. The models are correlated with the experimental data. Three narrow size fractions of the pyrite concentrate were subjected to batch and continuous bacterial oxidation, using a Thiobacillus ferrooxidans culture. Time profile data of the pyrite oxidation were obtained for the batch reactor study. Similarly, retention time profile data of pyrite oxidation was obtained for the single stage continuous reactor. The .gold extraction as a function of sulphide oxidation as well as fraction arsenic leached, was established.

APA, Harvard, Vancouver, ISO, and other styles

12

Salier, Brock Peter. "The timing and source of gold-bearing fluids in the Laverton Greenstone Belt, Yilgarn Craton, with emphasis on the Wallaby gold deposit." University of Western Australia. School of Earth and Geographical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0013.

Full text

Abstract:

[Truncated abstract] The Laverton Greenstone Belt (LGB), located in the northeastern part of the Eastern Goldfields Province (EGP) of the Yilgarn Craton, Western Australia, has a total contained gold endowment of over 690t. An important feature of the gold deposits in the LGB is their close spatial association with granitoids, with many gold deposits located adjacent to, or hosted by, granitoids. Recently-proposed genetic models for Archaean orogenic gold deposits have emphasised the role of granitoids in the formation of ore-deposits, but differ significantly in the nature of that role. Some models suggest that the granitoids are a source of ore-fluids and solutes, whereas others suggest that granitoids exert an important structural control on gold mineralisation. Such competing genetic models for gold mineralisation variably propose either a proximal-magmatic or distal-metamorphic, or less commonly distal-magmatic, source for goldbearing fluids, or mixing of fluids from multiple sources. Isotope geochemistry and geochronological studies are used to constrain the source and timing of auriferous fluids at nine gold deposits in the LGB in an attempt to differentiate between conflicting genetic models. To overcome the lack of detailed deposit-scale geological constraints inherent to any regional study, hypotheses generated from regional datasets are tested in a detailed case-study of the Wallaby gold deposit. The Pb-isotope compositions of ore-related sulphides from deposits in the LGB plot along the line representing crustal-Pb in the Norseman-Wiluna Belt of the EGP, with individual deposits clustering with other nearby deposits based on their geographic location. This trend is similar to that recorded in the Kalgoorlie-Norseman region in the southern EGP, and is consistent with a basement Pb reservoir for gold-bearing fluids. As such, data are consistent with a similar fluid source for all gold deposits. The Nd and Sr isotopic composition of goldrelated scheelite in the LGB clusters very tightly. The inferred ore-fluid composition has a slightly positive εNd, similar to ore fluids at other gold deposits in the EGP for which a proximal magmatic source is highly improbable. As such, Sr and Nd data are consistent with a similar fluid source for the gold deposits analysed in the LGB, but cannot unequivocally define that source. The median S, C and O isotopic compositions of ore minerals from all nine different gold deposits studied in the LGB fall in a very narrow range

APA, Harvard, Vancouver, ISO, and other styles

13

Pacanovsky, Aaron James. "Petrology of Gold Ore-Bearing Carbonates of the Helen Zone, Cove Deposit, Lander County, Nevada." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398682471.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Gómez, Suárez Adrián. "Synthesis and reactivity studies of mono- and diaurated species bearing N-heterocyclic carbene ligands." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6546.

Full text

Abstract:

The use of Au-NHC complexes in homogenous gold catalysis has become very popular during the last 10 years. The work described in this thesis represents a modest contribution towards a better understanding of the reactivity of these fascinating complexes and the intermediate species involved during gold-catalysed transformations. There are two main themes that permeate the following chapters: a) synthesis and reactivity studies of monoaurated species and b) synthesis and reactivity studies of diaurated species. The main motivation for the work presented herein was to develop more efficient synthetic routes towards a series of gold complexes, such as [Au(NHC)Cl], [Au(NHC)(OH)] and [{Au(IPr)}₂(μ-OH)][X], in order to be able to further explore their reactivity. Chapter 2 constitutes the first approach that I had with the chemistry of Au-NHC complexes, and describes our efforts to evaluate how the use of a highly sterically demanding NHC ligand affects gold-catalysed transformations. Chapters 3 and 4 explore alternative, more efficient synthetic routes towards known Au- NHC complexes. For example, a new, highly robust protocol has been developed for the synthesis of [Au(NHC)X] (X = Cl, Br, I) complexes, which are the starting materials to prepare a wide range of Au-NHC based species. Moreover, as a result of our investigations it has been possible to isolate a series of [Au(NHC)(OH)] species and to gain some insight into the stability of these complexes. Chapters 5 and 6 describe the synthesis and applications of digold hydroxide species [{Au(IPr)}₂(μ-OH)][X] in a series of catalytic and stoichiometric transformations. For example, they have been used as silver-free catalysts for water-inclusive gold-catalysed transformations or to access key intermediates in gold catalysis, such as gem-diaurated and σ,π-digold-acetylide species. Finally, Chapter 7 combines what we learned about the reactivity of [{Au(IPr)}₂(μ- OH)][X] in order to develop for the first time a gold-catalysed transformation where two gold centres independently react with two substrate molecules to catalyse the hydrophenoxylation of alkynes.

APA, Harvard, Vancouver, ISO, and other styles

15

Xavier, Roberto Perez. "The role of microstructural and fluid processes in the genesis of gold-bearing shear zones : Fazenda Maria Preta mine, Rio Itapicuru greenstone belt, Bahia, Brazil." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316478.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Mancini, Roberto [Verfasser]. "Detection of Y-chromosome bearing bovine sperm using laser-generated gold nanoparticle bio-conjugates / Roberto Mancini." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2015. http://d-nb.info/1073890228/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Gibson, Layton Scott 1956. "Geology and genesis of gold-bearing quartz veins on Ophir Mountain, near Murray, Shoshone County, Idaho." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/558056.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Anderson, Michael Richard. "A fluid inclusion and isotopic study of gold-bearing veins in the Transvaal Sequence, South Africa." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321197.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Daniel, Blakemore. "Insights into the History of Pyrite Mineralization at the Round Mountain Gold Mine, Nevada: A Detailed Microanalytical Study of the Type 2 Ore." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami15962291791253.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Ewart, D. Keith. "Studies on a moderately thermophilic mixed culture of bacteria and its application to the biooxidation of gold-bearing minerals." Thesis, King's College London (University of London), 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389882.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

HACHA, RONALD ROJAS. "MINERALOGICAL CHARACTERIZATION OF GOLD ORE OF THE RIO PARACATU MINERAÇÃO (RPM), AIMING AT THE DETERMINATION OF TITANIUM–BEARING MINERALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16974@1.

Full text

Abstract:

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Neste trabalho são apresentados os resultados da caracterização mineralógica de uma amostra de minério de ouro da RPM – Kinross, que teve como objetivo principal, identificar os minerais portadores de titânio e avaliar o espectro de liberação dos minerais de interesse. A metodologia empregada compreendeu a realização de análises granulométricas, separações em meio denso e magnética. Os estudos mineralógicos foram realizados por meio da difratometria de raios X (DRX), microscopia ótica e microscopia eletrônica de varredura (MEV) por meio do sistema Mineral Liberation Analyzer – MLA. Os produtos obtidos foram submetidos à análise química por espectrometria de fluorescência de raios X (FRX). As análises químicas indicaram que a amostra estava constituída essencialmente por SiO2 (66,4%), Al2O3 (14,2%), Fe2O3 (7,22%) e TiO2 (1%). Visando avaliar o espectro de liberação dos minerais portadores de titânio, o estudo foi focado em seis faixas granulométricas (-300+212; -212+150; - 150+104; -104+74; -74+53; e -53+37um). Cerca de 20% do material de todas as frações foi constituída por material afundado (meio denso), sendo composto principalmente de SiO2 (35%), Fe2O3 (30%), Al2O3 (>7%) e TiO2 (<5%). A fração flutuada é composta em sua maioria de SiO2 e Al2O3. As análises de DRX da fração afundada indicaram a presença de ilmenita, anatásio e rutilo. As frações afundadas foram submetidas à separação magnética no separador Frantz em diferentes intensidades de corrente (0,3 até 1,75A), através desta operação se concentrou até 8% em massa de TiO2 na fração -104+74um e a 0,5A. As frações afundadas foram submetidas a estudos sistemáticos no MEV com o sistema MLA, confirmando a presença de ilmenita, anatásio e rutilo como os minerais portadores de titânio. A liberação completa dos minerais carreadores de titânio foi aproximadamente de 1% em massa, já a ganga liberou-se mais de 90% em massa. A partir dos resultados obtidos se observou que é possível concentrar o TiO2 contido no minério.
This work presents studies in Minerals Characterization of gold ore sample from RPM-Kinross with objective to identify their titanium-bearing minerals and to assess its behavior in different size fraction (spectrum release). The methodology involved particle size analysis and minerals separation (separation in dense medium and magnetic separation), followed of mineralogical studies by XRay Diffraction, Optical Microscopy and Scanning Electron Microscopy (SEM) by using the Mineral Liberation Analyzer-MLA. The products obtained were submitted to Chemical Analysis of X-Ray Fluorescence. The analysis of X-Ray Fluorescence revealed that the sample studied was formed essentially by SiO2 (66,4%), Al2O3 (14,2%), Fe2O3 (7,22%) and TiO2 (1%). The studies were focused in six different sizes (-300+212; -212+150; -150+104; -104+74; -74+53 and - 53+37um). ). About 20% of the material from all fractions material is sunk (dense medium), composed mainly of SiO2 (35%), Fe2O3 (30%), Al2O3 (> 7%) and TiO2 (<5%). The floated fraction was composed mainly of SiO2 and Al2O3. The XRD of the sunken fraction indicated the presence of ilmenite, rutile and anatase. The sunken fractions were subjected to magnetic separation in the Frantz separator at different current intensities (0.3 to 1.75A), this operation was concentrated up to 8 wt% TiO2 in the fraction -104 +74um and 0.5A. The sunken fractions were subjected to systematic studies in the SEM system with MLA, confirming the presence of ilmenite, rutile and anatase as the titanium-bearing minerals. The gangue has been release of the mineral carrier of titanium was approximately 1% wt%, the denim has released more than 90% wt%. From the results it was observed that it is possible to concentrate the TiO2 contained in the ore.

APA, Harvard, Vancouver, ISO, and other styles

22

Breed, Ashley Wayne. "Studies on the mechanism and kinetics of bioleaching with special reference to the bioleaching of refractory gold-bearing arsenopyrite." Doctoral thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/5356.

Full text

Abstract:

Includes bibliographies.
Bioleaching is now an established technology for the leaching of whole-ore copper heaps and the pre-treatment of refractory arsenical gold ores and concentrates. For the case of refractory arsenical gold concentrates, it offers an economically feasible alternative to pressure oxidation and has environmental advantages over roasting with regard to the quality of the liquid and gaseous effluent (Van Aswegen, 1993). The major disadvantage of bioleaching is the low residence time required to achieve high oxidation levels. Other potential complications include the solubilisation of substances in the mineral, or the use of reagents, that are toxic to the micro-organisms.

APA, Harvard, Vancouver, ISO, and other styles

23

Chuang, Skylar T. "Apolipoprotein E3 Mediated Targeted Brain Delivery of Reconstituted High Density Lipoprotein Bearing 3, 10, And 17 Nm Hydrophobic Core Gold Nanoparticles." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10602927.

Full text

Abstract:

We have developed a high density lipoprotein (HDL)-based platform for transport and delivery of hydrophobic gold nanoparticles (AuNP). The ability of apolipoprotein E3 (apoE3) to act as a ligand for the low-density lipoprotein receptor (LDLr) was exploited to gain entry of HDL with AuNP into glioblastoma cells. AuNP of 3, 10 and 17 nm diameter, the latter two synthesized by phase transfer process, were solubilized by integration into reconstituted HDL (rHDL). Absorption spectroscopy indicated the presence of stable particles with signature surface plasmon bands, while electron microscopy revealed AuNP embedded in rHDL core. The rHDL-AuNP complexes displayed robust binding to the LDLr, were internalized by the glioblastoma cells, and appeared as aggregated AuNP in the endosomal-lysosomal compartments. The rHDL-AuNP generated little cytotoxicity and were able to cross the blood brain barrier. The findings bear significance since they offer an effective means of delivering AuNP across tumor cell membrane.

APA, Harvard, Vancouver, ISO, and other styles

24

Gilbow, Justin R. "Gold-bearing carbonate, sulfide, and silicate veining in igneous and sedimentary lithologies of the Helen Zone, Cove Deposit, Fish Creek Mountains, Nevada." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460139388.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Bailey, Andrew Douglas. "An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations." Doctoral thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/21417.

Full text

Abstract:

Bibliography: pages 121-132.
Bacterial oxidation is currently finding significant application for the oxidative pretreatment of refractory gold-bearing sulphides. Plants processing sulphide concentrates have commonly been operated at solids concentrations of between 18 and 20 per cent (m/v) (Le 180 and 200 kg.m-3). At higher concentrations, a decline in the bio-oxidation rate has been observed. Other metallurgical processes, such as chemical leaching and cyanidation, are performed at higher solids concentrations of between 40 and 50 per cent (400 and 500 kg.m-3), providing an incentive to increase the solids concentration at which bio-oxidation plants are operated. A review of literature indicated the following factors to be potential causes of reduced bio-oxidation rates at high solids concentrations: oxygen and carbon dioxide mass transfer; a low bacteria-to-solids ratio; mechanical damage of the bacte.ria; and the build-up of inhibitory oxidation products. Interaction of these factors in the completely-mixed reactors that are commonly used for biooxidation, has confounded the interpretation of the effects of individual factors. Analysis of literature data revealed a link between the sulphide grade of a particular material and the highest solids concentration at which the bacterial oxidation rate was maximal. The oxygen demand is directly proportional to the sulphide concentration in the reactor. Correlations were used to predict the oxygen transfer potential in the experimental reactors and it was found that as long as the oxygen transfer potential exceeded the oxygen demand, the biooxidation rate was proportional to the solids concentration for a specific material. Wh~n the oxygen demand equalled or exceeded the oxygen transfer potential, then the bacterial oxidation rate was limited by oxygen availability. The sulphide grade is characteristic of a particular ore or concentrate and from the data analysis oxygen availabiiity appeared to be the underlying reason why low grade materials could be oxidised at the maximum specific bio-oxidation rate at far higher solids concentrations than high-grade f!laterials. Abstract ii The experiments performed in this study were designed to further investigate the apparent relationship, identified by analysis of literature data, between sulphide grade and the solids concentration at which the bacterial oxidation rate was maximal. The effect of both solids concentration and sulphide grade on the biooxidation rate was investigated and related to the oxygen availability in the reactor.

APA, Harvard, Vancouver, ISO, and other styles

26

Olivo, Gema Ribeiro. "Les gites d'or palladifères des mines de Caue et de Conceicao, dans les formations de fer du type lac Supérieur du district d'Itabira, Craton Sao Francisco, Bresil : structure, minéralogie, géochronologie et métallogenie = (Palladium-bearing gold deposits of the caue and conceicao mines, hosted by lake superior-type iron-formations of the Itabira district, Sao Francisco craton, Brazil : structure, mineralogy, geochronology and metallogeny) /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1994. http://theses.uqac.ca.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Souther, David F. "How does God answer your most important questions?" Theological Research Exchange Network (TREN) Access this title online, 2005. http://www.tren.com.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Coleman, Dermot. "Being good with money : economic bearings in George Eliot's ethical and social thought." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3224.

Full text

Abstract:

In a world of material needs and wants, economics and ethics are inextricably linked. George Eliot recognised this seminal inter-relationship and sought to unravel its intricacies and complexities through her writing. My thesis explores this contention by reference to two principal questions: how did Eliot conceptualise economic value within her broader individual and social ethics? And how was the integration of economic and wider concepts of the “good” explored and tested within the novels? I frame these questions against the great changes in how economics was theorised over her writing career and, by tracing intellectual connections with Adam Smith, John Stuart Mill and later writers attempting to define and secure the moral underpinnings of political economy, I argue that Eliot was better informed and engaged with that process than most criticism has acknowledged. I also re-examine the equally remarkable developments in Eliot’s life and material circumstances, particularly after the success of her first novels. Her wealth and management of financial capital brought a particular focus to all questions of valuation, not least in relation to her own work and intellectual property. I contend that an inability fully to reconcile the moral and aesthetic core of her art and the high financial rewards it was generating gave the economic ethics she tested in the novels an extraordinary urgency and complexity. In my readings of, in particular, the later novels, I argue that the crucial motivations and actions by which her characters attempt to manage economic choice simultaneously parallel and are contained within competing contemporary moral philosophical systems. I conclude that her dissatisfaction with any rule-based system, whether of outcome or duty, led her to consider an essentially Aristotelian ethics of virtue in relation to economic ethics. My final chapters look out beyond individual ethical choice to consider how Eliot’s social and political vision accommodated the economic and its attendant institutions and to suggest a connection with the new liberalism which was starting to emerge in the final years of her life.

APA, Harvard, Vancouver, ISO, and other styles

29

Briggs, Cece Woods. "Psychic objectivity and the Eye of God| Bearing witness to the myth of the apocalypse." Thesis, Pacifica Graduate Institute, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=3746304.

Full text

Abstract:

Exploring the symbolism of the eye alongside the ancient religious concept of the omniscient Eye of God, this dissertation engages in a depth psychological analysis of consciousness, the God-image, and postmodern notions of the apocalypse. By considering all aspects of the eye as represented throughout mythology and religious texts, this study addresses everything from blindness to the comprehensive sight of mystical union. The one-eyed Cyclops, the Eye of Horus, the figure of the many-eyed Argus, and the third eye of the Buddha are examples that elucidate the range of eye types addressed.

The penetrating image of the eye as it emerges within the unconscious in dreams and visions is given ample consideration through the work of Carl Jung and other prominent depth psychologists. Theories regarding the archetypal dimension of the eye are discussed including Jung’s contention that the eye acts as a regulating principle, or yantra within the psyche, restoring balance in times of psychological chaos, upheaval, and transition. As the nucleus of a psychic mandala, the eye serves as a centering force while simultaneously making its numinous presence clear and felt to the individual ego. Edward Edinger’s contention that the eye marks the ego’s encounter with an overwhelming other is given credence while the difference between a feeling-tone of judgment versus equanimity perceived by the observed is weighed.

Connecting eye symbolism to the God-image, this dissertation embarks upon an exegesis of the eye in religious texts and challenges the omniscient Eye of God in its traditional projected, sky-bound sense. Arguing for personal responsibility in relation to the God-image, this study advocates for a reengagement with anima mundi or the world soul through the advancement of consciousness on a personal level. The recognition of the immanence of divinity and the need for an earth-based religiosity is emphasized. This study points out that eye symbolism is cropping up with increasing regularity in our current, apocalyptically entranced culture in an effort to jolt us from an unconscious slumber and provide the necessary psychic objectivity required to survive a planetary transformation.

Keywords: Apocalypse, Consciousness, Depth Psychology, Eye, God-Image, Mythology, Objectivity, Postmodern, Self, Witness

APA, Harvard, Vancouver, ISO, and other styles

30

Irawan, Paulus Bambang. "Bearing Together the Weight of Reality: The Mission of a Jesuit University in Nurturing an Ethic of Collaboration for the Common Good in Post-Authoritarian Indonesia." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:104938.

Full text

Abstract:

Thesis advisor: David Hollenbach
This dissertation tries to show the contribution and challenge of a Jesuit university in nurturing an ethic of collaboration for the common good by responding to the problem of fragmentation in post-authoritarian Indonesia. The history of compartmentalization since Dutch colonization, the unleashing of greedy elites after the fall of the Suharto regime and the silent penetration of neoliberal ideology through commodification of higher education on one hand contribute to the decline of the massive civic movement in higher education, but on the other hand open a new form of social movement through various local initiatives (Chapter I). It is in responding to this tension that an ethic of collaboration proves to be helpful, both in initiating a strong alliance among various groups and in respecting the plurality of its manifestations. The tradition of post-Vatican II Catholic Social Teaching, especially in Sollicitudo Rei Socialis and Caritas in Veritate, provides a solid grounding for proposing such an ethic of collaboration with its three recurring important themes: solidarity, subsidiarity, and the common good (Chapter II). This normative vision of collaboration for the common good is not alien to the Indonesian world view. Three Indonesian pedagogues (Ki Hajar Dewantara, Nicolaus Driyarkara and Mochtar Buchori) not only support the possibility of a cross-cultural dialogue between an ethic of collaboration for the common good based on Post-Vatican II Catholic Social Teaching and the Indonesian virtue of gotong royong (working together), but also show how the didactic of such a vision should be started in various forms and levels of education (Chapter III). Therefore, enlightened by Ignacio Ellacuría, the historical mission of a Jesuit university in the context of a post-authoritarian society is to provide space to engage with the people’s struggle to attain its personal and communal wellbeing. This commitment to be a-different-kind-of-university is carried out through research, pedagogy and community service (Chapter IV). In so doing, Jesuit higher education in post-authoritarian Indonesia will embody the mystique of service and bears a theologal dimension in its various collaborative practices to historicize the reign of God which is in process toward its fullness (Chapter V)
Thesis (STD) — Boston College, 2016
Submitted to: Boston College. School of Theology and Ministry
Discipline: Sacred Theology

APA, Harvard, Vancouver, ISO, and other styles

31

Froelich, Carey D. "Equipping Christians at University Baptist Church to use a dialogical model to foster spiritual growth among persons alienated from God." Online full text .pdf document, available to Fuller patrons only, 2002. http://www.tren.com.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Mitchell, Kevin G. "Equipping a volunteer group at First Baptist Church, Wolfe City, Texas, to develop "personal crisis testimonies" which express thanks to God for his faithfulness in providing strength for recovering from difficulties so that participants will use their experiences in comforting others who are hurting and witnessing to the lost /." Theological Research Exchange Network (TREN) Access this title online, 2005. http://www.tren.com.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Taleb, Farah. "Etude du comportement mécanique de sédiments argileux contenant des hydrates de gaz à partir de mesures in situ Hydromechanical properties of gas hydrate‐bearing fine sediments from in situ testing, in Journal of Geophysical Research: Solid Earth 123(11), November 2018." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0114.

Full text

Abstract:

Les hydrates de gaz (GH) sont composés de molécules de gaz, souvent du méthane, piégées dans des cages d’eau. Ils se trouvent principalement dans les sédiments des marges continentales et du pergélisol, où les conditions de stabilité (haute pression et basse température) nécessaires à leur présence sont réunies. Les GH sont considérés comme une source d’énergie mais aussi un facteur aggravant des aléas sous-marins et une source de gaz à effet de serre. Il est indispensable de comprendre les conséquences de la présence de ces composés métastables sur les propriétés géo-mécaniques des sédiments qui les contiennent (GHBS). Ifremer a mené plusieurs campagnes océanographiques visant à évaluer ce type d’aléas géologique dans le Golfe de Guinée, où un système à flux de gaz élevé avait pu être observé. La base de données est composée d’un ensemble de mesures in-situ acoustiques, géotechniques et de mesures de dissipation de pression interstitielle, ainsi que de carottes sédimentaires et de profils sismiques.Dans le but de comprendre l’effet de la saturation en GH et de leur morphologie et distribution sur les propriétés mécaniques des GHBS, ce travail de thèse a exploité l’ensemble de ces données. Cette étude a révélé que les GHBS argileux ont un comportement contractant lors du cisaillement qui s’oppose au comportement dilatant des sédiments sableux. En outre, différentes morphologies des GH ont été associées aux différents traits de comportement mécanique des GHBS. Pour des saturations en GH élevées (>10%), la diffusivité hydraulique des GHBS a tendance à augmenter avec l’accroissement de la concentration de ces hydrates. Ce phénomène est lié à la présence de fractures ou à la diminution de la compressibilité du sédiment. Un nouveau modèle constitutif basé sur le principe d’ « indices des vides équivalents » a été utilisé pour simuler le comportement mécanique des GHBS. Les résultats ont montré qu’un seul paramètre lié à la présence et la morphologie des GH est nécessaire au modèle pour reproduire correctement le comportement mécanique des GHBS
Gas hydrates (GH) are composed of gas molecules, often methane, trapped in a lattice of hydrogen-bonded water molecule. They are found in sediments of continental margins and permafrost, lakes and inland seas, where their stability conditions (high pressure and low temperature) are met. GH are considered as a potential energy resource but furthermore as a potential submarine geohazard and source of greenhouse gases. It is essential to understand the consequences of the presence of these metastable components on the geo-mechanical properties of their host sediment (GHBS). Ifremer has conducted several oceanographic campaigns aiming to assess such geohazard in an area of the deep-water Niger Delta, characterised by hydrates which formed in high gas flux environments in clayey sediment. The database is composed of in-situ acoustic, geotechnical, pore-pressure dissipation measurements, as well as cores and seismic profiles.The PhD work exploited the dataset with the aim of understanding the effect of GH content, morphology and distribution on the mechanical and hydraulic properties of the GHBS. This rare field study revealed that marine GH-bearing clays have a contractive behaviour upon shearing, which contrasts with the dilative behaviour of sandy GHBS often discussed in litterature. Alternatively, different morphologies of GH have been linked with different features of the mechanical behaviour of GHBS. For high GH saturtion (> 10%), the hydraulic diffusivity of the GHBS was observed to increase with increasing GH content, which was linked to fractures or decrease in compressibility. A new simple constitutive model based on “equivalent skeleton void ratio” was used in order to simulate the mechanical behaviour of GHBS.Preliminary results show that only one additional parameter related to the morphology of hydrate is necessary to correctly simulate the mechanical behaviour of GHBS

APA, Harvard, Vancouver, ISO, and other styles

34

DeSisto, STEPHANIE. "Dynamic Arsenic Cycling in Scorodite-Bearing Hardpan Cements, Montague Gold Mines, Nova Scotia." Thesis, 2008. http://hdl.handle.net/1974/1641.

Full text

Abstract:

Hardpans, or cemented layers, form from precipitation and subsequent cementation of secondary minerals in mine tailings and can act as both physical and chemical barriers. During precipitation, metals in the tailings are sequestered, making hardpan a potentially viable method of natural attenuation. At Montague Gold Mines, Nova Scotia, tailings are partially cemented by the iron (Fe) arsenate mineral scorodite (FeAsO4•2H2O). Scorodite is known as a phase that can effectively limit aqueous arsenic (As) concentrations due to its relatively low solubility (<1 ppm, pH 5) and high As content (~30 wt.%). However, scorodite will not lower As concentrations from waters to below the Canadian drinking water guideline (0.010 ppm). To identify current field conditions influencing scorodite precipitation and dissolution and to better understand the mineralogical and chemical relationship between hardpan and tailings, coexisting waters and solids were sampled to provide information on tailings-water interactions. Hardpan cement compositions were found to include Fe arsenate and Fe oxyhydroxide in addition to scorodite. End-member pore water chemistry was identified based on pH and dissolved concentration extremes (e.g. pH 3.78, As(aq) 35.8 ppm) compared to most other samples (avg. pH 6.41, As(aq) 2.07 ppm). These end-member characteristics coincide with the most extensive and dispersed areas of hardpan. Nearly all hardpan is associated with historical arsenopyrite-bearing concentrate which provides a source of acidity and dissolved As+5 and Fe+3 for scorodite precipitation. A proposed model of progressive arsenopyrite oxidation suggests localized As cycling involving scorodite is occurring but is dependent on sulfide persistence. Therefore, permanent As sequestration is not expected. Remediation efforts would have to consider the possibility of scorodite dissolution after complete sulfide consumption or as a consequence of applying certain technologies, such as a cover. Conversely, if scorodite stability were maintained, the hardpan could be considered as a component in remediating the tailings at Montague.
Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2008-12-22 09:36:08.157

APA, Harvard, Vancouver, ISO, and other styles

35

Fraser, Allan William. "Minimising uncertainty in measurement and improving limit of detection in gold bearing materials from concentrations predicted by linear regression in atomic absorption spectrometry." Thesis, 2015. http://hdl.handle.net/10210/15057.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Johnson, Thomas Kenneth. "Structural, kinematic, and hydrothermal fluid investigation of the gold-bearing Murray Shear Zone, northeastern Minnesota /." Diss., 2010. http://purl.umn.edu/60701.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Chang, Deng-Yuan, and 張鐙元. "Evaluation of photothermal therapeutic efficacy of PEGylated gold nanostar in an ovarian cancer-bearing mouse model." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/nxs4ee.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Kedda, Sean Waugh. "Geochemical and stable isotope studies of gold bearing granitoids in the Murchison Schist Belt, North Eastern Transvaal." Thesis, 2012. http://hdl.handle.net/10539/11161.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Apua, Momboyo Clotilde. "An investigation into hydrochloric acid leaching of low grade gold-bearing material and oxidized cobalt-copper ores." Thesis, 2012. http://hdl.handle.net/10210/5008.

Full text

Abstract:

M.Tech.
The efficiency of hydrochloric acid leaching of gold from low grade gold-bearing material has been investigated in the presence of sodium hypochlorite (NaOCl) to produce in situ chlorine gas which is an oxidizing agent able to oxidize gold metal to gold soluble forms: Au+ and Au3+. The effect of concentrations of HCl, NaOCl, and mixtures HCl + NaOCl was sought. An investigation on chlorine species was conducted to predict their stability areas. The reactions involved and their mechanisms were established. Prior to leaching, the feed was subjected to fire assay, Atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) analyses, to quantify the various elements, and to find out the chemical composition and the different mineralogical phases which are present. The main minerals found in the feed were: quartz, pyrite, muscovite-2M1, (M); and clinochlore. The grade was found to be 0.62 g/t. It was found from the hydrochloric acid leaching process that most of metals constituents (iron and potassium) of the feed were leached and consumed all the hydrochloric acid. Therefore, leaching of gold from low grade gold-bearing materials in aqueous chlorine solution is not an effective process for now. Hydrochloric acid leaching of cobalt and copper from four oxidized cobalt-bearing ores was studied in the presence of FeCl2 to produce in situ Fe2+ that is a reducing agent able to reduce Co3+ to Co2+ which is the soluble form of cobalt. The effects of the concentrations of HCl, FeCl2, mixture HCl + FeCl2, leaching time, particle size, and the dissolution kinetics were investigated. Prior to leaching the feeds were characterized with XRD, XRF, FTIR, AAS, Scanning electron microscopy (SEM), and gravimetric analysis. Cobalt contents were found to be between 2.59% and 39.76% in the four ores namely, high Cu ore, high Co ore, low Co ore, and high Co ore with mica. Effect of FeCl2 concentrations in HCl solutions involving 35.06 g; 70.13 g; and 105.18 g corresponding to 0.25 M; 0.5 M; and 0.75 M respectively, were studied and the reactions mechanism established. It was found that an increase in FeCl2 concentration increases the Co dissolution due to the reduction of Co3+ into Co2+ which is soluble. High Co extractions of 99%, 99%, 99%, and 95% were obtained when mixtures 1 M HCl + 105.18 g FeCl2 were used as lixiviants for high Cu ore, high Co ore, low Co ore, and high cobalt ore with mica, respectively. Copper recoveries of 88%, 77%, 75%, and 86% were obtained for high Cu ore, high Co ore, low Co ore, and high Co ore with mica, respectively. The increase in FeCl2 concentration did not have any important effect on the Cu extraction. Mechanisms of involved reactions were established. The order of cobalt leaching reaction was found to be 2 with respect to cobalt concentration. Optimum leaching conditions were found to be: leaching time: 30 minutes, reagent concentrations: mixture 1 M HCl + 105.18 g FeCl2, S/L ratio = 1:20, stirring speed avoiding the vortex, room temperature, pH values from 2.28 to 0.03, and ORP values from 0.402 to 0.322 V.

APA, Harvard, Vancouver, ISO, and other styles

40

Dilworth, Katherine M. "Geological setting, nature and evolution of reduced intrusions and gold bearing quartz veins of the 4021 prospect, Goodpaster district, east-central Alaska." Thesis, 2003. http://hdl.handle.net/2429/14296.

Full text

Abstract:

Gold deposits associated with Cretaceous reduced granitic rocks are common in Yukon and Alaska. The Liese zone and spatially related prospects in the Goodpaster district, eastcentral Alaska, are associated with an arcuate, easterly trending belt of Cretaceous reduced granite to tonalite that compose the older of two Early Cretaceous intrusive suites. A younger suite of calc-alkaline diorite rocks (-94 Ma) are slightly more oxidized and are unrelated to the gold mineralization. Both calc-alkalic suites have low magnetic susceptibilities and oxidation states. The older suite, which includes a phase of the Goodpaster Batholith, is weakly peraluminous and contains monazite and zircon. Biotite is common and hornblende is subordinate to absent. Older granitoids of the suite are deformed and syn- to- late kinematic to regional metamorphism at about 109-107 Ma (U-Pb; zircon and monazite). Post-kinematic intrusions of the suite are as young as 104 Ma (U-Pb SHRTMP-RG). Sulphide deposition at -104.3 Ma in the Liese Zone, inferred by a Re-Os date on molybdenite, indicates a temporal overlap. Gold veins in the region have a reduced sulphide assemblage (lollingite and pyrrhotite stable) and are characterized by an Au-Bi-Te geochemical signature. Fluid inclusions from gold veins and pegmatite are similar and contain ubiquitous aqueous-carbonic fluid inclusions ± CH4. Locally, complex saline fluids coexist with C02-rich fluids. Sulphide minerals from the Liese zone and gold prospects have Pb isotopic values (²⁰⁶Pb/²⁰⁴Pb =19.4-19.5) that generally overlap with thase of the reduced granite to tonalite (206Pb/204Pb= 19.4-19.6). The sulphide Pb isotopic values extend to slightly higher ²⁰⁶Pb/²⁰⁴Pb values, likely due to fluid rock interaction with the isotopically heterogeneous host gneiss of the Yukon-Tanana terrane. The diorite suite has lower values (²⁰⁶Pb/²⁰⁴Pb = 19.1-19.2) than most of the sulphides, and thus is precluded from contributing Pb to the bulk of the sulphides. Gold in the Pogo area is related to a suite of reduced granite to tonalite intrusions that were emplaced late- to post-kinematic to regional deformation in the late Early Cretaceous. Gold-bearing quartz veins formed from magmatic-hydrothermal fluids exsolved from the reduced granites and were focused along shallowly dipping regional folation.

APA, Harvard, Vancouver, ISO, and other styles

41

Nkosi, Nomqhele Zamaswazi. "Seismological and mineralogical studies of the world’s deepest gold-bearing horizon, the Carbon Leader Reef, West Wits Line goldfields (South Africa): implications for its poor seismic reflective character." Thesis, 2016. http://hdl.handle.net/10539/21713.

Full text

Abstract:

A dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science, School of Geosciences. Johannesburg, 2016.
The measurements of physical rock properties, seismic velocities in particular, associated with ore deposits and their host rocks are crucial in interpreting seismic data collected at the surface for mineral exploration purposes. The understanding of the seismic velocities and densities of rock units can help to improve the understanding of seismic reflections and thus lead to accurate interpretations of the subsurface geology and structures. This study aims to determine the basic acoustic properties and to better understand the nature of the seismic reflectivity of the world’s deepest gold-bearing reef, the Carbon Leader Reef (CLR). This was done by measuring the physical properties (ultrasonic velocities and bulk densities) as well as conducting mineralogical analyses on drill-core samples. Ultrasonic measurements of P- and S-wave velocities were determined at ambient and elevated stresses, up to 65 MPa. The results show that the quartzite samples overlying and underlying the CLR exhibit similar velocities (~ 5028 m/s-5480 m/s and ~ 4777 m/s-5211 m/s, respectively) and bulk densities (~ 2.68 g/cm3 and 2.66 g/cm3). This is due to similar mineralogy and chemical compositions observed within the units. However, the CLR has slightly higher velocity (~ 5070 m/s-5468 m/s) and bulk density (~ 2.78 g/cm3) than the surrounding quartzite units probably due to higher pyrite content in the reef, which increases the velocity. The hangingwall Green Bar shale exhibits higher velocity (5124 m/s-5914 m/s) and density values (~ 2.89 g/cm3-3.15 g/cm3) compared to all the quartzite units (including the CLR), as a result of its finer grain size and higher iron and magnesium content. In the data set it is found that seismic velocities are influence by silica, iron and pyrite content as well as the grain size of the samples, i.e., seismic velocities increase with (1) decreasing silica content, (2) increasing iron and pyrite content and (3) decreasing grain size. Reflection coefficients calculated using the seismic velocities and densities at the boundaries between the CLR and its hangingwall and footwall units range between ~0.02 and 0.05, which is below the suggested minimum of 0.06 required to produce a strong reflection between two lithological units. This suggests that reflection seismic methods might not be able to directly image the CLR as a prominent reflector, as observed from the seismic data. The influence of micro-cracks is observed in the unconfined uniaxial compressive stress tests where two regimes can be identified: (1) From 0 - 25 MPa the P-wave velocities increase with progressive loading, but at different rates in shale and quartzite rocks owing to the presence of micro-cracks and (2) above stresses of ~20 - 25 MPa, the velocity stress relationship becomes constant, possibly indicating total closure of micro-cracks. The second part of the study integrates 3D reflection seismic data, seismic attributes and information from borehole logs and underground mapping to better image and model important fault systems that might have a direct effect on mining in the West Wits Line goldfields. 3D seismic data have delineated first-, second- and third-order scale faults that crosscut key gold-bearing horizons by tens to hundreds of metres. Applying the modified seismic attribute has improved the imaging of the CLR by sharpening the seismic traces. Conventional interpretation of the seismic data shows that faults with throws greater than 25 m can be clearly seen. Faults with throws less than 25 m were identified through volumetric (edge enhancement and ant-tracking seismic attributes) and horizon-based (dip, dip-azimuth and edge detection seismic attributes) seismic attribute analysis. These attributes provided more accurate mapping of the depths, dip and strikes of the key seismic horizon (Roodepoort shale), yielding a better understanding of the relationship between fault activity, methane migration and relative chronology of tectonic events in the goldfield. The strato-structural model derived for the West Wits Line gold mines can be used to guide future mine planning and designs to (1) reduce the risks posed by mining activities and (2) improve the resource evaluation of the goldbearing reefs in the West Wits Line goldfields.
LG2017

APA, Harvard, Vancouver, ISO, and other styles

42

Olivo, Gema Ribeiro. "Les gites d'or palladifères des mines de Caue et de Conceicao, dans les formations de fer du type lac Supérieur du district d'Itabira, Craton Sao Francisco, Bresil : structure, minéralogie, géochronologie et métallogenie = (Palladium-bearing gold deposits of the caue and conceicao mines, hosted by lake superior-type iron-formations of the Itabira district, Sao Francisco craton, Brazil : structure, mineralogy, geochronology and metallogeny)." Thèse, 1994. http://constellation.uqac.ca/1215/1/1513762.pdf.

Full text

Abstract:

Les mines de fer de Cauê et de Conceiçao sont situées dans le District d'Itabira, dans la partie sud du Craton Sao Francisco, au Brésil. Trois unités géologiques, métamorphosées au faciès amphibolite, sont présentes aux deux mines: (1) une séquence volcano-sédimentaire Archéenne; (2) une formation de fer Protérozoïque et; (3) une unité de quartzite Protérozoïque. La formation de fer est recoupée par des dykes d'amphibolite et est tectoniquement imbriquée avec des schistes à talc et des amphibolites de la séquence volcano-sédimentaire. Les roches des trois unités ont été affectées par trois phases de déformation, subissant les chevauchements et boudinages associés. Dans la formation de fer, les structures associées à D1 et à D2 ont été générées par un cisaillement simple progressif dont la direction de transport est de l'Est vers l'Ouest. La structure D3 est caractérisée par des plis ouverts auxquels sont associés des clivages de crénulation. La jacutinga est la roche hôte des minéralisations d'or palladifère exploitées dans les formations de fer des mines de Cauê et de Conceiçao. La jacutinga est un faciès fortement cisaillé, métamorphisé et hydrothermalement altéré de la formation de fer de type Lac Supérieur, et est composée d'hématite, de quartz, de talc, de phlogopite, et de quantités mineures de tourmaline, d'apatite et de monazite. Le gisement aurifère de Cauê est composé de cinq corps minéralisés: Corpo Y, Corpo X, Central, Aba Leste et Aba Norte. Dans le corps minéralisé Corpo Y, les plus fortes concentrations d'or sont rencontrées dans les veines de quartz, alors que dans les quatre autres corps minéralisés les plus fortes concentrations d'or sont dans les veines d'hématite localement enrichies en quartz. Les veines riches en or sont parallèles à la foliation S1 dans tous les corps minéralisés, sauf pour Aba Norte où les veines d'hématite boudinées enrichies en or sont parallèles à S2. L'or et le palladium du minerai se trouvent dans les minéraux suivants: l'or, l'or palladifère, le palladium, l'oxyde de palladium, la palladséite et l'arsénopalladinite. La teneur en palladium dans les grains d'or varie de 1 à 20 %. Les plus hautes teneurs de palladium sont rencontrées dans les corps minéralisés Corpo X et Corpo Y, là où les grains d'or contiennent des inclusions d'oxyde cuivre-palladium se présentant sous forme d'îlots et sous forme de reliques en texture de remplacement. Dans le corps minéralisé Aba Leste, le palladium forme un alliage homogène avec l'or. Dans le corps Aba Norte, les grains d'or ne contiennent pas de palladium mais sont plutôt porteurs de rhodium à des teneurs jusqu'à 1,5 %. L'unique corps minéralisé en or et palladium de la mine de Conceiçao est parallèle à la foliation mylonitique. Cette minéralisation se retrouve dans le flanc des plis macroscopiques associés à D1 et à D2 et a été démembrée par la déformation de cisaillement progressif. L'or se trouve sous forme de grains aplatis, parallèles à la foliation mylonitique, et sous forme d'inclusions dans les grains d'hématite commune dans les horizons de goethite résultant de l'altération des carbonates. Une teneur en palladium jusqu'à 0,8 % est rencontrée dans les grains d'or en plaquettes recourbées. Le principal événement minéralisateur est contemporain au maximum du métamorphisme thermique (T=600°C), durant les cisaillements et chevauchements associés à D1. L'âge de l'événement minéralisateur a été estimé à 1,9 +/- 0,2 Ga par datation isotopique Pb/Pb. Cet âge est en accord avec l'âge métamorphique du Supergroupe du Minas, et correspond à l'âge de l'Orogène Transamazonien dans la partie sud du Craton Sao Francisco. L'altération hydrothermale associée à cet événement tectonique, caractérisée par la formation de talc, de phlogopite et de tourmaline, et par la formation de veines d'hématite et de quartz, a engendré la roche de type jacutinga. L'altération superficielle de la jacutinga a résulté en l'altération des silicates en kaolins et des oxydes en goethite. Aux hautes températures et hautes fugacités d'oxygène, le palladium et l'or ont pu être transportés sous forme de complexes chlorures; leur déposition serait reliée à une augmentation du pH. Il est proposé que cette augmentation du pH ait été causée par la réaction entre le fluide minéralisateur et la roche précurseur de la jacutinga, une itabirite dolomitique. La source la plus probable des métaux précieux est la séquence volcano-sédimentaire Archéenne. Les caractéristiques des minéralisations de Cauê et de Conceiçao amènent la définition d'un nouveau type de gisement aurifère, que nous nommons "Gisement d'or palladifère associé aux formations de fer de type Lac Supérieur fortement cisaillées et métamorphisées". D'autres occurences d'or palladifère sont aussi rencontrées dans la jacutinga, le long de la frontière est de la partie sud du Craton Sao Francisco, suggérant que cet environnement géologique est exceptionnellement favorable pour le type de minéralisation décrit.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Gold bearing'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles