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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Mostafa A. El-Sayed; Committee Member: Adegboyega K. Oyelere; Committee Member: Bridgette Barry; Committee Member: Joseph W. Perry; Committee Member: Mark R. Prausnitz.

The object of geophysical surveys in mineral exploration has traditionally been to detect subsurface geological features, which may reflect the presence of mineralization in depth and, if possible, to measure the dimensions of the causative body. Geophysical methods may also be used to locate extensions to known mineralization and for determining the size, depth and internal characteristics of an orebody. Marked improvements in geological concepts of ore genesis have led to a better appreciation, amongst geologists, of mineralized environments, and this has had an effect on the use of geophysics in recent years. Geophysical surveys are being increasingly used as an aid in environmental reconstructions and the results of regional surveys may be used to provide an indirect guide to ore. One of the main applications of geophysics lies in areas where the orebodies and associated structures are not exposed, as most geophysical measurements are more expensive than surface geological or geochemical surveys.

The Wolf and Capoose prospects represent two distinctly different types of precious metal deposits in volcanic rocks of the Stikinia terrane, central British Columbia. At the Wolf prospect, auriferous and argeniferous metallic minerals are in bladed quartz-carbonate veins and heterolithic breccias within Lutetian calc-alkaline rhyolite of the Ootsa Lake Group. Electrum, native silver, and silver sulphosalts occur as inclusions in and adjacent to pyrite in five silicic zones which have eight recognisable phases of veining and brecciation and are bordered by argillic and sericitic altered rhyolite. Fluid inclusions define growth zones in precious metal-bearing quartz-carbonate veins and precious metal-poor drusy quartz veins. The inclusions are primary, two-phase, liquid-rich, low salinity, and low C0₂. Homogenization temperatures of quartz-carbonate veins are 270°C and 170°C and in the late drusy quartz veins, 250°C. Oxygen and hydrogen isotope compositions of vein quartz, rhyolite, and alkali feldspar phenocrysts indicate that depositional fluids were ¹⁸0 depleted by 4 to 9 0/00. Ootsa Lake Group rocks at Wolf are formed by explosive eruptions and flows, related to a ring fault. Flat-lying rhyolite tuffs and flows are intruded by cogenetic stocks and dykes in a caldera collapse setting. Precious metal deposition occurred as one event related to quartz-carbonate veins. Later drusy quartz veins precipitated from a different fluid. Primary fluid inclusion homogenization temperatures show that fluids which deposited quartz-carbonate were boiling and existed under both hydrostatic and near lithostatic pressures at depths of about 100 m. Oxygen and hydrogen isotope compositions indicate a high degree of isotopic exchange between rhyolite and large volumes of low ¹⁸0 content meteoric fluids. The fluids evolved to a non-boiling, lower salinity, extremely ¹⁸0 depleted, precious metal-poor variety which precipitated late drusy quartz veins. Geological setting, vein and breccia textures, alteration, metal distribution and depositional fluid evolution at Wolf resemble a low sulphur, epithermal hot spring or silicified stockwork deposit. At the Capoose prospect, auriferous and argeniferous metallic minerals occur as inclusions within disseminated galena and sphalerite in calc-alkaline Maastrichtian rhyolite sills intrusive into Lower and Middle Jurassic Hazelton Group volcanic and sedimentary rocks. Flow-banded, spherulitic rhyolite sills are preserved within a minor horst. Spessartines in the sills are similar in composition to plutonic garnets with less than 5% change in end member composition from rim to core. They occur adjacent to disseminated, aggregate and vein galena, sphalerite, pyrite, arsenopyrite and chalcopyrite. Sulphide and spessartine accummulations are commonly surrounded by muscovite and quartz coronas. Sulphide poor quartz and calcite veining is in hornfelsed Hazelton Group rocks peripheral to the sills. Phyllic alteration is restricted to the sills and overprints mineralized zones. Primary two-phase, liquid-rich, low salinity, low C0₂ fluid inclusions from late silicate veins homogenize from 285°C to 335°C. Rhyolite sills are not depleted in ¹⁸0 whereas sericite, quartz and calcite are. Spessartine in rhyolite sills at Capoose crystallized as late phenocrysts stabilized by high manganese content. They provided a nucleus for sulphide deposition shortly after sill emplacement in groundwater saturated, permeable Hazelton Group rocks. Cooling, crystallization and fracture development in the sills initiated hydrothermal circulation and phyllic alteration with late quartz and calcite veins related to collapse of the hydrothermal system. Lead-zinc mineralization occurred as two events, with only one related to precious metal and copper deposition. Oxygen isotope compositions of quartz-garnet mineral separate pairs indicate crystallization of garnets and sulphides from magmatic fluids at temperatures from 528°C to 725°C. Sericite, quartz and calcite precipitated from meteoric fluids. In summary, hydrothermal fluids at the Capoose prospect evolved from early, high temperature magmatic fluids to late lower temperature, low salinity, meteoric fluids. The geological setting, silicate and sulphide mineralogy, alteration, metal distribution and depositional fluid compositions at Capoose resemble a low-grade, epigenetic, intrusion-related, porphyry-style deposit. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Thesis (PhD)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The objective of this work was to achieve a completely automated fire assay system for the analysis of process control samples on a flotation plant in less than 120 minutes. With this in mind, a systems engineering approach was undertaken. The physical and chemical characteristics of the technology for each subsystem were investigated in turn and the critical factors that influenced accuracy, precision and analysis time were identified and optimised. Some of the key developments achieved during this work were: · Existing technology for the sampling, filtering, drying and grinding of flotation plant samples were evaluated and where necessary, modified for this application. · The fusion system was totally re-designed with a bottom-loading configuration called FIFA (Fast In-line Fire Assay) to make automation with a central robot possible. With the fast fusing flux developed, a quantitative collection of the platinum group elements with a fifteen-minute fusion was achieved compared to an hour for the classical method. · A robust automated separator system was developed to isolate the lead collector from the fusion in the molten state thereby separating it quantitatively from the slag. This allowed the automation of the entire fire assay process. · Methods to prepare lead standards for calibration were developed. These were used to optimise analytical protocols for the analysis of platinum group elements in lead using a spark optical emission spectrometer. This made it possible to accurately determine the quantities of platinum group elements in lead samples prepared by the automated fire assay system. · A fully automated system was developed that could meet the accuracy and precision requirements for the analysis of tailings and feed grade samples in concentrator slurry streams in less than one hour compared with the 24-72 hours required when using classical methods. The new fire assay technology including flux, FIFA system, oxygen lance and separator were all patented along with the automation vendor. This technology has made the first fully automated fire assay system a reality. / AFRIKAANSE OPSOMMING: Die hoofoogmerk van die studie was om ‘n totale geoutomatiseerde vuuressaieering stelsel te ontwerp vir die ontleding van prosesbeheermonsters van ‘n flotasieaanleg in ‘n bestek van 120 minute. Gedurende die ontwerp is ‘n ingeneursstelselbenadering gebruik. Die fisiese en chemiese kenmerke van elke deel van die tegnologie is eers afsonderlik en dan as ‘n geheel ondersoek. Die bepalende faktore wat akkuraatheid, presisie en ontledingstyd beinvloed het was geidentifiseer en geoptimeer. Die hoofpunte van die werk behels onder andere die volgende: · Bestaande tegnologie vir monsterneming, filtrasie, droging en vermaling van flotasiemonsters was ondersoek en is, waar nodig, aangepas vir die finale stelsel. · Die smeltingsisteem was in geheel herontwerp om monsters van onder in die FIFA (Fast In-line Fire Assay) sisteem te laai en sodoende die outomatisering met ‘n sentrale robot te vergemaklik. ‘n Vinnig smeltende vloeimiddel was ontwikkel wat ‘n kwantitatiewe versameling van die platinum groep elemente binne ‘n tydsduur van vyftien minute moontlik gemaak het, in vergelyke met die oorspronklike duur van die klassieke smelt metode van een uur. · ‘n Outomatiese skeier was ontwikkel waarmee die gesmelte loodversamelaar geskei kon word van die slakfase. Met die nuwe stelsel kon die hele vuuressaieerproses outomaties verloop. · Metodes is ontwikkel om loodstandaarde vir kalibrasie doeleindes te berei. Die standaarde is op hulle beurt weer gebruik om ‘n ontleding protokol daar te stel vir die analiese van die platinum groep elemente in lood, met behulp van ‘n vonkontlading-optiese-uitstraling-spektrometriese instrument. Ten einde was dit moontlik om outomaties klein hoeveelhede van die platinum groep elemente in monsters akkuraat te bepaal, na voorbereiding met behulp van die geoutomatiseerde vuuressaieering stelsel. · Die volle geoutimatiseerde stelsel was ontwikkel wat aan die akkurate en noukeurige vereistes voldoen het vir die ontleding van flotasie-uitskot-envoergraad monsters van die konsentraataanleg binne die bestek van ‘n uur. Die nuwe vuuressaieer tegnologie, insluitend die vinnig smeltende vloeimiddel, FIFA en skeier stelsels, asook die suurstof lanset is gepatenteer met die vervaardiger. Die studie het gelei tot die eerste volle geoutomatiseerde vuuressaieering stelsel wat tans gebruik word in die industrie.

This paper examines the role that gold and other precious metals play in portfolio construction as hedges and safe havens in comparison with the Volatility Index (VIX), a derivative of market volatility. Gold has long been considered to be among the best assets for reducing portfolio volatility due to its lack of correlation with the overall market. However, the major finding of this paper is that while gold and the other precious metals do serve in this role to varying extents, the VIX performs this function far better. Both econometric and portfolio analyses reveal that the VIX improves overall portfolio performance to a greater extent, and most importantly serves as an effective safe haven relative to the market.

Thesis (Ph.D.)--City University of Hong Kong, 2009. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references.

This research emphasizes on the use of seeded growth in synthesis of noble metal nanocrystals with precise control over the size, shape, and composition. In the first part of this work, I have produced Au nanocrystals with single-crystal structure and truly spherical profiles and investigated their optical properties and self-assembly as induced by dilution with water. These Au nanospheres were generated in high yield and purity, together with controllable sizes continually increased from 5 to 150 nm. I also found these Au nanospheres self-assembled into dimers, larger aggregates, and wavy nanowires, respectively, as diluted with water. In the second part of this work, I demonstrate the kinetic control can be implemented to control the shape of mono- and bi-metallic nanocrystals in seeded growth. The as-prepared single-crystal nanospheres of Au were employed as seeds to synthesize of tetrahedral Au nanocrystals and Au@Pd core-shell nanocrystals with six distinct shapes. The success of the two demonstrations relies on manipulation of reaction kinetics to achieve different product shapes. The reaction kinetics was controlled by varying a set of reaction parameters, including the type and concentration of capping agent, the amount of reductant, and the injection rate of metal precursor solution. In the final part of this work, I will discuss an unusual change in crystallinity observed in seeded growth of Au nanocrystals on Au seeds. In particular, single-crystal Au seeds treated with a chemical species could develop twin defects during the seed-mediated growth process to yield multiply twinned products.

Thesis (PhD)--University of South Australia, 1996

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.