The Western Gneiss Region (WGR) in Norway is home to some of the world’s most spectacular exposures of high pressure (HP) and ultrahigh pressure (UHP) eclogites. Despite extensive petrological studies into their pressure, temperature and time (PTt) histories, relatively few have reported on their trace element compositions. Such data can be used to supplement our understanding of the provenance and history of Norwegian eclogites, as well as to further our understanding of trace element fluxes during HP to UHP metamorphism in subduction zone settings. In order to address this shortfall in data availability, the first step was to investigate and apply the best dissolution techniques for preparing eclogite samples for chemical analysis. Eclogites commonly contain up to a few weight percent rutile (TiO2), which is known to be an important host for a variety of major and trace elements (e.g. Ti, Nb and Ta). However, typical rock digestion procedures are incapable of dissolving rutile, and thus may lead to inaccurate measurements. It was found that that total dissolution of rutile can be achieved by dissolving samples in sealed pressure vessels at increased pressures and temperatures, ultimately leading to greatly increased data accuracy for analyses of any rutile-bearing lithology. The solutions were analysed by standard ICP-MS techniques and the results compared to analyses of powders by XRF spectrometry. Our high-accuracy and high-precision data were subjected to immobile trace element discriminant analyses that suggested eclogites belonged to three broad geochemical groups: eclogites with mid ocean ridge Basalt (MORB)-like composition; eclogites with arc-like composition; and eclogites with geochemical signatures significantly perturbed by metamorphism. The geochemistry of eclogites in the first two groups are shown to likely reflect protolith composition, and as such we used model protolith compositions to calculate estimated element mobilities (EMMs) for those elements considered relatively mobile during metamorphism. It was not possible to determine protoliths for eclogites in the third category using trace elements alone. Finally, the trace element geochemistry of a large number of separated eclogite-hosted rutiles was studied. The data collected were used to demonstrate that rutile contains significant amounts of the whole-rock’s high field strength element (HFSE) budget, and may exert significant control on the HFSE composition of passing hydrothermal fluids. Furthermore, Zr-in-rutile thermometry (ZRT) was applied to separated rutiles. This temperature information was used to better our understanding of the thermal history of the WGR, as well as to create a map of eclogite temperatures in the Nordfjord-Statlandet area. This high-resolution thermal map of arguably the most important area of the WGR, supports current interpretations that during the Caledonian Orogeny the leading edge of the Baltica plate was consumed in a northwest to north-northwest-dipping subduction zone under Laurentia. Furthermore, isotherms on this map mimic several major fold hinges in the region rather well, thus providing support to the hypothesis that such structures were most likely formed during the collapse of the Scandinavian Caledonian Orogen after the peak metamorphism of most eclogites.

A study has been carried out on the Becher and Summit Processes with the aim of understanding the mechanism and critical parameters required for the production of a range of pure iron oxide pigments, as well as high quality synthetic rutile from reduced ilmenite . The Becher Process currently produces a large quantity of worthless mixed phase iron oxides. However, this study has shown that the range of iron oxides formed are all derived from the transformation of lepidocrocite (y-FeOOH) through the solution phase in iron(II) solutions. The results of a kinetic study of the transformation of lepidocrocite found that the rate exhibited an induction period at low pH, was dependent on temperature and was linearly related to log [H+] and log [Fe2+]. The rate determining step was found to be the formation of suitable product nuclei, following dissolution of the initial oxide at the surface of the crystal lattice. An electrochemical study of these reactions showed that the product formed from the transformation of lepidocrocite was a function of the solution potential and an experimental Eh-pH diagram was constructed to predict the iron oxide phase produced from hydrolysis and transformation reactions. The results from this fundamental study were then applied on both a laboratory and plant scale to produce pure iron oxide phases. A modified Summit Process, involving the removal of metallic iron from the porous reduced ilmenite matrix using FeCl 3, regeneration of iron(III) and the production of pure iron oxide pigments from the waste iron(II) chloride solution, was also investigated in detail. A kinetic study of pure iron dissolution in iron(III) solutions, comparing three electrochemical techniques and a standard solution sampling method, gave consistent rate constants provided allowance was made for the reaction with the proton. The iron dissolution mechanism was found to be iron(III) diffusion controlled, while the dissolution in HC1 was under mixed control. A study using both pure iron and pressed reduced ilmenite discs found that acid consumption could be minimised by the addition of citrate or by the addition of A1 3+ or Fe 2+ , which are believed to block the adsorption of the proton. It was found that iron(III)-citrate complexes inhibited iron(II1) hydrolysis in the reduced ilmenite pores and enhanced the purity of the synthetic rutile product. A study of the oxidation of iron(II) by atmospheric oxygen using copper(II) and activated carbon catalysts found that these catalysts were inefficient for complete iron(III) regeneration. The heating of carbon in the presence of cu2+ was found to enhance the initial rate of iron(II) oxidation, however it is believed that surface oxide redox couples formed on the carbon control the iron(II)/ iron(III) ratio in solution, and prevent complete iron(I1) oxidation. The production of iron oxide pigments under the controlled conditions afforded by the Summit Process, resulted in superior quality pigments than are presently attainable from the Becher Process. However, controlled ageing and crystal growth using waste lepidocrocite from the Becher Process would result in similar quality pigments being produced.

Submitted by Bruna Rodrigues (bruna92rodrigues@yahoo.com.br) on 2016-09-27T11:47:25Z No. of bitstreams: 1 DissMD.pdf: 3874080 bytes, checksum: f245af64331a5190649cede80208ac01 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-04T18:10:35Z (GMT) No. of bitstreams: 1 DissMD.pdf: 3874080 bytes, checksum: f245af64331a5190649cede80208ac01 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-04T18:10:41Z (GMT) No. of bitstreams: 1 DissMD.pdf: 3874080 bytes, checksum: f245af64331a5190649cede80208ac01 (MD5) / Made available in DSpace on 2016-10-04T18:10:51Z (GMT). No. of bitstreams: 1 DissMD.pdf: 3874080 bytes, checksum: f245af64331a5190649cede80208ac01 (MD5) Previous issue date: 2015-03-30 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / This dissertation studies the application of rutile substrate as an alternative support for anatase films, specifically, on the growth and properties of anatase films. The films were utilized as catalysts for the photodegradation of water contaminants (Atrazine and Rhodamine B). Ti4+ precursor resin was prepared by the polymeric precursor method and deposited by spin coating onto polycrystalline rutile and rutile coated glass substrates. The films were calcined at different temperatures (350 °C to 500 °C) to form anatase TiO2 films. The influence of temperature on the properties of the films has been reported in this study. A comparative study of the films was also done using X-ray diffraction technique (XRD), grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). XRD and GIXRD results confirmed the formation of anatase on the (101) plane depending on the calcination temperature. Bandgap modification of the films with respect to calcination temperature was measured by UV visible diffuse reflectance spectroscopy. The bandgaps were in the range of 2.74 to 2.85 eV. Photocatalytic activity of the films supported on rutile substrate was studied for the degradation of Atrazine (ATZ) and Rhodamine B (Rhod-B) under UV light. Further, the stability of the films was evaluated on four consecutive cycles where the films maintained their photocatalytic properties in all cases. The kinetics of Rhod-B and ATZ degradation followed a pseudo first order and first order exponential decay respectively. The films calcined at 450 °C and 500 °C showed superior photocatalytic activity for Rhod-B degradation than the films calcined at 350 °C and 400 °C. This is attributed to the adequate crystallinity of anatase. For ATZ degradation, the films were also efficient but no specific trend was observed. The results can contribute towards the development of TiO2 films on rutile phase substrates. / Esta dissertação estuda a aplicação de substratos de rutilo como suportes alternativos para filmes de anatase, especificamente, sobre o crescimento e propriedades de filmes de anatase sobre rutilo. Os filmes foram utilizados como catalisadores para a fotodegradação de contaminantes de água (Atrazina e Rodamina B). A resina de Ti4+ foi preparada pelo método de precursores poliméricos e depositada por spin coating sobre rutilo policristalino e em substratos de vidro revestido de rutilo. As amostras foram calcinadas a diferentes temperaturas (350 a 500 °C) para formar filmes de anatase TiO2. Um estudo comparativo dos filmes foi feito usando a técnica de difração de raios X (DRX), difração de raios X com ângulo rasante (DRXR), microscopia de força atômica (AFM) e microscopia eletrônica de varredura (MEV). Os resultados de DRX e DRXR confirmaram a formação de anatase nos filmes ao longo do plano (101) dependendo da temperatura de calcinação. Modificações do bandgap dos filmes de acordo com a temperatura de calcinação foram medidas por reflectância difusa de UV-visível onde os bandgaps variou de 2,74 para 2,85 eV. Atividade fotocatalítica dos filmes imobilizados sobre substrato de rutilo foi estudada para a degradação de Atrazina (ATZ) e Rodamina B (Rhod-B) sob luz UV. Além disso, a estabilidade dos filmes foi avaliada em quatro ciclos consecutivos onde os filmes mantiveram suas propriedades fotocatalíticas em todos os ciclos. As cinéticas de degradação de Rhod-B e de ATZ seguiram um ajuste de pseudo-primeira ordem e decaimento exponencial de primeira ordem, respectivamente. Os filmes que foram calcinados a 450 °C e 500 °C mostraram atividade fotocatalítica superior para a degradação de Rhod-B aos filmes calcinados a 350 °C e 400 °C. Isto foi atribuído à cristalinidade adequada da fase anatase. Para ATZ, os filmes foram eficientes mas nenhuma tendência especifica foi observada. Os resultados podem contribuir para o desenvolvimento de filmes de TiO2 imobilizados sobre substratos de rutilo.

No description available.

The Old Hickory mine is a world class placer titanium deposit located at the boundary of the Coastal Plain and the Piedmont in Virginia, astride the Sussex-Dinwiddie county line (77°34' W Long, 36°55'N Lat., Cherry Hill Quad). The Old Hickory deposit, discovered in 1987 by C. R. Berquist, was opened as a commercial mine in 1997, and is presently operated by Iluka Resources. Heavy minerals constitute an average of 8% of the sediment, but locally reach concentrations as rich as 60%. The ore minerals, in order of decreasing concentrations, are ilmenite, rutile, and zircon, which are believed to have been derived from weathering of Piedmont and Blue Ridge sources. After fluvial transport to the coast, the ore minerals were redistributed laterally along the coast by longshore currents, and ultimately concentrated by intense wave action, probably generated by large storms. The ores occur over an area of 8 km x 3 km, with ore minerals being found from the surface to up to depths of 12 meters, and appear to occur in at least two distinct ore horizons. This study examines the general ore mineralogy and differences in the mineralogy, grain sizes, secondary textures, and geochemistry of the ore minerals in the two distinct ore zones. Distinguishable differences between the two zones include a slightly coarser grain size, more angular grains of rutile, and a higher percentage of accessory minerals (epidote, garnet, etc) in the younger zone. Approximately 40% of all the ilmenite grains contain exsolution lamellae of hematite, a residual texture from the time of original ilmenite crystallization. Weathering of these ilmenite grains has preferentially dissolved out the hematite while preserving the original texture; thus the weathering increases the titanium content of the ore by removing some of the iron. The weathering also affects the distribution of minor elements such as aluminum, manganese, and chromium. At Old Hickory, the zircon population can be divided into two main types (thin, elongate rounded pink prisms, and short, thicker white to clear prisms) that may represent either multiple source regions or multiple generations of heavy mineral deposition. The variations in grain size, angularity, and rutile content are likely to be mappable and may prove useful in continuing stratigraphic studies, and in distinguishing separate ore zones. / Master of Science

No description available.

"The phase content and grain size of titanium dioxide often have a strong influence on properties for a variety of applications. In many cases it would be desirable to produce the stable rutile phase with an ultra-fine particle size (<10nm), but most low temperature synthesis methods produce predominantly the metastable anatase phase. The anatase-rutile transformation in TiO2 is known to be affected by dopant type and concentration, as well as the titanium precursor used in solution chemical synthesis. Recently, use of cavitation in the synthesis process has been shown to yield smaller grain size for a variety of oxides. However, the relative importance of these synthesis variables on the grain size and phase content of TiO2 is not well understood. In this study, Taguchi analysis was used to determine the relative effects of dopants (Sn), titanium precursor (butoxide, sulfate, chloride), and cavitation power on grain size and phase content. Precursor residuals were also measured by analytical chemistry. Grain size and phase content results were analyzed statistically to determine whether there is a size dependence of the anatase-rutile transformation. Results show that grain size is strongly dependent on the concentration of chlorine. Absent chlorine, a definite grain size-phase content correlation exists; rutile content increases as grain size decreases. An L-4 orthogonal Taguchi analysis shows chlorine content and tin content as the major influences on the final product. With minimum grain size and maximum rutile content being considered optimal, our best result was 100% rutile and an average grain size of 5nm, which was achieved by acoustic synthesis with 3% tin dopant and low residual chlorine. "

The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel + orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and analytical methods were developed to determine the trace element concentrations and Hf isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17; Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta = <0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen, from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr (SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite, which indicates that they have common parent magmas and sources. The parent magmas were derived from a relatively depleted mantle reservoir that appears to be the primary source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin of Laurentia during the Proterozoic.

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The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel + orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and analytical methods were developed to determine the trace element concentrations and Hf isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17; Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta = <0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen, from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr (SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite, which indicates that they have common parent magmas and sources. The parent magmas were derived from a relatively depleted mantle reservoir that appears to be the primary source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin of Laurentia during the Proterozoic.