Dissertations / Theses: 'Accessory mineral'

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Paterson, Bruce Andrew. "Accessory mineral growth histories : implications for granitoid petrogenesis." Thesis, University of St Andrews, 1990. http://hdl.handle.net/10023/11059.

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Accessory minerals in granitoids are major repositories of several geochemically-important trace elements and isotopes and in order to quantify the influence that they have over granitoid petrogenesis it is necessary to characterize fully their behaviour. In particular it is necessary to understand accessory mineral/melt partitioning of trace elements and within grain elemental diffusivities, the latter is of relevance when assessing the state of isotopic equilibration between a refractory accessory phase and a contacting melt. In this study the backscattered electron (BSE) imaging technique, coupled with quantitative electron microprobe analysis indicate that granitoid zircons and titanites (mainly taken from Caledonian intrusive complexes) are commonly compositionally zoned. The zoning textures observed in these minerals, namely crystal face-parallel zoning, non-planar compositional zoning (included here are subhedral and anhedral core structures) and compositional sector zoning, indicate that the kinetic factors of crystal growth, i.e. within magma elemental diffusion rates, crystal growth rates, interface kinetics and dissolution kinetics, are largely responsible for the patterns of compositional zoning that have been observed. This fording is in marked contrast to other studies which have assumed that kinetics are not important in crystallizing plutonic granitoid magmas. Accessory mineral growth histories have been studied in a few well constrained samples from the Caledonian-age Strontian Complex of NW Scotland. The zircons from the central intrusion of this composite pluton have abundant inherited cores. The cores contain a variety of zoning structures and have a wide range of composition, which are taken to indicate that the cores had a wide variety of ultimate sources. Titanites from both the outer and inner intrusions have compositional sector zoning and the range of composition shown by the titanites is largely due to this fact. In this pluton magma composition appears to have little influence on titanite chemistry. The REE abundances in both parts to the intrusion are largely controlled by the accessory phases and each of these phases have very different rock-normalised REE distribution patterns. These abundance patterns are dependent on the relative partition coefficients that each phase has for the REE, the accessory mineral assemblage present and the crystallization order of that assemblage. The zircons from the central acid member of the Strontian Complex, which are known to have substantial U-Pb inheritance were extracted and analysed for their Sm-Nd isotopic composition. The results apparently indicate that refractory zircons can also preserve their Sm-Nd isotopic composition, a phenomenon not previously reported. That is diffusion of Sm and Nd (and presumably the other REE) within refractory zircon at elevated temperatures appears to be sufficiently slow that complete isotopic equilibration between a zircon and a contacting melt may not always occur. Such disequilibrium potentially enables granitoid magma provenance to be studied with much greater resolution than hitherto possible.

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Goldschmidt, Gunther Karl. "Cloning, Sequencing and Partial Characterization of the Accessory Gene Region of Plasmid pTC-F14 isolated from the Biomining Bacterium Acidithiobacillus caldus f." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1588.

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Thesis (MSc (Microbiology))--University of Stellenbosch, 2005.
Plasmid pTC-F14 is a 14.2kb promiscuous, broad-host range IncQ-like mobilizable plasmid isolated from Acidithiobacillus caldus f. At. caldus is a member of a consortium of bacteria (along with Acidithiobacillus ferrooxidans and Leptospirilum ferrooxidans) that is used industrially for decomposing metal sulphide ores and concentrates at temperatures of 40ºC or below which is now a well-established industrial process to recover metals from certain copper, uranium and gold-bearing minerals or mineral concentrates. These biomining microbes are usually obligately acidophilic, autotrophic, usually aerobic iron- or sulphur-oxidizing chemolithotrophic bacteria. Their remarkable physiology allows them to inhabit an ecological niche that is largely inorganic and differs from those environments populated by the more commonly studied non-acidophilic heterotrophic bacteria. At. caldus, is a moderately thermophilic (45 to 50ºC), highly acidophilic (pH1.5 to 2.5) sulphur-oxidizing bacterium, and its role as one of the major players in the industrial decomposition of metal sulphide ores has become evident in recent years. At. caldus f from which pTC-F14 was isolated was found to be one of two dominant organisms in a bacterial consortium undergoing pilot-scale testing for the commercial extraction of nickel from ores.

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Betkowski, Wladyslaw Benedykt. "A STUDY OF PHOSPHATE ACCESSORY MINERALS, THEIR REACTIVITIES, REPLACEMENTS AND GEOCHRONOLOGY: IMPLICATIONS FOR THE LLALLAGUA TIN PORPHYRY EMPLACEMENT AND MINERALIZATION." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1532539010237075.

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Senni, Filippo. "Studio dei minerali accessori del basamento Varisico delle Alpi Apuane." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14453/.

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L’oggetto della relazione di laurea è lo studio dei minerali accessori dei campioni rappresentativi il basamento Paleozoico delle Alpi Apuane. I minerali accessori sono quei minerali presenti in basse proporzioni modali ovvero <1%. Lo scopo è di caratterizzare la petrografia delle associazioni mineralogiche presenti in quattro campioni: due filladi inferiori dell'Unità di Massa, uno scisto porfirico e un metaporfiroide provenienti dall'Unità delle Apuane. Gli strumenti usati per effettuare le analisi sono stati il microscopio ottico a luce trasmessa polarizzata e il microscopio elettronico a scansione dotato di spettrometro a raggi X a dispersione di energia. Monazite, zircone, rutilo e apatite sono molto frequenti nelle rocce analizzate. Le microstrutture osservate suggeriscono un’origine detritica per questi minerali accessori. Pseudomorfosi di monazite, quarzo, e clorite su un precedente cristallo di allanite sono state osservate in un campione di fillade, ad indicare la crescita di monazite metamorfica durante gli eventi tettono-metamorfici miocenici. Sulla base di diagrammi di fase presenti in letteratura si è stimato che le condizioni del metamorfismo in facies scisti verdi avvennero a pressioni inferiori a 7 kbar e temperature massime di 350-500 °C.

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Kegley, Dalton Curtis. "Economic Potential of Rare Earth Elements Within Accessory Minerals of Granitic Pegmatite Mine Tailings." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104065.

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Rare Earth elements (REEs) are economically important due to their critical applications within multiple industries. This study investigates the Spruce Pine district of North Carolina, testing the economic feasibility of repurposing current mine waste tailings as a rare earth element resource. Spruce Pine is home to several active quartz and feldspar mining operations, with large waste tailing piles generated during the separation process for quartz and feldspar. The mineralogy, composition, and REE budget of the tailings was examined to assess the economic viability of rare earth element extraction. The local geology includes a series of muscovite class pegmatites of Devonian age (390 Ma), intruded into the primarily amphibolite-grade units of the Ashe and Alligator Back formations (Wood, 1996). The waste tailing piles of two on-going quartz mining operations were sampled to evaluate the potential economic feasibility of rare earth element extraction from key accessory phases, including apatite, remaining from the initial separation process. Sample characterization utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence (XRF), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD). The results of this investigation support the conclusion that, at the current recovery rate, price of rare earth elements, and cost of refinement, economic recovery of REE from the studied tailings is not viable. However, yttrium and dysprosium offer the highest potential for economic recovery. If some combination of improvements to the extraction process, reduction in refinement cost, or increases in price occur, yttrium and dysprosium are sufficiently abundant that extraction could become economically viable.
Master of Science
Rare Earth elements (REEs) are comprised of the Lanthanide series of elements as well as yttrium and scandium. REEs are economically important due to their critical applications within multiple industries. Current uses include electronics, magnets, lasers, electric motors, optical fibers, nuclear reactor control rods, visual displays, etc. Although the demand for REEs is high, the current sourcing of REEs is quite scarce. This study investigates the Spruce Pine district of North Carolina, testing the economic feasibility of repurposing current mine waste tailings as a rare earth element resource. Spruce Pine is home to several active quartz and feldspar mining operations, with large waste tailing piles generated during the separation process for quartz and feldspar. The mineralogy, composition and REE budget of the tailings was examined to assess the economic viability of rare earth element extraction. The waste tailing piles of two on-going quartz mining operations were sampled to evaluate the potential economic feasibility of rare earth element extraction from key accessory phases, including apatite, remaining from the initial separation process. The results of this investigation support the conclusion that, at the current recovery rate, price of rare earth elements, and cost of refinement, economic recovery of REE from the studied tailings is not viable. However, yttrium and dysprosium offer the highest potential for economic recovery. If some combination of improvements to the extraction process, reduction in cost of refinement, or increase in price were to occur, yttrium and dysprosium are sufficiently abundant that extraction could become economically viable.

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Childe, Fiona. "Uranium-lead geochronology of metamorphic accessory minerals south of the Grenville Front, western Québec, Canada." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61060.

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U-Pb ages were determined on single grains of monazite and xenotime as well as small populations of rutile from amphibolite to granulite facies metasediments of the Quebec Gneiss Segment of the Grenville Province in an area extending 45 to 135 km south of the Grenville Front in La Verendrye Park, Quebec. Recent geochronological studies include Pb-isotope ratios of metamorphic minerals corresponding to ages of 2.5 to 2.65 Ga and U-Pb monazite ages to 2649 to 2655 Ma, which define a lower discordia intercept of approximately 1.01 Ga. Recent thermobarometric studies indicate the presence of two metamorphic episodes in the region.
Monazite and xenotime grains obtained from high grade metasediments at five locations between 45 and 70 km southeast of the Grenville Front yielded $ sp{207}$Pb/$ sp{206}$Pb ages of 999 $ pm$ 5 Ma to 1021 $ pm$ 2 Ma. Monazite from the norther part of this terrane also defined an upper intercept age of 2596 $ pm$ 3 Ma.
The southernmost sample location, 135 km south of the Grenville Front, yielded both monazite and rutile. Monazite gave an age of 1072 $ pm$ 2 Ma. Small populations of rutile yielded an age of 916 $ pm$ 2 Ma. (Abstract shortened by UMI.)

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Prent, Alexander Martijn. "Microchemical and Microstructural Analysis of Major and Accessory Minerals During Fluid-Rock Interactions and Deformation." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/77367.

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In order to improve our understanding of the relation between fluid-rock interactions and deformation, deep crustal rocks that show evidence of hydration reactions have been analyzed, using microchemical and microstructural analysis techniques. Monazite from the Reynolds Range, proved capable of recording hydrous melt evolution. The combination of monazite and apatite determined timing of shear zone activity in central Australia and the analyses of pyroxene showed its recrystallization was dependent on the fluid flux present.

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Louw, Lilly-Ann. "Analysis of an 18kb accessory region of plasmid pTcM1 from Acidithiobacillus caldus MNG." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1667.

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Thesis (MSc (Microbiology))--University of Stellenbosch, 2009.
Biomining organisms are generally found in metal-rich, inorganic environments such as iron and sulfur containing ores; where they play a vital role in mineralization and decomposition of minerals. They are typically obligatory acidophilic, mesophilic or thermophilic, autotrophic, usually aerobic, iron-or sulfur oxidizing chemolithotrophic bacteria. The most prominent biomining organisms used in bioleaching of metal sulfides are Acidithiobacillus ferrooxidans, At. thiooxidans, At. caldus, Sulfobacillus spp. and Leptospirillum spp. Biomining enables us to utilize low grade ores that would not have been utilized by conventional methods of mining. Research has focused on the backbone features of plasmids isolated from bacteria of biomining environments. The aim of this study is to sequence and analyze an 18 kb region of the 66 kb plasmid pTcM1 isolated from At. caldus MNG, focusing on accessory genes carried by this plasmid. Fifteen putative genes / open reading frames were identified with functions relating to metabolism and transport systems. The genes are located in two divergently located operons. The first operon carries features related to general metabolism activities and consists of a transcriptional regulator (ORF 2), a succinate / fumarate dehydrogenase-like subunit (ORF 3), two ferredoxin genes (ORF 4 and ORF 7), a putative HEAT-like repeat (ORF 6) which is interrupted by an insertion sequence (ORF 5) and a GOGAT-like subunit (ORF 8). The second operon contains an ABC-type nitrate / sulfonate bicarbonate-like gene (ORF 9), a binding protein-dependent inner membrane component-like gene, another ABC sulfonate / nitrate-like gene (ORF 12i and 12ii) which is interrupted by an insertion sequence (ORF 13) and two hypothetical proteins with unknown functions (ORF 14 and ORF 15). Southern hybridization analysis have shown that most of the genes from the two operons are found in other At caldus strains #6, “f”, C-SH12 and BC13 from different geographical locations. Expression of the GOGAT-like subunit and the succinate / fumarate-like subunit was demonstrated in At. caldus MNG showing that these genes are functional and actively transcribed. The transcriptional regulator (ORF 2) has been shown to repress the downstream genes of putative operon 1. The persistence of these genes on plasmids together with the fact that they are being expressed, represents a potential metabolic burden, which begs the question why they have been maintained on the plasmid from geographically separated strains (and perhaps also growing under very different nutrient availability conditions) and therefore what possible role they may play.

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Reid, Christopher Peter. "The role of accessory minerals in inhibiting bentonite erosion in the geological disposal of higher activity radioactive waste." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27847.

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The chemical erosion of bentonite buffer material, during periods of glaciation, is a point of concern in the approval of safety cases for disposal of radioactive waste in crystalline rock. Currently, quantitative mass loss assessments are based on a 100% montmorillonite buffer and lead to unacceptable mass loss predictions. In practice however, the buffer will be comprised of ≈80% montmorillonite and ≈20% accessory minerals. A better understanding therefore of the role accessory minerals play in the erosion process is required to inform more realistic mass loss assessments. As indeed is the presence of fracture aperture variability on the extrusion/erosion process, as almost exclusively, research carried out to date has been in uniform aperture fracture flow cells. Four month duration erosion experiments were undertaken, designed to mimic groundwater flow through, and buffer extrusion/erosion into, a fracture intersecting a deposition hole in the KBS-3V disposal concept upon contact with dilute water. Purified montmorillonite in a planar aperture fracture was examined, as was the reference bentonite buffer material for the KBS-3V concept, MX80 (with accessory minerals), in both planar and naturally variable aperture fractures. In line with work by other researchers, the purified montmorillonite exhibited a steady mass loss throughout the experiment, with no mechanism in place to attenuate mass loss. Data correlated for the experiments with MX80 to reveal an erosion mechanism in which the accessory minerals serve to inhibit erosion when deposited at the extrusion/groundwater interface at a critical thickness. Irrespective of whether a variable or planar aperture fracture was used. Aperture variability plays a role in that, after deposition of the minerals at a critical thickness and subsequent decrease in mass loss from the system, force chain development in the accessory minerals against the variable aperture wall facilitated a rise in swelling pressure, resulting in breach of the accessory mineral barrier. An erosive period ensues, during which the breach is healed and the barrier regains its integrity. Simplified assessments, scaling the experiments to a repository scenario by incorporating the mitigating effect of the presence of accessory minerals into current quantitative mass loss assessments, predict mass loss over the course of a repository assessment period to be within acceptable limits.

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Miles, Andrew James. "Genesis of zoned granite plutons in the Iapetus Suture Zone : new constraints from high-precision micro-analysis of accessory minerals." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7751.

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The Trans-Suture Suite (TSS) of granitic plutons located in Northern Britain span the Iapetus Suture and represent a particularly enigmatic stage of post-Caledonian Devonian magmatism. Despite calc-alkaline affinities, proximity to the Iapetus Suture precludes a direct relationship to active subduction. Furthermore, the absence of inherited zircons distinguishes the TSS from plutons of a similar age throughout the Scottish Highlands, and is not easily reconciled with the abundance of peraluminous and S-type granites. Micro-analytical techniques are employed to analyse accessory zircon and apatite from three TSS plutons (Criffell, Fleet and Shap) in order to investigate connections between magmatic and tectonic processes within a continental suture zone. Accessory minerals contain a robust and accessible record of magma evolution. However, their trace element compositions are shown to document the final stages of pluton emplacement only, and are determined primarily by competitive crystallisation of other accessory phases at shallow crustal levels. By contrast, whole-rock compositions record an earlier stage of magma evolution that occurred in deeper and open-system crustal hot zones. The absence of inherited zircon in the final crystal assemblage reflects resorption during rapid and potentially adiabatic ascent of super-liquidus and water-rich magmas from the crustal hot zone. The concentrations of REE in apatite inclusions decrease with increasing crystallisation of other accessory minerals and in some samples have been distinguished on the basis of their host phase. In metaluminous granodiorites, no preferred crystallisation sequence is observed between host phases. In peraluminous samples, zircon-hosted apatite compositions appear more primitive compared to those hosted by other phases and reflects earlier saturation of zircon in these magmas. The isotopic record of zircon is shown to be biased towards earlier stages of magma evolution in peraluminous magmas and provides a means of assessing zircon isotope compositions in the context of often protracted histories during silicic magma evolution. The Mn content of apatite varies independently to whole-rock composition, correlating positively with decreasing oxygen fugacity and indices of increasing reduction. Apatite is proposed as a robust and effective redox proxy with application to magmatic, detrital and lunar studies of redox conditions. Zircon O-HfU- Th-Pb isotope compositions have identified increasing degrees of compositional heterogeneity in more silicic components of the TSS, including the involvement of more mafic magmas in the generation of the large S-type pluton of Fleet. Compositional trends between zircons from plutons emplaced on both sides of the Iapetus Suture are used to identify a common Avalonian component beneath the Southern Uplands and English Lake District related to Avalonian underthrusting beneath the Laurentian margin during the late Caledonian. New geochronological dating indicates that pluton emplacement occurred during periods of both pre- and post-Acadian transtension. The distinguishing characteristics of these plutons relative to other Caledonian plutons reflect their unique emplacement into the hydrated lithosphere of the Iapetus Suture Zone. Oxygen isotope disequilibrium between the magmatic compositions recorded by zircon and those of the whole-rock and some quartz crystals reflect hydrothermal alteration of the latter two archives. Hydrothermal alteration and exchange caused by 18O-rich magmatic fluids has elevated the 18O compositions of the whole-rock and some quartz crystals, with most disequilibrium observed around the outer margins of the plutons due to further fluid interaction with local 18O-rich sediments. The hydrothermal history of the TSS is markedly different from that of the British Tertiary Igneous Province where hydrothermal alteration resulted from circulation of meteoric water, reflecting significantly different magmatic and emplacement histories.

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Chard, Julian Alexander. "Petrochronology of Accessory Minerals in relation to Metamorphism and Fluid-Flow across the Albany-Fraser Orogen and Eucla Basement, Western Australia." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/85448.

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Petrochronology of uranium-bearing accessory minerals (zircon, monazite, rutile and titanite) across the Albany-Fraser Orogen and Eucla basement was undertaken to provide insight into transient metamorphism and fluid-flow events and their link to geodynamic triggers. This study includes the oceanic accretion of the Madura Province and crustal thickening, identifying a distal footprint to gold mineralisation related to Stage II of the Albany-Fraser Orogeny and mineral deformation within the Fraser Shear Zone.

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Ver, Hoeve Thomas James. "Applications of LA-ICP-MS analysis to zircon : assessing downhole fractionation and pre-treatment effects for U-Pb geochronology and trace element variations in accessory minerals from the Bushveld Complex." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60201.

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Zircon and other U-Th-Pb-bearing minerals are now recognized as key geochemical and geochronological tracers of the evolution of late-stage fractionated interstitial melt in mafic layered intrusions. Two separate, yet complementary, applications of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) on zircon from layered intrusions are presented with the goals of advancing the analytical capabilities of LA-ICP-MS and showcasing the powerful geochemical fingerprinting of zircon. The effects of downhole fractionation, the time-dependent evolution of Pb-U ratios during laser ablation, represents a significant limitation on the accuracy of U-Th-Pb zircon geochronology by LA-ICP-MS. Exponential downhole correction models developed from the analyses of three common zircon reference materials (Plešovice, Temora-2, 91500) and applied to low-U zircon from Precambrian mafic intrusions (Laramie, Bushveld, Stillwater) indicate that successful correction requires careful matrix-matching the reference zircon to the unknowns. Pre-treatment protocols, including annealing and leaching, applied to all analyzed zircon produces strong effects on downhole fractionation with correlative impact on the relative accuracy of the calculated ages as a function of the downhole behaviour in the reference material used. In the Paleoproterozoic Bushveld Complex, the world’s largest layered intrusion, the trace element systematics of zircon provide temperature-composition constraints on the near-solidus crystallization of mafic-ultramafic cumulates and overlying granitic rocks. Zircon occurs with other late-stage interstitial minerals (e.g., quartz, biotite, Na-plagioclase) and crystallized at temperatures ranging from 950°C down to 690°C based on Ti-in-zircon thermometry. Forward modeling using rhyolite-MELTS of proposed Bushveld parental magmas yields similar zircon saturation temperatures from melts of intermediate-silicic composition, representing less than ~15% remaining melt, and reproduces the observed mineral assemblages. Anomalously high and variable Th/U in zircon from the Critical Zone (e.g., UG2 chromitite, Merensky Reef) reflects U loss to late, oxidized Cl-rich fluids that exsolved from the fractionated interstitial melt, a process that may be a characteristic feature of large open-system layered intrusions (e.g., Neoarchean Stillwater Complex). The presence of late-stage interstitial zircon and other accessory minerals in layered intrusions provides new in situ geochemical and geochronological tools for evaluating the origin and evolution of mafic-ultramafic magmatism in the Earth’s crust throughout geological time.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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Ahamdach, Noureddine. "Mobilité de l'uranium, du thorium et des éléments de terres rares au cours de l'altération latéritique, de l'infiltration d'eau météorique en milieu granitique et de la diagenèse d'une formation volcano-sédimentaire." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL125N.

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Les processus de transfert de l'uranium et de ses descendants, du thorium et des éléments des terres rares ont été étudiés dans trois environnements géologiques différents: (1) un environnement caractérise par des processus de pédogenèse (profils latéritiques de lagoa real, état de Bahia, Brésil); (2) un environnement caractérisé par l'infiltration d'eaux météoriques dans un granite (episyenite minéralisée de Peny, nord-ouest du massif central français) et; (3) un environnement caractérisé par des processus d'altérations dia génétiques (bassin volcano-sédimentaire de Lodève, sud-est du massif central français). Dans les sols latéritiques, les minéraux accessoires a U-Th-ETR sont détruits des le saprolite et l'uranium libéré par la destruction de ces minéraux est adsorbe préférentiellement sur les oxy-hydroxydes de fer et les produits titanes. Les ETR sont en partie immobilisées sous forme de phosphates alumineux et de cerianite. Dans l'episyenite de Peny, les migrations de l'uranium et du radium se font sur de courtes distances (de l'ordre de quelques cm). La mobilité du radium peut être réduite par les oxy-hydroxydes de fer. Le rôle metallogenique du volcanisme du bassin de Lodève a été démontré par l'étude géochimique des cinérites et des inclusions vitreuses. Ce volcanisme est de nature rhyolitique et sa teneur en uranium est de 6 ppm. L'uranium libéré lors de la dissolution de la phase vitreuse est piégé par la matière organique et les oxydes de fer constituant ainsi une preconcentration dés le permien

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Amidon, William Henry. "Cosmogenic ³He and ²¹Ne Dating in Accessory Mineral Phases." Thesis, 2010. https://thesis.library.caltech.edu/5817/2/thesis_final.pdf.

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The development of terrestrial cosmogenic nuclide dating has led to applications as varied as the dating of glacial moraines, establishing slip-rates on faults, measuring the erosion rates of basins, and measuring rates of soil formation. Studies in many of these fields could greatly benefit from analysis of far more samples than can be easily dated using ¹⁰Be, ²⁶Al, and ³⁶Cl. The rapid preparation and analysis of samples for cosmogenic ³He often allows a greater number of samples to be analyzed, but has so far been applied primarily to olivine and pyroxene in mafic rocks. Because ³He is produced in all mineral phases, it can potentially be applied in almost any lithology. The goals of this thesis is to expand the range of target lithologies suitable for cosmogenic ³He dating by calibrating production rates of cosmogenic ³He in accessory mineral phases such as apatite, zircon, and garnet. Results are presented from three calibration studies: glacial moraine boulders in the Nepal Himalaya, young rhyolite surfaces from California’s Coso volcanic field, and rhyolite surfaces scoured by the Bonneville flood near Twin Falls, Idaho. Both the Nepal and Coso studies compare ³He in zircon, apatite, and garnet against ¹⁰Be in quartz, finding that higher than expected ³He concentrations are likely due to anamolous elevation scaling in the Himalaya, and to production of ³He via neutron capture on ⁶Li at Coso. The Idaho calibration study is unique in that it is calibrated against the age of the Bonneville outburst flood (known by ¹⁴C dating), and uses a shielded sample to definitively document Li-produced ³He components in the deep sub surface. Collectively, these studies highlight several challenges associated with cosmogenic ³He dating of accessory phases: the difficulty in measuring small amounts of cosmogenic ³He in the presence of large amounts of radiogenic ⁴He, the importance of production of ³He via neutron capture on ⁶Li, and the redistribution of energetic ³He and ³H between adjacent mineral phases. Despite these challenges, adopting a ¹⁰Be production rate of 4.51 at g^-1 a^-1 in quartz (Balco et al., 2008), brings three independent ³He production rate estimates into good agreement with grand means of 103 ± 3, 133 ± 6, and about 134 ± 13 at g^-1 a^-1 in zircon, apatite, and spessartine garnet respectively. Such agreement suggests that these phases are suitable for cosmogenic dating. ³He in accessory phases may enable a range of unique applications including the study of ancient sediments, paleo-altimetry, and rates of chemical weathering in soils.

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Aird, Hannah Mary. "Sulfide and Accessory Mineral Assemblages in the Sulfur-Poor Regions of the Stillwater Complex, Montana, USA." Diss., 2014. http://hdl.handle.net/10161/8737.

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Layered igneous intrusions such as the Stillwater Complex in Montana contain the most economic concentrations of platinum-group elements (PGE) in the world, yet the processes involved in the enrichment of these PGE remain unclear. Some researchers propose that the PGE were enriched into sulfide phases through purely magmatic processes, while others postulate that late-stage, high-temperature fluids caused remobilization of the more soluble elements upwards from the base of the crystal pile. Although much work has been carried out on the economic PGE-enriched ore zone (J-M reef), the silicate mineralogy and the bulk geochemistry of the Complex, the detailed petrographic trends have not been investigated. This dissertation comprises a detailed petrographic study into the assemblages associated with sulfide and other trace minerals throughout the stratigraphy.

Sampling was carried out from both surface outcrops and drill cores over four consecutive field seasons. Polished thin sections were produced which were then examined by petrographic microscope and electron microprobe. In addition, bulk rock analysis was carried out by x-ray fluorescence spectrometry (XRF).

In brief, the sulfide and trace mineral assemblage studies described below reveal a number of interesting observations. An upwards trend from pentlandite-rich to pyrrhotite-rich to chalcopyrite + pyrite-rich assemblages is observed below the reef, and the same trend occurs above the reef with the transition occurring just below the reef, in upper GN-I. Trace element analysis shows that Cu levels are higher above the reef than below it, and that although Zn and Cu contents are correlated below the reef, a restricted range of Zn contents occurs above the reef, while Cu is highly variable. As all `low-temperature' assemblages (those associated with extensive silicate alteration or the presence of greenschist facies minerals such as chlorite, clinozoisite and epidote) were discounted, the majority of sulfide assemblages present were either pristine(multiphase, often globular in shape, with no associated silicate alteration) or high-temperature (multiphase, with high-temperature minerals such as biotite, hornblende, carbonates, etc, and with little associated silicate alteration) in occurrence. Some differences were observed between the hanging-wall and footwall rocks, including the presence of native copper, sphalerite in a calcite-hornblende vein, and high-temperature carbonates in footwall and not hanging-wall rocks. The high-temperature carbonates observed comprise dolomite with exsolved patches of calcite. The textural relationships and Fe-Mn compositions of the Stillwater carbonates are similar to those of mantle carbonates. High-temperature desulfidation is also observed both above and below the reef, in the form of pyrite being converted to magnetite, and chalcopyrite to a Cu-Fe-oxide (delafossite). Both sets of assemblages are associated with little to no silicate alteration. When taken together, the upwards increase in Cu and S, the variable Cu contents above the reef, the native copper, high-temperature carbonates and high-temperature sphalerite-bearing veins below the reef, and the evidence for desulfidation are all most readily explained by the remobilization of selected phases by a high-temperature fluid. This dissertation provides evidence that the fluid present in the latter stages of Stillwater formation had a carbonic as well as a Cl-rich component, and would therefore have been efficient in PGE remobilization.

Dissertation

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McFarlane, Christopher R. M. "Diffusion, closure temperatures, and accessory mineral petrogeneses in a high-temperature aureole : refining the integration of P-T and t /." Thesis, 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p3116116.

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Luvizotto, George Luiz [Verfasser]. "Trace element signatures in rutile : characterization of standards and applications to accessory mineral behavior in metamorphic rocks / vorgelegt von George Luiz Luvizotto." 2008. http://d-nb.info/992028906/34.

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Alexander, Brian W. Brantley Susan Louise. "Controls on groundwater chemistry in the Cape Cod Aquifer, Massachusetts the impact of accessory mineral phases on solute concentrations, 87sr/86sr, and rare earth element distributions /." 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-3742/index.html.

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Reguir, Ekaterina. "Distribution of incompatible trace elements in rock-forming and accessory minerals from carbonatites as a tracer of magma evolution." 2011. http://hdl.handle.net/1993/4761.

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Abstract:

Carbonatites are igneous rocks comprising more than 50 modal percent of carbonate minerals and characterized by highly variable modal compositions. The majority of carbonatites are confined to intra-continental rifts, whereas occurrences associated with plate margins and orogenic settings are less common. Petrogenesis of carbonatites has been a matter of intense debate for several decades. The possible genetic models include crystallisation from a primary carbonatite magma, liquid immiscibility and crystal fractionation from carbonate-rich silicate magma. In contrast to the voluminous bulk-rock trace-element data and major-element analyses of minerals from carbonatites available in the literature, there has been no systematic study concerned with the trace-element signatures of the most common constituents of these rocks. This work is the first comprehensive study of the interrelations between the trace-element chemistry of the most common constituents of carbonatites, the geochemistry of these rocks, and their tectonic setting. The rock samples examined represent 21 different localities worldwide. The extent of major- and trace-element substitutions in amphibole, clinopyroxene, trioctahedral micas, dolomite, magnetite and perovskite is investigated in detail. The silicate minerals from carbonatites exhibit much larger compositional diversity than previously recognized. They can incorporate significant amounts of such petrogenetically important elements as Sr, REE, Zr, Nb and Ta. The majority of studied clino-amphibole- and clinopyroxene-group minerals exhibit previously unrecognized a bimodal distribution patterns of REE, which can be explained in terms of crystal chemistry of these phases. The trace-element signature of phlogopite from carbonatites, particularly Nb, Mn, Ni and Cr, is distinctly different from that of phlogopite from kimberlites, and can be used as a reliable petrogenetic indicator. Compositional variations in dolomite reflect magmatic and subsolidus processes in carbonatites. Magnetite from carbonatites follows a well-defined magmatic and previously unrecognized reaction trend. Contrary to prior studies, this mineral is only a minor host of HFSE in carbonatitic rocks. The U-Pb age data, trace-element and Sr-isotopic composition of perovskite from the Afrikanda carbonatite and clinopyroxenite suggest that the two rocks are not related by crystal fractionation. This study underlines the importance of a systematic approach in petrogenetic studies based on trace-element distribution.

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Wall, Corey J. "Uranium-Lead Geochronology of Granophyres from the Archean Stillwater Complex, Montana (USA): Characterization of Uranium-Bearing Accessory Minerals (Zircon, Titanite, Rutile) and Preliminary Dating Results." 2009. http://hdl.handle.net/2429/6732.

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Abstract:

The ca. 2.7 Ga Stillwater Complex is a mafic-ultramafic layered intrusion located in the Beartooth Mountains of southwest Montana. The intrusion is dominated by mafic-ultramafic cumulate rocks, but also contains volumetrically minor granophyres that were emplaced as latestage differentiates within the plagioclase-rich Banded Series of the complex. The granophyres consist primarily of albite (or oligoclase) + quartz and display a wide variety of textures, including granophyric, graphic, equigranular, and pegmatitic. The granophyres are discordant bodies and typically range in thickness from a few centimetres up to tens of metres. High-U accessory minerals (zircon, titanite, rutile) are present in the granophyres and were separated from whole rock samples for characterization by scanning electron microscopy (SEM) and age determination by U-Pb geochronology using isotope dilution thermal ionization mass spectrometry (ID-TIMS). The chemical abrasion pre-treatment technique (annealing and leaching) was employed for determining the age of single grains of zircon. In this study, four separate granophyres were sampled from different stratigraphic levels in the Banded Series (lower, middle, and upper). Three samples yielded mostly euhedral prisms of zircon (ranging from 100-300 μm) that are highly metamict due to very high U-contents (87.3 to 1438.2 ppm). The U-Pb systematics of these zircon grains have been strongly disturbed since crystallization due to self-irradiation (metamictization) and subsequent fluid infiltration events, which resulted in substantial Pb-loss. In contrast, zircon grains from a pegmatic core to a gabbroic pegmatoid that cross-cuts the layered cumulates of the Lower Banded Series are clear, interstitial, pale-pink, high-quality grains, of low to moderate U-content (76.2 to 237.1 ppm). A U-Pb concordia age of 2709.6 ± 0.8 Ma (2σ) was determined from this sample and is interpreted as a minimum age for the crystallization of the Stillwater Complex. This age is consistent with previously published U-Pb zircon geochronology of basal sill and dikes that yielded ages mostly in the range from 2710 to 2712 Ma and suggests that the Stillwater Complex was emplaced within a few million years.

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Dissertations / Theses on the topic 'Accessory mineral'

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