To provide an increased breadth in the knowledge of tephra dispersal, this pilot study examines a peat core from Lakselv in Finnmark County in northern Norway. Peat samples are exposed to burning, HCl, density separation and polarized light microscopy. One sample from a depth of 37.5-40 cm was analysed using an electron microprobe analyser (EMPA). At least two tephra horizons were identified, one at a depth of 12.5-17.5 cm and one at 37.5-40 cm. The lower horizon shows a chemical composition similar to eruptives from Jan Mayen and São Miguel, Azores while the origin of the upper horizon is unknown as no geochemical analysis was performed for that depth.

Extensive research has shown that electrochemistry is one of the factors that govern the flotation of sulfide minerals. Flotation is often adversely affected by uncontrolled oxidation, which is also an electrochemical process. The interest in pyrrhotite recovery arose after observing that there is a substantial loss of PGM due to the depression of pyrrhotite and the subsequent loss of any PGMs associated with it. The first part of this study focuses on the influence of chemical composition and crystal structure on the electrochemical behaviour of pyrrhotite in a 0.05 M Na2B4O7 solution. Rest potential and polarisation resistance measurements, as well as anodic polarisation diagrams, showed that the magnetic 4C type pyrrhotite is anodically more reactive than the non-magnetic 6C type pyrrhotite. It was also shown in cathodic polarisation diagrams that the non-magnetic 6C type pyrrhotite is a better substrate for oxygen reduction and is less susceptible to oxidation. ToF-SIMS showed the formation of an oxide layer on the pyrrhotite surface after oxidation. In the second part of this work, the influence of galvanic interactions on the electrochemical behaviour of pyrrhotite in contact with pentlandite was investigated. It was observed that, under oxygen-saturated conditions, as the amount of pentlandite increases, the reactivity towards oxidation of the mixed mineral system is reduced. Impedance measurements showed a decrease in capacitance values, indicating the formation of a continuous oxide layer on the surface and an increase in oxide layer thickness with decreasing pentlandite content. Anodic polarisation diagrams showed that under oxygen-deficient conditions and in the low potential region, pentlandite behaves as an inert material and does not have an influence on the oxidation behaviour of pyrrhotite. Hence, the anodic activities of the different magnetic 4C type pyrrhotites from Sudbury Gertrude, Phoenix and Russia were compared. It was shown that the oxidation reactivity decreased in the following order: Sudbury Gertrude magnetic 4C pyrrhotite > Phoenix magnetic 4C pyrrhotite > Russian magnetic 4C pyrrhotite; it also varied according to location. In the transpassive region, higher anodic currents were observed on the mixed samples because both pentlandite and pyrrhotite reacts. The reactivity increased in the order: pure pyrrhotite (Russia) < medium-pentlandite (Sudbury Gertrude) < high-pentlandite (Phoenix). In the presence of potassium ethyl xanthate, there was no change in the initial anodic reactivities of the different pyrrhotites. The anodic polarisation diagrams of the pure and mixed samples showed a reduction in the maximum anodic peak current, suggesting the presence of xanthate on the surface, which hinders oxidation of the mineral surface. In addition, the influence of cleaning of oxidised pyrrhotite with gaseous carbon dioxide was studied, using electrochemical and microflotation measurements. Electrochemical measurements indicated that CO2 treatment resulted in depassivation of the oxidised surfaces; this was supported by ToF-SIMS measurements that demonstrated a reduction in the oxide layer thickness after CO2 treatment. Anodic polarisation diagrams showed a higher anodic peak current, indicating that the surface is more reactive. Gaseous carbon dioxide conditioning of oxidised pyrrhotite resulted in improved flotation response of pyrrhotite with the aid of copper activation and higher air flow rate. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Materials Science and Metallurgical Engineering / unrestricted

A multi-scale high-resolution geophysical and geological study was conducted in the Sevier Desert, central Utah, found within the Colorado Plateau-Basin and Range Transition Zone. The region is marked by with Quaternary volcanics and faulting as young as 660 yr B.P., with many fault scarps thought to have the potential for 7+ magnitude earthquakes. Three locations within the Sevier Desert which represent three different tectonic expressions of possible faulting at the surface were selected. These include a location found within surface sedimentation, a location with surface sedimentation and sub-surface basalts and a location with basalts, at the surface with very limited sedimentation. A suite of geophysical data were obtained including the use of P-wave, SH-wave, ground-penetrating radar (GPR). Auger holes, microprobe glass analysis, and mapping information were also completed in order to constrain and gain a more complete understanding of the sub-surface structure. These data were used to determine if there are sub-surface expressions of the possible surface scarps and if all the faults within the fault zone have the same structural style. The possible surface fault expressions were found to be connected to sub-surface fault expressions but with differing results within both sediments and basalts. Our data show that a multi-scale approach is needed to obtain a complete view of tectonic activity. The area faulting in the Sevier Desert penetrates at depth involving multiple complex styles that include some faulting that cuts recent lava flows and some that do not. The evidence also indicates that in at least some area faulting was episodic and others may be single events having implications on level of activity and hazard.

The Arlanda area is a construction intensive area facing problems with risk of leaching of arsenic (As) from the bedrock to surface- and groundwater. Construction projects in the area have had problems with high levels of As in the bedrock and the risk of leaching increases through processing of aggregates and blasting of the bedrock. Additionally, there are high concentrations of As in potable water and elevated concentrations are correlated with occurrences of metasedimentary rock, but may also be related to other rock types. The existing geological information of the area was collected in the 1960´s and modern petrographic information as well as modelling of P-T and redox conditions are needed to understand the As mineralogy of the bedrock. Methods used in this project include field work, optical microscopy, electron microprobe analyses, geothermometry calculations, pseudosection modelling in Perple_X and geochemical modelling in PHREEQC. The results indicate that the As-rich bedrock domain include rocks of both igneous and sedimentary origin. As-bearing minerals löllingite and arsenopyrite were found in the matrix of two of the metasedimentary rock samples, while no As-minerals were found in metavolcanic samples. P-T estimates from several geothermobarometry models all suggest amphibolite facies metamorphism for the area, with pressure of 3.0-5.5 kbar and temperature of 490-640 °C. Simple modelling of equilibration of löllingite and arsenopyrite in pure water indicate that As(III) is the dominating oxidation state of As and that the molality of As increases with increasing T and decreasing pH. The results of this thesis provide new information on the petrography and P-T conditions for metamorphism of As-bearingsupracrustal rocks in the Arlanda area, but future research is needed to be able to predict the spatial occurrence of As in the bedrock. / Arlandaområdet är ett av de mest expansiva områdena i Sverige där en stor mängd infrastrukturprojekt är planerade under de närmaste 5-20 åren. Tidigare byggnadsprojekt i området har dock stött på problem med höga bakgrundshalter av arsenik (As) i berggrunden och det finns även en risk för urlakning av As från berggrunden till både yt-och grundvatten. Denna risk ökar under byggnadsarbeten i och med till exempel sprängning av berg. Ytterligare ett problem är att det i området runtomkring Arlanda ofta är höga halter av arsenik i dricksvattenbrunnar. Från data över As-halter i bergborrade brunnar har man kunnat se att höga halter av As ofta förekommer i metasedimentära bergarter, men även kan uppträda i andra bergarter. Den tillgängliga geologiska informationen över området är insamlad på 60-talet och ny petrografisk information, samt modellering av tryck- och temperaturförhållanden är nödvändig för att förstå förekomst av As i berggrunden. Målet med detta projekt är att med hjälp av fältarbete, optisk- och elektronmikroskopering, samt termodynamisk modellering få djupare kunskap kring ytbergarterna i området och utvärdera förekomsten av arsenik i dessa. Under vilka tryck- och temperaturförhållanden som de metamorfa bergarterna omvandlats studeras genom beräkningar från mineralsammansättningar samt modellering i programmet Perple_X. Resultatet från projektet visar att bergarter i As-anrikade zoner är av både magmatiskt och sedimentärt ursprung. Arsenikmineralen löllingit och arsenikkis dokumenterades endast i bergarter av sedimentärt ursprung. Bergarternas kemiska sammansättning tyder också på att de högsta As-halterna finns i de metasedimentära bergarterna. Modellering i PHREEQC visar att As(III) är den dominerande formen av As när löllingit och arsenikkis reagerar med vatten. Tryck- och temperaturberäkningar samt tryck- och termodynamisk modellering tyder på metamorfos under amfibolitfacies, med tryck omkring 3.0-5.5 kbar och temperatur omkring 490-640 °C. Resultaten från detta projekt ger ny information om de metamorfa bergarterna i Arlanda området och förekomst av As i dessa. Vidare studier är nödvändiga för att kunnaförutse i vilken form och i vilka bergarter As förekommer.

Pour mieux comprendre le processus géodynamique qui a permis la destruction du craton Nord Chinois (NCC), le rôle des fluides mantelliques a été examiné. Pour cela, les distributions des teneurs en eau et des compositions isotopiques du Lithium dans le manteau lithosphérique NCC ont été déterminées à partir des xénolites de péridotite entrainés par les basaltes mésozoïques et cénozoïques. Une variation temporelle des teneurs en eau est observée. Le manteau lithosphérique cénozoïque est appauvri en eau, sans doute suite à l'amincissement crustal et au réchauffement du manteau résiduel par un flux ascendant asthénosphérique. Le manteau lithosphérique mésozoïque montre des teneurs en eau intermédiaire entre les teneurs élevées du Crétacé et les teneurs basses cénozoïques, indiquant une déshydratation du manteau commençant dès le début de sa destruction. Cette déshydratation, facilitée par la destruction du manteau lithosphérique profond, permet de renforcer la rigidité de la lithosphère et lui permet de résister à la convection mantellique. Les distributions élémentaire et isotopique du Li montrent une grande hétérogénéité, aux échelles intra et inter-cristallines. Par simulation numérique, nous démontrons que deux enrichissements successifs ont affecté le manteau, un enrichissement limité (<5ppm) avec une signature pauvre en 7Li ([delta]7Li ~ -20 [pour mille]), suivi d'un enrichissement important (> 100 ppm) avec une signature riche ([delta]7Li ~ +20 [pour mille]), précédent de peu l'exhumation des xénolites. La formation des liquides métasomatiques responsables de ces enrichissements nécessite une distribution hétérogène dans le manteau NCC d'éléments recyclés lors de la subduction à l'est du NCC / In order to investigate the geodynamic cause for destruction of the North China Craton (NCC), the role of mantle fluids is examined. The aim of the PHD work is to clarify H2O contents and lithium isotopic compositions of the NCC lithospheric mantle by studying peridotite xenoliths hosted by Mesozoic-Cenozoic basalts across eastern NCC. A temporal variation of H2O content has been revealed, and it has deep implications for processes of craton destruction. The Cenozoic lithospheric mantle was featured by low H2O content, interpreted to be the relict mantle that survived the lithospheric thinning and has been dewatered by reheating from upwelling asthenospheric flow. The late-Mesozoic lithospheric mantle showed relatively high H2O content, a hydrous status intermediate between the Cretaceous hydration and the Cenozoic dryness, indicating the dehydration of the NCC mantle with time during NCC destruction. The dehydration, facilitated by thinning of weak mantle pieces at bottom, is one way by which the lithosphere strengthens itself to survive in the convecting mantle. Extreme Li and isotopic disequilibria were observed intra- and inter-mineral in the peridotites. With numerical simulations, we demonstrate two superimposed Li enrichment events occurring at the mantle: a limited Li enrichment (< 5 ppm) and large delta7Li depletion (-20~-10[per 1000]) of the mantle domain, followed by a recent and transient infiltration of high Li and delta7Li (up to +20 [per 1000]) melts/fluids. The anomalous Li isotopic compositions of mantle metasomatic agents call upon the same of their mantle sources, and we assume recycled components, both Li isotopically heavy and light, in the mantle beneath the eastern NCC

A roller coaster manufacturer became aware that improperly heat treated track couplings were sent to a construction site for assembly. Concerns were that suspect couplings might not meet the engineering specifications and could be vulnerable to sudden failure. A testing company in Oak Ridge, TN that specializes in in-situ and laboratory mechanical testing was contacted by the manufacturer for help in this endeavor. The construction company elected to enlist a local testing firm to perform field tests on the components instead of the company in Oak Ridge. The test methods used are incapable of providing quantitative results that could be measured to the engineering specifications, making it unlikely to identify anything but the worst material conditions. This study is an example that the need for accurate analysis is very important. The manufacturer reported that 60 couplings were replaced, but it is presently unknown how many should have been replaced.

La thèse s’inscrit dans la problématique du dépôt de couches minces en procédés de pulvérisation réactive cathodique magnétron continu basse puissance (R-DC) et pulsé haute puissance (R-HiPIMS). Le mode réactif consiste à ajouter, dans l’argon, un gaz réactif tels que l’oxygène ou l’azote. Les oxydes et les nitrures ont de très nombreuses applications industrielles. Néanmoins, les exigences des nouvelles applications nécessitent de mieux comprendre, contrôler et maîtriser les processus fondamentaux gouvernant le transport de la matière pour optimiser ces procédés plasmas. L’objectif principal de cette thèse est d’étudier le transport des atomes pulvérisés de titane (Ti) en mélange Ar/N2 et d’établir des corrélations avec les propriétés des dépôts de type TiN. La fluorescence induite par diode laser (résolue en temps dans le cas du procédé HiPIMS) a été développée pour mesurer les fonctions de distribution en vitesse des atomes neutres Ti à l’état fondamental en fonction de la pression, de la distance par rapport à la cible et du mélange gazeux. Le degré de liberté supplémentaire qu'offre la dimension temporelle du plasma HiPIMS a permis de caractériser leur cinétique de transport en ayant la possibilité de séparer les temps caractéristiques des différents processus, et de mettre en évidence trois populations d’atomes (énergétique, quasi-thermalisée et thermalisée). Les fonctions de distribution en énergie des ions Ti+ ont été mesurées par spectrométrie de masse et des hypothèses sont proposées pour pouvoir expliquer les quatre populations identifiées. Enfin, les couches minces déposées ont été analysées par MEB, DRX et microsonde de Castaing. / The growth of thin layers in reactive-direct current magnetron sputtering (R-DC) and reactive-high power impulse magnetron sputtering (R-HiPIMS) processes is the general framework of this PhD. Reactive processes consist in the addition, in argon gas, of a reactive gas such as oxygen or nitrogen, and allow the deposition of oxides and nitrides which have many industrial applications. Nevertheless, the high level of expectations regarding new applications requires a better understanding, controlling, mastering of basic processes governing atoms transport in the view of process optimization. The main goal of this PhD is to study the transport of sputtered titanium atoms (Ti) in Ar/N2 gas mixture and to establish correlations with TiN film properties. Tunable diode laser induced fluorescence technique (time resolved in the case of HiPIMS process) has been developed in order to measure velocity distribution functions of neutral Ti atoms at the ground state, function of the pressure, the distance from the target and the gas mixture. In HiPIMS, the additional degree of freedom, given by time dimension, allowed to characterize their kinetic of transport while at the same time providing the possibility to separate characteristic time scales of different processes. Three atoms populations have been highlighted (energetic, quasi-thermalized and thermalized ones). Energy distribution functions of Ti+ ions have been measured using mass spectrometry and four populations have been observed and explained. Finally, deposited thin films have been analyzed by means of SEM, XRD and electron microprobe methods.

[1] Four specimens of zoned tourmaline from granitic pegmatites are characterised in detail, each having unusual compositional and/or morphologic features: (1) a crystal from Black Rapids Glacier, Alaska, showing a central pink zone of elbaite mantled by a thin rim of green liddicoatite; (2) a large (~25 cm) slab of Madagascar liddicoatite cut along (001) showing complex patterns of oscillatory zoning; and (3) a wheatsheaf and (4) a mushroom elbaite from Mogok, Myanmar, both showing extensive bifurcation of fibrous crystals originating from a central core crystal, and showing pronounced discontinuous colour zoning. Crystal chemistry and crystal structure of these samples are characterised by SREF, EMPA, and 11B and 27Al MAS NMR and Mössbauer spectroscopies. For each sample, compositional change, as a function of crystal growth, is characterised by EMPA traverses, and the total chemical variation is reduced to a series of linear substitution mechanisms. Of particular interest are substitutions accommodating the variation in [4]B: (1) TB + YAl ↔ TSi + Y(Fe, Mn)2+, where transition metals are present, and (2) TB2 + YAl ↔ TSi2 + YLi, where transition metals are absent. Integration of all data sets delineates constraints on melt evolution and crystal growth mechanisms. [2] Uncertainty has surrounded the occurrence of [4]Al and [4]B at the T-site in tourmaline, because B is difficult to quantify by EMPA and Al is typically assigned to the octahedral Y- and Z-sites. Although both [4]Al and [4]B have been shown to occur in natural tourmalines, it is not currently known how common these substituents are. Using 11B and 27Al MAS NMR spectroscopy, the presence of [4]B and [4]Al is determined in fifty inclusion-free tourmalines of low transition-metal content with compositions corresponding to five different species. Chemical shifts of [4]B and [3]B in 11B spectra, and [4]Al and [6]Al in 27Al spectra, are well-resolved, allowing detection of very small (< ~0.1 apfu) amounts of T-site constituents. Results show that contents of 0.0 < [4]B, [4]Al < 0.5 apfu are common in tourmalines containing low amounts of paramagnetic species, and that all combinations of Si, Al and B occur in natural tourmalines.

[1] Four specimens of zoned tourmaline from granitic pegmatites are characterised in detail, each having unusual compositional and/or morphologic features: (1) a crystal from Black Rapids Glacier, Alaska, showing a central pink zone of elbaite mantled by a thin rim of green liddicoatite; (2) a large (~25 cm) slab of Madagascar liddicoatite cut along (001) showing complex patterns of oscillatory zoning; and (3) a wheatsheaf and (4) a mushroom elbaite from Mogok, Myanmar, both showing extensive bifurcation of fibrous crystals originating from a central core crystal, and showing pronounced discontinuous colour zoning. Crystal chemistry and crystal structure of these samples are characterised by SREF, EMPA, and 11B and 27Al MAS NMR and Mössbauer spectroscopies. For each sample, compositional change, as a function of crystal growth, is characterised by EMPA traverses, and the total chemical variation is reduced to a series of linear substitution mechanisms. Of particular interest are substitutions accommodating the variation in [4]B: (1) TB + YAl ↔ TSi + Y(Fe, Mn)2+, where transition metals are present, and (2) TB2 + YAl ↔ TSi2 + YLi, where transition metals are absent. Integration of all data sets delineates constraints on melt evolution and crystal growth mechanisms. [2] Uncertainty has surrounded the occurrence of [4]Al and [4]B at the T-site in tourmaline, because B is difficult to quantify by EMPA and Al is typically assigned to the octahedral Y- and Z-sites. Although both [4]Al and [4]B have been shown to occur in natural tourmalines, it is not currently known how common these substituents are. Using 11B and 27Al MAS NMR spectroscopy, the presence of [4]B and [4]Al is determined in fifty inclusion-free tourmalines of low transition-metal content with compositions corresponding to five different species. Chemical shifts of [4]B and [3]B in 11B spectra, and [4]Al and [6]Al in 27Al spectra, are well-resolved, allowing detection of very small (< ~0.1 apfu) amounts of T-site constituents. Results show that contents of 0.0 < [4]B, [4]Al < 0.5 apfu are common in tourmalines containing low amounts of paramagnetic species, and that all combinations of Si, Al and B occur in natural tourmalines.

Dans le cadre du développement des technologies Na-ion, le composé NaFePO4, équivalent chimiquedu matériau très attractif LiFePO4, représente une alternative intéressante aux problèmes deressourcement du lithium. Toutefois, les composés LiFePO4 et NaFePO4 de structure olivineprésentent des divergences de comportement structural et électrochimique lors de l'insertioncationique. Ce travail présente une analyse des mécanismes de (dés)insertion des ions Li+ et Na+ ausein de la phase FePO4 par voie chimique et électrochimique. Les échantillons de LiFePO4 ont étésynthétisés par deux méthodes différentes (hydrothermale et précipitation), puis délithiéschimiquement via différents procédés. Dans un premier temps, les analyses structurales (DRX)associées aux analyses nucléaires ont permis d'effectuer un suivi de la cinétique de réaction. Nousavons montré que la présence de joints de grains, issus du traitement thermique effectué, limitefortement la vitesse de délithiation. L'analyse de l’évolution des domaines de cohérences a permis deproposer un mécanisme de délithiation original de type "Coeur-Coquille" avec un coeur de LiFePO4,confirmé par HRTEM et STEM-EELS. Dans un deuxième temps, afin de comparer les mécanismes dedélithiation chimique et électrochimique, l’insertion et la cyclabilité des ions Li+ et Na+ ont étécaractérisées en demi-cellules lithium et sodium. Bien que la signature électrochimique des matériauxLiFePO4 et NaFePO4 soit différente, les performances en termes de capacité restituée ou de tenue enpuissance s'avèrent similaires. Enfin, l'insertion électrochimique des ions Li+ et Na+ au sein d'unepoudre comportant des défauts structuraux a été caractérisée par DRX Operando durant un cycle decharge / décharge effectué à régime lent. Ces analyses ont révélées que la co-insertion cationiques'effectue via une solution solide de type LixNayFePO4 (0<x+y<1). / As part of the development of Na-ion technology, NaFePO4 compound, chemical equivalent of theattractive LiFePO4 material, would be a promising option facing possible lithium shortage. However,olivine-type LiFePO4 and NaFePO4 display different structural and electrochemical behaviors duringcationic insertion. This thesis presents an analysis of the (de)insertion mechanisms of Li+ and Na+ ionswithin olivine-type FePO4 by chemical and electrochemical means. Samples of LiFePO4 weresynthesized by two different methods (hydrothermal and precipitation), then chemically delithiated bydifferent processes. In a first step, structural analysis (XRD) associated with nuclear analyses enabledfollowing the reaction kinetics. We have pointed out that the presence of grain boundaries, resultingfrom the heat treatment, strongly limits the delithiation kinetics. The analysis of the evolution of thecoherency domains enabled us to propose an original "Shrinking Core" type delithiation mechanismwith a core of LiFePO4, observed by HRTEM and STEM-EELS. In a second step, in order to comparechemical and electrochemical mechanisms, insertion and cyclability of Li+ and Na+ were characterizedin lithium and sodium half-cells. Although the electrochemical signature of LiFePO4 and NaFePO4materials is different, the performances in terms of restored capacity or power capability are similar.Finally, electrochemical insertion of Li+ and Na+ in a powder comprising structural defects wascharacterized by operando XRD, during a charge / discharge cycle performed at low rate. Theseanalyses revealed that the cationic co-insertion takes place via a solid solution LixNayFePO4(0<x+y<1).