Detta arbetes mål har varit att hjälpa företaget SMA Mineral att utreda de rödamissfärgningar som allt oftare påträffats i deras marmor. Rapporten är högst visuellpå mikroskopisk nivå, och avhandlar vad missfärgningarna beror på. Provmaterialhar undersökts och karakteriserats mineralogiskt och geokemiskt, och typer avmissfärgningen har identifierats. Även en förklaring över de geologiska processersom ger upphov till missfärgningarna har formats. De metoder som använts underarbetet är egna undersökningar med komplement av en litteraturstudie påavhandlingar som handlar om just missfärgningar i marmor. Provmaterial harinhämtats från tre olika platser i gruvan, dessa har sågats och tvättats och några haräven slipats och polerats. Detta material har sedan använts genom hela arbetet.Optiska observationer med hjälp av binokulär har dokumenterats digitalt, detta gavinformation om att missfärgningen ligger mellan karbonatkristallerna, och sannolikthar varit av en mer löslig karaktär i ett tidigare skede. Utifrån detta kategoriserasmissfärgningen till två olika typer. Typ A förekommer som asymmetriska,koncentrerade fläckar på och mellan kristaller men till synes oregelbundet, medantyp B följer mikrofina sprickor och kan ses i bandade regelbundna formationer imaterialet. Järnrika kristaller upptäcktes i missfärgningarnas omedelbara närhet ochhär skapades hypotesen om att det är järnoxider som orsakat föroreningarna. ÄvenSEM-analyser har gjorts för att kunna identifiera den geokemiska sammansättningenav missfärgningarna. Resultaten från SEM- och XRF-analyserna bekräftade tesen, dåjärn förekom i varierande grad i samtliga analyser utom en. Dessutom hittadeshematit som i sig lämnar röda spår, samt ren rost i form av goetit. Ävenlitteraturstudien bekräftade att förekomster av järnrika mineral i marmor förr ellersenare kommer att orsaka missfärgningar. / The goal of this project has been to assist SMA mineral, a limestone producer, tofind the source of red discolourations found in their crystalline limestone. Thediscolouration has appeared on a more regular basis than before and is starting tobecome a problem for the company.This is a highly visual report focused on a microscopical level, that follows thestudy and finding of the origin of the red discolourations. Specimens from threedifferent locations in the quarry have been collected, then cut to proper sizes to fitthe needs for the scans and examinations suited for the project. Some of the sampleswere polished to fit the requirements of SEM. The material has been opticallyanalysed through a binocular microscope and documented with high resolutionimages. This was the first major breakthrough, since the discolouration showed tobe placed between the carbonate crystals, and appeared to have been more of asolution-like substance at some point. Based on the findings, the discolourationcould be categorised inte two types, type A appears as an irregular spotting oncrystal surfaces with a deeper red colour, whilst type B can be found in fine cracksin the material and follows a more regular pattern. Lots of minerals rich in ironwere also found in close proximity to the discolourations, which led to a hypothesisthat iron oxides might be the source of the problem. The thesis was confirmed bySEM- and XRF analyses of the material. Iron in different weight-percentages wasfound in all of the analyses except for one.The mineralogical and geochemical properties of the discolouration has beendefined, and the geological process that leads to the discolouration is explained.

Carbonate geochemistry plays an important role in understanding environmental conditions during the time of precipitation. The studies for this dissertation research were focused on carbonate precipitation and crystallization in different chemical and physical environments. The first project aimed to precipitate aragonite at low oxygen levels to identify a correlation between partitioning of trace elements and anoxic and suboxic conditions. The second study focused on the precipitation of amorphous calcium carbonate in varying magnesium concentrations to determine the identity of crystalline material after transformation of ACC. Lastly, the third project was developed to understand transformation of CaCO3 polymorphs. Specifically, whether or not geochemistry is retained from one polymorph to the next. All projects could aid in development of paleoproxies to be used for determining past environmental and climatic conditions in the past.

This dissertation includes theoretical and applied components that address the effect of coatings on rates of mineral reactions that occur in acid mine drainage (AMD) environments. The two major projects investigated how diffusion-limited transport of reactants through pore spaces in coatings on mineral grains affects the reaction rate of the underlying mineral. The first project considered the growth of gypsum coatings on the surface of dissolving limestone in anoxic limestone drains (ALD), which reduces the neutralization rate of the dissolving limestone and the subsequent effectiveness of this treatment. The second project investigated the conditions where iron oxyhydroxide coatings form on oxidizing pyrite and the potential strategies to prevent "runaway" AMD by reducing the rate of acid production to the point that the acid can be neutralized by the surrounding rocks. In both studies, experiments were conducted to measure reaction rates for the underlying minerals, as coatings grew thicker. These experimental data were fit to a diffusion model to estimate diffusion coefficients of reactants through pore spaces in coatings. These models are extrapolated to longer times to predict the behavior of the coated grains under field conditions. The experimental results indicate that management practices can be improved for ALDs and mine waste piles. For example, supersaturation with respect to gypsum, leading to coating formation, can be avoided by diluting the ALD feed solution or by replacing limestone with dolomite. AMD can be prevented if the rate of alkalinity addition to mine waste piles is faster than acid is produced by pyrite oxidation. The diffusion model developed in this study predicts when iron oxyhydroxide coatings will become thick enough that alkalinity from the surroundings is sufficient to neutralize acid produced by coated pyrite oxidation and additional alkalinity is no longer required. / Ph. D.

Fluid inclusion and mineralogical features indicative of boiling have been characterized in 855 samples from epithermal precious metals deposits along the Veta Madre at Guanajuato, Mexico. Features associated with boiling that have been identified at Guanajuato include colloform texture silica, plumose texture silica, moss texture silica, ghost-sphere texture silica, lattice-bladed calcite, lattice-bladed calcite replaced by quartz and pseudo-acicular quartz after calcite and coexisting liquid-rich and vapor-rich fluid inclusions. Most samples were assayed for Au, Ag, Cu, Pb, Zn, As and Sb, and were divided into high-grade and low-grade samples based on the gold and silver concentrations. For silver, the cutoff for high grade was 100 ppm Ag, and for gold the cutoff was 1 ppm Au. The feature that is most closely associated with high grades of both gold and silver is colloform texture silica, and this feature also shows the largest difference in grade between the presence or absence of that feature (178.8 ppm Ag versus 17.2 ppm Ag, and 1.1 ppm Au versus 0.2 ppm Au). For both Ag and Au, there is no significant difference in average grade as a function of whether or not coexisting liquid-rich and vapor-rich fluid inclusions are present. The textural and fluid inclusion data obtained in this study were analyzed using the binary classifier within SPSS Clementine. The models that correctly predicted high versus low grade samples most consistently (~70-75% of the tests) for both Ag and Au were the neural network, the C5 decision tree and Quest decision tree models. For both Au and Ag, the presence of colloform silica texture was the variable with the greatest importance, i.e., the variable that has the greatest predictive power. Boiling features are absent or rare in samples collected along a traverse perpendicular to the Veta Madre. This suggests that if an explorationist observes these features in samples collected during exploration that an environment favorable to precious metal mineralization is nearby. Similarly, good evidence for boiling is observed in the deepest levels of the Veta Madre that have been sampled in the mines and drill cores, suggesting that additional precious metal reserves are likely beneath the deepest levels sampled. / Master of Science

Le lac Saint-Augustin (Québec) est un lac montrant une eutrophisation avancée. L'eutrophisation, qui est un vieillissement accéléré d'un plan d'eau, est causée par l'apport excessif de phosphore (P) en provenance des sédiments qui sont contaminés en P et en métaux lourds. L'alimentation du lac est principalement souterraine ce qui contribue au relargage du P dans les eaux du lac. Un recouvrement actif est envisagé pour contrer le relarguage du phosphore. Ce recouvrement est constitué de calcite qui a la capacité d'adsorber le phosphore. Une étape préliminaire est envisagée afin de diminuer la teneur de phosphore dans la colonne d'eau par un traitement de coagulation/floculation avec de l'alun. Le projet de maîtrise vise à estimer la performance du recouvrement actif en essais en colonnes de grande taille. Ces essais reproduisent les conditions de terrain en laboratoire dans deux colonnes de près de trois mètres de hauteur. Les méthodes de réhabilitation y sont appliquées. Les deux colonnes sont différentes car seulement l'une des deux subit le prétraitement à l'alun à raison de 20 mg/l d'alun dans la colonne d'eau. Par contre, les deux colonnes contiennent la couche de recouvrement qui a une épaisseur de 15 cm de calcite surmontée d'une couche de 15 cm de sable (pour protéger et maintenir la calcite en place). Les essais en colonnes ont duré six mois. La calcite a montré une capacité élevée de rétention du phosphore avec une adsorption moyenne de 317 ± 106 mg de Pextractibie/kg calcite dans la colonne sans alun. La colonne avec alun n'a pas été aussi efficace, probablement à cause d'une vitesse de percolation plus rapide due à une perméabilité des sédiments trop élevée. Les conditions d'opération n'ont pas donné les résultats escomptés en terme de performance mais ont permis de démontrer le bon potentiel d'une couche de calcaire comme recouvrement actif pour contrer l'eutrophisation du lac Saint-Augustin.

[pt] A injeção de fluidos é uma prática comum na indústria de petróleo e um dos objetivos desta operação é aumentar o fator de recuperação dos campos petrolíferos. À medida que o óleo vai sendo produzido há naturalmente perda da quantidade de energia nativa, inerente ao reservatório, que manteria a continuidade da produção. Nesse ponto, fazem-se necessárias intervenções nos poços para dar continuidade à produção, lançando-se mão dos métodos de recuperação, dos quais a injeção de fluidos é um deles. As formulações desses fluidos de injeção são via de regra baseadas na utilização de água do mar (que é rica em magnésio) e em solução supercrítica com gás carbônico oriundo do próprio reservatório. Esses fluidos quando em contato com as rochas carbonáticas do pré-sal, propiciam a uma condição de ambiente químico nunca vivenciada quando este tipo de operação era realizada nos reservatórios nacionais anteriores à exploração no pré-sal. As rochas carbonáticas são reativas e a injeção de fluidos pode provocar alterações tanto na composição mineralógica quanto na composição dos fluidos produzidos. O objetivo deste trabalho é buscar evidências objetivas, identificação e quantificação, da precipitação ao longo do tempo de espécies minerais contendo magnésio formadas a partir de interações de rocha calcária (mais especificamente a calcita (CaCO3)) e fluido de injeção utilizado na recuperação avançada de poços de petróleo. Realizaram-se experimentos em que uma rocha calcária conhecida interagiu com CO2 supercrítico em meio a uma solução salina de água do mar sintética sob condições de temperatura e pressão da ordem de grandeza das encontradas em reservatórios do pré-sal. As amostras de rocha foram expostas ao fluido a 150 graus Celsius e 276 bar sob diferentes tempos de reação. Em seguida foram realizados ensaios de DRX e de composição química elementar (ICP-OES) onde ficou evidenciada a presença de magnésio na calcita após interação com o fluido de injeção, as análises por DRX não conseguiram constatar alterações na estrutura cristalina dessas calcitas pós reação. / [en] Fluid injection is a common practice in oil industry and one of its targets is to increase the recovery factor of oil fields. As the oil is being produced, there is naturally loss in the amount of the reservoir native energy to sustain production. At this point, human intervention is necessary to continue production, so recovery methods are used, of which fluid injection is one of them. These injection fluid formulations are usually based on seawater (which is rich in magnesium) and supercritical carbon dioxide solution from the reservoir itself, which in contact with the pre-salt carbonate rocks will lead to a condition of chemical environment never experienced when this operation was performed in national reservoirs prior to presalt exploration. The carbonate rocks are reactive and fluid injections can cause changes in both mineral composition and produced fluids composition. This work objectives the searching for evidences, identification and quantification, of mineral species precipitation containing magnesium from interactions of limestone (more specifically calcite (CaCO3)) and injection fluid used in the enhanced oil recovery. Experiments were performed in which a known powdered limestone rock interacted with supercritical CO2 in a saline solution of synthetic sea water under tipical conditions (temperature and pressure) found at pre-salt reservoirs. The rock samples were exposed to fluid at 150 Celsius degrees and 276 bar under different reaction times. Then, XRD analysis and elemental chemical composition (ICP-OES) tests were performed, showing the presence of magnesium in the calcite after interaction with the injection fluid, although the XRD analysis failed to verify changes in the crystalline structures of these calcites after reaction.

Thermal waters in Karlovy Vary are characterized by carbonate sedimentation in places of their emergence. These sediments contain radium. Radium bond in every type of sinter (aragonite, calcite) has been investigated experimentally by acid sinter dissolution. It has been found out, that radium can join dissoluble fraction in both sinter types . The original hypothesis that radium can bond only aragonite-type of sinter has been refuted. Additional experiments have been processed using synthetic radiobarite. Present radium in radiobarite can be partly dissoluted using acids. If radium was incorporated in radiobarite (it is known from locality Vřídlo in Karlovy Vary and elsewhere) then maybe it would be partly dissoluted in experiments.

Microbial Induced Calcite Precipitation (MICP) is an attractive alternative for a variety geotechnical ground improvement practices commonly used today and has a variety of potential applications. This research focuses primarily on its use as a soil stabilization technique using the bacteria Sporosarcina Pasteurii and a single injection point percolation method adapted from previous research in granular soils. This method, and most published data, show an inherent variability in both physical and engineering properties due to the distribution of precipitated calcite within the specimen. The focus of this research is on the quantification of the variability in shear strength parameters induced by MICP treatment in sand. Also, on the initial development of a new treatment method which aims to reduce this inherent variability and offer a more feasible option for field applications. The MICP treated soil columns were sampled at constant intervals from the injection point and then subject to direct shear testing (DST) and calcite distribution analysis. This analysis reiterates previously documented reduction in cementation as distance from injection point increases. The reduction in cementation results in reduced shear strength parameter improvements. This research also concluded a minimum of two percent mass of calcite per total mass of treated soil for significant strength improvements.

Microbially induced calcite precipitation (MICP) has been used for a number of years as a technique for the improvement of various geological materials. MICP has been used in a limited capacity in organic rich soils with varying degrees of success. Investigators hypothesized that microbially-induced cementation could be improved in organic soils by using a surfactant. Varying amounts of Sodium Dodecyl Sulfate (SDS) were added to soils of varying organic content and a mixing procedure was used to treat these soils via MICP. Treated specimens were tested for unconfined compressive strength (UCS). Results appeared to show direct relationships between SDS content and treated specimen strength although significant variability was present in the data. In addition, results also indicated that while addition of SDS during MICP treatment strengthens soil, the strengthening is likely from the formation of a calcium dodecyl sulfate (CDS) complex in which the CDS surrounds the soil in a matrix, and formation of MICP-induced calcite has very little to do with overall soil performance. As such, a new method for stabilizing loose soils dubbed ‘Surfactant-induced soil stabilization’ (SISS) was further explored by treating additional soil specimens. Samples treated using this technique showed increases in strength when compared to untreated specimens. In addition, preliminary data indicated that SISS treated specimens were insoluble. The SISS technique presents a number of advantages when compared to traditional soil stabilization techniques. In particular it should be relatively low-cost and simple to administer since its only components are SDS and calcium chloride. Additionally, these constituents are relatively more sustainable than chemicals associated with more-traditional loose soil stabilization techniques.

La concentration croissante de CO2 dans l'atmosphère et les dangers potentiels qu'elle représente pour la terre au travers des changements climatiques, l'acidification des océans et l'élévation du niveau de la mer a conduit à un certain nombre de projets qui tentent de trouver un moyen sûr et inoffensifs pour capturer et stocker le CO2 dans des formations géologiques. Une de ces tentatives se déroule actuellement en Islande à la centrale géothermique Hellisheiði, située à proximité de la capitale, Reykjavik (le projet CarbFix). Le dioxyde de carbone et d'autres gaz comme H2S, N2, H2, CH4, et Ar sont des sous-produits de l'exploitation de l'énergie géothermique et l'objectif est de stocker tout ce CO2 dans les formations basaltiques qui se situent sous Hellisheiði. Le CO2 est dissous dans un courant d'eau injecté par pompage dans des puits jusqu'à à 350 mètres de profondeur et qui s'écoule ensuite au sein d'horizons mixtes de verre basaltique et de basalte cristallin. Les roches basaltiques sont caractérisées par des teneurs élevées en cations divalents comme Mg2+, Fe2+ et Ca2+ et des vitesses de dissolution relativement rapides. L'eau acide chargée en CO2 dissout le basalte, libérant ainsi des cations qui peuvent réagir avec les ions carbonates pour former des minéraux carbonatés (magnésite, sidérite, calcite, ankérite ainsi que des solutions solides (Ca-Mg-Fe)CO3)). Si on admet que c'est la dissolution des roches basaltiques qui contrôle ce processus de séquestration du carbone, on peut en déduire que tout ce qui pourra limiter cette dissolution sera préjudiciable à l'ensemble du processus de confinement du CO2. Mon rôle dans le projet CarbFix a été d'examiner les effets de la formation de revêtements de carbonate de calcium sur la dissolution des phases primaires de basalte. Je me suis concentrée sur le verre basaltique et le clinopyroxène, diopside, afin de comparer des phases cristallines et non cristallines. En outre, une série d'expériences ont été menées pour étudier l'effet de la structure du minéral primaire sur la nucléation de calcite. Ces expériences ont été faites pour vérifier si les différentes structures de silicate conduiraient à une différente étendue de la nucléation et croissance de la calcite à la surface des silicates. Enfin, de nombreuses expériences de dissolution de verre basaltique ont été menées en présence de bactéries hétérotrophes mortes et vivantes, Pseudomonas reactans, afin de déterminer l'effet des bactéries sur la dissolution des roches dans le système des eaux souterraines du site Hellisheiði. Les expériences de dissolution de verre basaltique et de diopside ont été réalisés à 25 et 70 °C pour un pH de 7-8 dans des réacteurs à circulation alimentés en solutions de forces ioniques > 0,03 mol / kg contenant CaCl2 ± NaHCO3. Deux séries d'essais ont été menés simultanément, une série appelée essais de 'précipitations' au cours de laquelle la solution dans le réacteur était sursaturée par rapport à la calcite, et l'autre série appelée essais de 'contrôle', pour laquelle la modélisation PHREEQC ne prévoyait pas formation de minéraux secondaires. Ainsi, il a été possible de comparer les vitesses de dissolution du verre basaltique et du diopside à 25 °C avec et sans la formation de carbonate de calcium et d'autres minéraux secondaires afin d'en déduire leur effet sur les vitesses de dissolution. Les images de microscopie électronique à balayage ont montré que des quantités importantes de carbonate de calcium ont précipité au cours des expériences de 'précipitations' mais, dans le cas du verre basaltique la croissance primaire se présente sous forme gros amas discrets de calcite et d'aragonite qui ne se forment pas sur le verre lui-même. Par contre, plusieurs des cristaux de diopside ont été largement envahis par des revêtements de calcite sans aragonite décelable. Dans les deux cas, la présence de calcite / aragonite n'a pas eu d'incidence sur les vitesses de dissolution du verre basaltique et de diopside qui sont les mêmes que celles mesurées dans la série 'contrôle'. Il semblerait que la couverture discontinue et poreuse de carbonates permet aux ions des phases primaires de continuer à diffuser sans entrave à travers la couche secondaire. Pour mieux évaluer l'effet de la surface des silicates sur la nucléation de la calcite, les vitesses de dissolution de six minéraux et roches silicatés ont été mesurées à 25 °C dans des réacteurs à circulation en présence de solutions de pH ~ 9,1 sursaturées par rapport à la calcite. Les phases silicatées étaient les suivantes: olivine, enstatite, augite, labradorite, verre basaltique et péridotite. Les résultats montrent que le temps d'induction pour la nucléation de calcite et l'étendue de la couverture de carbonatée avec le temps varient selon la phase silicatée. Dans un même laps de temps l'olivine, l'enstatite et la péridotite (principalement composé d'olivine riche en Mg) étaient les plus couvertes par les précipitations de calcite, suivis par l'augite, la labradorite et enfin le verre basaltique. Toute la croissance de calcite a eu lieu sur la surface du silicate, y compris sur le verre basaltique. La cinétique favorise la croissance de calcite par nucléation sur les minéraux orthorhombiques (enstatite et olivine) par rapport aux minéraux monocliniques et tricliniques. Les plus faibles quantités de calcite ont été trouvées sur le verre qui n'a pas de structure silicatée ordonnée. Des bactéries hétérotrophes, Pseudomonas reactans ont été extraites de l'un des puits de contrôle à Hellisheiði et ont ensuite été séparées, purifiées et cultivées en laboratoire. Avec le bouillon de culture utilisé, les conditions de croissance optimales de cette bactérie sont 5-37 °C et un pH de 7,0 à 8. Cette bactérie, très commune dans l'eau et le sol, est une bonne candidate pour tester l'impact des bactéries hétérotrophes en général lors de la séquestration du CO2 dans un aquifère naturel comme en Islande. Les vitesses de dissolution du verre basaltique ont été mesurés à 25 °C dans des nouveaux réacteurs à circulation permettant d'opérer en présence de bactéries (BMFR) dans des solutions tamponnées transportant 0,1 à 0,4 g/L de bactéries mortes et 0,9 à 19 g/L de bactéries vivantes à 4 ≤ pH ≤ 10. Les résultats ont montré que la présence de ces bactéries n'avait quasiment pas d'effet effet sur la vitesse de dissolution. La conclusion générale de cette étude est que ni les revêtements de carbonate, ni les bactéries n'ont d'impact majeur sur les vitesses de dissolution des phases primaires silicatées. Ainsi, leur effet devrait être négligeable sur le processus de séquestration du CO2 sur le site Hellisheiði en Islande. Le basalte cristallin pourrait être recouvert plus rapidement en carbonate de calcium, mais le verre basaltique pourrait aussi servir de support pour la nucléation de calcite.