Boreholes NG1 and NG2 were drilled on the farm Nooitgedacht 406 KQ to intersect the lower Critical and lower Zones of the western Bushveld Complex. The aim of this study is to describe the textural features and chemical characteristics of the olivine-bearing rocks in the intersections, as determined by petrographic studies, XRF analysis and microprobe analysis. The olivine-bearing rocks are dunites, harzburgites and olivine pyroxenites. They comprise olivine and orthopyroxene, with minor chromite, clinopyroxene and plagioclase, and their textures vary between adcumulate, mesocumulate and poikilitic. The sequence intersected can be broadly correlated with that in the eastern Bushveld Complex. Of the whole-rock inter-element ratios, the MMF (MgO)/[MgO+FeO])ratio is the clearest indicator of cyclicity. The olivine-rich rocks are more primitive than the associated rocks, and seem to become more primitive with height in most intervals. The plagioclase in the olivine-bearing rocks is unusually sodic in corrposition, having a maximum Na₂0 content of 8.12%. A comparison of olivine and plagioclase compositions with those in other intrusions has revealed that the only other major intrusion with sodic plagioclase is the Kiglapait intrusion of Canada. In the Kiglapait intrusion the sodic plagioclase occurs in conjunction with fayalitic olivine as opposed to the forsteritic variety of this study. Chemical variations in the rocks sampled indicate that periodic replenishment of the magma from which the rocks crystallised must have occurred. In some of the olivine-bearing intervals where little fractionation is evident, replenishment seems to have been continuous. In other intervals fractionation appears to have continued uninterrupted for significant periods, prior to rejuvenation by fresh influxes of magma.

Cette thèse concerne une étude de la gazéification du Miscanthus X giganteus (MXG). Le MXG présente de nombreux avantages (rendement, pérenne, peu d’entretien, facile à récolter…) qui lui permet d’être un candidat en terme d’énergies renouvelables. Il a fait l’objet de nombreux travaux dans le domaine agricole, mais notre étude est la première concernant sa gazéification afin de produire un gaz de synthèse. La première partie de ce travail concerne l’étude de la gazéification, effectuée dans un réacteur à lit fluidisé en présence de catalyseurs à base d’olivine. Les résultats obtenus lors des différentes campagnes d’essais ont donné d’excellents rendements en gaz (CO + H2) comparables à d’autres biomasses. La caractérisation des catalyseurs, par DRX et MEB a montré un bon comportement de l’olivine (tenue mécanique, régénération), de son côté le Niolivine a permis de meilleurs résultats. L’analyse des goudrons, par IRTF et GC/MS a montré essentiellement la présence de HAP, majoritaire à haute température (>800°C). La deuxième partie de cette étude porte sur le vaporeformage du méthyl-naphtalène, représentatif de la composition des goudrons issus de la gazéification du MXG. Le vaporeformage a été effectué en utilisant les mêmes catalyseurs qu’en gazéification. A côté de la réaction principale, cette étude a permis de mettre en évidence l’importance des réactions secondaires comme la réaction du gaz à l’eau. De plus, ces tests ont confirmé la bonne efficacité du Ni-olivine pour l’élimination des goudrons. Un mécanisme général a été proposé, mettant en jeu le rôle déterminant de l’oxygène radicalaire issu de la décomposition de l’eau / This study presents the gasification of Miscanthus X giganteus (MXG). The MXG presents many advantage (high yield, perennial crop, easily harvesting…) so it’s a good candidate in terms of renewable energy sources. Several works have been carried out in the agricultural field, but this study is the first dealing with gasification in order to produce a syngas. The first part of this work concerns the study of gasification in fluidized bed reactor with olivine-based catalysts. The results obtained in different tests gave a good gas yield (CO + H2) comparable to others biomass. The catalyst characterisation by XRD and SEM is related to the properties of olivine (mechanical strength, recycling), while Ni-olivine gave much better results. Tar analysis by FTIR and GC/MS showed the presence of mainly PAH at high temperature (>800°C).The second part of this study deals with the steam reforming of methylnaphthalene which is representative of the tar composition issued from the MXG gasification. The steam reforming performed with the same catalysts as in the case of gasification. In addition to the main reaction, this study allowed us high lights the existence of secondary reaction such as the water gas shift reaction. Moreover these tests confirmed the high efficiency of Ni-olivine for tar removing. An overall mechanism was proposed with the important role of catalytic oxygen issued from water decomposition

The subsurface igneous biome contains a vast portion of Earth's total biomass, yet we still know so little about it. Igneous environments such as iron-rich ocean crust and lava tubes may also host analogs to chemolithotrophically-driven life on other planets, so studying life in this biome is essential to understanding how life may survive on other planets. In this study, three igneous surface and subsurface environments were investigated for microbial preference for olivine, microbial physiologies and phylotypes present on olivine, and microbial growth on olivine in the laboratory via iron oxidation. These environments include a subseafloor borehole drilled into the ocean crust basalt basement, a lava tube with perennial ice, and a trio of Columbia River basalt-hosted freshwater terrestrial habitats. The subseafloor borehole (IODP Hole 1301A) is situated on the eastern flank of Juan de Fuca Ridge (JFR) and was used in the first long-term deployment of microbial enrichment flow cells using osmotically-driven pumps. The flow cells contained igneous minerals and glasses, for which cell density and microbial abundances were evaluated. Total cell density and viable oligotrophs were highest for Fe(II)-rich olivines. Organotrophic bacterial isolates were capapble of iron oxidation and nitrate reduction, and grew on olivine in the laboratory. Putative neutrophilic iron oxidizers were also isolated from igneous riparian and cave environments in northwest and central Oregon. Isolated bacteria from all three environments were capable of chemolithotrophic growth with olivine and oxygen or nitrate in the laboratory. Bacteria isolated from river basalt were putatively capable of producing alteration textures on olivine surfaces in culture. Microbial life in the igneous subsurface preferentially attach to Fe²⁺-rich minerals, which suggests that life in the subsurface is heterogeneously distributed. The isolation of oligotrophic iron oxidizers that grow on olivine suggests that olivine supports a chemolithotrophic subsurface community based on primary productivity via iron oxidation. This generation of biomass on olivine surfaces creates organic carbon-rich coated mineral surfaces that may support a more complex community. The identification of Mars analogs living in Oregon lava tubes and the discovery that iron oxidizers may produce biosignatures on olivine surfaces are key findings that may provide the foundation for a new chapter in the search for life on Mars.

Indiana University-Purdue University Indianapolis (IUPUI) / This dissertation has three main focuses: (1) identify the distribution of a new rock type (Mg-spinel lithology) on the Moon and explore the likely petrogenesis of Mg-spinel; (2) investigate the presence of olivine in the crater central peaks and analyze the sources of olivine; (3) determine the compositional variations of lunar crust with depth, and establish a new model to describe the structure of the lunar crust.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 315-334. / Ph.D.

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Water and other volatiles (e.g. CO2, H2, CH4, etc.) are crucial components on Earth that ensure the habitability of the planet and play an important role in many geological processes. Small aliquots of these fluids can be preserved in the geological record as fluid inclusions and can provide valuable information about the physical and chemical environment in which they formed. The ocean is the largest water reservoir on the Earth's surface, and seawater participates in important water-rock reactions such as hydrothermal alteration of the ocean floor, a process that is currently in the spotlight for hypotheses on the origin of life, as it is an environment where generation of abiotic carbohydrates occur. The ocean chemistry varied in the geologic past to reflect major changes in the intensity of weathering, rates of midocean ridge hydrothermal discharge, changes in the climate and atmospheric CO2 concentration, and also played an important part in mass extinction events. Understanding the history of Earth's ancient oceans may hold the key to answer some of the important questions about the future of the Earth. Today, oceans hold valuable resources, such as offshore basalt formations which have been considered for submarine CO2 sequestration to mitigate greenhouse gas emissions associated with global warming. In the chapters of this dissertation, the reader will be presented with studies using fluid inclusions to advance our knowledge about the chemical evolution of seawater and reaction kinetics involving CO2, seawater and olivine – an abundant mineral in the oceanic lithosphere. Chapter I "Redox conditions in Late Permian seawater based on trace element ratios in fluid inclusions in halite from the Polish Zechstein Basin" describes application of a new redox proxy for paleo-seawater that involves analysis of redox-sensitive trace elements (e.g., Fe, Mn, U, V, Mo) in ancient seawater trapped as fluid inclusions in halite. Chapter II "Partitioning behavior of trace elements during evaporation of seawater" investigates the behavior of trace elements during the evaporation of seawater. This information is required to interpret trace element data from fluid inclusions in halite. In Chapter III "In situ monitoring of the carbonation of olivine under conditions relevant to carbon capture and storage using synthetic fluid inclusion micro-reactors: Determination of reaction rates", fluid inclusions are used as micro-reactors to monitor the reaction progress of olivine carbonation in situ and in real time at elevated temperatures (50-200 °C) and pressures using non-destructive analytical techniques such as Raman spectroscopy. / Doctor of Philosophy / Many geological processes on Earth involve water and other volatiles (e.g. CO2, H2, CH4, etc.) which are crucial components that ensure the habitability of the planet. These fluids can be preserved in the geological record in the form of fluid inclusions which are small aliquots of fluids trapped in minerals that provide information about the physical and chemical environment in which they formed. The majority of water on the Earth's surface is stored in the oceans. Seawater participates in important water-rock reactions, one of which is the hydrothermal alteration of the ocean floor. This reaction is in the spotlight currently because it represents an environment where generation of abiotic carbohydrates occur, giving rise for hypotheses about the origin of life on Earth. The chemical composition of seawater varied in the geologic past reflecting major changes in the intensity of weathering, discharge rate of midocean ridge hydrothermal systems, climate, and atmospheric CO2 concentration, and affected the survival of various marine species throughout Earth's history. For example, periodic extensions of oxygen minimum zones in the oceans played an important part in mass extinction events in the last 488 million years. Understanding the history of Earth's ancient oceans may hold the key to answer some of the important questions about the future of the Earth. Today, oceans hold valuable resources, such as offshore basalt formations which have been considered for submarine CO2 sequestration to mitigate greenhouse gas emissions associated with global warming. This dissertation explores ways to use fluid inclusions to advance our knowledge about the chemical evolution of seawater in the past and present, and the reaction of seawater with CO2 and olivine – an abundant mineral in the oceanic lithosphere – to facilitate long-term storage of CO2 in minerals to decrease the rate of global warming. Chapter I describes the application of a new redox proxy for paleo-seawater that involves analysis of redox-sensitive trace elements (elements whose solubility changes significantly as the oxidation state changes, such as Fe, Mn, U, V, Mo) in ancient seawater trapped as fluid inclusions in halite. The results suggest that trace element abundances in fluid inclusions in halite vary in response to redox changes in seawater and provide a potential redox proxy. Chapter II investigates the behavior of trace elements during the evaporation of seawater. This information is required to interpret trace element data from fluid inclusions in halite. The results of this study indicate that some elements remain in the water during evaporation of seawater (e.g. Li, B, Mo, U), while others are partially removed by precipitation of various mineral phases (e.g. Ba, Sr, Cs, Rb, Mn, V) as seawater evaporates. In Chapter III, fluid inclusions are used as micro-reactors to monitor the reaction progress of olivine carbonation in situ and in real time at elevated temperatures (50-200 °C) and pressures using non-destructive analytical techniques such as Raman spectroscopy. The results highlight that this reaction occurs rapidly, which makes it an ideal candidate for safe storage of CO2 by commercial CO2 injection projects in mafic and ultramafic rocks.

Silicate minerals are the most common mineral group in the earth's crust so it is not surprising that their weathering reactions dominate the chemistry of many earth surface processes. This project used forsterite as a model system to identify the important factors that affect silicate mineral dissolution rates and grain lifetimes in the weathering environment. I determined an empirical rate law for forsterite dissolution of forsterite in oxalic acid solutions: based on a series of 124 semi-batch reactor experiments over a pH range of 0 to 7 and total oxalate concentrations between 0 and 0.35 m at 25°C. These experiments show that oxalate-promoted dissolution rates depend upon both oxalate concentration and pH. I propose a reaction mechanism in which a hydrogen ion and an oxalate ion are simultaneously present in the activated complex for the reaction that releases H4SiO4 into solution. By analogy, I propose that water acts as a ligand in the absence of oxalate. I also ran 82 batch reactor experiments in magnesium and sodium sulfate and magnesium and potassium nitrate solutions. These experiments show that ionic strength up to 12 m, log mMg up to 4 m, and log mSO4 up to 3 m have no effect on forsterite dissolution rates. However, decreasing aH2O slows forsterite dissolution rates. The effect of decreasing dissolution rates with decreasing aH2O is consistent with the idea that water acts as a ligand that participates in the dissolution process.Forsterite dissolution rate data from previously published studies were combined with results from my experiments and regressed to produce rate laws at low and high pH. For pH < 5.05 or and for pH > 5.05 or I then developed a diagram that shows the effect rate-determining variables on the lifetime of olivine grains in weathering environments using these rate laws. / Ph. D.

Serpentinization is a complex set of hydration reactions, where olivine and pyroxene are replaced by serpentine, magnetite, brucite, talc and carbonate minerals. Serpentinization reactions alter chemical, mechanical, magnetic, seismic, and hydraulic properties of the crust. To understand the complicated nature of serpentinization and the linkages between physical and chemical changes during the reactions, I performed flow-through laboratory experiments on cylindrically cored samples of ultramafic rocks. Each core had a well-mated through-going tensile fracture, to investigate evolution of fracture permeability during serpentinization. The samples were tested in a triaxial loading machine at an effective pressure of 30 MPa, and temperature of 260°C, simulating a depth of 2 km under hydrostatic conditions. Fracture permeability decreased by one to two orders of magnitude during the 200 to 340 hour experiments. Electron microprobe and SEM data indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture, and chemical analyses of sampled pore fluids were consistent with dissolution of ferro-magnesian minerals. The rate of transformation of olivine to serpentine in a tensile fracture is calculated using the data on evolution of fracture permeability assuming the fracture permeability could be represented by parallel plates. Assuming the dissolution and precipitation reactions occur simultaneously; the rate of transformation at the beginning of the experiments was ~ 10-8-10-9 (mol/m2s) and decreased monotonically by about an order of magnitude towards the end of the experiment. Results show that dissolution and precipitation is the main mechanism contributing to the reduction in fracture aperture. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems may be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses may be required to maintain fluid circulation. Another set of flow through experiments were performed on intact samples of ultramafic rocks at room temperature and effective pressures of 10, 20 and 30 MPa to estimate the pressure dependency of intact permeability. Porosity and density measurements were also performed with the purpose of characterizing these properties of ultramafic rocks. The pressure dependency of the coefficient of matrix permeability of the ultramafic rock samples fell in the range of 0.05-0.14 MPa-1. Using porosity and permeability measurements, the ratio of interconnected porosity to total porosity was estimated to be small and the permeability of the samples was dominantly controlled by microcracks. Using the density and porosity measurements, the degree of alteration of samples was estimated. Samples with high density and pressure dependent permeability had a smaller degree of alteration than those with lower density and pressure dependency. / Ph. D.