A series of hydrothermal experiments at 2000 bars have been conducted in order to investigate the systematic relation between biotite composition on the join phlogopite-annite and the composition of pyrrhotite. In an attempt to bracket the sulfide-silicate compositional pairs, three layers within a single capsule were used: 1) pyrite + Fe-rich biotite in the top, 2) sanidine + magnetite in the middle, and 3) troilite + Mg-rich biotite in the bottom. At the conclusion of a bracketing run, the biotite in the top was found to have become more Mg-rich and the biotite in the bottom was found to have become more Fe-rich while a pyrrhotite of apparently homogeneous composition was found throughout the capsule. Five equilibrium determinations at 700°C have been located: (N)_Po = 0.928, (Fe/(Fe + Mg))_Bi = 0.496 0.936 0.530 0.945 0.541 0.947 0.581 0.950 0.585 The data demonstrate that biotites tend to become more Mg-enriched with increasingly sulfur-rich compositions of pyrrhotite. This study can be applied to natural systems in which a pyrrhotite-biotite-magnetite-K-spar assemblage is present. Since sulfides have been observed to re-equilibrate at lower temperatures while the composition of the Fe-Mg silicates still mirror the conditions of metamorphism, silicate compositions can potentially be used as a measure of f_S₂ and f_O₂. From this, one can attempt to calculate the properties of the vapor during the alteration of the silicates and ore genesis. / Master of Science

Weathering of biotite supplies nutrients such as K+ and weathers into vermiculite/montmorillonite or kaolinite, which have varying influences on soil properties and characteristics. This study was conducted to determine if the weathering mechanisms of biotite are controlled by temperature, or if other factors, such as vegetation or leaching intensity dominantly influence the weathering process. A column study investigation was conducted to assess the influence of different acids, simulated rainfall rates, surface horizons, and temperature on the weathering and cation release of biotite. A field investigation was also conducted on the clay mineral fraction of soils in Grayson County, VA formed above biotite granite. Selected acid leachates did show a greater Al+3, Fe+2, and Si+4 release with organic acids (ascorbic, citric, and fulvic) than that with hydrochloric acid treatment at high leachate rates. Loss of K+ is greater with ascorbic acid than all other acids at high leachate rates. Leachate rate interaction with low temperature was an influencing factor in cation release. Field investigations revealed a greater weathering intensity at high elevations evidenced by; (i) higher clay content, (ii) a dominance of 2:1 minerals, (iii) greater surface area in the upper horizons, (iv) minerals indicative of later stages in the biotite weathering mechanism, and (v) precipitation of halloysite in the C horizon at the high elevation site where temperature is lower and a suspected higher leaching intensity occur. / Master of Science

The relationships between ferric iron content and the P-T-fH₂ conditions of formation were examined for two biotite compositions: annite (K₂Fe₅Al₄Si₅O₂₀(OH)₄) and siderophyllite (K₂Fe₆Al₂Si₆O₂₀(OH)₄). The synthesized phases were annealed at fixed hydrogen fugacities using both the solid oxygen buffering technique of Eugster (1957) and the H₂ buffering technique of Shaw (1967). Resulting hydrogen fugacities ranged from 0.004 bars (at T = 400°C, P_T = 2 kb) to 51 bars (at T = 750°C, P_T = 1 kb). Ferrous iron contents of the annealed biotites were determined by wet chemical analyses. Total iron was determined by microprobe analyses to be equal to the stoichiometric values. The data confirm the predictions of Hazen and Wones (1972, 1978) that: 1) There is a structural limit imposed upon the Fe³⁺ content of annite due to the misfit between the octahedral and tetrahedral layers. This misfit requires a minimum of 11% Fe³⁺ in annite. 2) The steric misfit in annite can be corrected by a substitution of Al^vi + Al^iv for Fe^vi + Si^iv, so that there is no Fe³⁺ in siderophyllite at high hydrogen fugacities. A model relating Fe³⁺/Fe²⁺ ratios, fH₂, and T is proposed. The model accounts for the amount of Fe³⁺ needed to correct the steric misfit in annite and allows for variation in Fe, Al, and Mg contents among biotites. A simple oxidation-reduction reaction is used to relate changes in the non-steric ferric iron to hydrogen fugacity and temperatures for the Fe-Mg-Al biotites. The equilibrium constant for the reaction can be expressed as: (1) log K= 3607.2/T - 4.47 where, depending on composition, K is expressed as follows and R is a constant proportional to the U structurally required iron. (2) Al^vi/0.3 + Mg/0.72 ≥ 1, K = Fe³⁺/Fe²⁺ fH₂^1/2 (Al^vi + Mg ≥ 1) (3) Al^vi/0.3 + Mg/0.72 > 1, K = Fe³)/Fe²⁺ - (1-Al^vi-MG) fH₂^1/2 (Al^vi + Mg < 1) (4) Al^vi/0.3 + Mg/0.72 < 1, K = [Fe³⁺/(Fe²⁺ - (1-Al^vi-MG)) -0.185] fH₂^1/2 (Al^vi + Mg < 1) / Master of Science

It is generally believed that oxidation of ferruginous biotites proceeds by the oxybiotite substitution: Fe²⁺ + OH = Fe³⁺ + 0²⁻ + ½H₂ The role of this mechanism as an equilibrium process in hydrothermal systems was studied for two compositions, annite, KFe₃,AISi₃O₁₀(OH)₂, and siderophyllite, KFe₂․₅AI₂,Si₂․₅O₁₀(OH)₂ , an annite with one Tschermak’s substitution. These biotites were synthesized from oxide mixes and then annealed in Shaw-type bombs under controlled hydrogen fugacities. Run conditions were chosen near the maximum thermal stability limit and within the biotite stability field along lines of constant hydrogen fugacity. Yields range from 93-96% for annite and 95-98% for siderophyllite. Sanidine is the major impurity identified along with minor amounts of fayalite or magnetite. The ferrous iron contents of the biotites were determined by the wet chemical technique developed by Whipple (1974). Total iron as FeO, as well as K₂O, AI₂O₃, and SiO₂ were determined with the electron microprobe, and the biotite compositions were found to be close to the stoichiometry of the ideal end members. Ferric iron was determined by the difference between total and ferrous iron. Hydrogen contents were measured by heating the sample in vacuo, reducing all hydrogen species released, and determining the moles of 1-1, volumetrically. The hydrogen contents of the biotites are low (<3% H₂O) and do not vary with hydrogen fugacity for a given composition. The ratio of ferrous to total iron was found to be directly proportional to the hydrogen fugacity regardless of temperature. For hydrogen fugacities of 1 to 100 bars, this ratio varies from 0.76 to 0.90 for the annites and from 0.86 to 0.96 for the siderophyllites. The amounts of ferrous iron and the nearly constant difference in ferrous iron content between the two compositions is consistent with the proposed instability of a completely reduced annite due to structural misfit between the octahedral and tetrahedral layers (Hazen and Wones, 1972). The annite stability field as presented by Eugster and Wones (1962) can thus be contoured with lines of constant ferrous iron content. The curves mimic the trends of the solid oxygen buffers which suggests that the mechanism of oxidation is similar for both. Moreover, when mineral formulas are calculated on the basis of 12 anions there is an excess of atoms in the octahedral sites. This excess varies directly with the hydrogen fugacity of the runs. Recalculation of the formulae on the basis of seven octahedral and tetrahedral cations results in a variable number of anions (11.6-12.0) that is positively correlated with the amount of ferrous iron. This, together with the lack of variation of the hydrogen contents in response to changing oxidation state, suggests that the oxybiotite substitution is not the controlling mechanism in hydrothermal biotite oxidation. The data support the following as an alternative reaction: Fe²⁺ + ¼O₂ = Fe³⁺ + ½O²⁻ In this model the reduced biotites have anion vacancies that are filled as oxidation proceeds without changing the hydrogen content. The data also suggest that other anion vacancy producing reactions may be occurring in addition to the reaction above. / Master of Science

The interplay between geology and biology has shaped the Earth during billions of years. Microbe-mineral interactions are prime examples of this interplay and underscore the importance of microorganisms in making Earth a suitable environment for all forms of life. The present thesis takes an interdisciplinary approach to obtain an integrated understanding of microbe-mineral interactions. More specifically it addresses how the composition and distribution of biogenic weathering agents (siderophores) differ with regard to soil horizon and mineral type in situ, what siderophore type soil microorganisms produces under laboratory conditions, what role microbial surface attachment plays in mineral weathering reactions and what central roles and applications siderophores have in the environment. Podzol, the third most abundant soil in Europe, and most abundant in Scandinavia, was chosen for a field experiment, where three minerals (apatite, biotite and oligoclase) were inserted in the organic, eluvial and upper illuvial soil horizons. The study started with an investigation of the siderophore composition in the bulk soil profile and on the mineral surfaces (paper I), which was followed by a study of the siderophore producing capabilities of microorganisms isolated from the soil profile under laboratory conditions (paper II). Subsequently, a study was done on the impact of microbial surface attachment on biotite dissolution (paper III). Finally, the roles of siderophores in nature and their potential applications were reviewed (paper IV). The major findings were that the concentration of hydroxamate siderophores in the soil attached to the mineral surfaces was greater than those in the surrounding bulk soil, indicating that the minerals stimulate the microbial communities attached to their surfaces to produce more siderophores than the microorganisms in the bulk soil. Each mineral had a unique assemblage of hydroxamate siderophores, that makes the mineral type one of the main factors affecting siderophore composition in the natural environment. Siderophore production varied between the microbial species originating from different soil horizons, suggesting that the metabolic properties of microbes in deep soil horizons function differently from those at upper soil horizons. Microbial surface attachment enhanced the biotite dissolution, showing that attached microbes has a greater influence on weathering reactions in soil than planktonic populations. In conclusion, our findings reflected that the complicated relationship between microorganisms and mineral surfaces reinforces the central theme of biogeochemistry that the mineral controls the biological activity in the natural environments. However, the importance of these relationships to the biogeochemical systems requires further investigation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: In press.</p><p> </p>

A scapolite-hornblende-biotite schist from the Grenville province of the Canadian Shield has been analysed for Tl by an atomic absorption technique with a high sensitivity. K, Rb and some major oxides were determined by wet chemistry. Tl, K/Rb, K/Tl and Tl/Rb were compared to several other rocks and for this report were found to be 432ppb, 429, 4.85x10³ and 88.4x10⁻³ respectively. These values are similar to those quoted for other rocks. / Thesis / Bachelor of Science (BSc)

No description available.

Kyanite is generally considered to be a product of metamorphism. This study investigates a set of kyanite-bearing pegmatites that represent a case in which kyanite crystallized directly from melt. The pegmatites intrude spinel orthopyroxene hornblendite in the Buncombe Pegmatite District in the Eastern Blue Ridge of North Carolina. One site was studied in detail and survey studies of two other occurrences were made. The pegmatites contain quartz, large euhedral crystals of plagioclase, biotite, and kyanite, as well as apatite, muscovite, tourmaline, and microscopic primary sillimanite. Potassium feldspar is notably absent. One site, the Thomas Mine, was examined in detail in order to determine the mode of occurrence for these rocks. Excavation revealed pegmatite with two texturally and mineralogically distinct zones. Biotite-rich rocks surrounding the pegmatite indicate strongly potassic alteration of the host hornblendite. Trace element data obtained for kyanite and biotite from the pegmatite show clear patterns related to chemical fractionation of these components during crystallization. Major element geochemistry of the pegmatite and host ,I rocks are consistent with magmatic intrusion. Reaction of the pegmatite melt with the host rocks led to the formation of large amounts of biotite, and depleted the melt in potassium. The remaining melt became saturated in aluminum silicate and crystallized kyanite and sillimanite. Wallrock assemblages, fluid inclusions in pegmatite quartz, the coexistence of kyanite and sillimanite as primary phases, and geothermobarometry on nearby unaltered rocks all indicate conditions of formation of approximately 600-800 MPa and 625-675°C, near those of peak metamorphism for the region. / Master of Science

In order to assess the importance of particle size on elemental composition, structure, morphology, and charge characteristics of 2:1 micas, mechanically produced clay separates were analyzed by; electron probe microanalysis (EPMA), transmission electron microscopy (TEM), thermogravimetry, specific surface area analysis, and ion exchange. Books of biotite and muscovite were reduced to clay size « 2.0 μm) particles by mechanical comminution, then further fractionated into coarse (0.2-2.0 μm), medium (0.08-0.2 μm), and fine (< 0.08 μm) clay sizes. Composition of the clay size micas was particle size dependent, compositional changes being smaller for the medium and coarse clays. Grinding produced significant losses of interlayer K, decreased crystallinity, but increased water content as particle size decreased. The medium and coarse clays maintained coherent basal diffractions, whereas, significant peak broadening of x-ray diffraction maxima was observed for the fine clays. Diffracted peak broadening was due to the reduced crystallite size and the semirandom orientation of lath shaped particles. Specific surface area, adsorbed water. and structurally coordinated water increased as particle size decreased. Specific surface areas were determined by adsorption of molecular nitrogen, at liquid nitrogen temperatures. The increased water contents were measured by thermogravimetric analysis. An increase in CEC of the muscovite clays was detected with decreasing particle size, increasing solution pH, and increasing ionic strength. Assignment of specific exchange capacities for the three clays was confounded by AI hydrolysis and depressed solution pH. / Master of Science

Les interactions organo-minérales contrôlent la stabilisation de la matière organique du sol. Les nanominéraux, résultant de l'altération continue des minéraux, précipitent à partir d'espèces ioniques à leur surface. Les derniers travaux de simulation en laboratoire se sont focalisés sur les nanophases de Fe et Al. Dans ce travail, des simulations en laboratoire ont été réalisées sur les processus d'altération de la biotite et les néoformations résultantes, après hydrolyse d’espèces dissoutes d'un système Si Fe Al Mg et K, en présence et en absence de C. La structure des phases a été caractérisée par TEM- EDX et Fe-EXAFS.En l'absence de C, des nanominéraux amorphes de 10-60nm sont formés, la composition étant contrôlée par le pH en fin d'hydrolyse. A pH4.2 et 7, leur composition est dominée par Fe, dont la polymérisation est perturbée par Al Si Mg et K. Inversement, à pH5, la polymérisation du Fe est limitée par la précipitation de grandes quantités de Si. En présence de C, les complexes organo-minéraux synthétisés sont des particules amorphes de 2-200nm. Leur taille augmente avec la teneur croissante en C jusqu'à un ratio métal/C de 1. La précipitation engendre 2 familles: (1) les petites particules chimiquement similaires à la solution de lixiviat; (2) les plus grosses fortement contrôlées par la teneur de C. La composition de ces dernières est dominée par Si lorsque C est faible, et par Fe lorsque C est élevé. Le changement de chimie entre les particules plus petites et plus grandes ainsi que le rôle de Si sont importants mais souvent négligés. Ainsi, ces résultats éclairent l'effet des variations de C sur l'affinité des espèces inorganiques dans les systèmes naturels / Organo-mineral interactions, due to the high reactivity of nanominerals, play a major role in soil organic matter stabilization. Nanominerals, which are the result of the continuous alteration of minerals, precipitate from ionic species at the mineral solution interface. In literature, only Fe and Al get emphasis with regard to batch-synthesized nanomineral studies. In this work, laboratory simulations were carried out on the post biotite alteration processes and the resulting neoformations after hydrolysis of the dissolved species from a Si Fe Al Mg and K system, in the presence and absence of C. New phases were characterized by TEM-EDX and EXAFS at the Fe K-edge.In C absence, 10-60nm sized amorphous nanominerals are formed whose composition is controlled by pH at the end of the hydrolysis. For pH4.2 and 7 phases, composition is dominated by Fe, whose polymerization is hindered by Al, Si, Mg and K. Conversely, at pH5, the overall presence of Fe is counteracted by precipitation of high amounts of Si. In C presence, precipitates are amorphous 2-200nm sized particles. This size increases with increasing C presence until a molar Metal:C=1. Precipitation resulted into two distinct size ranges. Smaller particles chemically resemble the leachate solution, while for larger particles it is influenced by C concentration. Composition of larger particles is dominated by Si at low C compositions while by Fe at higher ones. Interesting is the change in chemistry between smaller and larger particles as well as the role of Si often overlooked in other studies. Therefore, these results emphasize on effect of C variations on affinity of inorganic species in natural systems.