Fluids are associated with a wide range of physical and chemical processes in the Earth, including transporting and concentrating important ore elements such as Cu, Au, Zn, and Pb. Significant amounts of fluid may be generated as a result of dehydration or decarbonation reactions, and the volatile content of a magma is directly linked to the explosivity of eruptions. In most cases, small amounts of the fluids involved in the formation or alteration of rocks are trapped within minerals in the form of fluid inclusions. These fluid inclusions may be studied to understand the composition and pressure and temperature of the original fluid involved in the geologic process of interest, however, an understanding of the composition of the fluid as well as how the fluid behaves under changing pressure and temperature conditions is essential to reconstruct the fluid evolution path based on data obtained from fluid inclusions. Several analytical techniques are involved in the study of fluids, including fluid inclusion microthermometry and Raman spectroscopy. Microthermometry is the heating/cooling of fluid inclusions to observe and record temperatures of phase changes which, in turn, are used to determine properties such as salinity (based on the freezing point depression of liquid), or density based on the temperature at which all phases within the fluid inclusion homogenize to a single phase. Raman spectroscopy is a non-destructive analytical technique that measures the vibrational frequency of molecules in a given material. The Raman spectral properties of fluids act as a "fingerprint" of the chemical species within the fluid and serve to identify both the presence of chemical species, such as H2O, N2, CO2, and CH4, and the density of the fluid. Microthermometric and Raman spectroscopic experiments involving synthetic fluid systems are necessary to elucidate the pressure-volume-temperature-composition (PVTX) and Raman spectral behavior of the fluid systems, which then aids in the study and characterization of natural fluids. In chapter 1, the partitioning of NaCl and KCl between coexisting immiscible fluid phases during boiling is experimentally determined at temperatures and pressures relevant to magmatic-hydrothermal systems using synthetic fluid inclusions. The partitioning behavior is then combined with literature data to calculate the Na/K ratio of the original silicate melt phase in a magma body before the exsolution of a fluid phase. In chapter 2, we explore the Raman spectral behavior of N2, CO2, and CH4 in pure, single-component systems from PT conditions corresponding to the liquid-vapor curve to elevated temperatures and pressures, and relate the changes in the spectral behavior to changes in the bonding environment of the molecules through intermolecular attraction and repulsion. In chapter 3, the observations and relationships determined for pure fluids and described in chapter 2 are used to explore the Raman spectral properties of N2, CO2, and CH4 in the N2-CO2-CH4 ternary system and the manner in which the spectral behavior of each component in the system varies with changing temperature, pressure, molar volume, and fugacity. / Doctor of Philosophy / Water and other fluids play an important role in the formation of mineral deposits that are the source of the many metals, such as copper, silver, gold, and others, that are needed by a modern technological society. In addition, water and other fluids affect the way rocks behave under stress and can promote earthquakes and influence the explosivity of volcanoes. When minerals in a rock form, often small amounts of the fluid will be trapped within the minerals in the form of fluid inclusions. These fluid inclusions contain samples of the fluid involved in the geologic process of interest and can be studied using a variety of methods to determine the chemistry and the temperature and pressure conditions of rock formation. Two of the many methods used to study fluid inclusions are microthermometry and Raman spectroscopy. Microthermometry involves heating and/or cooling the fluid inclusion while it is being observed on a microscope, and this method can be used to determine the salinity of water in the inclusion and the fluid density. The density of the fluid may then be used to determine the pressure or temperature at which the fluid was encapsulated into the rock, and by extension the temperature and pressure at which the rock formed. Raman spectroscopy is an analytical technique in which a rock or fluid is illuminated using a laser. The laser light interacts with the rock or fluid and gains or loses energy, and this change in energy serves as a "fingerprint" to identify the molecules in the rock or fluid. The Raman spectrum can also be used to determine fluid density because the signal generated when the laser interacts with the fluid depends on the density of the fluid. Experiments on fluids at carefully-controlled laboratory conditions are necessary to understand the behavior of fluids trapped in natural samples. In chapter 1, the preference of sodium and potassium to go into either a liquid or a gas phase during boiling at high pressures and temperatures is determined. In chapter 2, gases containing only nitrogen, carbon dioxide, or methane are studied using Raman spectroscopy and the changes in the Raman behavior of the gases with changing pressure and temperature are related to molecular interactions. In chapter 3, the results from chapter 2 are used to understand the Raman behavior of nitrogen, carbon dioxide, and methane in gas mixtures as pressure and temperature are changed and how this relates to the interactions of the molecules.

This work is focused on study of fluid inclusions in quartz and carbonate gangue of selected Ag-Pb-Zn vein type deposits of the Blanice graben. Samples from localities Ratibořské Hory, Hradové Střimelice and Zvěstov were studied. Geology and mineralogy of the localities mentioned above were described. Optic microthermometry, which allows to determine concentration of salts in enclosed solutions and to identify possible temperatures of fluid inclusion formation, was the main method used during the studies. The results of microthermometrical measurements of the samples showed, that salinity of fluid inclusions ranges from 1,4 to 11 wt. % eq. NaCl. Paragenetically first stages of mineralization formed from fluids of higher salinity (6 - 11 wt. % eq. NaCl), later stages formed from fluids of low salinity. Only aqueous fluids were detected, which can be approximated by H2O-NaCl, ±MgCl2, and ±FeCl2 systems. Temperatures of homogenization of primary inclusions range mostly from 150 to 200 řC. Actual temperatures of mineralization can be higher, but probably not more than by 50 řC.

Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition (PTX) of the environment of formation, hence understanding PTX properties of the fluid inclusions is required. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of geologic events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Synthetic fluid inclusions trapped in the one-fluid-phase field are formed at a known and relatively constant temperature. However, microthermometry of synthetic fluid inclusions often reveals Th variations of about ± 1- 4 degrees Centigrade, or one order of magnitude larger than the precision of the measurement for an individual inclusion. The same range in Th was observed in well-constrained natural FIAs where the inclusions are assumed to have been trapped at the same time. The observed small variations are the result of the effect of the fluid inclusion size on the bubble collapsing temperature. As inclusions are heated the vapor bubble is getting smaller until the pressure difference between the pressure of the vapor and the confining pressure reaches a critical value and the bubble collapses. It was observed that smaller inclusions reach critical bubble radius and critical pressure differences at lower temperatures than larger inclusions within the same FIA. Homogenization temperature (Th) variations depend on many factors that vary within different geological environments. In order to determine minimum and acceptable Th ranges fro FIAs formed in different environments we investigated several geologic environments including sedimentary, metamorphic, and magmatic hydrothermal environments. The observed minimum Th ranges range from 1-4 degrees Centigrade and acceptable Th range from 5-25 degrees Centigrade. The variations are mostly caused by the fluid inclusion size, natural temperature and pressure fluctuations during the formation of an FIA and reequilibration after trapping. Fluid inclusions containing H₂O-CO₂-NaCl are common in many geologic environments and knowing the salinity of these inclusions is important to interpret PVTX properties of the fluids. A technique that combines Raman spectroscopy and microthermometry of individual inclusions was developed to determine the salinity of these inclusions. In order to determine the salinity, the pressure and temperature within the inclusion must be known. The pressure within the inclusions is determined using the splitting in the Fermi diad of the Raman spectra of the CO₂ at the clathrate melting temperature. Applying the technique with to synthetic fluid inclusions with known salinity suggests that the technique is valid and useable to determine salinity of H₂O-CO₂-NaCl fluid inclusions with unknown salinity. / Ph. D.

La nucléation, la croissance et la dissociation des hydrates de gaz au voisinage d’un ménisque eau – gaz dans des capillaires de verre sont étudiées par vidéo-microscopie et spectroscopie Raman à température, pression, mouillabilité et géométrie du substrat contrôlées. Dans ce travail, deux hydrates simples de structure I (hydrate de CO2 et hydrate de CH4), deux hydrates simples de structure II (N2 et Cyclopentane) et un hydrate double (cyclopentane + CO2) sont examinés. En baissant la température bien au-dessous de 0 °C, i.e., sous un fort sous-refroidissement, tous ces hydrates, excepté l’hydrate de cyclopentane, nucléent sans que la glace soit formée. L’hydrate forme d’abord une croûte polycristalline sur le ménisque eau-molécule invitée (guest). Ensuite, il se propage rapidement à partir de ce ménisque dans l’eau sous forme de fibres ou dendrites et le long de la paroi capillaire sous forme d’une croûte fine et polycristalline appelée ”halo”. Sur un substrat hydrophile, ce halo avance du côté de la phase invitée, alimenté par une couche d’eau entre le halo et la paroi interne du capillaire. Symétriquement, sur un verre hydrophobe (traité au silane), le halo et une couche de la phase invitée se propagent du côté eau. Aucun halo n’est observé sur un substrat de mouillabilité intermédiaire. La croissance et la morphologie du halo d’hydrate et l’épaisseur de sa couche sous-jacente d’eau (ou de phase invitée) dépendent fortement du sous-refroidissement. Grâce au faible volume du capillaire utilisé et à la vitesse rapide de refroidissement, la limite de métastabilité de l’hydrate de CO2 est approchée pour différentes pressions et mouillabilité. Le régime des faibles sous-refroidissements est également étudié : une nouvelle morphologie d’hydrate de CO2 est découverte pour des sous-refroidissements inférieurs à 0,5 °C, constituée d’un cristal creux, générée au niveau du ménisque eau – guest et avançant du côté guest le long du verre, alimenté par une épaisse couche d’eau prise en sandwich entre le verre et ce cristal. Une nouvelle procédure est proposée pour détermination des conditions d’équilibre des hydrates de gaz dans une large plage de température et de pression, y compris l’extension métastable de la ligne triphasique (eau liquide – hydrate – guest) jusqu’à des températures bien inférieures à 0 °C. Enfin, les mécanismes par lesquels le CO2 et le cyclopentane agissent en synergie pour former l’hydrate de structure II sont discutés. / The nucleation, growth and dissociation of gas hydrate across a water – gas meniscus in glass capillaries are investigated by means of video-microscopy and confocal Raman spec- troscopy under controlled temperature, pressure, cooling rate and substrate wettability and geometry. Structure I and II hydrates are examined, with the following guest molecules: CO2, CH4, N2, cyclopentane, and cyclopentane + CO2. By lowering the temperature well below 0 °C, i.e., under strong subcooling, all these hydrates but the cyclopentane hydrate nucleate without forming ice on the liquid water – guest meniscus, which is rapidly covered with a polycrystalline crust. The hydrate then propagates from this meniscus as fast-growing fibers or dendrites in bulk water and as a thin polycrystalline crust, or halo, along the capillary wall. On water-wet substrates, this halo advances on the guest side of the meniscus, fed by a water layer sandwiched between the halo and glass. Symmetrically, on guest-wet (silane-treated) glass, the halo and an underlying guest layer grow on the water side of the interface. No halo is observed on intermediate-wet glass. The hydrate halo growth and morphology and the thickness of its underlying water (or guest) layer strongly depend on subcooling. Thanks to the small capillary volume and the rapid temperature descent, the metastability limit of CO2 hydrate is approached for various pressures and substrate wettabilities. The low subcooling regime is investigated as well: a novel CO2 hydrate morphology is discovered for subcoolings below 0.5 °C, which consist of a hollow hydrate crystal originating from the water – guest meniscus and advancing on the guest side along glass, fed by a thick water layer sandwiched between glass and this crystal. A new procedure is proposed to determine gas hydrate dissociation conditions in a large temperature and pressure range, including the metastable extension of the three-phase (liquid water – hydrate - guest) down to temperatures well below 0 °C. Finally, the mechanisms by which CO2 and cyclopentane synergistically act to form the structure II hydrate are discussed.

De fortes concentrations d'40Ar radiogénique en excès ont été découvertes sur des remplissages quartzeux de fissures alpines par la méthode de datation conventionnelle K - Ar. Cet argon radiogénique en excès se localiserait préférentiellement dans les inclusions fluides du quartz. La caractérisation thermo-barométrique de ces inclusions indique qu'elles ont piégé des fluides associés au métamorphisme régional. Leur analyse K - Ar a montré des rapports isotopiques 40 Ar /36Ar d'argons anormaux à l'échelle régionale. Le piégeage de ces fluides s'effectuerait au début du refroidissement général, juste après le pic du métamorphisme. La datation conventionnelle des phyllosilicates fournit des résultats hétérogènes et plus vieux que l'âge géologique possible. Mais, si l'on considère que l'âge K - Ar d'un phyllosilicate métamorphique correspond aussi au début du refroidissement, il y a identité entre l'âge de ces phyllosilicates et le moment du piégeage des inclusions fluides des quartz. Ceci autoriserait la simple soustraction de l'excès d'argon radiogénique contenu dans les quartz de celui mesuré dans les phyllosilicates. De façon surprenante, bien que ce procédé ne puisse être considéré comme totalement valide, les âges corrigés calculés correspondent à l'âge supposé du métamorphisme. Le fait caractéristique majeur des unités étudiées dans ce travail, est leur relative"imperméabilité". Tout événement métamorphique affectant ces séquences, provoque la libération de l'argon radiogénique préalablement accumulé. Cet argon ne peut s'échapper totalement et reste partiellement dissout dans les fluides formés durant le métamorphisme. Ces fluides sont donc enrichis en 40Ar radiogénique, et piégés dans "tous les minéraux", y compris les quartz, pendant leur croissance.