<p> Phase equilibrium relations were determined in the system NaAlSiO8-NaAlSiO4-H2O on a P-T projection in the P-T range 0.5-10Kb and 150°-900°C, and on three isobaric (2Kb, 5.15Kb and 7. 32Kb) T-X projections. The T-X stability field of analcite determined in this study has a relatively large distorted pentagonal shape. The petrogenetic problem of analcite is fully discussed. On the composition join NaAlSiO4-H2O, the phase relation is not binary for the transition: nepheline hydrate I = nepheline + H2O; there exists a narrow three-phase zone for the transition. The true P-T curve was determined in terms of a ternary univariant reaction: nepheline hydrate I+ analcite = nepheline + H2O. Another univariant reaction (zeolite species P. = analcite + nepheline hydrate I+ H2O) was found at 2Kb/215°C and 5.15Kb/235°C and determined on a P-T projection. In the system NaAlSi3O8-SiO2-H2O, albite contains a maximum of about 5 Wt.% silica in solid solution at 5.15Kb/670°C.</p> <p> The equilibrium compositions of various univariant phases were determined essentially by phase boundary-location on several isobaric T-X projections. Three singular points were determined: two of them are approximately located at 0.8Kb/390°C and 9.4Kb/475°C on a univariant curve (N-h I+ Anl =Ne+ H2O). The other one is approximately located at 6Kb/655°C on the (Ab) univariant curve.</p> </p> A simple method for determining H2O-solubility in melts was developed and applied to the study of the system NaAlSi3O8-NaAlSiO4-H2O. Using this method, solubility data are simply obtained as by-products of the experimental runs made for the investigation of the phase equilibria. The amount of water required to make an H2O-saturated melt (from the total amount of water in the original charge) is taken as the dissolved water in the melt; the solubility value is corrected by determining the amount of moisture originally absorbed in the starting powder. The method is generally applicable to the determination of H2O-content in any hydrous phase. The H2O-solubility in a melt is not too sensitive to a variation in anhydrous composition of the melt (~ 6±1 Wt.% H2O at 2Kb and ~11±1 Wt.% H2O at ~5Kb in the range of compositions Ab100Ne0-An40Ne60). H2O-solubility in the (Anl) and (Ne) univariant melts was determined up to l0Kb (H2O contents: 4.7 Wt.%/1.1Kb and 850°C, 6.2 Wt. %/2Kb and 804°C, 10.8 Wt. %/5.2Kb and 672°C, l2.2 Wt.% /6.6Kb and 655°C, 13.2 Wt. %/7.3Kb and 652°C and 14(?) Wt.% /10Kb and 632°C ). The origin of water bubbles in quenched hydrous glasses is essentially attributed to the exsolution of the dissolved water in melts upon quenching.</p> <p> The sequence of P-T curves around a quaternary invariant point (~5Kb and ~635°C) in the system NaAlSiO4-KAlSiO4-SiO2-H2O was theoretically discussed. The most probable four P-T diagram types are proposed, one of which is expected to be the real one.</p> <p> Phase relations in the system NaAlSi3O3-NaAlSiO4-H2O are theoretically discussed up to ~15Kb. The discussion is largely based on the equilibrium compositions of invariant phases approximately estimated from data presented in Parts 1 and 2. Six invariant points are examined. Two of them, I5 and I6, have been predicted to occur; I5 is inferred to be located at ~13Kb/~500°C where five phases Jd, N-h I, Anl, Ne and V coexist, and I6 to be located at ~0.5Kb/-375°C where Ab, Ne, Anl, N-h I and V coexist. The phase relations around the other four are partly modified. The maximum P-T stability field of analcite is deduced. The stability field of solidus analcite is extremely large whereas that of liquidus analcite is very much limited. The maximum stability field of liquidus analcite is a small triangular area defined by three invariant points I1 (5.15Kb/657°C), I2 (11Kb/650°C) and I4 (12.5Kb/575°C).</p> / Thesis / Doctor of Philosophy (PhD)

L’évolution des assemblages pétrologiques avec l’augmentation de pression et de température est couramment perçue à l’équilibre et figée dans le temps. Le développement des sources synchrotron de rayons X permet à présent de mesurer in situ et en temps résolu les vitesses de transformations minéralogiques à haute pression (HP), haute température (HT). Cette thèse présente l’utilisation de cette technologie dans 2 contextes géologiques. (i) Le potentiel sismogène de la déstabilisation des minéraux hydratés dans les plaques en subduction est vérifié. Les cinétiques de déshydratation du talc, de la phase à 10Å et de l’antigorite ont été mesurées à HP-HT en système clos. Nous avons identifié que l’antigorite se déshydrate en passant par un stade intermédiaire. Toutes les vitesses de libération de fluides associées sont plus rapides que la déformation visqueuse des roches et sont donc compatibles avec le déclenchement de rupture. (ii) Les cinétiques de transition olivine-ringwoodite ont été déterminées dans la loupe de costabilité pour des compositions riches en Fe. Elles mettent en évidence une amorphisation partielle de l'olivine en début de transformation. Cela pourrait perturber de manière significative la vitesse des ondes sismiques lors de leur passage au niveau de la zone de transition mantellique. Par ailleurs, les temps caractéristiques de réaction et la réduction conséquente de la taille des grains, indiquent qu’une telle transition de phase induit une atténuation sismique importante. Ces résultats expérimentaux in situ HP-HT révèlent des mécanismes originaux de transition de phase et contribuent ainsi à une meilleure compréhension des modèles géodynamiques / The evolution of petrological assemblies with increasing pressure and temperature is commonly perceived at equilibrium and fixed within time. The development of X-ray synchrotron sources now enable to measure in situ, time-resolved rates of mineralogical transformations at high pressure (HP), high temperature (HT). This thesis presents the application of this technology in two geological settings. (i) The seismogenic ability of breakdown of hydrated minerals within the subducting slab is checked. The dehydration kinetics of talc, 10Å phase and antigorite were measured at HP-HT in a closed system. We have found that antigorite dehydrates through an intermediate stage. All associated rates of released fluids are faster than the viscous deformation of rocks and are therefore compatible with the trigger of rupture. (ii) The kinetics of olivineringwoodite transition were determined within the co-stability loop for Fe-rich compositions. They show a partial amorphization of olivine at the beginning of the transformation. This could significantly affect the velocities of seismic waves when crossing the mantle transition zone. Moreover, the characteristic times of this reaction and the substantial reduction in grain size, indicate that such a phase transition may induce a significant seismic attenuation. These in situ HP-HT experimental results reveal novel mechanisms of phase transition and thus contribute to a better understanding of geodynamic models