<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)