EQUILIBRIUM PHASE DIAGRAM OF THE SYSTEM NaAlSiO4-KAlSiO4-SiO2-H2O at PH2O=5kb

The phase relations of the undersaturated part of the system Ne-Ks-Q-HO at P=5kb aredetermined in this paper, and the liquidus maximum (NeKsQ, 715℃) on the field boundary betweenalkali-feldspar and nepheline was first found by the authors. In the system Ne-Ks at P=5kb, thefact that the solidus intersects the nepheline-kalsilite solvus means that the field boundary between nephe-line and kalsilite extends from the side line and forms a "ternary" invariant point at NeKsQand630℃. The paths of crystallization of K-rich liquids at high pressure can be applied to explain thecrystallization processes of natural alkali rocks which are rich in KO.