High-pressure phase transitions of kalsilite and related potassium bearing aluminosilicates

抄録

Phase behaviours of kalsilite and its related potassium bearing aluminosilicates (orthoclase and leucite) have been investigated in the pressure region between 120 and 300kbar and at about 1, 000°C in a diamond-anvil press coupled with laser heating. Kalsilite, similar to leucite, has been found to decompose into a mixture of the hollandite-type KAlSi₃O₈ plus a proposed high-pressure form of KAlO₂. The transition was observed at loading pressures greater than 170kbar, and it may be accompanied by a 46% increase in the zero-pressure density. Results of this study show that the hollandite-type KAlSi₃O₈ is the only so-far-known potassium bearing silicate which is stable under the lower mantle conditions.