High-pressure phase transformations of albite, jadeite and nepheline

Abstract

Phase behaviors of albite, jadeite and nepheline have been studied in the diamond-anvil press employing YAG laser heating from about 100 to 280 kbar and at about 1000°C. Incorporating earlier work, the sequences of phase transformations with increasing pressure are as follows: [Display omitted] where the percentages are the decreases in zero-pressure volume from one to the other. Both NaAlSi 3O 8 hollandite and NaAlSiO 4 (CaFe 2O 4-type) are new sodium aluminosilicates. The latter is the most likely host for sodium in the earth's lower mantle. High-pressure phases or phase assemblages revealed in albite and jadeite by static experiments are poorly defined by shock-wave studies of albitite and jadeite to about 900 and 1200 kbar respectively.