Clinopyroxene with Si < AlIV in the Join CaFeAlSiO6-CaTiAl2O6

Kosuke Onuma and Masahide Akasaka
Department of Geology and Mineralogy, Hokkaido University, Sapporo, 060, Japan

Summary: Unusual clinopyroxenes were synthesized in the study of the join CaFeAlSiO6-CaTiAl2O6 in air at I atm. Clinopyroxene solid solution, hibonite solid solution, X-phase, perovskite, and corundum are present, and at subsolidus temperatures the clinopyroxene singlephase field extends up to about 19 wt% CaTiAl2O6. The CaTiAl2O6 component in the clinopyroxene however increases beyond the clinopyroxene single-phase field and attains 23 wt%. These clinopyroxene solid solutions are extremely poor in SiO2 and extremely rich in Al2O3, Fe2O3, and TiO2, and more than half of tetrahedral sites are occupied by AlIV, contravening the aluminium avoidance principle.

Mineralogical Magazine; September 1980 v. 43; no. 331; p. 851-856; DOI: 10.1180/minmag.1980.043.331.05
© 1980, The Mineralogical Society
Mineralogical Society (