Quaternary (Ca-Fe-Mg-Mn) garnet: Displaced equilibrium experiments and implications for current garnet mixing models
Koziol, Andrea M.
European Journal of Mineralogy Volume 8 Number 2 (1996), p. 453 - 460
published: Apr 26, 1996
manuscript accepted: Oct 31, 1995
manuscript received: Dec 6, 1994
ArtNo. ESP147050802008, Price: 29.00 €
Abstract The mixing properties of a spessartine-rich garnet composition (Alm64.5Prp10.5SpS25) with grossular garnet have been determined by phase-equilibrium experiments at 1000 and 900 °C and 8 to 13 kilobars (kb) in the assemblage garnet-plagioclase-kyanite-quartz. The addition of 2 to 4wt.% Li2MoO4 promoted equilibration. The results indicate that the addition of up to 21 mol.% spessartine to almandine-rich Ca-Mg-Fe garnets does not significantly perturb the activity coefficient of grossular relative to Ca-Mg-Fe garnet and therefore does not affect pressures calculated with the GASP (garnet-alumino-silicate-quartz-plagioclase) geobarometer. Limited data do not allow retrieval of Margules parameters for pyrope-spessartine mixing