Precise determinations of the equilibria kyanite <--> sillimanite and kyanite <--> andalusite and a revised triple point for Al₂SiO₅ polymorphs

Investigates the equilibria kyanite ??? sillimanite and kyanite ??? andalusite using the piston-cylinder apparatus to refine the phase relationships among Al2SiO3 polymorphs. Experiments at the US Geological Survey constrain the kyanite ??? sillimanite equilibrium to 14.3-14.6, 11.4-11.7, 9.5-10.0, and 6.0-6.5 kbar at 1000, 900, 800, and 600??C, respectively. At UCLA, experiments limite the equilibrium to 14.4-14.6, >12.9, 11.8-12.2 and 7.0-8.0 kbar at 1000, 950, 900, and 700??C, respectively. The equilibrium kyanite ??? andalusite was reversed between 7.4 and 8.0 kbar, 800??C at UCLA. -from Authors