Stability relations of grossularite and hydrogrossularite at high temperatures and pressures

Abstract

The equilibrium relations between hydrogrossularite + quartz and anorthite + wollastonite + water have been determined to 15,500 bars and 810 degrees C. by means of the "simple squeezer" high-pressure apparatus. There is a continuous solid-solution series from grossularite, 3CaO.Al ₂ O ₃ .3SiO ₂ , through hydrogrossularite to hibschite, 3CaO.Al ₂ O ₃ .2SiO ₂ .2H ₂ O. The composition of hydrogrossularite, above 500 degrees C. and in equilibrium with quartz, is determined almost entirely by temperature. Grossularite is stable above 780 degrees and 15 kilobars H ₂ O pressure in the presence of quartz.