CONVERSION OF KYANITE (AL2SIO5) TO CORUNDUM (AL2O3) AND SIO2

Abstract

Ecologite, consisting of kyanite garnet, clinopyroxene and accessory rutile, coesite and diamond was repeatedly subjected to high dynamic loads, under which it underwent considerable changes, manifested in granulation, loss of structure, recrystallization and melting. We studied the nature of kyanite alteration in ecologite. Summing up the data on natural systems and experimental work, we draw the following conclusions. 1. Diamond-bearing coesite-kyanite and kyanite eclogites were formed at high temperatures (1050° to 1480°C) and pressures (< 3 GPa). 2. Their constituent minerals underwent repeated thermodynamic transformations. 3. Kyanite breaks down into its oxides at 1000 to 1500°C and 10 GPa via complex intermediate phases.