Critical phenomena and granatization of water-containing eclogite at P = 3,7-4,0 GPa, T = 1000-1300 °C

Abstract

The phase relationships have been experimentally studied at eclogitization of basalts and the melting of H2O‑containing eclogite in the basalt-H2O system at P = 3,7-4,0 GPa, T = 1000-1300 C. It is established that the phase relationships depend on temperature. The formation of a supercritical fluid-melt occurs at T = 1000 C, P = 3,7 GPa, conversion eclogite-granatite occurs at T = 1000-1100 C, P = 3,9 GPa, partial melting of eclogite with the formation of Na-alkali silicate melt and clinopyroxenite restite at 1150 C and 1300 C. The supercritical fluid-melt has a high reactivity, resulting in the formation of megacrists of garnet, its enrichment with Ti, the replacement of garnet with clinopyroxene, the formation of ilmenite, K‑containing amphibole, the conversion of eclogite into garnetite as a result of mass crystallization of garnet.