Cluster of water molecules in garnet from ultrahigh-pressure eclogite

Abstract

Through the use of transmission electron microscopy and infrared spectroscopy, hydrous components have been identified as hydroxyl and free water (H 2 O) in elongate garnet of ultrahigh-pressure eclogite from the Dabie Mountains, eastern China. The H 2 O occurs as clusters of water molecules and as hydroxyl in garnet; the clusters of water molecules are interpreted to have promoted elongation of garnet through hydrolytic weakening. The presence of hydrous species in ultrahigh-pressure garnet from continental-crust protoliths indicates that such protoliths are able to carry water into the mantle during the subduction of continental lithosphere.