Through the use of transmission electron microscopy and infrared spectroscopy, hydrous components have been identified as hydroxyl and free water (H2O) in elongate garnet of ultrahigh-pressure eclogite from the Dabie Mountains, eastern China. The H2O 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.

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