Mantle olivines contain small amounts of hydrogen, structurally bound as hydroxyl, and constitute a possible reservoir for water in the mantle. The SIMS analyses showed the hydrogen concentration (10 to 60 parts per million H2O by weight) and the correlation of hydrogen with monovalent and trivalent cations. The content varied with equilibration temperature and pressure of the host rocks. Since the content reflects pre-eruptive hydrogen conditions in the mantle, it is an important clue to understanding rheological feature and magmatic process in the mantle.
