The presence of water can dramatically influence the chemical and physical properties of minerals that comprise the Earth's mantle. In order to understand these effects itis important to identify the phases in which water may exist under mantle conditions. High-pressure experiments on the stability of hydrous minerals likely to be present in the Earth's mantle provide constraints on the distribution of water in the mantle. In this article, the significance of hydrated subducting slab is evaluated as a water carrier, transporting water from the earth's surface into the subduction zone, where it isreleased to the overlying mantle wedge through the breakdown of hydrous minerals. The capacityt store and transport water in the hydrated part of the subducted slab is controlledby the pressure-temperature stability of hydrous phase assemblages in bulk compositions of peridotite, sediment, basalt, and harzburgite.
