Stability of Hydrous Minerals and Water Reservoirs in the Deep Earth Interior

This chapter summarizes water storage capacities in hydrous phases and nominally anhydrous minerals in the deep mantle. Water has significant effects on the phase boundaries of the phase transformations of the mantle minerals and can explain some topography of the 410 and 660km seismic discontinuities. There are several electrical conductivity studies of wadsleyite and ringwoodite to determine the water content in the mantle transition zone, since electrical conductivity is very sensitive to the hydrogen contents in minerals. The mantle transition zone has a high water storage capacity due to high water solubility in its major constituents, wadsleyite and ringwoodite, and stores significant amount of water at least locally. Hydrous phase H, MgSiO2(OH)2, and its solid solution with isostructural phase δ-AlOOH store water in the lower mantle, and they transport water into the bottom of the lower mantle by slab subduction.