THE ROLE OF WATER IN THE DEEP UPPER MANTLE AND TRANSITION ZONE: DEHYDRATION OF STAGNANT SLABS AND ITS EFFECTS ON THE BIG MANTLE WEDGE
E. Ohtania, D. Zhao b
a Institute of Mineralogy, Petrology, and Economic Geology, Tohoku University, Sendai 980-8578, Japan
b Department of Geophysics, Tohoku University, Sendai 980-8578, Japan
Keywords: Diffusion, hydrogen, mantle, subduction slabs
Pages: 1073-1078
Abstract
Mineral physics data related to the deep dehydration of stagnant slabs are summarized. The hydrogen diffusion in minerals of the mantle transition zone is not fast enough to homogenize the transition zone on the geological time scale, and hydrogen is expected to be unevenly distributed there. The hydrous fluid formed in the transition zone tends to percolate into shallower depths (410 km) to form gravitationally stable hydrous magmas at the base of the upper mantle. We need further studies on the relation of intraplate volcanism above the stagnant slab and deep dehydration, because we expect the geochemical fingerprints of deep dehydration to be quite different from those of shallow dehydration from the subducting slabs.
|
