Abstract
Hydrous magnesium silicate phase D plays a key role in the transport of water from the upper to the lower mantle via subducted slabs. Here we report pressure dependence hyperfine and lattice parameters of FeAl-bearing phase D up to megabar pressures using synchrotron nuclear forward scattering and X-ray diffraction in a diamond anvil cell at room temperature. FeAl-bearing phase D undergoes a two-stage high-spin to low-spin transition of iron for Fe2+ at 37–41 GPa and for Fe3+ at 64–68 GPa. These transitions are accompanied by an increase in density and a significant softening in the bulk modulus and bulk velocity at their respective pressure range. The occurrence of the dense low-spin FeAl-bearing phase D with relatively high velocity anisotropies in deep-subducted slabs can potentially contribute to small-scale seismic heterogeneities in the middle-lower mantle beneath the circum-Pacific area.
Original language | English |
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Pages (from-to) | 6411-6420 |
Number of pages | 10 |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 121 |
Issue number | 9 |
DOIs | |
Publication status | Published - Sep 1 2016 |
Keywords
- lower mantle
- phase D
- spin transition of iron
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science