Abstract
Spin and valence states of iron in single-crystal bridgmanite (Mg0.89Fe0.12Al0.11Si0.89O3) are investigated using X-ray emission and Mössbauer spectroscopies with laser annealing up to 115 GPa. The results show that Fe predominantly substitutes for Mg2+ in the pseudo-dodecahedral A site, in which 80% of the iron is Fe3+ that enters the lattice via the charge-coupled substitution with Al3+ in the octahedral B site. The total spin momentum and hyperfine parameters indicate that these ions remain in the high-spin state with Fe2+ having extremely high quadrupole splitting due to lattice distortion. (Al,Fe)-bearing bridgmanite is expected to contain mostly high-spin, A-site Fe3+, together with a smaller amount of A-site Fe2+, that remains stable throughout the region. Even though the spin transition of B-site Fe3+ in bridgmanite was reported to cause changes in its elasticity at high pressures, (Fe,Al)-bearing bridgmanite with predominantly A-site Fe will not exhibit elastic anomalies associated with the spin transition.
Original language | English |
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Pages (from-to) | 6952-6959 |
Number of pages | 8 |
Journal | Geophysical Research Letters |
Volume | 43 |
Issue number | 13 |
DOIs | |
Publication status | Published - Jul 16 2016 |
Keywords
- bridgmanite
- high pressure
- lower mantle
- mineral physics
- spin and valence states
- spin transition
ASJC Scopus subject areas
- Geophysics
- Earth and Planetary Sciences(all)