Single-crystal refinement of (Fe,Al)-bearing bridgmanite structure at high pressure
Abstract
Bridgmanite (Bgm), the most abundant mineral in the Earth's lower mantle, can contain approximately 10% Fe and 7% Al in its crystal structure. The valence and spin states of Fe and its coupled substitution with Al can have significant effects on physical and chemical properties of bridgmanite in the lower mantle and thus our understanding of the geophysical and geochemical processes of the region. Here we conducted single-crystal X-ray diffraction measurements on high-quality single-crystal (Fe,Al)-bearing bridgmanite up to ~50 GPa in a wide-opening diamond anvil cell equipped with Almax-Boehler anvils at 13-BMC of the Advanced Photon Source. Refinements of the high-resolution single-crystal diffraction spots (~230 reflections for each given P) reveal detailed lattice parameters, atomic positions, bond lengths and shapes of the A and B cationic sites, and octahedral tilting angles. Our results show that the A-O and B-O bond lengths of the pseudo-dodecahedral and octahedral sites decrease linearly with increasing pressure, and longer A-O bonds shrink faster than shorter A-O bonds. Analysis of the bond lengths shows an intensified A site lattice distortion of bridgmanite at higher pressures. Additionally, the dissolution of Fe can significantly enhance octahedral tilting and local distortion of the pseudo-dodecahedral A site. These results are used to help understand recent research results on electronic structures of iron in bridgmanite and its elastic properties in the lower mantle.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR22A..01W
- Keywords:
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- 3919 Equations of state;
- MINERAL PHYSICS;
- 3924 High-pressure behavior;
- MINERAL PHYSICS;
- 3939 Physical thermodynamics;
- MINERAL PHYSICS;
- 3994 Instruments and techniques;
- MINERAL PHYSICS