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6CCVD Research

Single-crystal X-ray diffraction on the structure of (Al,Fe)-bearing bridgmanite in the lower mantle

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2023-07-07
JournalAmerican Mineralogist
AuthorsSuyu Fu, Stella Chariton, Yanyao Zhang, Takuo Okuchi, Vitali B. Prakapenka
InstitutionsKyoto University, The University of Texas at Austin
Citations1

Abstract

Section titled ā€œAbstractā€

Abstract Here we have performed single-crystal X-ray diffraction (SCXRD) experiments on two high-quality crystal platelets of (Al,Fe)-bearing bridgmanite (Mg0.88Fe0.0653+Fe0.0352+Al0.03)(Al0.11Si0.90)O3 (Fe10-Al14-Bgm) up to 64.6(6) GPa at room temperature in a Boehler-Almax type diamond-anvil cell. Refinements on the collected SCXRD patterns reveal reliable structural information of single-crystal Fe10-Al14-Bgm, including unit-cell parameters, atomic coordinates, and anisotropic displacement parameters. Together with Mƶssbauer and electron microprobe analyses, our best single-crystal refinement model indicates that the sample contains ~6.5 mol% Fe3+, 3.5 mol% Fe2+, and 3 mol% Al3+ in the large pseudo-dodecahedral site (A site), and ~11 mol% Al3+ in the small octahedral site (B site). This may indicate that Al3+ in bridgmanite preferentially occupies the B site. Our results show that the compression of Fe10-Al14-Bgm with pressure causes monotonical decreases in the volumes of AO12 pseudo-dodecahedron and BO6 octahedron (VA and VB, respectively) as well as the associated A-O and B-O bond lengths. The interatomic angles of B-O1-B and B-O2-B decrease from 145.2-145.8Ā° at 4.2(1) GPa to 143.3-143.5Ā° at 64.6(6) GPa. Quantitative calculations of octahedral tilting angles (Š¤) show that Š¤ increases smoothly with pressure. We found a linear relationship between the polyhedral volume ratio and the Š¤ in the bridgmanite with different compositions: VA/VB = -0.049Ī¦ + 5.549. Our results indicate an increased distortion of the Fe10-Al14-Bgm structure with pressure, which might be related to the distortion of A-site Fe2+. The local environmental changes of A-site Fe2+ in bridgmanite could explain previous results on the hyperfine parameters, abnormal lattice thermal conductivity, mean force constant of iron bonds and other physical properties, which in turn provide insights into our understanding on the geophysics and geochemistry of the planet.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
  1. 1991 - Evolution of the distortion of perovskites under pressure: An EXAFS study of BaZrO3, SrZrO3 and CaGeO3 [Crossref]
  2. 2019 - Deep magma ocean formation set the oxidation state of Earthā€™s mantle [Crossref]
  3. 2007 - On the polyhedral volume ratios V A/V B in perovskites ABX3 [Crossref]
  4. 2009 - Mƶssbauer modeling to interpret the spin state of iron in (Mg,Fe)SiO3 perovskite [Crossref]
  5. 2006 - New diamond cell for single-crystal X-ray diffraction [Crossref]
  6. 2012 - Effect of chemistry on the compressibility of silicate perovskite in the lower mantle [Crossref]
  7. 2010 - X-ray diffraction and Mossbauer spectroscopy of Fe3+-bearing Mg-silicate post-perovskite at 128-138 GPa [Crossref]
  8. 2011 - Effects of the Fe3+ spin transition on the properties of aluminous perovskiteā€”New insights for lower-mantle seismic heterogeneities [Crossref]
  9. 2013 - High pressure single-crystal micro X-ray diffraction analysis with GSE_ADA/RSV software [Crossref]
  10. 2004 - Equations of state of six metals above 94 GPa [Crossref]

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