Abnormal Elasticity of Fe-Bearing Bridgmanite in the Earth's Lower Mantle

Suyu Fu, Jing Yang, Yanyao Zhang, Takuo Okuchi, Catherine McCammon, Hyo Im Kim, Sung Keun Lee, Jung Fu Lin

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We measured the effect of pressure on the compressional and shear wave velocity (VP, VS) as well as density of Fe-bearing bridgmanite, Mg0.96(1)Fe2+ 0.036(5)Fe3+ 0.014(5)Si0.99(1)O3, using impulsive stimulated light scattering, Brillouin light scattering, and X-ray diffraction, respectively, in diamond anvil cells up to 70 GPa at 300 K. A drastic softening of VP by ~6(±1)% is observed between 42.6 and 58 GPa, while VS increases continuously with increasing pressure. A significant reduction in Poisson's ratio from 0.24 to 0.16 occurs at ~42.6–58 GPa, while VS increases by ~3(±1)% above ~40 GPa compared to MgSiO3-bridgmanite. Thermoelastic modeling of the experimental results shows that the observed elastic anomaly of Fe-bearing bridgmanite is consistent with a spin transition of octahedrally coordinated Fe3+ in bridgmanite. These results challenge traditional views that Fe enrichment will reduce seismic velocities, suggesting that seismic heterogeneities in the mid-lower mantle may be due to a spin transition of Fe in Fe-bearing bridgmanite.

Original languageEnglish
Pages (from-to)4725-4732
Number of pages8
JournalGeophysical Research Letters
Volume45
Issue number10
DOIs
Publication statusPublished - May 28 2018

Keywords

  • bridgmanite
  • elasticity
  • lower mantle
  • spin transition

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Fu, S., Yang, J., Zhang, Y., Okuchi, T., McCammon, C., Kim, H. I., Lee, S. K., & Lin, J. F. (2018). Abnormal Elasticity of Fe-Bearing Bridgmanite in the Earth's Lower Mantle. Geophysical Research Letters, 45(10), 4725-4732. https://doi.org/10.1029/2018GL077764