Spin state of ferric iron in MgSiO3 perovskite and its effect on elastic properties

Krystle Catalli, Sang Heon Shim, Vitali B. Prakapenka, Jiyong Zhao, Wolfgang Sturhahn, Paul Chow, Yuming Xiao, Haozhe Liu, Hyunchae Cynn, William J. Evans

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106 Scopus citations

Abstract

Recent studies have indicated that a significant amount of iron in MgSiO3 perovskite (Pv) is Fe3+ (Fe3+/ΣFe = 10-60%) due to crystal chemistry effects at high pressure (P) and that Fe3+ is more likely than Fe2+ to undergo a high-spin (HS) to low-spin (LS) transition in Pv in the mantle. We have measured synchrotron Mössbauer spectroscopy (SMS), X-ray emission spectroscopy (XES), and X-ray diffraction (XRD) of Pv with all iron in Fe3+ in the laser-heated diamond-anvil cell to over 100 GPa. Fe3+ increases the anisotropy of the Pv unit cell, whereas Fe2+ decreases it. In Pv synthesized above 50 GPa, Fe3+ enters into both the dodecahedral (A) and octahedral (B) sites approximately equally, suggesting charge coupled substitution. Combining SMS and XES, we found that the LS population in the B site gradually increases with pressure up to 50-60 GPa where all Fe3+ in the B site becomes LS, while Fe3+ in the A site remains HS to at least 136 GPa. Fe3+ makes Pv more compressible than Mg-endmember below 50 GPa because of the gradual spin transition in the B site together with lattice compression. The completion of the spin transition at 50-60 GPa increases bulk modulus with no associated change in density. This elasticity change can be a useful seismic probe for investigating compositional heterogeneities associated with Fe3+.

Original languageEnglish (US)
Pages (from-to)68-75
Number of pages8
JournalEarth and Planetary Science Letters
Volume289
Issue number1-2
DOIs
StatePublished - Jan 15 2010
Externally publishedYes

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Keywords

  • elastic properties
  • ferric iron
  • lower mantle
  • silicate perovskite
  • spin transition

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Catalli, K., Shim, S. H., Prakapenka, V. B., Zhao, J., Sturhahn, W., Chow, P., Xiao, Y., Liu, H., Cynn, H., & Evans, W. J. (2010). Spin state of ferric iron in MgSiO3 perovskite and its effect on elastic properties. Earth and Planetary Science Letters, 289(1-2), 68-75. https://doi.org/10.1016/j.epsl.2009.10.029