Behavior of iron in (Mg,Fe)SiO3 post-perovskite assemblages at Mbar pressures

The electronic environment of the iron sites in post-perovskite (PPv) structured (Fe-57,Mg)SiO3 has been measured in-situ at 1.12 and 1.19 Mbar at room temperature using 57 Fe synchrotron Mossbauer spectroscopy. Evaluation of the time spectra reveals two distinct iron sites, which are well distinguished by their hyperfine fields. The dominant site is consistent with an Fe3+-like site in a high spin state. The second site is characterized by a small negative isomer shift with respect to alpha-iron and no quadrupole splitting, consistent with a metallic iron phase. Combined with SEM/EDS analyses of the quenched assemblage, our results are consistent with the presence of a metallic iron phase coexisting with a ferric-rich PPv. Such a reaction pathway may aid in our understanding of the chemical evolution of Earth's core-mantle-boundary region. Citation: Jackson, J. M., W. Sturhahn, O. Tschauner, M. Lerche, and Y. Fei (2009), Behavior of iron in (Mg,Fe)SiO3 post-perovskite assemblages at Mbar pressures, Geophys. Res. Lett., 36, L10301, doi: 10.1029/2009GL037815.