Partitioning of Fe within high‐pressure silicate perovskite: Evidence for unusual geochemistry in the lower mantle

Using synchrotron radiation, Fe x‐ray absorption spectra have been collected from a Mg0.88Fe0.12SiO3 perovskite quenched from 50 GPa and ∼ 2000 K. Least‐squares fits of the Extended X‐ray Absorption Fine Structure (EXAFS) data yield an Fe coordination number of 5.5 (±0.8) oxygens, an Fe‐O distance of 214 (± 4) pm, and a static and thermal disorder parameter of 147 pm². The absorption edge spectrum shows a weak pre‐edge feature suggesting little deviation from centrosymmetry for the Fe site. These results indicate that Fe in this silicate perovskite partitions predominantly into the six‐coordinated site and may provide the first evidence for Si occupying an 8‐12 coordinated site.