2:15 PM - 2:30 PM
[SIT21-15] Ultralow-velocity zones possibly explained by light element-enriched iron compounds
Keywords:Core–mantle boundary, Ultralow-velocity zones, Light elements, Iron compounds
Given the steep geothermal gradient across the CMB, the hydrogen-bearing iron peroxide FeO2Hx likely undergoes high-temperature decomposition into anhydrous iron oxides (e.g., Fe2O3) and fluids. We measured the sound velocity of Fe2O3 post-perovskite (ppv) through inelastic X-ray scattering up to 132 GPa and 1,800 K, relevant to the lowermost mantle. Combined with first-principles investigations, we are able to show that Fe2O3 ppv has very low sound velocities and strong anisotropy with respect to lower-mantle silicates. Therefore, both hydrogen-bearing iron peroxide FeO2Hx and post-perovskite Fe2O3 are candidate phases for ultralow-velocity zones at the CMB.
Funding acknowledgment: This work was supported by the JSPS Japanese–German Graduate Externship.