Very low sound velocities in iron-rich (Mg,Fe)O : Implications for the core-mantle boundary region.
The sound velocities of (Mg{sub .16}Fe{sub .84})O have been measured to 121 GPa at ambient temperature using nuclear resonant inelastic x-ray scattering. The effect of electronic environment of the iron sites on the sound velocities were tracked in situ using synchrotron Moessbauer spectroscopy. We found the sound velocities of (Mg{sub .16}Fe{sub .84})O to be much lower than those in other presumed mantle phases at similar conditions, most notably at very high pressures. Conservative estimates of the effect of temperature and dilution on aggregate sound velocities show that only a small amount of iron-rich (Mg,Fe)O can greatly reduce the average sound velocity of an assemblage. We propose that iron-rich (Mg,Fe)O be a source of ultra-low velocity zones. Other properties of this phase, such as enhanced density and dynamic stability, strongly support the presence of iron-rich (Mg,Fe)O in localized patches above the core-mantle boundary.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; NSF
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1004866
- Report Number(s):
- ANL/XSD/JA-69211
- Journal Information:
- Geophys. Res. Lett., Journal Name: Geophys. Res. Lett. Journal Issue: Aug. 10, 2010 Vol. 37; ISSN GPRLAJ; ISSN 0094-8276
- Country of Publication:
- United States
- Language:
- ENGLISH
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