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Slip systems in MgSiO3 post-perovskite: implications for D'' anisotropy
Lowell Miyagi1, Waruntorn Kanitpanyacharoen, Pamela Kaercher
1Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
Science (New York, N.Y.)
|October 9, 2010
Summary
MgSiO(3) post-perovskite slip on (001) planes strengthens seismic anisotropy in Earth's lower mantle. This clarifies deformation mechanisms and seismic interpretations in the D'' layer.
Area of Science:
- Mineral Physics
- Geophysics
- Seismology
Background:
- Deformation of mineral phases in the lowermost mantle is crucial for interpreting seismic anisotropy.
- Controversy exists regarding deformation-induced slip in MgSiO(3) post-perovskite.
Purpose of the Study:
- To investigate the deformation mechanisms and preferred orientation of MgSiO(3) post-perovskite under high pressure.
- To clarify the role of slip in generating seismic anisotropy in Earth's D'' region.
Main Methods:
- High-pressure experiments simulating conditions in Earth's lower mantle.
- X-ray diffraction to observe lattice plane orientation and preferred orientation evolution.
- Modeling of deformation and anisotropy based on experimental results.
Main Results:
- MgSiO(3) post-perovskite exhibits (001) lattice plane orientation at high angles to compression post-transformation.
- Preferred orientation strength increases significantly with compression from 148 GPa to 185 GPa, indicating (001) slip.
- Results contrast with previous studies, attributing preferred orientation to deformation rather than solely phase transformation.
Conclusions:
- Slip on (001) lattice planes is a key mechanism for MgSiO(3) post-perovskite deformation under lower mantle conditions.
- The findings support the interpretation of seismic anisotropy, specifically shear-wave splitting, in the D'' region.
- This study refines our understanding of mineral behavior and seismic wave propagation in Earth's deep interior.
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