The enigma of post-perovskite anisotropy: deformation versus transformation textures

Journal Article · Fri Jan 20 04:00:00 EST 2012 · Phys. Chem. Miner.

DOI:https://doi.org/10.1007/s00269-011-0439-y· OSTI ID:1029837

Miyagi, Lowell; Kanitpanyacharoen, Waruntorn; Stackhouse, Stephen; Militzer, Burkhard; Wenk, Hans-Rudolf ^[1]

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1. Yale

The D'' region that lies just above the core mantle boundary exhibits complex anisotropy that this is likely due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO{sub 3} post-perovskite is widely thought to be the major mineral phase of the D''. Texture development has been studied in various post-perovskite phases (MgSiO{sub 3}, MgGeO{sub 3}, and CaIrO{sub 3}), and different results were obtained. To clarify this controversy, we report on transformation and deformation textures in MgGeO{sub 3} post-perovskite synthesized and deformed at room temperature in the diamond anvil cell. Transformed from the enstatite phase, MgGeO{sub 3} post-perovskite exhibits a transformation texture characterized by (100) planes at high angles to the direction of compression. Upon subsequent deformation, this texture changes and (001) lattice planes become oriented nearly perpendicular to compression, consistent with dominant (001)[100] slip. When MgGeO{sub 3} post-perovskite is synthesized from the perovskite phase, a different transformation texture is observed. This texture has (001) planes at high angle to compression and becomes slightly stronger upon compression. We also find that the yield strength of MgGeO{sub 3} post-perovskite is dependent on grain size and texture. Finer-grained samples exhibit higher yield strength and are harder to induce plastic deformation. Strong textures also affect the yield strength and can result in higher differential stresses. The inferred dominant (001) slip for pPv is significant for geophysics, because, when applied to geodynamic convection models, it predicts the observed anisotropies of S-waves as well as an anti-correlation between P- and S-waves.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFUNIVERSITYNNSA
• OSTI ID: 1029837
• Journal Information: Phys. Chem. Miner., Journal Name: Phys. Chem. Miner. Journal Issue: (9) ; 06, 2011 Vol. 38; ISSN 0342-1791; ISSN PCMIDU
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
COMPRESSION
CONVECTION
DEFORMATION
DIAMONDS
ENSTATITE
GEOPHYSICS
GRAIN ORIENTATION
GRAIN SIZE
PEROVSKITE
PLASTICS
S WAVES
SLIP
STRESSES
TEXTURE
TRANSFORMATIONS
YIELD STRENGTH