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High Shear Strain of Olivine Aggregates: Rheological and Seismic Consequences
M. Bystricky,*K. Kunze,L. Burlini,J.-P. Burg
High-pressure and high-temperature torsion experiments
on olivine aggregates in dislocation creep show about 15 to 20% strainweakening before steady-state behavior, characterized by
subgrain-rotationrecrystallization and a strong lattice preferred
orientation.Such weakening may provide a way to focus flow in the
upper mantlewithout a change in deformation mechanism. Flow laws
derived fromlow strain data may not be appropriate for use in modeling
highstrain regions. In such areas, seismic wave propagation will beanisotropic with an axis of approximate rotational symmetry aboutthe
shear direction. In contrast to current thinking, the anisotropywill
not indicate the orientation of the shear plane in highlystrained,
recrystallized olivine-rich rocks.
Geologisches Institut, ETH-Zentrum, 8092 Zürich,
Switzerland.
*
To whom correspondence should be addressed. E-mail:
misha{at}erdw.ethz.ch
