Affiliation:
1. School of Physics and Astronomy University of Minnesota‐Twin Cities Minneapolis MN USA
2. Now at Department of Earth Sciences University of Cambridge Cambridge UK
3. Department of Earth and Environmental Sciences University of Minnesota‐Twin Cities Minneapolis MN USA
Abstract
AbstractTo study the mechanical behavior of polymineralic rocks, we performed deformation experiments on two‐phase aggregates of olivine (Ol) + ferropericlase (Per) with periclase fractions (fPer) between 0.1 and 0.8. Each sample was deformed in torsion at T = 1523 K, P = 300 MPa at a constant strain rate to a final shear strain of γ = 6 to 7. The stress‐strain data and calculated values of the stress exponent, n, indicate that Ol in our samples deformed by dislocation‐accommodated sliding along grain interfaces while Per deformed via dislocation creep. At shear strains of γ < 1, the strengths of samples with fPer > 0.5 match model predictions for both phases deforming at the same stress, the lower‐strength bound for two‐phase materials, while the strengths of samples with fPer < 0.5 are greater than predicted by models for both phases deforming at the same strain rate, the upper‐strength bound. These observations suggest a transition from a weak‐phase supported to a strong‐phase supported regime with decreasing fPer. Above γ = 4, however, the strength of all two‐phase samples is greater than those predicted by either the uniform‐stress or the uniform‐strain rate bound. We hypothesize that the high strengths in the Ol + Per system are due to the presence of phase boundaries in two‐phase samples, for which deformation is rate limited by dislocation motion along interfacial boundaries. This observation contrasts with the mechanical behavior of samples consisting of Ol + pyroxene, which are weaker, possibly due to impurities at phase boundaries.
Funder
National Science Foundation
Publisher
American Geophysical Union (AGU)
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Geochemistry and Petrology,Geophysics
Cited by
1 articles.
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