Dislocation interactions in olivine control postseismic creep of the upper mantle

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Authors

David Wallis , Lars Hansen, Angus J. Wilkinson , Ricardo A. Lebensohn

Abstract

Changes in stress applied to mantle rocks, such as those imposed by earthquakes, induce a period of evolution in viscosity and microstructure. This transient creep is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the intragranular accumulation of stresses among dislocations is the dominant cause of strain hardening in olivine at low temperatures, raising the question of whether the same process contributes to transient creep at higher temperatures. Here, we demonstrate that olivine samples deformed at 25°C or 1150–1250°C both contain stress heterogeneities of ~1 GPa that are imparted by dislocations and have correlation lengths of ~1 μm. The similar stress distributions formed in both temperature regimes indicate that accumulation of stresses among dislocations also provides a contribution to transient creep at high temperatures. The results motivate a new generation of models that capture these intragranular processes and may refine predictions of evolving mantle viscosity over the earthquake cycle.

DOI

https://doi.org/10.31223/osf.io/y9wbt

Subjects

Condensed Matter Physics, Earth Sciences, Geology, Mineral Physics, Physical Sciences and Mathematics, Physics, Tectonics and Structure

Keywords

postseismic, olivine, dislocation, high-angular resolution electron backscatter diffraction, mantle, rheology, stress heterogeneity, transient creep

Dates

Published: 2020-06-29 16:17

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License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
Data will be made available upon publication of the final article and earlier requests will be considered by the corresponding author.

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