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Oriented grain growth and modification of ‘frozen anisotropy’ in the lithospheric mantle

Published version
Peer-reviewed

Type

Article

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Authors

Boneh, Y 
Hansen, LN 
Krawczynski, MJ 
Skemer, P 

Abstract

Seismic anisotropy throughout the oceanic lithosphere is often assumed to be generated by fossilized texture formed during deformation at asthenospheric temperatures close to the ridge. Here we investigate the effect of high-temperature and high-pressure static annealing on the texture of previously deformed olivine aggregates to simulate residence of deformed peridotite in the lithosphere. Our experiments indicate that the orientation and magnitude of crystallographic preferred orientation (CPO) will evolve due to the preferential growth of grains with low dislocation densities. These observations suggest that texture and stored elastic strain energy promote a style of grain growth that modifies the CPO of a deformed aggregate. We demonstrate that these microstructural changes alter the orientation distributions and magnitudes of seismic wave velocities and anisotropy. Therefore, static annealing may complicate the inference of past deformation kinematics from seismic anisotropy in the lithosphere.

Description

Keywords

olivine, crystallographic preferred orientation, grain growth, seismic anisotropy, mantle lithosphere

Journal Title

Earth and Planetary Science Letters

Conference Name

Journal ISSN

0012-821X
1385-013X

Volume Title

474

Publisher

Elsevier BV
Sponsorship
This research is supported by NSF EAR-1131985 (to PS), with additional support from the Institute of Materials Science and Engineering at Washington University in St. Louis. DW and LNH acknowledge support from the Natural Environment Research Council Grant NE/M000966/1.