Size effects resolve debate in 40 years of work on low-temperature plasticity in olivine

Kathryn M. Kumamoto, Chrostopher A. Thom, D. Wallis, Lars N. Hansen, David E.J. Armstrong, Jessica M. Warren, David L. Goldsby, Angus J. Wilkinson

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The strength of olivine at low temperatures and high stresses in Earth’s lithospheric mantle exerts a critical control
on many geodynamic processes, including lithospheric flexure and the formation of plate boundaries. Unfortunately,
laboratory-derived values of the strength of olivine at lithospheric conditions are highly variable and
significantly disagree with those inferred from geophysical observations. We demonstrate via nanoindentation that
the strength of olivine depends on the length scale of deformation, with experiments on smaller volumes of material
exhibiting larger yield stresses. This “size effect” resolves discrepancies among previous measurements of olivine
strength using other techniques. It also corroborates the most recent flow law for olivine, which proposes a much
weaker lithospheric mantle than previously estimated, thus bringing experimental measurements into closer alignment
with geophysical constraints. Further implications include an increased difficulty of activating plasticity in cold,
fine-grained shear zones and an impact on the evolution of fault surface roughness due to the size-dependent deformation
of nanometer- to micrometer-sized asperities.
Original languageEnglish
Article numbere1701338
Number of pages7
JournalScience advances
Volume3
Issue number9
DOIs
Publication statusPublished - 13 Sept 2017

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