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- Title
The Effect of Intracrystalline Water on the Mechanical Properties of Olivine at Room Temperature.
- Authors
Kumamoto, Kathryn M.; Hansen, Lars N.; Breithaupt, Thomas; Wallis, David; Li, Bo‐Shiuan; Armstrong, David E. J.; Goldsby, David L.; Li, Yang; Warren, Jessica M.; Wilkinson, Angus J.
- Abstract
The effect of small concentrations of intracrystalline water on the strength of olivine is significant at asthenospheric temperatures but is poorly constrained at lower temperatures applicable to the shallow lithosphere. We examined the effect of water on the yield stress of olivine during low‐temperature plasticity using room‐temperature Berkovich nanoindentation. The presence of water in olivine (1,600 ppm H/Si) does not affect hardness or yield stress relative to dry olivine (≤40 ppm H/Si) outside of uncertainty but may slightly reduce Young's modulus. Differences between water‐bearing and dry crystals in similar orientations were minor compared to differences between dry crystals in different orientations. These observations suggest water content does not affect the strength of olivine at low homologous temperatures. Thus, intracrystalline water does not play a role in olivine deformation at these temperatures, implying that water does not lead to weakening in the coldest portions of the mantle. Plain Language Summary: At high temperatures (>1,000°C), incorporating small amounts of water in a crystalline structure can dramatically affect the strength of that crystal. There are many theories as to why this is the case, and each theory makes a prediction for how water might affect the strength of crystals at low temperatures. Thus, by conducting experiments at room temperature, we can distinguish between some of these theories. Our data indicate that water does not have a significant effect on the strength of olivine at room temperature, and any minor effect that water may have is far outweighed by the effect of crystal orientation. These observations rule out theories in which water causes a decrease in the strength of olivine at all temperatures, implying that water does not lead to weakening in the coldest portions of the mantle. Key Points: Room‐temperature nanoindentation tests on wet and dry olivine yield very similar mechanical resultsAny effect of water incorporation on yield stress is outweighed by the effect of orientation anisotropyWater may only weaken olivine at high temperatures and therefore not influence strength in the coldest portions of the lithosphere
- Subjects
OLIVINE; NANOINDENTATION tests; NANOINDENTATION; YIELD stress; YOUNG'S modulus; CRYSTAL orientation
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 4, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL106325