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Title: Deformation of Forsterite Polycrystals at Mantle Pressure. Comparison with Fe-bearing Olivine and the Effect of Iron on its Plasticity

Rheology of polycrystalline forsterite was investigated in the Deformation-DIA (D-DIA) using insitu X-ray diffraction at pressure between 3.1 and 8.1 GPa, temperature in the 1373–1673 K range, and at steady-state strain rate ranging from 0.5 × 10 -5 to 5.5 × 10-5 s -1. Microscopic observations of the run products show characteristic microstructures of the so-called “dislocation creep regime” in wet conditions. Based on the present data at 1473 K, the pressure effect on forsterite plasticity is quantified using an activation volume V* F0 = 12.1±3.0 cm 3 mol -1. Moreover, a comparison between the strain rates of San Carlos olivine and forsterite specimens deformed together indicates that, at the experimental conditions, they compare with each other within less than half an order of magnitude. Our comparison also allows for the determination of the stress exponent of forsterite of n Fo = 2.3 ± 0.6. Our results, combined with data from the literature, indicate a clear trend of increasing stress exponent with Fe content in olivine.
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  1. CNRS Lille University of Science and Technology (France)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0031-9201
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of the Earth and Planetary Interiors; Journal Volume: 240
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; olivine; forsterite; rheology; aggregate; dislocation creep; high pressure; D-DIA; stress exponent; activation volume