Physics
Scientific paper
Feb 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009georl..3604304d&link_type=abstract
Geophysical Research Letters, Volume 36, Issue 4, CiteID L04304
Physics
3
Mineral Physics: Creep And Deformation, Physical Properties Of Rocks: Plasticity, Diffusion, And Creep, Physical Properties Of Rocks: Fracture And Flow
Scientific paper
Rheological properties of mantle minerals and rocks at temperatures (T) appropriate to much of Earth's lithosphere have remained poorly constrained, even though past experimental studies on olivine single crystals and polycrystalline aggregates have quantified the high-temperature creep mechanisms (T > 1200°C). Consequently, we have performed deformation experiments on crystals of San Carlos olivine at lower temperatures, from 900° to 1200°C, in triaxial compression along the [101]c direction. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at differential stresses of 100 to 500 MPa. Several samples were deformed at constant displacement rate and others at constant load, in order to provide insight into possible effects of work-hardening. Under the deformation conditions investigated, little evidence of work-hardening was observed. The data follow a power-law dependence on stress, as in previous high-temperature deformation studies. The samples were, however, considerably weaker than predicted by the experimentally determined high-temperature constitutive equation for olivine crystals of this orientation from the study of Bai et al. (1991). The mechanical behavior correlates instead with the weaker of the two mechanisms (flow laws) that contribute to the high-temperature constitutive equation. Thus, our experiments demonstrate that published high-temperature constitutive equations overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at lower temperatures than previously inferred.
Demouchy Sylvie
Kohlstedt David L.
Mackwell Stephen J.
Schneider Stephen E.
Zimmerman Mark E.
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