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Climb of jogs as a rate-limiting process of screw dislocations motion in olivine dislocation creep
  • Lin Wang,
  • Tomoo Katsura
Lin Wang
Carnegie Institution for Science, Carnegie Institution for Science

Corresponding Author:liwang@carnegiescience.edu

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Tomoo Katsura
University of Bayreuth, University of Bayreuth
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Abstract

Dislocation recovery experiments were conducted on pre-deformed olivine single crystals at temperatures of 1,450 to 1,760 K, room pressure, and oxygen partial pressures near the Ni-NiO buffer to determine the annihilation rates constants for [001] (010) edge dislocations. The obtained rate constants were comparable with those of previously determined [001] screw dislocations. The activation energies for the motion of both dislocations are identical. This suggests that the motion of screw dislocations in olivine is not controlled by cross-slip but by the same rate-limiting process of the motion of edge dislocations, i.e. climb, at low-stress and high-temperature conditions. The diffusivity derived from dislocation climb indicates that dislocation recovery is controlled by pipe diffusion. The conventional climb controlled model for olivine can be applied to the motions of not only edge but also screw dislocations. The softness of the asthenosphere cannot be explained by the cross-slip controlled olivine dislocation creep.