Temperature dependence of [100](010) and [001](010) dislocation mobility in natural olivine

- Same activation energy of mobility of [100](010) and [001](010) dislocations.
- The activation energy of dislocation mobility is identical to that of Si diffusion.
- Temperature cannot cause olivine fabric transition from A-type to B-type.
- The AG-type fabric may be produced by low stress.
- Decrease of stress with depth may cause decrease of seismic anisotropy.

Dislocation recovery experiments were conducted on pre-deformed olivine single crystals at 1450 to 1760 K, room pressure, and oxygen partial pressures near the Ni-NiO buffer to determine the annihilation rates for [100] and [001] dislocations on the (010) plane. Olivine single crystals were first deformed to activate the desired slip systems under simple shear geometry and then annealed at target conditions. The edge and screw dislocations with Burgers vectors, b, of [100] and [001], respectively, both elongated in the [001] direction were produced by the deformation. The dislocation annihilation rate constants of both types of dislocations are identical within 0.3 log unit. The activation energies for both dislocations are also identical, i.e., ∼400 kJ/mol, which is also identical to that of the Si self-diffusion coefficient. This correspondence suggests that olivine dislocation creep controlled by a diffusion-controlled process under low-stress and high-temperature conditions. This study offers a potential insight into the formation of AG-type fabric in olivine.