Grain boundary migration in olivine at atmospheric pressure

Annealing experiments in order to study grain boundary migration (GBM) were carried out at temperatures of 1513–1773 K from 10 min to 100 hours at atmospheric pressure. Grain growth due to GBM is observed in the formation of margins of neoblastic grains which display very different structures of dislocations from that of consumed porphyroclastic and initial neoblastic grains.The velocity of GBM obtained here is approximated to be $\text{c=}\text{gh}$ in which k is 1.15×10^?9 cm³ s^?1, Q is the activation energy for GBM in olivine at 210±20 kJ mol^?1 and ρ is the dislocation density of consumed olivine (cm^?2.Inasmuch as GBM in static annealing reduces stored strain energy in olivines, it is one of the softening processes counteracting work-hardening by dislocation multiplication and tangling as well as dislocation annihilation. GBM-softening is dominant in low temperature annealing but in high temperatures dislocation recovery predominantly takes place.