大变形橄榄石动态重结晶的实验观测研究

In this paper torsion experiments on Fe rich olivine aggregates were conducted in a high-pressure and high-temperature gas medium torsion apparatus under anhydrous condition to analyze the grain size changes and dynamic recrystallization under different deformation. The Fe rich aggregates were synthesized from Fa100 and Fa10 mixture. The geometry of the sample was a cylinder with ~ 9. 6mm in diameter and ~4. 86mm in length encapsuled by the Ni sleeve to buffer the oxygen fugacity at olivine stability field. The small element in the sample undergoes deformation at constant strain rate by simple shear. A temperature of 1473 K and a confining pressure of 300MPa at a constant angular velocity were applied during the torsion experiment. The applied shear strain rate ranged from 1. 35 X 10 to 3. 11 X 10 s, yielding shear stresses of 72 ~ 99MPa supported by the sample and an accumulative shear strain of 3. 98 were achieved at the end. Mierostrueture was analyzed with optical and electron microscopy. A series of parallel sections were examined starting near the outside edge of the cylindrical sample and proceeding to the central section. The Electron Baekscatter Diffraction (EBSD) was performed on the central profile to determine the Lattice Preferred Orientation (LPO) changes with different strains. The observation is consistent with the LPO reported by Bystrieky et at. (2000) for samples of San Carlos Fo90 olivine.