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× 10 -4 to 3. 11 × 10-4 s-1, yielding shear stresses of 72 ~99MPa supported by the sample and an accumulative shear strain ofrn3. 98 were achieved at the end. Microstructure was analy2ed 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 Backscatter 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 Bystricky et al. (2000) for samples of San Carlos Fo90 olivine.%本文利用高温高压大变形扭转实验,对富铁橄榄石大变形情况下的动态重结晶和颗粒尺度变化的特点进行了实验观测分析.富铁橄榄石集合体由纯铁橄榄石Fa100和圣卡罗橄榄石Fa10混合物经人工合成得到,试件的几何形状为圆柱体,直径9.6mm,高度4.86mm.实验在常角速率条件下进行,温度为1473K,围压为300MPa,剪应力为72 ～ 99MPa,剪应变率为1.35×10-4～3.11×10-4s-1,累积剪应变为3.98.对变形后样品的微结构进行了光学和扫描电镜的观测分析,得到橄榄石颗粒随应变增加而产生动态重结晶的具体物理图像,由EBSD观测结果给出了晶格取向随外加应变增加而产生的变化过程,利用两种统计方法得到了颗粒尺寸随应变增加而变化的过程,探讨了橄榄石动态重结晶的微观机制.与已有三轴压缩、简单剪切以及圣卡罗橄榄石的扭转变形结果进行了对比分析,同时对实验结果在地球物理方面的应用进行了讨论.
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