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对(Mg_(0.5),Fe_(0.5))_2SiO_4和(Mg_(0.7)、Fe_(0.3))_2SiO_4橄榄石集合体进行了高温高压扭转大变形实验研究。试验在高精度和高分辨率 Paterson 气体介质变形试验机上进行,试验温度为1473K,围压为300MPa,应变率为10~(-4)～10~(-5)S~(-1),剪切应力为82～124MPa,剪切应变为～400%,将变形后试件沿轴向切开进行了显微结构分析,确定了不同纵截面上橄榄石的颗粒尺寸。由蠕变数据拟合出的流动律中,应力指数为与三轴压缩实验给出的应力指数吻合。利用 EBSD 方法分别对变形前后试件中橄榄石的晶格最优取向(LPO)进行了测定。在富铁橄榄石样品中观测到的最优晶格取向表明滑动属于(okl)[100]滑动系统。这个结果与 Bystricky 等人在 Fo_(90)种观测到的最优晶格取向特征是一致的。
Large deformation experiments of (Mg_ (0.5), Fe_ (0.5)) _2SiO_4 and (Mg_ (0.7), Fe_ (0.3)) _2SiO_4 olivine aggregates were carried out under high temperature and high pressure. The test was carried out on Paterson gas medium deformation testing machine with high precision and high resolution. The test temperature was 1473K, the confining pressure was 300MPa, the strain rate was 10 ~ (-4) ~ 10 ~ (-5) S ~ (-1) The shear stress was 82-124 MPa and the shear strain was ~ 400%. Microstructural analysis of the deformed specimens was carried out along the axial direction to determine the grain size of olivine in different longitudinal sections. In the flow law fitted by creep data, the stress exponent is in agreement with the stress exponent given by the triaxial compression experiment. The optimal lattice orientation (LPO) of olivine in the specimens before and after deformation was measured by EBSD method. The optimal lattice orientation observed in the fossil-rich olivine samples indicates that the slip belongs to the okl [100] slip system. This result is consistent with the best lattice orientation observed by Bystricky et al. In Fo_ (90).