Synthesized polycrystalline samples composed of enstatite and olivine with different volumetric ratios were deformed in compression under anhydrous conditions in a Paterson gas-medium apparatus at 1150–1300°C, an oxygen fugacity buffered at Ni/NiO, and confining pressures of 300 or 450 MPa (protoenstatite or orthoenstatite fields). Mechanical data suggest a transition from diffusion to dislocation creep with increasing differential stress for all compositions. Microstructural analyses by optical and scanning electron microscopy reveal well-mixed aggregates and homogeneous deformation. Crystallographic preferred orientations measured by electron backscatter diffraction are consistent with activation of the slip systems (010)[100] and (010)[001] for olivine and (100)[001] and (010)[001] for enstatite, as expected at these conditions. Nonlinear least-squares fitting to the full data set from each experiment allowed the determination of dislocation creep flow laws for the different mixtures. The stress exponent is 3.5 for all compositions, and the apparent activation energies increase slightly as a function of enstatite volume fraction. Within the limits of experimental uncertainties, all two-phase aggregates have strengths that lie between the uniform strain rate (Taylor) and the uniform stress (Sachs) bounds calculated using the dislocation creep flow laws for olivine and enstatite. Calculation of the Taylor and Sachs bounds at strain rate and temperature conditions expected in nature (but not extrapolating in pressure) indicates that using the dislocation creep flow law for monomineralic olivine aggregates provides a good estimate of the viscosity of olivine-orthopyroxene rocks deforming by dislocation creep in the deeper lithosphere and asthenosphere.

中文翻译：

---

顽辉石-橄榄石聚集体的高温变形

由不同体积比的顽辉石和橄榄石组成的合成多晶样品在 Paterson 气体介质装置中无水条件下压缩变形，温度为 1150-1300°C，氧逸度为 Ni/NiO 缓冲，围压为 300 或 450 MPa （原辉石或原辉石矿场）。机械数据表明，随着所有成分的差异应力的增加，从扩散到位错蠕变的转变。光学和扫描电子显微镜的微观结构分析揭示了混合良好的聚集体和均匀变形。正如预期的那样，通过电子背散射衍射测量的晶体择优取向与橄榄石滑移系统 (010)[100] 和 (010)[001] 以及顽辉石滑移系统 (100)[001] 和 (010)[001] 的激活一致在这些条件下。对每个实验的完整数据集进行非线性最小二乘拟合，可以确定不同混合物的位错蠕变流动定律。所有组合物的应力指数均为 3.5，并且表观活化能作为顽火石体积分数的函数略有增加。在实验不确定性的限制内，所有两相聚集体的强度均位于使用橄榄石和顽火辉石的位错蠕变流定律计算的均匀应变率 (泰勒) 和均匀应力 (萨克斯) 界限之间。在自然界中预期的应变率和温度条件下（但不外推压力）泰勒和萨克斯界限的计算表明，使用单矿物橄榄石聚集体的位错蠕变流动定律可以很好地估计由位错变形的橄榄石-斜方辉石岩石的粘度在更深的岩石圈和软流圈中蠕变。