Deformation of Post-Spinel Under the Lower Mantle Conditions
Deformation of Post-Spinel Under the Lower Mantle Conditions
复制标题
下地幔条件下后尖晶石的变形
作者：
Xu F
为了研究硼镁石和铁方镁石聚集体的粘度，利用DT Cup装置在1773 K和上下地幔压力下对预合成后尖晶石相和硼镁石双层样品进行了单轴压缩变形实验。直到0.25 ± 0.05的应变，观察到的桥镁石和后尖晶石样品的相当应变表明桥镁石主导后尖晶石的体积粘度，而方镁石中没有应变局部化。变形后尖晶石样品的显微结构显示出方镁石的类似应变与体应变的证据，而没有应变分配。硼镁石的织构分析表明主要滑移面（100），在0.12 ± 0.01的应变范围内达到稳态组构强度。目前的实验没有提供关于应变局部化开始的证据，方镁石为0.25应变。我们的观测结果提供了直接的实验验证的低应变幅度下的Bridgmanite控制流变学，这应该考虑在地球动力学模型，包括地幔成分和流变演化在下地幔。
To study the viscosity of bridgmanite and ferropericlase aggregate, uniaxial compression deformation experiments on pre‐synthesized post‐spinel phase and bridgmanite two‐layered samples were conducted under top lower mantle pressure and 1773 K utilizing DT‐Cup apparatus. Up to the strain of 0.25 ± 0.05, the observed comparable strain of the bridgmanite and post‐spinel samples suggests the bridgmanite dominates the bulk viscosity of the post‐spinel without strain localization in periclase. The microstructures of the deformed post‐spinel samples show evidence of a similar strain of periclase with the bulk strain without strain partitioning. Texture analyses of bridgmanite indicate a dominant slip plane (100), with a steady state fabric strength achieved within the strain of 0.12 ± 0.01. The current experiment has provided no evidence about an onset of strain localization of ∼30 vol.% periclase at 0.25 strain. Our observations provide direct experimental verification of bridgmanite controlled rheology under low strain magnitude, which should be considered in geodynamical models which include mantle compositional and rheological evolution in the lower mantle.