Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution
Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution
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DOI：
10.1029/2019jb017968
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
K. Kumamoto;J. Warren;L. Hansen
中科院分区：
文献类型：
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作者：
K. Kumamoto;J. Warren;L. Hansen
由于橄榄石晶体流动方向而言，地震症在上地幔中出现。变形样品，我们呈现跨微观结构的样品这些剪切区的约瑟芬橄榄石样品中的三个剪切区显示出与干燥条件和橄榄石的一级激活相关的A型纹理[100]（010）滑移系统，E-Type的质地与湿润条件和特征的主要激活相关联。 CPO类型不发展作为应变或水的功能，我们使用微机械模型来评估橄榄石CPO进化的质地和运动学的作用POS和变形运动学应在在自然变形的岩石和上层地震各向异性中测量的CPO的解释。
Seismic anisotropy arises in the upper mantle due to the alignment of olivine crystal lattices and is often used to interpret mantle flow direction. Experiments on the evolution of olivine crystal‐preferred orientation (CPO) have found that the texture that develops is dependent on many factors, including water content, differential stress, preexisting CPO, and deformation kinematics. To evaluate the role of these factors in naturally deformed samples, we present microstructural transects across three shear zones in the Josephine Peridotite. Samples from these shear zones exhibit a mixture of A‐type textures, which have been associated with dry conditions and primary activation of the olivine [100](010) slip system, and of E‐type textures, which have been associated with wetter conditions and primary activation of the [100](001) slip system. CPOs with characteristics of both A‐type and E‐type textures are also present. CPO type does not evolve systematically as a function of either strain or water content. We used a micromechanical model to evaluate the roles of preexisting texture and kinematics on olivine CPO evolution. We find that the preexisting texture controls CPO evolution at strains up to 5 during simple shear. Kinematics involving a combination of simple shear and pure shear can explain the olivine CPOs at higher strain. Hence, preexisting CPOs and deformation kinematics should be considered in the interpretation of CPOs measured in naturally deformed rocks and of large‐scale patterns in upper‐mantle seismic anisotropy.