In situ Study of Lattice Preferred Orientation at Mantle Conditions

地球的固体部分在一百万年的时间尺度上是极其动态的。固体的塑性流动以岩石水晶积木排列的形式留下了历史。要解开这段历史，需要通过在地球内部的压力和温度条件下进行实验，了解创造这种结构的过程。在这里，我们利用国家同步加速器光源开发的新设施来探测受地球深处变形条件影响的矿物系统。其目的是更好地理解这些过程，定义改变诱导组构的时间尺度，并定义压力和温度条件对生产这些组构的效率的控制。地球的动态历史现在可以由地震波速度的各向异性来约束。地球深处岩石的结构被认为是导致这种各向异性的原因，而正是岩石的塑性流动创造了这种结构。对地幔条件下岩石变形的实验室研究使这一认识上的突破成为可能。以往的方法一般都是解决大变形的最终产物。织物生产的效率作为环境变量的函数仍然没有很好的定义。小应变将在多大程度上产生弹性各向异性还没有通过实验来量化。对于织构形成过程中的相互作用，如再结晶和位错滑移的相对作用，我们缺乏清晰的认识。新的研究需要在地幔压力和温度下进行，以确保适当的过程是活跃的。对这一方案的研究将提供有关固体塑性变形的重要信息。它将提供可用于评估变形量和变形机制的指标。这为工程应用中评估结构材料的失效状态提供了潜在的工具。正弦应力场的初步实验表明，这里提出的技术有很大的成功几率，并由理论模型很好地定义。

The solid portion of the Earth is extremely dynamic on a million year time scale. Plastic flow of the solid leaves a history in the form of alignment of the crystalline building blocks of rocks. Unraveling this history requires understanding the processes that create this fabric through experiments at the pressure and temperature conditions of the Earth's interior. Here we capitalize on new facilities that have been developed at the National Synchrotron Light Source to probe mineral systems subjected to the deforming conditions of the deep Earth. The goal is to better understand these processes, to define the time scale for changing the induced fabric, and to define the control of the pressure and temperature conditions on the efficiency of producing these fabrics.The dynamic history of the Earth can now be constrained by the anisotropy of seismic wave velocities. Texture in the rocks of the deep Earth is understood to give rise to this anisotropy and it is the plastic flow of the rocks that creates the texture. This breakthrough in understanding was enabled by laboratory investigations of rock deformation at mantle conditions. The former approaches generally resolve the end-product of large deformation. The efficiency of fabric production as a function of the environmental variables is still not well defined. The degree to which small strains will create elastic anisotropies has not been experimentally quantified. We lack a clear understanding of the interactions of the grains during the texture formation such as the relative roles of recrystallization and dislocation glide. New studies need to occur at mantle pressures and temperatures to assure that the proper processes are active. The research of this proposal will provide important information about plastic deformation of solids in general. It will provide metrics that can be used to evaluate the amount of deformation and the mechanism of deformation. This provides potential tools for assessing the failure state of structural materials in engineering applications. Preliminary experiments with sinusoidal stress fields indicate that the techniques proposed here have a strong probability of success and are well defined by theoretical models.