Acquisition of a Rock Deformation Apparatus to Study Rheology and Microstructure

该项目将支持购置一台新的仪器，用于研究高压和高温下粘性变形岩石的性质。岩石的粘性流动是山脉生长、地幔对流和构造板块运动的重要方面。此外，岩石的变形是许多地质灾害的基本因素，如地震、海啸和火山喷发。通过在受控实验室环境中研究岩石流变学，我们可以发展对岩石材料科学的新见解，并为大量的地质或地球物理调查提供工具。与许多其他学科不同，岩石变形实验室中使用的主要仪器不能以商业方式购买，但必须按规格建造。岩石变形实验室中使用的几乎每一种仪器都具有特殊的能力，可以进行特定类型的调查。将为该项目建造的仪器对于研究经历极大变形的岩石特别有用，例如那些可能沿构造板块之间的边界发生剪切的岩石。该项目的目标是在现有成功设计的基础上，建造第二个大体积扭转(LVT)装置。LVT有几个关键特征，使其在岩石变形仪器中独一无二。它能够在足够大的样品上产生高压和温度，以及大的剪切应变，以提供关于变形微观结构的有统计意义的信息。压力高达几GPA，使用锥形Drickamer风格的铁锤和固体陶瓷限制介质产生。电阻加热器产生高达1600K的温度，通过使一个砧座相对于另一个砧座旋转，可以产生大的剪切应变(10)。有一些正在进行的项目使用了来自LVT仪器的数据，以及未来努力的几个目标。通过两相复合材料的变形和混合实验，了解糜棱岩的成因和板缘剪切带的流变性。大范围剪切应变下的颗粒尺寸演化实验有助于阐明应变弱化过程。为了更好地解释地幔中的地震各向异性，用实验研究了晶体择优取向的发展。在低应变率下的实验将被用来阐明微结构演化的速率依赖性。购买第二台仪器将有效地使位于圣路易斯的华盛顿大学岩石变形实验室的能力翻一番，使PI能够培训更多的学生，接待游客，开发新技术，并探索新的参数空间。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will support the acquisition of a new apparatus to study the properties of viscously deforming rocks at high pressure and temperature. The viscous flow of rocks is an essential aspect of the growth of mountains, the convection of the mantle, and the motion of tectonic plates. Moreover, the deformation of rocks is elemental to numerous geologic hazards, such as earthquakes, tsunami, and volcanic eruptions. By studying rock rheology in controlled laboratory setting we can develop new insight into the materials science of rocks, and provide tools for numerous geological or geophysical investigations. Unlike many other disciplines, the primary instrumentation used in rock deformation laboratories cannot be purchased commercially, but must be built to specification. Nearly every apparatus used in a rock deformation lab has special capabilities that enable specific types of investigations. The apparatus that will be built for this project is particularly useful for the study of rocks that experience extremely large magnitudes of deformation, such as those that might be sheared along the boundaries between tectonic plates. The objective of this project is to construct a second Large Volume Torsion (LVT) apparatus, building upon an existing successful design. The LVT has several key characteristics that render it unique among rock deformation apparatuses. It is able to generate high pressures and temperatures, as well as large shear strains, on samples that are large enough to provide statistically meaningful information about deformation microstructures. Pressure, up to several GPA, is generated using tapered Drickamer-style anvils and a solid ceramic confining medium. Resistance heaters generate temperatures up to 1600 K. Large shear strains ( 10) can be generated by rotating one anvil with respect to the other. There are a number of projects underway that use data from the LVT apparatus, as well as several targets for future efforts. Experiments on the deformation and mixing of two-phase composites are used to understand the origins of mylonites and the rheology of plate boundary shear zones. Experiments on grain-size evolution over a large range of shear strains help clarify strain-weakening processes. Experiments to investigate the development of crystallographic preferred orientation are used to better interpret seismic anisotropy in the mantle. Experiments at low strain-rates will be used to elucidate the rate dependence of microstructural evolution. The acquisition of a second apparatus will effectively double the capacity of the rock deformation lab at Washington University in St. Louis, allowing the PIs to train more students, host visitors, develop new techniques, and explore new parameter space.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.