CSEDI Collaborative Research: Grand Challenge for Experimental Study of Plastic Deformation Under Deep Earth Conditions

这项研究计划的目标是开发和利用研究地球深部条件下岩石塑性性质的实验能力。随着地质时间的推移，我们看到大陆已经被撕裂，板块边界被地震和火山打断。然而，在地球上的广大地区，这些过程进行得既顺利又缓慢。虽然地震表现了地球变形的动态特征，但大陆的缓慢运动提供了驱动力。促成这种大规模运动的过程是整个地幔岩石的塑性变形。板块构造论的基础是岩石在地球深部的高压和温度下缓慢但稳定地变形。这项研究计划将继续建立实验能力，以量化岩石的塑性特征作为地球深度的函数。该项目工作在高压仪器开发和国家同步加速器设施的结合点，可以提供高强度的X射线探头。这一联盟承诺的实验能力将把我们可以接近的地球深度范围扩大到以前研究的100倍，并进行高精度的测量。来自该计划的数据将使测试和修改地球演化模型成为可能。这些形变设施为地幔压力和温度下的地球物质研究提供了新的方向，包括地震频率下的弹性波衰减、反应动力学、热扩散系数以及晶格择优取向与变形几何的关系，后者将地震各向异性与流动历史联系起来。它们还为研究材料在极端条件下的强度和塑性提供了潜在的设备和技术诀窍，例如在下一代发电厂中产生的材料。应力、应变、压力和温度是变形实验中需要测量的主要变量。在国家同步加速器(先进的光子源和国家同步加速器光源)的帮助下，研究人员开发了进行这些测量的工具。他们还建造了第一代高压装置，将大体积高压技术引入变形机。他们现在能够在比10年前高出1到2个数量级的压力下进行精确的流变学实验。下一阶段是充分利用目前的静液压高压设备，包括制造多晶钻石的先进技术，以达到下地幔条件。该计划的目标是1)将变形实验的压力范围增加到30-40 Gpa，深入到下地幔；2)通过硬件和软件开发的结合，提高应力和应变的测量分辨率；3)能够同时测量样品的特性，如颗粒的择优取向和声速；4)探索先进的技术，如同步加速器社区开发的那些可能对地球科学目标有用的技术。这些通常是高风险但高回报的工具，如白色光束劳厄衍射，可以产生关于多晶体中单个颗粒的非常详细的信息。

The goal of this research program is to develop and utilize experimental capabilities for studying the plastic properties of rocks at conditions of the deep Earth. Over geologic time we see that continents have been ripped apart with plate boundaries punctuated by earthquakes and volcanoes. However, over the vast regions of the Earth, these processes proceed smoothly and slowly. While earthquakes express the dynamic character of Earth deformation, the slow movement of the continents provides the driving force. The enabling process for this large-scale motion is the plastic deformation of rocks throughout the Earth's mantle. The foundation of plate tectonics rests on the contention that rocks deform slowly but surely at the high pressure and temperature of the deep Earth. This research program is to continue to build experimental capabilities to quantify the plastic character of rocks as a function of depth in the Earth. This program works at the juncture of high-pressure apparatus development and national synchrotron facilities that can provide intense x-ray probes. This union promises experimental capabilities that increase the depth range of the Earth that we can access, with high precision measurement, by a factor of 100 from previous studies. The data that will come from this program will enable testing and modifying of models of Earth evolution. These deformation facilities enable new directions in Earth material research at mantle pressure and temperature including elastic wave attenuation at seismic frequencies, reaction kinetics, thermal diffusivity, and relationship of lattice preferred orientation to deformation geometry, which links seismic anisotropy to flow history. They also provide a potential facility and technical knowhow for studying material strength and plasticity at extreme conditions such as those generated in the next generation power plants.Stress, strain, pressure, and temperature are the primary variables that need to be measured during a deformation experiment. With the aid of the national synchrotrons (the Advanced Photon Source and the National Synchrotron Light Source), the investigators have developed the tools to make these measurements. They have also built the first generation of high-pressure apparatus for introducing 'large - volume high pressure' technology into deformation machines. They are now able to make accurate rheology experiments at pressures 1 to 2 orders of magnitude higher than could be achieved 10 years ago. The next phase is to take full advantage of the current hydrostatic high-pressure equipment, including advanced technologies for making polycrystalline diamonds, to reach lower mantle conditions. The goals of this program are to 1) increase the pressure range for deformation experiments to 30 - 40 GPa, well into the lower mantle, 2) improve measurement resolution of stress and strain with a combination of hardware and software developments, 3) enable simultaneous measurements of a sample properties such as preferred orientation of grains and acoustic velocity, 4) explore advanced techniques such as those developed by the synchrotron community but may be useful to earth science goals. These are often high risk, but high return tools such as white beam Laue diffraction that could yield very detailed information about the individual grains within a polycrystal.