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

在发展我们对地球和其他类地行星的动力学和演化的理解方面，最关键的实验数据之一是其组成材料的流变学性质的数据。行星内部的物理和化学条件非常广泛，特别是在压力方面。流变学性质实验研究的主要挑战是发展获得行星内部条件下流变学定量数据的技术。在以前的研究中，公认的流变数据仅限于在压力小于0.5 GPa时获得的数据。在上一个资助期间，研究人员将其扩展到~15 GPa，并获得了地球地幔过渡区条件下流变特性的初步结果。然而，他们的研究也强调了几个重要的挑战：（i）即使在相对较低的压力（10 GPa）下，实验结果也存在很大差异（橄榄石）在不同的实验室，（ii）水逸度在以前的实验中没有控制，以及（iii）定量变形实验的最大压力仍然有限，实际上对下地幔的流变学没有任何定量的了解of the Earth.这个新阶段的大挑战项目的目标是：（i）通过改进的X射线衍射和实验室间的比较，建立一个定量变形实验的压力下的策略，（ii）开发新的方法控制水逸度在高压下，和（iii）扩大这些研究的压力（和温度）范围。实验研究将作为一项团队工作进行，涉及全国这一研究领域的专家。博士后和学生将参与这项工作，其结果将通过技术报告和直接合作向社区开放。该项目的结果将为我们提供一种新的工具，通过这种工具，我们可以在广泛的条件下确定矿物的流变特性（在高压和受控的水逸度下），使用这些技术将得出的科学结果将成为地球和行星内部地球动力学研究的基础。

One of the most critical experimental data in developing our understanding of dynamics and evolution of Earth and other terrestrial planets are the data on rheological properties of their constituent materials. The physical and chemical conditions in planetary interior are very broad particularly in terms of pressure. The major challenge in the experimental studies on rheological properties is to develop techniques to obtain quantitative data on rheological under the conditions of planetary interiors. Well-accepted rheological data in the previous studies were limited to those obtained at pressure less than 0.5 GPa. In the previous funding period, the investigators have extended this to ~15 GPa and obtained initial results on rheological properties under the transition zone conditions of Earth''s mantle. However, their studies have also underlined several important challenges: (i) even at relatively low pressures (10 GPa) there is a large discrepancy in the experimental results (on olivine) among different laboratories, (ii) water fugacity in the previous experiments were not controlled, and (iii) the maximum pressure of quantitative deformation experiments is still limited and virtually nothing quantitative is known about the rheology of the lower mantle of the Earth. The goals of this new phase of the grand challenge project are: (i) to establish a strategy for quantitative deformation experiments under pressures through improved x-ray diffraction and inter-laboratory comparisons, (ii) to develop new methods of controlling water fugacity under high-pressures, and (iii) to expand the pressure (and temperature) range of these studies. The experimental studies will be conducted as a team effort involving experts in this research area across the country. Post-docs and students will be involved in this group effort and the results will be open to the community both through technical reports and through direct collaborations.The results of this project will provide us with a new tool by which we can determine rheological properties of minerals under a broad range of conditions (under high pressures and controlled water fugacity), and the scientific results that will come out using these techniques will form the basis for geodynamic studies of Earth and planetary interiors.