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

为了加深我们对地球和其他类地行星动力学和演化的理解，最关键的实验数据之一是其构成材料的流变特性数据。行星内部的物理和化学条件非常广泛，特别是在压力方面。流变特性实验研究的主要挑战是开发获得行星内部条件下流变定量数据的技术。先前研究中广为接受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，研究人员已将其扩展至~15 GPa，并获得了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，不同实验室（橄榄石）的实验结果也存在很大差异，（ii）以前的实验中的水逸度没有得到控制，（iii）定量变形实验的最大压力仍然有限，并且对地球下地幔的流变性几乎没有定量的了解。大挑战项目新阶段的目标是：(i) 通过改进的 X 射线衍射和实验室间比较，建立压力下定量变形实验的策略，(ii) 开发控制高压下水逸度的新方法，以及 (iii) 扩大这些研究的压力（和温度）范围。实验研究将由全国该研究领域的专家组成的团队共同努力进行。博士后和学生将参与该小组的工作，其结果将通过技术报告和直接合作向社会开放。该项目的结果将为我们提供一种新工具，通过它我们可以确定矿物在广泛条件下（高压和受控水逸度下）的流变特性，并且使用这些技术得出的科学结果将构成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.