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关于它们组成物质的流变性的数据。行星内部的物理和化学条件非常广泛，特别是在压力方面。在流变性的实验研究中，主要的挑战是开发技术来获得行星内部条件下的流变性的定量数据。在以前的研究中，公认的流变学数据仅限于在压力低于0.5 GPa时获得的数据。在之前的资助期间，研究人员已将其扩展到~15 Gpa，并在地球S地幔的过渡带条件下获得了初步的流变性结果。然而，他们的研究也强调了几个重要的挑战：(I)即使在相对较低的气压(10 Gpa)下，不同实验室之间(关于橄榄石的)实验结果也有很大差异，(Ii)以前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，几乎没有关于地球下地幔流变学的定量知识。这一重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，建立压力下的定量变形实验战略，(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。实验研究将作为团队努力进行，全国这一研究领域的专家将参与其中。博士后和学生将参与这个小组的工作，结果将通过技术报告和直接合作向社会开放。这个项目的结果将为我们提供一个新的工具，通过它我们可以在广泛的条件下(在高压和受控的水逸度下)确定矿物的流变性，使用这些技术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.