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

合作研究：CSEDI--深地条件下塑性变形实验研究的重大挑战

• 批准号: 0968858
• 负责人: Shun-ichiro Karato
• 金额: $ 57.02万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0968858&HistoricalAwards=false
• 关键词: Collaborative; Research; CSEDI; Grand; Challenge

The main goal of this joint project is to further develop the experimental techniques of studying plastic deformation under deep Earth conditions. When a large force (stress) is applied to minerals or rocks under shallow Earth conditions, they will be deformed by brittle fracture. In the deep interior of Earth, temperature is higher and then plastic deformation becomes possible. This plastic deformation helps material circulation by convection that cools Earth and causes most of geological activities including mountain building and deep circulation of water and other materials. However, to date very little is known on the plastic flow properties of materials under deep Earth conditions due mainly to the technical difficulties. For example, in the deep interior of Earth, not only is temperature high, but also pressure is high. Usually pressure suppresses atomic motion and hence plastic deformation becomes difficult under high-pressure conditions. Does the role of pressure become more important than temperature and hence the viscosity of materials increases with depth? Also most of minerals undergo a series of phase transformations. How do these phase transformations affect the plastic properties? These issues are critical to our understanding of the dynamics and evolution of Earth and other terrestrial planets. Despite its importance, almost nothing was known about these deep earth deformation as recently as ~ten years ago. Recognizing this need, the investigators started a group effort to develop new techniques of plastic deformation under deep Earth conditions in 2002. Based on the studies during the previous funding periods, they have made major progress including the development of new types of deformation apparatus and the improvements to the stress (and strain) measurements using synchrotron x-ray sources. As a result, we can now conduct quantitative deformation experiments to ~20 GPa and ~2000 K. However, these conditions correspond only to the depth of ~500 km. Earth's mantle extends to ~2900 km. Also, there has been very poor control of water content in materials previously studied. In this new phase of technical development, the team of investigators will focus on (i) extending the maximum pressure to ~30 GPa and higher (~1000 km depth), (ii) improving the control of chemical environment (such as water fugacity) under high-pressure conditions, and (iii) improving the stress measurements through the use of new hardware and theory. These developments will allow investigation of the plastic properties of Earth materials to the conditions equivalent to the shallow part of the lower mantle under well-controlled chemical environment. Applications of these techniques will shed important new light into our understanding of dynamics of whole Earth. The project is a collaboration among teams at four institutions, and will provide enhanced infrastructure to the experimental geophysics community, including new facilities at national synchrotron beamlines that will be available to the broader community. The developments will include training and mentoring of graduate students and post doctoral scholars.

该联合项目的主要目标是进一步开发在深层条件下研究塑性变形的实验技术。当将大力（应力）施加到浅地条件下的矿物或岩石上时，它们会因脆性断裂而变形。在地球的深内部，温度更高，然后塑性变形成为可能。这种塑性变形有助于通过对流冷却地球并引起大多数地质活动，包括山地建筑和深度循环水和其他材料。 但是，迄今为止，在深层条件下材料的塑性流量特性很少，这主要是由于技术困难。例如，在地球深内部，温度不仅很高，而且压力也很高。通常，压力抑制原子运动，因此在高压条件下塑性变形变得困难。压力的作用是否比温度更重要，因此材料的粘度随深度的增加吗？大多数矿物也经历了一系列相变。这些相转换如何影响塑料特性？这些问题对于我们对地球和其他陆地行星的动态和演变的理解至关重要。尽管它很重要，但几乎没有什么都没有知道这些深地球变形了十年前。认识到这一需求，研究人员开始了一项小组努力，以在2002年在深地球条件下开发新的塑性变形技术。根据先前的资助期间的研究，他们取得了重大进展，包括开发新型变形设备以及使用Synchrotrotron X射线X射线来源的压力（和应变）测量的改进。结果，我们现在可以将定量变形实验对〜20 GPA和〜2000K进行。但是，这些条件仅对应于〜500 km的深度。地球的地幔延伸至约2900公里。而且，先前研究的材料中对水含量的控制非常不佳。在这一新的技术开发阶段，研究人员将集中在（i）将最大压力扩展到约30 GPA和更高（〜1000 km的深度），（ii）在高压条件下改善化学环境（例如水的控制），以及（iii）通过使用新硬件和理论来改善应力测量值。这些发展将允许研究地球材料的塑性特性，适用于在良好控制的化学环境下等于下地幔浅的条件。这些技术的应用将使我们对整个地球动力学的理解介绍重要的新光明。 该项目是四个机构的团队之间的合作，将为实验地球物理学社区提供增强的基础设施，包括国家同步梁上的新设施，这些设施将用于更广泛的社区。这些发展将包括对研究生的培训和指导和博士后学者。