Collaborative Research: Theoretical and Experimental Investigation of Grain Damage and the Formation of Plate Boundaries

合作研究：颗粒损伤和板块边界形成的理论和实验研究

• 批准号: 1853155
• 负责人: Philip Skemer
• 金额: $ 16.7万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1853155&HistoricalAwards=false
• 关键词: Collaborative; Research; Theoretical; Experimental; Investigation

Plate tectonics describes the motion of Earth's upper-most rocky layers and governs almost all geological activity on Earth, such as earthquakes and volcanoes. Plate tectonics is only known to occur on Earth, but not on Venus and Mars, and whether Earth always had plate tectonics in its 4.5 billion-year history is unknown. The emergence of plate tectonics on Earth depends on how rocks in the cold uppermost layers of the mantle - the lithosphere - deform. As rocks deform they can weaken through the process of damage, which concentrates deformation, resulting in more damage, and so on. This positive feedback focuses lithospheric deformation into weak narrow plate boundaries, which are the locus of most seismic and volcanic activity. This project will develop and apply the physics of how mineral grains in rocks are damaged (termed "grain-damage") through combined theoretical and laboratory approaches. When mineral grains are deformed they accumulate defects, which eventually leads to grains breaking down into smaller grains, and this in turn makes the rocks weaker. This process is evident in rocks called mylonites that are often found at plate tectonic boundaries. This project will use grain damage physics to understand how and when plate tectonics arose on early Earth. The project will also study how damage in grains influences cycles of earthquakes at plate boundaries, specifically how rocks weaken, recover and transmit stress to other rocks and eventually trigger more earthquakes. Plate boundary processes have a significant human impact, including evolution of plate boundary fault systems and earthquake recurrence. The project promotes diversity through the support and professional development of two early career female scientists, specifically with interdisciplinary training in theoretical and experimental methods. The project will also involve organization of a symposium on the evolution of plate boundaries for students and young scientists, and will contribute new scientific materials to education and outreach activities at an established scientific visualization facility. This project will advance the study of lithospheric grain-scale physics and deformation mechanisms, and their application to the generation and operation of plate tectonics. The PI's will extend the grain damage theory for lithospheric weakening and plate boundary formation to include mineralogical phase mixing and dislocation dynamics in polymineralic materials, with calibration and testing by rock deformation experiments. These new developments are necessary to address two major scientific questions:1. Emergence of plate tectonics: How did tectonic plate boundaries form in the ancient Archean Earth? Did thermal and petrological evolution in the early Earth, namely cooling, decreasing crustal production, and changes in lithospheric composition, affect localization of deformation in the lithosphere and the emergence of plate tectonics? Specifically, the PI's hypothesize that temperature and melting affect mineral composition, which can then influence rock weakening through the positive feedback of grain damage and mixing between petrological phases.2. Post-seismic creep and lithospheric shear zones: How does transient ductile behavior in the lithosphere, with associated changes in microstructure like grain-size and dislocation density, influence the accumulation, transmission and release of stress following an earthquake? How does this response affect earthquake recurrence cycles and triggering? Does inherited lithospheric weakness, and thus age of a plate boundary, influence post-seismic recovery and earthquake cycles?To address these questions, the investigators will connect new developments in grain-scale physics to plate-scale geodynamic models using experimentally determined rheological laws. These multi-scale models will provide the platform for coupling plate-boundary formation to thermo-chemical evolution of the upper mantle, and to seismogenic behavior in the crust. The ultimate scientific goal of this project is to understand emergence of plate tectonics on early Earth, and how plate boundary evolution and behavior influences post-seismic response and earthquake cycles. These issues span the time scales of the evolution of Earth's surface in deep time, the development of the neotectonic environment, and the behavior of seismically active zones. The proposed work will use theory and experiments to better understand Earth's tectonic processes on the geological and human time scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

板块构造描述了地球上层最高岩层的运动，并控制着地球上几乎所有地质活动，例如地震和火山。 板块构造仅在地球上发生，而在金星和火星上不发生，而地球在其45亿年的历史中是否总是具有板块构造。地球上板块构造的出现取决于地幔最上层的岩石如何 - 岩石圈变形。 随着岩石的变形，它们会通过损害过程削弱，这会浓缩变形，从而导致更多的损坏等等。这种积极的反馈将岩石圈变形集中在弱狭窄的板块边界上，这是大多数地震和火山活性的轨迹。该项目将通过合并的理论和实验室方法来开发并运用岩石中矿物晶粒如何损坏（称为“谷物破坏”）的物理学。当矿物颗粒变形时，它们会积聚缺陷，最终导致谷物分解成较小的谷物，这反过来又使岩石较弱。这个过程在称为甲状腺菌的岩石中很明显，这些岩石岩通常在板块构造边界上发现。该项目将使用晶粒损伤物理学来了解板块构造在地球早期的如何以及何时出现。 该项目还将研究谷物的损害如何影响板边界处地震周期，特别是岩石如何削弱，恢复和传递应力向其他岩石，并最终触发更多的地震。板边界过程具有重大的人体影响，包括板边界断层系统的演变和地震复发。该项目通过两位早期职业女科学家的支持和专业发展促进多样性，特别是在理论和实验方法中进行跨学科培训。该项目还将涉及关于学生和年轻科学家的板界发展的研讨会，并将在既定的科学可视化设施中为教育和外展活动贡献新的科学材料。该项目将推进岩石晶晶尺度物理学和变形机制的研究，以及它们在板块构造的生成和运行中的应用。 PI的晶粒损伤理论将扩展岩石圈弱化和板界形成的晶粒损伤理论，以包括矿物质相混合和多层材料中的脱位动力学，并通过岩石变形实验进行校准和测试。这些新的发展对于解决两个主要科学问题是必要的：1。板块构造的出现：古代大帝地球中的构造板边界如何形成？地球早期的热和岩石学演化是否会冷却，减少地壳产生以及岩石圈组成的变化会影响岩石圈中变形的定位以及板块构造的出现？具体而言，PI的假设是温度和熔化会影响矿物质成分，然后通过谷物损伤的积极反馈和岩石学阶段的混合而影响岩石弱的岩石。2。后震后蠕变和岩石圈剪切区：岩石圈中的瞬时延性行为如何以及微观结构（如晶粒大小和位错密度）的相关变化，影响地震后的累积，释放和释放压力的累积，转移和释放？这种反应如何影响地震复发周期和触发？遗传的岩石圈弱点，因此会影响地震后恢复和地震周期吗？为了解决这些问题，研究人员将使用实验确定的流变学定律将晶粒规范物理学的新发展与板尺度的地球动力学模型联系起来。这些多尺度模型将为上地幔的热化学演化以及地壳中的地震构成行为提供耦合板界形成的平台。该项目的最终科学目标是了解板块构造在地球早期的出现，以及板界的进化和行为如何影响后的后反应和地震周期。这些问题涵盖了地球表面在深度，新原子环境的发展以及地震活动区域的行为的时间尺度。拟议的工作将使用理论和实验来更好地了解地球和人类时间尺度上的地球构造过程。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估来获得支持。

项目成果

A coupled model for phase mixing, grain damage and shear localization in the lithosphere: comparison to lab experiments

岩石圈中相混合、颗粒损伤和剪切局部化的耦合模型：与实验室实验的比较

• DOI: 10.1093/gji/ggac428
• 发表时间: 2022
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Bercovici, David;Mulyukova, Elvira;Girard, Jennifer;Skemer, Philip
• 通讯作者: Skemer, Philip