Microphysics of evolving rock viscosity in the seismic and glacial cycles

地震和冰川循环中岩石粘度演化的微观物理

• 批准号: MR/V021788/1
• 负责人: David Wallis
• 金额: $ 139.27万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FV021788%2F1
• 关键词: Microphysics; evolving; rock; viscosity; seismic

Despite being the epitome of strength, the solid rocks below Earth's surface can flow surprisingly rapidly over human timescales, impacting processes of societal relevance. This project aims to deliver new equations describing this flow based on the underlying processes operating in the rocks.Major earthquakes and the melting of ice sheets cause deflections of Earth's surface that are facilitated by viscous flow of the hot rocks below. This deformation creates important feedbacks. During the seismic cycle, earthquakes induce viscous flow of rocks beneath the fault zone that impacts the spatial and temporal distributions of future earthquakes. During the glacial cycle, viscous flow of rocks beneath melting ice sheets causes ground uplift that impacts sea-level change. Therefore, modelling these systems requires knowledge of the viscosity of rocks in Earth's lower crust and upper mantle.Unfortunately, the viscosities of these rocks are not constant but instead undergo a transient evolution whenever there is a change in the applied forces. Whilst we know that this viscosity evolution occurs, we do not know why. Without knowing the microscale processes that control the viscosity evolution, we cannot formulate equations that reliably predict flow of rocks in the Earth over the seismic and glacial cycles. At a time when populations exposed to seismic risk are rapidly expanding and when the modelling of ice-sheet dynamics is of unprecedented importance, it is critical to develop new models for the viscosity evolution of the rocks that underpin these systems.Deciphering the microphysical processes that control the viscosity evolution of rocks requires an ambitious multidisciplinary approach. Each element of the research will be centred on the novel adaptation of techniques from the forefront of the materials sciences to analyse key geological minerals. Experiments will be conducted at temperatures up to 1500 degrees Celcius and will induce viscosity evolution by imposing instantaneous changes in the applied forces, analogous to those imposed by earthquakes. For the first time, a subset of the experiments will be performed inside a scanning electron microscope allowing the samples to be directly imaged during the tests. The microstructures of the samples will be analysed using state-of-the-art microscopy techniques, pioneered by our group, to measure distortions of the crystal lattices and the forces trapped within them. The combined mechanical data and microstructural observations will provide the new insights necessary to determine the key processes operating in the crystal lattices of the minerals that cause their viscosities to evolve.The interpretations from the laboratory will be subject to two critical tests. To check the consistency and robustness of the interpretations, we will employ the latest models of deforming crystalline materials. We will adapt these models, developed to simulate metals, to analyse geological materials. The relevance of the laboratory experiments to natural rocks will be tested by comparing the microstructures of minerals from both settings. We will utilise samples from the deep portions of major fault zones that provide direct records of viscous flow in the lower crust and upper mantle.The critical information gained from experiments, microstructural analyses, and modelling will be used to construct and calibrate new equations describing viscosity evolution. For the first time, the equations will be based on rigorous analyses of the specific underlying processes. These equations will unlock the next generation of large-scale models that incorporate the impacts of viscosity evolution in the seismic and glacial cycles. The mechanical and microstructural data generated in this project will be made freely available, providing a new and unique digital resource. Similarly, the techniques pioneered in this project will open new frontiers in the dynamics of geological materials.

尽管是强度的缩影，地球表面下的固体岩石可以在人类的时间尺度上惊人地快速流动，影响社会相关性的过程。该项目旨在根据岩石中的基本过程提供描述这种流动的新方程。大地震和冰盖融化导致地球表面偏转，这是由下面热岩石的粘性流动促进的。这种变形产生了重要的反馈。在地震周期中，地震引起断层带下岩石的粘性流动，影响未来地震的空间和时间分布。在冰川循环期间，融化的冰盖下岩石的粘性流动导致地面隆起，影响海平面变化。因此，建立这些系统的模型需要了解地球下地壳和上地幔岩石的粘度。不幸的是，这些岩石的粘度不是恒定的，而是在所施加的力发生变化时经历短暂的演变。虽然我们知道这种粘度变化会发生，但我们不知道为什么。如果不知道控制粘度演化的微尺度过程，我们就不能用公式可靠地预测地震和冰川循环中地球岩石的流动。在人口暴露于地震风险迅速扩大，冰盖动力学的建模是前所未有的重要性时，它是至关重要的，以开发新的模型的粘度演变的岩石，这些systems.Deciphering控制粘度演变的岩石的微物理过程需要一个雄心勃勃的多学科的方法。研究的每一个要素都将集中在材料科学前沿技术的新适应上，以分析关键的地质矿物。实验将在高达1500摄氏度的温度下进行，并将通过施加类似于地震施加的力的瞬时变化来诱导粘度演变。第一次，实验的一个子集将在扫描电子显微镜内进行，允许样品在测试过程中直接成像。样品的微观结构将使用我们小组开创的最先进的显微镜技术进行分析，以测量晶格的扭曲和被困在其中的力。结合力学数据和微观结构观察将提供必要的新见解，以确定矿物晶格中导致其粘度演变的关键过程。实验室的解释将受到两个关键测试的影响。为了检查解释的一致性和鲁棒性，我们将采用最新的变形晶体材料模型。我们将调整这些为模拟金属而开发的模型，以分析地质材料。实验室实验与天然岩石的相关性将通过比较两种环境中矿物的微观结构来进行测试。我们将利用主要断裂带深部的样品，直接记录下地壳和上地幔的粘性流，从实验、显微结构分析和建模中获得的关键信息将用于构建和校准描述粘度演化的新方程。这是第一次，这些方程将基于对具体基本过程的严格分析。这些方程将解锁下一代大规模模型，其中包括地震和冰川周期中粘度演变的影响。该项目产生的力学和微观结构数据将免费提供，提供一个新的和独特的数字资源。同样，该项目中开创的技术将在地质材料动力学方面开辟新的领域。

项目成果

The Effect of Intracrystalline Water on the Mechanical Properties of Olivine at Room Temperature

室温下结晶水对橄榄石力学性能的影响

• DOI: 10.1029/2023gl106325
• 发表时间: 2024
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Kumamoto, Kathryn M.;Hansen, Lars N.;Breithaupt, Thomas;Wallis, David;Li, Bo‐Shiuan;Armstrong, David E. J.;Goldsby, David L.;Li, Yang;Warren, Jessica M.;Wilkinson, Angus J.
• 通讯作者: Wilkinson, Angus J.

The Role of Grain Boundaries in Low-Temperature Plasticity of Olivine Revealed by Nanoindentation

纳米压痕揭示晶界在橄榄石低温塑性中的作用

• DOI: 10.1029/2023jb026763
• 发表时间: 2023
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Avadanii D

Grain-Size Effects During Semi-Brittle Flow of Calcite Rocks

方解石岩石半脆性流动过程中的粒度效应

• DOI: 10.1029/2023jb026458
• 发表时间: 2023
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Harbord C

High-magnitude stresses induced by mineral-hydration reactions

矿物水合反应引起的高强度应力

• DOI: 10.1130/g50493.1
• 发表时间: 2022
• 期刊: Geology
• 影响因子: 5.8
• 作者: Plümper O

Grain growth of natural and synthetic ice at 0 °C

0℃下天然冰和合成冰的晶粒生长

• DOI: 10.5194/tc-17-3443-2023
• 发表时间: 2023
• 期刊: The Cryosphere
• 作者: Fan S