Calibration of a new model for mantle viscosity: the role of grain boundaries from bicrystal experiments

地幔粘度新模型的校准：双晶实验中晶界的作用

• 批准号: NE/S001727/1
• 负责人: Julian Mecklenburgh
• 金额: $ 21.15万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FS001727%2F1
• 关键词: Calibration; new; model; mantle; viscosity

The solid rocks within Earth's interior can flow, analogous to ice in a glacier, given sufficient time and temperature. This flow, or viscous deformation, has a strong influence on a variety of processes over short and long time scales. Over long time scales, the viscous deformation of rocks controls the motion of Earth's tectonic plates. Over short timescales, the viscous deformation of rocks controls the rate at which stresses buildup on overlying, earthquake-generating faults. However, there are major gaps in our understanding of how these rocks deform, which results in significant uncertainties in modeling these large-scale processes on Earth.One of the largest sources of uncertainty is in understanding how grain boundaries, that is the regions between crystals, deform at extreme conditions. This lack of understanding has major implications for predicting processes in Earth. For instance, if grain boundaries are weak relative to the interiors of crystals, then the rates at which stresses build up on large, earthquake-generating faults may increase tenfold. To address this shortcoming, we will carry out experiments at extreme conditions in which we slide two crystals past each other. In some cases, we will add water to the boundary to test if water increases how fast the crystals slide. The data from many experiments will be used to create an equation that describes how fast the crystals slide under a wide range of conditions. To investigate how individual grain boundaries influence the properties of a rock made up of many crystals, these equations will be incorporated into numerical simulations that predict the behavior of an aggregate of crystals. These simulations will be used to understand the importance of grain boundaries in a variety of important large-scale geologic processes.

如果有足够的时间和温度，地球内部的固体岩石可以流动，就像冰川中的冰一样。这种流动，或称粘性变形，在短时间和长时间尺度上对各种过程都有很大的影响。在很长的时间尺度上，岩石的粘性变形控制着地球构造板块的运动。在很短的时间内，岩石的粘性变形控制着上覆的地震发震断层上应力积累的速度。然而，我们对这些岩石如何变形的理解存在很大差距，这导致在模拟地球上这些大规模过程时存在很大的不确定性。最大的不确定性来源之一是理解晶界，即晶体之间的区域在极端条件下是如何变形的。这种缺乏理解对预测地球上的过程有重大影响。例如，如果晶界相对于晶体内部较弱，那么在大型地震发震断层上应力积累的速度可能会增加十倍。为了解决这一缺点，我们将在极端条件下进行实验，在这种条件下，我们将使两个晶体相互滑动。在某些情况下，我们会在边界上加水，以测试水是否增加了晶体滑动的速度。许多实验的数据将被用来建立一个方程，描述晶体在各种条件下滑动的速度。为了研究单个晶界如何影响由许多晶体组成的岩石的性质，这些方程将被纳入预测晶体聚集体行为的数值模拟中。这些模拟将被用来理解晶界在各种重要的大规模地质过程中的重要性。