Integrated field and numerical investigations on multiscale structures in Earth's lithosphere

我们建议开发强大的大陆岩石圈变形的数值模型，并测试这些模型的自然变形带的面向外地的研究。我们的目标是建立一个严格的框架来研究小尺度结构，以便它们可以用来推断大尺度构造和大陆岩石圈流变学。地球是太阳系中唯一的类地行星，它具有板块构造，导致岩石圈板块在板块边界和内部区域变形。了解这种变形的物理机制，对于理解地球和其他行星的演化具有重要的科学意义，对于生活在岩石圈上的人类的福祉、减轻自然灾害以及从中获取能源、矿物和其他资源也具有重要的实践意义。尽管它与人类有着密切的关系，并且与我们对海洋岩石圈的理解水平形成鲜明对比，大陆变形的长期（数百万年）和巨大的空间尺度（相当于北美大陆的大小）仍然知之甚少。这是因为在大范围的观测尺度上，大陆岩石圈的力学性质远比大洋岩石圈的不均匀。经过几十年的研究，我们仍然缺乏一个有效的手段来处理这样的非均匀体的变形在多尺度上。这项研究将建立在申请人的最新进展和联合收割机直接地质调查的变形结构，这是过去的岩石圈变形的“签名”，与一种新的数值模拟方法的基础上连续微观力学，它解决了多尺度变形的异质材料。如何有效地处理流变非均匀大陆岩石圈的变形，并模拟其伴随的多尺度构造的发展，是构造地质学和构造学领域最基本的问题，也是制约其发展的瓶颈。40多年来，结构和构造学界一直采用单尺度模型（大多是同质的，具有运动学性质），尽管它们长期以来被认为是非常不现实的。解决这一问题的关键是找到一种严格的方法来处理像大陆岩石圈这样的非均匀物质中流场的巨大变化。最近，申请人已经成功地开发了基于非牛顿粘性材料（被认为是地球岩石圈的最佳代表）的微观力学的多阶幂律方法（MOPLA），其首次将结构建模置于严格的力学基础上。该提案要求提供资金：1）将MOPLA开发成一个更强大的模型，一个自洽的模型，其中包含变形过程中由于织物堆积而产生的流变学变化的显著影响，以及2）通过在明确的自然变形区进行实地研究来测试模型预测。这一研究成果有望成为构造地质学和构造学的里程碑式成就。研究目标与我的长期研究目标相一致，即建立一个研究小型结构的综合理论，数值和现场方法。研究活动将包括理论制定和实施的数值模型和现场和实验室工作。这些活动将涉及许多研究生和其他研究人员。因此，这项研究提供了一个平台，为本科生，研究生和初级科学家教授先进的实地考察，实验室和计算技能，结合科学调查与新科学家的培训。

We propose to develop robust numerical models for the deformation of the continental lithosphere and to test these models by field-oriented studies of natural deformation zones. Our goal is to establish a rigorous framework for studying small-scale structures so that they can be used to infer large-scale tectonics and the rheology of the continental lithosphere.The Earth is unique among the terrestrial planets in the solar system in that it has plate tectonics which causes lithospheric plates to deform in plate boundary and interior regions. Understanding the physics of this deformation is of paramount significance both scientifically, for understanding the evolution of Earth and other planets, and practically for the welfare of human beings who live on the lithosphere, mitigate natural hazards, and derive energy, mineral, and other resources from it. Despite its close relationship to humanity and in contrast to our level of understanding of the oceanic lithosphere, continental deformation over long terms (millions of years) and across vast spatial scales (comparable to the size of a continent like the North America) remains poorly understood. This is because the continental lithosphere is far more heterogeneous mechanically than the oceanic lithosphere on a wide range of observation scales. After many decades of research, we still lack an effective means to tackle the deformation of such a heterogeneous body on multiscales. This research will build on the applicant’s recent progress and combine direct geological investigations on deformation structures, which are “signatures” of past lithospheric deformation, with a novel numerical modeling approach based on continuum micromechanics, which addresses the multiscale deformation of heterogeneous materials. How to tackle effectively the deformation of a rheologically heterogeneous continental lithosphere and to model the accompanying development of multiscale structures have been most fundamental issues in the field of structural geology and tectonics, and bottle necks to its advances. For over 4 decades, the structural and tectonics community has resorted to single-scale models (mostly homogeneous and of a kinematic nature), although they have long been recognized as highly unrealistic. The key to the problem is to find a rigorous means to address the great variability in the flow field in a heterogeneous material like the continental lithosphere. Recently, the applicant has succeeded in developing a MultiOrder Power Law Approach (MOPLA) based on micromechanics for non-Newtonian viscous materials (believed to be the best representation of Earth's lithosphere) which, for the first time, places fabric modeling on rigorous mechanical grounds. This proposal requests funds 1) to develop MOPLA into a more robust model, a self-consistent one that incorporates the significant effect of the evolving rheology due to fabric buildup in the process of deformation, and 2) to test the model predictions by field studies in well-defined natural deformation zones. The outcome of this research is expected to be a landmark achievement in structural geology and tectonics. The research objectives align with my long-term research goal to establish an integrated theoretical, numerical, and field methodology for studying small structures. The research activities will include theoretical formulation and implementation of numerical models and field and laboratory work. These activities will involve many graduate students and other research associates. Thus the research provides a platform for teaching advanced fieldwork, laboratory, and computational skills to undergraduate, graduate students, and junior scientists, combining scientific investigation with the training of new scientists.