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

地球岩石圈多尺度结构的综合实地和数值研究

• 批准号: RGPIN-2014-04885
• 负责人: Jiang, Dazhi
• 金额: $ 2.19万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611307
• 关键词: Integrated; field; numerical; investigations; multiscale

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.

我们建议开发大陆岩石圈变形的稳健数值模型，并通过自然变形区的实地研究来测试这些模型。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的流变学。 地球在太阳系的类地行星中是独一无二的，因为它具有板块构造，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原理对于理解地球和其他行星的演化，以及实际上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、矿物和其他资源都具有至关重要的意义。尽管它与人类关系密切，并且与我们对海洋岩石圈的理解水平相反，但长期（数百万年）和跨广阔空间尺度（与北美等大陆的大小相当）的大陆变形仍然知之甚少。这是因为在广泛的观测尺度上，大陆岩石圈的机械异质性远高于海洋岩石圈。经过几十年的研究，我们仍然缺乏有效的手段来解决这种异质体的多尺度变形。这项研究将建立在申请人最近取得的进展的基础上，将对变形结构（过去岩石圈变形的“标志”）的直接地质调查与基于连续微观力学的新颖数值模拟方法结合起来，该方法解决了异质材料的多尺度变形问题。 如何有效处理流变非均质大陆岩石圈的变形并模拟多尺度结构的伴随发展一直是构造地质学和构造学领域最根本的问题，也是其发展的瓶颈。四十多年来，结构和构造界一直采用单尺度模型（大多是均质的且具有运动学性质），尽管它们长期以来被认为是高度不现实的。问题的关键是找到一种严格的方法来解决大陆岩石圈等非均质物质中流场的巨大变化。最近，申请人成功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）微力学的多阶幂律方法（MOPLA），该方法首次将织物建模置于严格的力学基础上。该提案要求提供资金：1）将 MOPLA 开发成一个更稳健的模型，这是一种自洽模型，其中包含由于变形过程中织物堆积而导致的流变学演变的显着影响；2）通过在明确定义的自然变形区域进行现场研究来测试模型预测。这项研究的成果预计将成为构造地质学和构造学领域的里程碑式成就。研究目标与我的长期研究目标一致，即建立一种研究小型结构的综合理论、数值和现场方法。研究活动将包括数值模型的理论制定和实施以及现场和实验室工作。这些活动将涉及许多研究生和其他研究助理。因此，该研究为本科生、研究生和初级科学家提供了一个教授高级实地考察、实验室和计算技能的平台，将科学研究与新科学家的培训结合起来。