Two-Phase Damage Theory and the Generation of Plate Tectonics

两相损伤理论与板块构造的生成

• 批准号: 0537599
• 负责人: David Bercovici
• 金额: $ 33.5万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-15 至 2011-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0537599&HistoricalAwards=false
• 关键词: Two; Phase; Damage; Theory; Generation

Shear localization is the process by which deformation in a solid material becomes highly focused into narrow bands that weaken the material. Shear localization is apparent in many fields of physics, materials science and geoscience; at the largest scale, it plays an important role in how plate tectonics arises from thermal convection in the Earth's rocky mantle. In the last few decades, studies of how rocks deform (flow, break, bend, etc.) have shown that the long-term deformation of the lithosphere (the coldest strongest part of the mantle near the surface) is likely controlled by complex behavior such as simultaneous breaking and fluid-like flow; and reduction in the size of mineral grains inside of rocks. Such mechanisms are known to lead to focused or localized deformation and thus play a crucial role in the evolution and structure of boundaries between tectonic plates upon which most of the worlds volcanism and seismicity are focused. Thus, the development of a complete theory of tectonic plate boundary generation from microcrack generation and grainsize reduction in the lithosphere-mantle system is paramount for understanding how plate tectonics arises out of mantle convection. This project continues development of one such new theory called two-phase damage theory. This theory states that (1) a damaged material (with voids/microcracks, defects, grain boundaries) is, in its simplest form, a two-phase material (a rock phase, and a fluid phase representing void-filling or intergranular matter); and (2) the energy going into damage is deformational work that is stored as surface energy on the crack wall and/or grain boundary. The theory has been used to predict shear localization, failure envelopes in rocks, and generation of plate-like motion from simple fluid-dynamical models. These results stress the importance of, and competition between, crack- or void-generating damage and grainsize reducing damage in models of mantle-lithosphere dynamics. The ongoing project incorporates into the theory new important physics of (1) grain-grain boundaries; (2) mass exchange and chemical reactions between phases (e.g., for healing, melting, etc); and (3) evolution in grainsizes and grainsize distributions by coarsening and damage. Applications relevant to lithospheric compression, extension, shear, gravitational collapse, and convectively driven flow are constructed to test the various new physical effects that are added to the theory. This work furthers our understanding of the fundamental processes of mantle dynamics, lithospheric deformation and the origin of plate tectonics. Moreover, since the project involves a fundamental theory, it contributes to many problems of geological fluid mechanics (magma dynamics, glaciology, and hydrological systems), rock mechanics (small-scale damage zones, localization and failure), as well as general material science and engineering (e.g., elastodynamic damage, metallurgy, and complex fluids such as colloids and suspensions).

剪切定位是固体材料中的变形高度聚焦于削弱材料的狭窄带中的过程。 在许多物理，材料科学和地球科学领域，剪切定位显而易见。在最大的尺度上，它在地球岩石地幔中的热对流中如何产生板块构造方面起着重要作用。在过去的几十年中，对岩石的变形（流动，断裂，弯曲等）的研究表明，岩石圈的长期变形（地面附近最冷的最强部分）可能受到复杂行为的控制，例如同时破裂和流体流动流动。并减少岩石内部矿物颗粒的大小。 已知这种机制会导致聚焦或局部变形，从而在构造板之间的边界的进化和结构中起着至关重要的作用，而构造板的大多数世界火山和地震性都集中在这些构造板之间。 因此，构造板边界产生的完整理论从微裂片产生和岩石圈螺丝膜系统中的晶体降低是为了理解板块构造是如何源于地幔对流而产生的。该项目继续开发一种称为两相损害理论的新理论。该理论指出，（1）以最简单的形式是两相材料（岩石相和代表空隙填充或晶间物质的流体相）的损坏的物质（带有空隙/微裂纹，缺陷，晶界）； （2）造成损伤的能量是变形工作，将表面能量存储在裂纹壁和/或晶界。 该理论已用于预测剪切定位，岩石中的故障信封以及从简单的流体动力模型中产生类似板的运动。 这些结果强调了裂纹或空隙生成损伤的重要性和竞争的重要性，并使地幔层动力学模型中的损害减少了损害。 正在进行的项目融入了（1）谷物谷物边界的新重要物理学理论中； （2）相之间的质量交换和化学反应（例如，用于愈合，融化等）； （3）通过粗糙和损坏的晶状化和晶格分布的进化。 构建了与岩石圈压缩，扩展，剪切，重力塌陷和对流驱动流有关的应用，以测试添加到理论中的各种新物理效应。 这项工作进一步了解了我们对地幔动力学，岩石圈变形和板块构造的起源的基本过程的理解。此外，由于该项目涉及基本理论，因此它导致了许多地质流体力学（岩浆动力学，冰川学和水文系统），岩石力学（小规模损害区，定位和失败）以及一般物质科学和工程（例如，弹性动力学损害，金属菌株以及诸如colloids colloids和sissensens和sissensens和sissenss）和速率）的许多问题。