Effects of Deformation-Induced Microstructure, Texture and the Spatial Distribution of Phases on the Steady-State Rheology and Attenuation Response(s) of Mantle Materials

变形引起的微观结构、织构和相空间分布对地幔物质稳态流变和衰减响应的影响

• 批准号: 0609869
• 负责人: Reid Cooper
• 金额: $ 37.2万
• 依托单位: Brown 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: 2006-11-01 至 2011-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0609869&HistoricalAwards=false
• 关键词: Effects; Deformation; Induced; Microstructure; Texture

Research Program Abstract: EAR-0609869Effects of Deformation-Induced Microstructure, Texture and the Spatial Distribution of Phases on the Steady-State Rheology and Attenuation Response(s) of Mantle MaterialsReid F. Cooper, Principal InvestigatorDepartment of Geological SciencesBrown UniversityThe geophysical understanding of the structure of Earth's upper mantle is predicated on the propagation velocity and absorption (attenuation) of seismic waves. Interpretation of seismological data depends on understanding the dynamic mechanical response of appropriate mineral assemblages as functions of a variety of thermodynamic and microstructural factors. The actual database for characterization of dynamic response at appropriate seismic and teleseismic frequencies is quite minimal; consequently, most seismological interpretations, e.g., of structure in Earth's upper mantle, are predicated on assumptions concerning the correlation of the attenuation response with the plastic (creep) response, where far more data are available. Recent experimental studies of attenuation in a variety of Earth and engineering materials indicate clearly, however, that the attenuation-creep correlation assumption is dubious at best, specifically because of inadequate consideration of spatial and temporal scaling effects in deformation. This project is an experimental and theoretical study of the effects of deformation-induced microstructure, texture and the spatial scaling of minerals on (i) the steady-state rheology and (ii) the attenuation response(s). Model upper-mantle materials--synthesized aggregates of dunite (polycrystalline olivine) and of harzburgite (polycrystalline mixture of olivine and orthopyroxene) as well as natural olivine single crystals--are studied. The experimental work emphasizes (a) characterization of spatial scaling of olivine-orthopyroxene phase separation as a function of the stress (or strain rate) and accumulated strain; (b) statistical characterization of deformation microstructure within the material via diffraction-based pole-figure analysis; (c) characterization of the stress-relaxation and "stress-dip" responses as a function of accumulated strain; and (d) direct measurement of attenuation response of deformed specimens. The theoretical work emphasizes application of Hart's [1970] plasticity equation-of-state model to the attenuation response of crystals and aggregates. This research addresses physical properties issues of direct interest to seismologists, particularly in the attempt to isolate effects, e.g., of "water," independent from that of temperature, on the attenuation response. But attenuation will be affected, too, by rock fabrics at a variety of scales (subgrain structure, lattice-preferred orientation and beyond), which have not yet been characterized on mineral assemblages at appropriate time-temperature conditions at all. Application (and proof-testing) of a stress-relaxation technique to the study of attenuation physics may allow knowledge of how to perform spatiotemporal extrapolation, as well as have the potential to isolate the effects of competing various thermodynamic factors on attenuation. The research pursues not only the reductionist physics of the microscopic mechanism(s) of attenuation in minerals, but moves beyond--to the nonequilibrium, dissipative thermodynamics of plasticity in rocks subjected to a relentless deviatoric stress. Thus, the science itself addresses issues of material "self-assembly" specifically through the use of large plastic strain; theories relating to hierarchical materials with unique physical (and, thus, economical) properties can be anticipated to be formulated through this research.

研究计划摘要：EAR-0609869变形引起的微观结构，质地和空间分布在地幔材料F. Cooper的稳态流变和衰减响应上的空间分布， （衰减）地震波。 地震学数据的解释取决于理解适当的矿物组合作为多种热力学和微结构因素的功能的动态机械响应。 在适当的地震和远距离震荡频率下表征动态响应的实际数据库非常小。因此，大多数地震学解释，例如地球上地幔中的结构，都基于关于衰减响应与塑料（蠕变）响应的相关性的假设，在这里可以使用更多数据。 然而，在各种地球和工程材料中衰减的最新实验研究清楚地表明，衰减 - reep相关性假设充其量是可疑的，特别是因为对变形中空间和时间缩放效应的考虑不足。 该项目是对变形诱导的微观结构，纹理和矿物空间缩放的影响的实验和理论研究，对（i）稳态流变学和（ii）衰减响应（i）。 模型的上层材料（多晶（多晶橄榄石）和Harzburgite（橄榄石和原拷贝的多晶混合物）以及天然橄榄石单晶体的混合物聚集体）研究了。 实验工作强调了（a）橄榄石 - 异耐氧相距的空间缩放表征（或应变速率）和累积应变的函数； （b）通过基于衍射的杆位分析，材料内变形微观结构的统计表征； （c）表征应力 - 释放和“应力浸入”反应与累积菌株的函数； （d）直接测量变形标本的衰减响应。 理论工作强调了Hart [1970]可塑性方程模型在晶体和聚集体的衰减响应中的应用。 这项研究探讨了对地震学家直接兴趣的物理性质问题，特别是在试图隔离效果的尝试，例如“水”，而不是温度，而不是温度的衰减反应。 但是，衰减也将受到各种尺度（亚晶体结构，晶状体优先取向及以后）的岩石织物的影响，这些尺寸尚未在适当的时间温度条件下在矿物组合上进行表征。 在衰减物理学的研究中，应力 - 浮肿技术的应用（和校对测试）可能允许了解如何进行时空外推，并且有可能隔离竞争各种热力学因素对衰减的影响的潜力。 这项研究不仅追求矿物质衰减微观机制的还原论物理学，而且还超越了岩石中岩石中可塑性的非平衡，耗散热力学的移动。 因此，科学本身通过使用大型塑性应变来解决材料“自组装”的问题。可以通过这项研究提出与具有独特物理（以及经济）特性的层次材料有关的理论。