Collaborative Research: Quantifying the Dependence of Fabric and Rheology on Finite Strain for Naturally Deformed Rocks

流变学是一个用来描述材料行为的术语，它量化了观测到的变形(应变)和施加的力(应力)之间的关系。岩石变形和构造板块演化的所有方面都是岩石流变学在地质时间尺度上的函数。描述岩石流变学的困难是因为地质过程的变形速度极慢，以及岩石的多相(两种以上矿物)性质。该项目的研究人员使用现场数据来约束和量化渐进有限应变与发育组构之间的关系，从而约束自然变形岩石的流变学。人们正在研究来自安大略省西北部的变质和变形的塞纳河砾岩，因为它们包含各种各样的岩石类型和显著的有限应变梯度。对这些砾岩中所有碎屑(岩石类型)群体的详细有限应变分析可以计算不同碎屑群体在单个露头处的相对应变率，并显示相对强度关系如何在有限应变梯度上变化。目前正在对应变梯度上的不同碎屑群进行详细的组构和质地分析。具体地说，这种分析包括每个碎屑组内每个矿物相的晶格择优取向、形状择优取向和连通性(小波分析)。这些织物和纹理数据集，当与有限应变数据相结合时，将显示每个不同的碎屑种群如何适应有限应变。这种方法明确地解决了以下两个方面的相对重要性：(1)组构发展在渐进有限应变期间碎屑群体变形行为的演变中，以及(2)初始成分、初始颗粒尺寸和初始组构的变化对变形行为的影响。

Rheology, a term used to describe material behavior, quantifies the relation between the observed deformation (strain) and the applied forces (stress). All aspects of rock deformation and evolution of the tectonic plates are a function of rock rheology over geological time scales. The difficulty in characterizing rock rheology occurs because of the extremely slow rates of deformation for geological processes and the polyphase (more than two minerals) nature of rocks. The researchers in this project use field data to constrain and quantify the relationships between progressive finite strain and developing fabrics, and thereby constrain rheology of naturally deformed rocks. The metamorphosed and deformed Seine conglomerates from northwestern Ontario are being studied because they contain a wide variety of rock types and a significant finite strain gradient. Detailed finite strain analysis of all clast (rock type) populations in these conglomerates allow calculations of the relative strain rates of the different clast populations at individual outcrops and show how the relative strength relationships change across the finite strain gradient. Detailed fabric and textural analyses of the different clast populations across the strain gradient are being conducted. Specifically, this analysis includes lattice preferred orientation, shape preferred orientation, and connectivity (wavelet analysis) of each mineral phase within each clast population. These fabric and texture data sets, when coupled with the finite strain data, will show how each different clast population accommodates finite strain. This approach explicitly addresses the relative importance of: (1) fabric development in the evolution of a clast population's deformation behavior during progressive finite strain, and (2) variations in initial composition, initial grain size, and initial fabric on deformation behavior.