Water-Induced Fabric Transitions in Olivine

PI在前几个资助期的实验研究表明，高水分条件下橄榄石中的变形组构(晶格择优取向：LPO)明显不同于缺水条件下的变形组构。自然变形的橄榄岩中的一些组构和上地幔中观察到的一些地震各向异性可能反映了橄榄石中这些由水引起的组构转变。然而，以前的研究有很大的局限性，因为没有量化组构转变的标度规律，也没有探索其他矿物如斜方辉石的作用。在这项新的建议中，研究人员建议将先前的研究扩展到以下方向。首先，他们将确定织物图的比例规律，重点是温度的影响。其次，他们将研究控制微观组织变化的微观机制，重点是变形机制边界。他们的初步结果表明，水可能比位错控制的过程更能促进扩散相关的过程。这项研究将利用实验室开发的大应变剪切变形技术和新安装的高分辨率扫描电子显微镜(SEM)。这一结果将对解释自然变形岩石的变形组构以及解释地震各向异性具有重要意义。这项提案中描述的研究将构成菲尔·斯凯默博士论文的主要组成部分。

EAR-0309448KaratoThe PI's experimental studies during the previous funding periods have demonstrated that the deformation fabrics (lattice preferred orientation: LPO) in olivine under high water content conditions are markedly different from those under water-poor conditions. Some of the fabrics in naturally deformed peridotites and some of the observed seismic anisotropy in the upper mantle may reflect these water-induced fabric transitions in olivine. However, previous research has major limitations in that the scaling laws for fabric transitions have not been quantified and the roles of other minerals such as orthopyroxene have not been explored. In this new proposal, the investigator proposes to extend the previous studies in the following directions. First, they will determine the scaling laws of fabric diagram with a focus on the effects of temperature. Second, they will investigate microscopic mechanisms controlling the varieties of microstructures with the emphasis on deformation mechanism boundary. Their preliminary results suggest that water may enhance diffusion-related processes more than dislocation-controlled processes. The large-strain shear deformation technique developed in the investigator's lab together with a newly installed high-resolution SEM (scanning electron microscope) will be utilized in this study. The results will have important implications for interpreting deformation fabrics of naturally deformed rocks as well as for the interpretation of seismic anisotropy. The research described in this proposal will comprise a major component of Phil Skemer's Ph D thesis.