EAR-PF: An Experimental Investigation of the Effect of Pressure, Mineralogy and Water on the Rheological Properties of the Upper Mantle: Implications for Mantle Dynamics

Janelle Homburg博士被授予美国国家科学基金会地球科学博士后奖学金，将在明尼苏达大学开展一项研究和教育计划。这项工作将研究矿物组成(橄榄石/辉石模式丰度)、水含量和压力对地球上地幔强度的影响，以更好地了解大尺度的动态地幔过程。为此，这项研究的一个重要目标是利用实验工作来开发包含成分、水和压力影响的流动规律(应力和应变率之间的关系)。实验将在橄榄石/辉石集合体(方辉橄榄岩)上进行，使用D-DIA高压变形设备。D-DIA的最新发展将使这项研究能够调查以前在实验室中无法获得的高压条件(3-12 Gpa)，并且更能代表整个上地幔的变形条件。除了分析每个实验的力学数据外，还将使用多种不同的技术(红外光谱、电子背散射衍射和透射电子显微镜)对运行产物进行分析，以加深对变形中涉及的微物理过程的了解。虽然浅层地球的力学行为被认为是相对较好的，但上地幔较深部分(深度大于~100公里)的变形行为仍然存在很大的不确定性。这种情况在很大程度上是由于在D-DIA出现之前，实验室中可以获得的压力范围相当有限。这项研究中计划的一系列实验将允许更好地了解整个上地幔中地球材料的变形行为，进而更好地了解各种关键的地球动力学过程，如俯冲。除了发展J.Homburg作为研究人员的技能外，该奖学金还将使她能够在课堂和外联环境中发展成为一名教育工作者。她将协助明尼苏达大学教授地质学课程，并指导本科生和研究生。她还将参与明尼苏达州科学博物馆的科学教育项目的发展。

Dr. Janelle Homburg has been awarded an NSF Earth Science Postdoctoral Fellowship to carry out a research and education plan at the University of Minnesota. This work will investigate the effects of mineralogical composition (olivine/pyroxene modal abundance), water content and pressure on the strength of Earth's upper mantle in order to better understand large-scale dynamic mantle processes. To this end, an important goal of this study is to utilize experimental work to develop flow laws (relationships between stress and strain rate) that incorporate the effects of composition, water and pressure. Experiments will be preformed on olivine/pyroxene aggregates ("harzburgite" rocks) utilizing the D-DIA, a high-pressure deformation apparatus. The recent development of the D-DIA will allow this study to investigate high-pressure conditions (3-12 GPa) that have previously been unobtainable in the lab and are more representative of deformation conditions throughout the upper mantle. In addition to analyzing the mechanical data from each experiment, the run products will be analyzed by a number of different techniques (infrared spectroscopy, electron backscatter diffraction, and transmission electron microscopy) in order to develop a deeper understanding of the microphysical processes involved in deformation. While the mechanical behavior of the shallow Earth is thought to be relatively well understood, great uncertainty still remains in the deformation behavior of the deeper portion of the upper mantle (depths greater then ~100 km). This situation is due in large part to the fact that prior to the advent of the D-DIA, the range of pressures accessible in the lab was fairly limited. The series of experiments planned in this research will allow for better understanding of the deformation behavior of earth materials throughout the entire upper mantle and, by extension, better understanding of a wide variety of key geodynamic processes, such as subduction.In addition to developing J. Homburg's skills as a researcher, this fellowship will allow her to develop as an educator both in classroom and outreach settings. She will assist in teaching geology courses and in mentoring undergraduate and graduate students at the University of Minnesota. She will also be involved in the development of science education programs at the Science Museum of Minnesota.