Collaborative Research: Elasticty of Hot-Pressed Polycrystalline High-Pressure Minerals of the Earth's Transition Zone

正在开发越来越复杂的地球模型，以显示地球内部的过程如何影响地表附近的条件。然而，这些模型必须受到准确和精确的实验室数据的约束。地球内部高压矿物相的弹性特性，以及这些特性如何受到温度、压力、矿物结构和成分变化的影响，是特别令人感兴趣和重要的数据。该项目是一项合作，旨在研究地球过渡带中几种矿物相的多晶样品的弹性行为。该合作将利用两个研究领域的个人专业知识。Gabriel Gwanmesia（特拉华州州立大学）将负责合成高压相的多晶样品。Donald Isaak（加州大学洛杉矶分校）将负责使用共振超声光谱（罗斯）技术测量这些样品在室温和高温下的弹性性能。以前尝试使用特殊技术（如罗斯）研究温度对高压相弹性的影响，但由于缺乏优质单晶而受阻。通过使用由专家在NSF资助多年开发的设施中合成的多晶样品，可以避免这些限制。本项目的一个具体目标，因此，是调查温度效应的弹性多晶试样的变化与镁/铁和水的浓度在橄榄石/wadsleyite/ringwoodite系统和钙浓度在单斜辉石/镁铝榴石/石榴石系统。当与弹性压力效应和地震层析成像数据一起使用时，这项研究的结果将更好地约束地球化学和地球动力学模型的整个地球构造，并有助于阐明过渡带的作用，在动力和热过程从地球的核心到表面。这个项目也将解决的主要目标，弹性大挑战的NSF-赞助的COMPRES联盟，该联盟将协调各种测量技术报告的弹性数据。具体而言，该项目代表了一种尝试，使用现有的弹性测量技术（罗斯），以提供重要的新的交叉检查与其他技术完成的弹性测量报告，并帮助区分，在某些情况下，在严重冲突的数据之间的组成和温度对弹性的高压阶段的影响。

Increasingly sophisticated Earth models are being developed that show how processes in Earth's interior affect conditions near the surface. These models, however, must be constrained by accurate and precise laboratory data. The elastic properties of high-pressure mineral phases in Earth's interior, and how these properties are affected by changes in temperature, pressure, and mineral structure and composition, are data of special interest and importance. This project represents a collaboration to investigate the elastic behavior of polycrystalline specimens of several mineral phases in Earth's transition zone.The collaboration will draw on individual expertise in two areas of research. Gabriel Gwanmesia (Delaware State University) will assume responsibility for synthesizing polycrystalline specimens of high-pressure phases. Donald Isaak (University of California at Los Angeles) will be responsible for measuring the elastic properties of these specimens at room temperature and elevated temperature using the resonant ultrasound spectroscopy (RUS) technique.Previous attempts to study temperature effects on elasticity of high-pressure phases using special techniques such as RUS have been hindered by the lack of quality single-crystals. These limitations can be avoided through use of polycrystalline specimens synthesized by specialists at facilities developed over many years through NSF funding. A specific goal of this project, therefore, is to investigate how temperature effects of elasticity of polycrystalline specimens vary with Mg/Fe and water concentrations in the olivine/wadsleyite/ringwoodite system and with Ca concentration in the clinopyroxene/majorite/garnet system. When used with data on pressure effects of elasticity and seismic tomography, results from this study will better constrain geochemical and geodynamical models of whole-Earth tectonics and help elucidate the role of the transition zone in dynamic and thermal processes from Earth's core to surface.This project will also address a primary goal of the Elasticity Grand Challenge of the NSF-sponsored COMPRES consortium which is to reconcile elasticity data reported from a variety of measuring techniques. Specifically, the project represents an attempt to use an existing elasticity measurement technique (RUS) to provide significant new cross checks on reports of elasticity measurements done with other techniques, and to help discriminate, in some cases, between data that are in serious conflict regarding composition and temperature effects on elasticity for high-pressure phases.