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

越来越复杂的地球模型正在被开发出来，以显示地球内部的过程如何影响地表附近的条件。然而，这些模型必须受到精确的实验室数据的约束。地球内部高压矿物相的弹性性质，以及这些性质如何受到温度、压力、矿物结构和成分变化的影响，是特别有趣和重要的数据。这个项目代表了一项合作，以研究地球过渡带几种矿物相的多晶标本的弹性行为。这项合作将利用两个研究领域的个人专业知识。Gabriel Gwanmesia（特拉华州立大学）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（RUS）技术测量这些样品在室温和高温下的弹性特性。以前尝试使用特殊技术（如RUS）研究温度对高压相弹性的影响，由于缺乏高质量的单晶而受到阻碍。这些限制可以通过使用由专家合成的多晶标本来避免，这些多晶标本是由NSF资助多年来开发的。因此，本项目的一个具体目标是研究多晶试样弹性的温度效应如何随橄榄石/瓦德利石/环木石体系中Mg/Fe和水浓度的变化以及斜辉石/多数石/石榴石体系中Ca浓度的变化而变化。当与弹性压力效应和地震层析成像数据结合使用时，该研究结果将更好地约束整个地球构造的地球化学和地球动力学模型，并有助于阐明过渡带在从地核到地表的动力和热过程中的作用。该项目还将解决由美国国家科学基金会（nsf）赞助的COMPRES联盟弹性大挑战的主要目标，即协调各种测量技术报告的弹性数据。具体来说，该项目代表了使用现有弹性测量技术（RUS）对其他技术完成的弹性测量报告提供重要的新交叉检查的尝试，并在某些情况下帮助区分关于高压相的成分和温度对弹性影响的严重冲突的数据。

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.