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性质，以及这些性质如何受到温度、压力以及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，旨在研究地球过渡带几种矿物相的多晶样品的弹性行为。这项合作将利用个人在两个研究领域的专业知识。加布里埃尔·格万梅西亚(特拉华州立大学)将负责合成高压相的多晶样品。加州大学洛杉矶分校的Donald Isaak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性质。以前使用特殊技术(如RUS)研究温度对高压相弹性的影响的尝试因缺乏高质量的单晶而受阻。这些限制可以通过使用专家合成的多晶样品来避免，这些样品是由国家科学基金会资助多年开发的设施中合成的。因此，这个项目的一个具体目标是研究多晶样品的弹性温度效应如何随橄榄石/水滑石/环木石系中的镁/铁和水浓度以及单斜辉石/白云母/石榴石系统中的钙浓度的变化而变化。当与弹性和地震层析成像的压力效应数据一起使用时，这项研究的结果将更好地约束全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球核心到地表的动态和热过程中的作用。该项目还将解决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。具体地说，该项目试图使用现有的弹性测量技术(RUS)来对使用其他技术进行的弹性测量报告提供重要的新的交叉检查，并在某些情况下帮助区分在高压相的组成和温度对弹性的影响方面存在严重冲突的数据。

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.