Radiative Thermal Conductivity of Upper Mantle and Transition Zone Minerals

地球内部的结构和动力学在很大程度上取决于热流，因此也取决于其组成部分的导热性。橄榄石、镁铁石、沃兹利岩和环伍德岩等地幔物质的热导率是地幔对流地球动力学模型的重要参数。这些矿物的辐射热导率的差异将影响岩石圈地热模式、俯冲动力学和岩石圈板块结构。然而，缺乏关于辐射热导率的实验数据，特别是在存在于深层内部的高压和高温下。本实验研究旨在补充不断发展的理论框架，将正在进行的项目扩展到地幔的所有主要成分，并使用原位光学光谱间接测量辐射热导率的温度-压力变化。该项目的一个主要目标是进一步了解自然界的主要驱动力——地球内部的热流。该项目建立在最近的原位光学测量的基础上，其中首次在高压和高温同时研究了两个主要的过渡带相，含水瓦德利岩和含水环伍德岩。PI报告了在过渡带条件下，含水瓦德利岩的辐射导热系数为1.5 Wm-1K-1，含水环伍德岩的辐射导热系数为1.2 Wm-1K-1。无水瓦德利岩和环伍德岩的辐射电导率分别高出40%和33%。研究结果表明，过渡带可能对地幔的热传递有重要贡献，并表明辐射传热在控制地球动力学过程中的重要性。目前的项目是对这些测量的延伸，以研究橄榄石、镁铁石、钾辉石和D相。样品厚度和成分变化（如铁和水浓度）对镁铁石、钾辉石、D相和橄榄石及其高压多晶态环木石和瓦德利石的导热性能的影响将被系统地研究。实验非常及时，因为理论模型正在开发中，需要实验数据来支持这些模型。这项研究具有高度协作的性质，并将利用全国以及国际实验室的专业知识和设施。这项工作将阐明一个广泛的受众，包括矿物物理学家、地震学家、地球动力学家、地球化学家和行星科学家，深切关注的基本跨学科主题。这项研究将为本科生提供宝贵的学习经验，以及重要的数据，这将有助于我们了解地球的传热，并最终导致地球内部的精细热模型。

The structure and dynamics of our planet's interior depend crucially upon heat flow and thus upon the thermal conductivity of its constituents. Thermal conductivities of Earth's mantle materials, such as olivine, majorite, wadsleyite and ringwoodite, are important parameters for geodynamic models of mantle convection. Differences in radiative thermal conductivities of these minerals will affect models of lithospheric geotherms, subduction dynamics, and the structure of lithospheric slabs. However, there is a lack of experimental data about radiative thermal conductivities, especially at the high pressures and temperatures that exist in the deep interior. This experimental study aims to complement evolving theoretical frameworks, extend ongoing projects to all major constituents of the Earth's mantle, and indirectly measure the temperature-pressure variation of radiative thermal conductivity using in-situ optical spectroscopy. A primary goal of the project is to further our understanding of a major driving force of nature - heat flow within the Earth. This project builds on recent in-situ optical measurements, in which two major transition zone phases, hydrous wadsleyite and hydrous ringwoodite, were studied for the first time at simultaneous high pressure and high temperature. The PI reported radiative thermal conductivities of 1.5 Wm-1K-1 for hydrous wadsleyite and 1.2 Wm-1K-1 for hydrous ringwoodite at transition zone conditions. For anhydrous wadsleyite and ringwoodite radiative conductivities were analytically derived to be 40% and 33% higher, respectively. The results indicate that the transition zone may contribute significantly to heat transfer in the mantle and demonstrate the importance of radiative heat transfer in controlling geodynamic processes. The current project is an extension of those measurements to study olivine, majorite, akimotoite and phase D. The effect of sample thickness and compositional changes (such as iron and water concentrations) on thermal conductivity properties of majorite, akimotoite, phase D and olivine and its high-pressure polymorphs ringwoodite and wadsleyite will be systematically investigated. The experiments are very timely, since theoretical models are in development and experimental data are needed to support such models. This research is of highly collaborative nature, and will take advantage of the expertise and facilities of laboratories across the nation, as well as internationally. This work will illuminate a fundamentally interdisciplinary topic of deep concern to a broad audience, including mineral physicists, seismologists, geodynamicist, geochemists, and planetary scientists. This study will provide a valuable learning experience for undergraduate students, as well as important data, which will contribute to our knowledge of heat transfer in the Earth and eventually lead to refined thermal models of the Earth's interior.