Radiative Thermal Conductivity of Upper Mantle and Transition Zone Minerals

上地幔和过渡带矿物的辐射热导率

• 批准号: 1417274
• 负责人: Sylvia-Monique Thomas
• 金额: $ 14.11万
• 依托单位: University of Nevada Las Vegas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1417274&HistoricalAwards=false
• 关键词: Radiative; Thermal; Conductivity; Upper; Mantle

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.

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。地幔物质（橄榄石、镁橄榄石、华德士来石和林伍德石）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型、俯冲动力学和岩石圈板片结构。然而，缺乏关于辐射热导率的实验数据，特别是在内部深处存在的高压和高温下。这项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球地幔的所有主要成分，并使用原位光谱法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一个主要驱动力-地球内部的热流。该项目建立在最近的原位光学测量，其中两个主要的过渡区阶段，含水wadsleyite和含水ringwoodite，首次同时在高压和高温下进行了研究。PI报告的辐射热导率为1.5 Wm-1 K-1的含水wadsleyite和1.2 Wm-1 K-1的含水ringwoodite在过渡区条件。对于无水wadsleyite和ringwoodite辐射传导率分析得出，分别高出40%和33%。结果表明，过渡带可能对地幔热传递有重要贡献，并表明辐射热传递在控制地球动力学过程中的重要性。目前的项目是这些测量的延伸，以研究橄榄石、镁橄榄石、akimotoite和D相。将系统地研究样品厚度和成分变化（如铁和水浓度）对镁橄榄石、赤霞岩、D相和橄榄石及其高压多晶型物林伍德石和华兹斯利石的热导率特性的影响。实验是非常及时的，因为理论模型正在开发中，需要实验数据来支持这些模型。这项研究是高度合作的性质，并将利用全国各地的实验室的专业知识和设施，以及国际。这项工作将阐明一个广泛关注的基本跨学科主题，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。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热传递，并最终导致地球内部的精细热模型。