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: 1215957
• 负责人: Sylvia-Monique Thomas
• 金额: $ 20.37万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1215957&HistoricalAwards=false
• 关键词: Radiative; Thermal; Conductivity; Upper; Mantle

Structure and dynamics of our planet's interior depend crucially upon heat flow and thus upon the thermal conductivity of its constituents. Temperature- and pressure-dependent thermal conductivity of Earth's mantle materials, such as olivine, is an important parameter for geodynamic models of mantle convection. Thermal conductivity variations affect models of lithospheric geotherms, subduction dynamics, and the structure of lithospheric slabs. Does the mantle transition zone between a depth of 410 and 660 km act as a heat flux regulator within the Earth's upper and lower mantle? Thermal conductivities of upper mantle and transition zone minerals are poorly constrained, and there is little experimental data on the radiative part of thermal conductivity, especially at the high pressures and temperatures that exist in those regions. This experimental study aims to complement continually evolving theoretical frameworks, extend ongoing projects to all major constituents of the Earth's mantle and indirectly measure temperature-pressure variation of radiative thermal conductivity using in-situ optical spectroscopy as powerful tool. 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 upon recent in-situ optical measurements, for the first time at simultaneous high-pressure and high-temperature, studying two major transition zone phases, hydrous wadsleyite and hydrous ringwoodite. We reported large radiative thermal conductivities, which reveal an energy transmission 'window' in the infrared and visible spectral range. We found that the mantle transition zone may contribute significantly to radiative heat transfer, and we confirmed predictions that hydration may enhance radiative heat flux. The current project will extend those studies to olivine, majorite, and phase D. In addition, we plan to systematically study the effect of compositional changes (such as iron and water concentrations) on thermal conductivity properties of olivine and it's high-pressure polymorphs wadsleyite and ringwoodite. 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, in particular the Geophysical Laboratory of the Carnegie Institution of Washington (optical measurements), the Earth and Planetary Science and Civil and Environmental Engineering departments at Northwestern University (spectroscopy) and the Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences (syntheses). This work will illuminate a fundamentally interdisciplinary topic of deep concern to a broad audience, including mineral physicists, seismologists, geodynamicist, geochemists, and planetary scientists. Our 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?s interior and will help to improve geophysical models of heat flux in the Earth.

地球内部的结构和动态在很大程度上取决于热流，因此取决于其组成部分的导热系数。橄榄石等地幔物质的热导率与温度和压力有关，是建立地幔对流地球动力学模型的重要参数。热导率的变化影响着岩石圈地温模型、俯冲动力学和岩石圈板块的结构。位于410至660千米深度之间的地幔过渡带在地球上、下地幔中是否起到了热流调节器的作用？上地幔和过渡带矿物的导热系数受到的限制很小，关于导热系数的辐射部分的实验数据很少，特别是在这些地区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幔的所有主要组成部分，并利用原位光学光谱作为强大的工具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加深我们对自然的一个主要驱动力--地球内部的热流的理解。该项目建立在最近的原位光学测量的基础上，首次在同时进行高压和高温的情况下，研究了两个主要的过渡带相--水合魏斯利石和水合环木石相。我们报道了大的辐射热导率，这揭示了在红外和可见光光谱范围内的能量传输“窗口”。我们发现地幔过渡带可能对辐射换热有很大的贡献，我们证实了水合作用可能增强辐射热流的预测。目前的项目将把这些研究扩展到橄榄石、莫来石和D相。此外，我们计划系统地研究成分变化(如铁和水的浓度)对橄榄石及其高压晶型黄辉石和环杉石导热性能的影响。这项研究具有高度协作性，将利用全国和国际实验室的专门知识和设施，特别是华盛顿卡内基研究所的地球物理实验室(光学测量)、西北大学的地球和行星科学以及土木工程和环境工程系(光谱学)以及亥姆霍兹中心波茨坦-GFZ德国地球科学研究中心(综合)。这项工作将从根本上阐明一个深受广大受众关注的跨学科主题，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。我们的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内部的热传递-S，并将有助于改进地球热流的地球物理模型。