Elasticity and Spin Transitions of Iron in the Earth's Lower Mantle

地球下地幔中铁的弹性和自旋跃迁

• 批准号: 1446946
• 负责人: Jung-Fu Lin
• 金额: $ 37.23万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1446946&HistoricalAwards=false
• 关键词: Elasticity; Spin; Transitions; Iron; Earth

Earth's mantle is a silicate rocky shell about 2900 km thick that constitutes approximately 84% of the planet's volume. It is further separated into three layers, upper mantle, transition zone, and lower mantle, as a result of the structural phase transitions of the olivine polymorphs. The lower mantle ranging from 670 km to 2900 km in depth is mainly made of bridgmanite (silicate perovskite) and ferropericlase in which iron is the most abundant transition metal. Deep-Earth scientists have recently discovered that the spin transitions of iron in these lower-mantle minerals can have a series of effects on physical, chemical, and transport properties of the host minerals. Studying the sound velocity profiles of the lower-mantle minerals across the spin transition of iron can thus help us understand the chemistry and physics of the region. With an emphasis on the effects of the spin transitions, this project aims broadly to understand thermal elasticity of the lower-mantle minerals at relevant pressure-temperature-composition conditions, providing direct mineral physics results and thermodynamic database to be integrated with seismic tomographic images, geochemical analyses, and geodynamic models of the mantle. The geophysical and geochemical consequences of the spin transition in the lower mantle will be examined through modelling the thermal elasticity and the partitioning coefficient of iron in ferropericlase and bridgmanite along an expected lower-mantle geotherm. These results will help test hypotheses on seismic wave profiles, elucidate the chemistry of iron and its compositional model, and determine the dynamic behavior of the Earth's deep mantle.The proposed mineral physics research uses synchrotron X-ray and in-house laser spectroscopies in a diamond anvil cell designed to probe structural and elastic properties of the mantle minerals at pressure-temperature conditions of the Earth's mantle. Under the initiatives of the project, students and postdoctoral researchers will have unique research opportunities to use advanced synchrotron X-ray facilities at the Advanced Photon Source and laser spectroscopies at the University of Texas at Austin to obtain laboratory results needed to decipher seismic and geochemical observations of the planet's lower mantle. These activities will contribute to the education of the next generation of independent researchers with a thorough knowledge of the Earth's deep interior. Outreach activities in this project focus on exposing underrepresented K-12th graders to deep-Earth research by involving them in the outreach summer programs. Research results from this award will be disseminated broadly through teaching, seminars, conferences, and peer-reviewed publications. The proposed work enhances infrastructure for research and education by using shared facilities and the development of new collaborations among researchers in different fields. The project will provide students and postdoc researchers with a great opportunity to collaborate with scientists in the multidisciplinary fields of seismology, geodynamics, and geochemistry.

地球的地幔是硅酸根岩石壳约2900公里，约占行星体积的84％。由于橄榄石多晶型物的结构相变，它将进一步分为三层，上地幔，过渡区和下地幔。深度为670 km至2900 km的下层套主要由Bridgmanite（硅酸盐钙钛矿）和铁磷酸盐酶制成，其中铁是最丰富的过渡金属。深地球科学家最近发现，在这些下层矿物质中铁的自旋过渡可以对宿主矿物的物理，化学和运输特性产生一系列影响。因此，研究跨铁的自旋跃迁的下层矿物质的声速曲线可以帮助我们了解该地区的化学和物理。该项目强调了自旋转变的影响，该项目旨在广泛地了解相关压力 - 温度复合条件下较低壁垒矿物的热弹性，提供直接的矿物质物理学结果和热力学数据库，以与地震层析成像图像集成，，并将其整合在一起。地幔的地球化学分析和地球动力学模型。下地幔中自旋跃迁的地球物理和地球化学后果将通过对铁磷酸盐酶中铁中铁的热弹性和分配系数进行建模，并沿着预期的下层Geotherm进行建模。这些结果将有助于检验关于地震波谱的假设，阐明铁的化学及其组成模型，并确定地球深地幔的动态行为。拟议​​的矿物质物理学研究使用同步X射线和内部激光镜在A中钻石砧细胞设计用于探测地幔矿物的结构和弹性特性，在地球地幔的压力温度条件下。在该项目的举措下，学生和博士后研究人员将有独特的研究机会，在德克萨斯大学奥斯汀分校的高级光子源和激光光谱中使用先进的同步器X射线设施，以获取破译所需的实验室成果，以破译地震和地球化学观察。地球下地幔的。这些活动将有助于对下一代独立研究人员的教育，并对地球深层内部有透彻的了解。该项目中的外展活动集中于通过使他们参与外展夏季计划来使代表性不足的K-12年级学生接触深地球研究。该奖项的研究结果将通过教学，研讨会，会议和经过同行评审的出版物进行广泛传播。拟议的工作通过使用共享设施以及不同领域的研究人员之间的新合作来增强研究和教育的基础设施。该项目将为学生和博士后研究人员提供一个很好的机会，可以与地震学，地球动力学和地球化学多学科领域的科学家合作。