Renewal: Chemistry of the Earth's Deep Mantle and Core

该项目的目标是确定下地幔和地核物质在相关地球深部条件下的化学性质，以便获得对地球内部化学成分、形成和演化的直接实验约束。该项目利用了现场高压技术的许多最新发展，包括同步加速器X射线衍射和光谱学，红外和光学光谱学，中子衍射和新的高P-T金刚石电池方法。该项目将解决有关相变，相关系和元素分配在深地幔硅酸盐和氧化物的新问题。这项工作将从深地幔相的高P-T结构研究开始，包括硅酸盐钙钛矿，镁橄榄石和最近发现的后钙钛矿相。将使用新的单晶X射线衍射和中子衍射技术对最高压力进行进一步研究。一系列互补的同步辐射X射线光谱技术，用于表征下地幔P-T范围内Fe的自旋和氧化态。然后，将使用原位高P-T技术和淬火相的新微观分析方法相结合，检查深部下地幔、D”和核幔边界区的主要组分的相关系。Fe对内核条件的高P-T行为对于限制内核的成分、热状态、演化和动力学至关重要。将研究在200 GPa和3000 K下Fe和Fe-Ni合金的额外的非常高的P-T相的问题。高分辨率的X射线发射，核共振前向散射，和拉曼光谱将被用来确定压力引起的变化，在电子，磁性和振动特性的铁合金的核心压力。在较低的压力范围内的高P-T X射线衍射测量也将允许调查的结构变化的液态铁。核心中轻元素的问题将在几个关键的铁镍与氧，硫，硅和氢的伪二元系统中使用相同的集成阵列的衍射和光谱技术进行检查。根据上述任务的进展，将检查其他元素和更复杂的成核化学系统。该项目的结果将用于了解地球深层内部的化学，从地球的陶瓷地幔到其中央富含铁的核心。特别是，目标是了解那里盛行的极端压力和温度（地球中心高达360万个大气压，可能为6000 K）如何影响构成地球上这些无法进入的区域的材料。因此，这项研究将为解释地震、火山爆发、深层岩石浮上地表以及其他各种地质、地球物理和地球化学现象的数据提供基础。这项工作还将提高我们对极端条件下材料整体的理解，因此将照亮地球科学以外的物理学，化学，材料科学，行星科学甚至生物学领域。这项工作将扩大和加强国家实验设施的活动（即，同步加速器和中子源），随着新技术的发展。此外，这项工作将展示基础科学与新技术发展之间的协同作用，包括单晶金刚石等新材料以及各种新的微量分析技术。该项目还将涉及对研究领域的学生以及初级和高级科学家的培训。

The goal of this project is to determine the chemical properties of lower mantle and core materials at relevant deep Earth conditions in order to obtain direct experimental constraints on the chemical composition, formation, and evolution of the planet's interior. The project takes advantage of numerous recent developments in in situ high-pressure techniques, including synchrotron x-ray diffraction and spectroscopy, infrared and optical spectroscopy, neutron diffraction, and new high P-T diamond-cell methods. The project will address new questions regarding phase transformations, phase relations, and element partitioning in deep mantle silicates and oxides. This work will start with high P-T structural studies of deep mantle phases, including silicate perovskites, magnesiowustite, and the recently discovered post-perovskite phases. Additional studies will be carried out using new single-crystal x-ray diffraction and neutron diffraction techniques to the highest pressures. A series of complementary synchrotron x-ray spectroscopic techniques used to characterize the spin and oxidation state of Fe throughout the P-T range of the lower mantle. The phase relations of the major components of the deep lower mantle, D", and core-mantle boundary region will then be examined using a combination of in situ high P-T techniques and new microanalytical methods on quenched phases. The high P-T behavior of Fe to inner core conditions is crucial for constraining the composition, thermal state, evolution, and dynamics of the core. The question of additional, very high P-T phases of Fe and Fe-Ni alloys at 200 GPa and 3000 K will be investigated. High-resolution x-ray emission, nuclear resonant forward scattering, and Raman spectroscopies will be used to identify pressure-induced changes in electronic, magnetic, and vibrational properties of iron alloys to core pressures. High P-T x-ray diffraction measurements in the lower pressure range will also allow investigations of structural changes in the liquid state of Fe. The problem of the light element in the core will be examined in a few key pseudo-binary systems of Fe-Ni with oxygen, sulfur, silicon, and hydrogen using the same integrated array of diffraction and spectroscopic techniques. Depending on progress in the above tasks, additional elements and more complex core-forming chemical systems will be examined. Results from this project will be used to understand the chemistry of the Earth's deep interior, from the planet's ceramic mantle to its central, iron-rich core. In particular, the goals are to understand how the combined the extreme pressures and temperatures that prevail there (up to 3.6 million atmospheres and perhaps 6000 K at Earth's center) affect the materials that comprise these inaccessible regions of the planet. As such, the research will provide a basis for interpreting data on earthquakes, volcanic eruptions, deep-seated rocks brought up to the surface, and a variety of other geological, geophysical, and geochemical phenomena. The work will also improve our understanding of materials as a whole under extreme conditions, and as a consequence and will illuminate areas beyond the geosciences, in physics, chemistry, materials science, planetary science, and even biology. The work will augment and enhance activities at national experimental facilities (i.e., synchrotron and neutron sources), with the development of new techniques. In addition, the work will showcase the synergy between fundamental science and the development of new technologies, including new materials such as single crystal diamond as well as a variety of new microanalytical techniques. The project will also involve the training of students and both junior and senior scientists in the area of research.