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

该项目的目标是确定下地幔和核心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。该项目利用了原位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、红外和光学光谱、中子衍射和新的高P-T钻石电池方法。该项目将解决有关深部地幔硅酸盐和氧化物中的相变、相关系和元素分配的新问题。这项工作将从深部地幔相的高P-T结构研究开始，包括硅酸盐钙钛矿、镁闪锌矿和最近发现的后钙钛矿相。将在最高压力下使用新的单晶X射线衍射和中子衍射技术进行更多的研究。一系列互补的同步加速器X射线光谱技术，用于表征铁在整个下地幔的P-T范围内的自旋和氧化状态。然后，将利用原位高P-T技术和淬火相新的显微分析方法相结合，研究深部下地幔主要组分D“和核-地幔边界区的相关系。Fe对核心条件的高P-T行为对于限制核心的成分、热状态、演化和动力学是至关重要的。我们将研究在200 Gpa和3000K下，Fe和Fe-Ni合金中存在额外的、非常高的P-T相的问题。高分辨率X射线发射、核共振前向散射和拉曼光谱将被用来识别压力引起的铁合金的电子、磁性和振动特性对核心压力的变化。在较低压力范围内的高P-T X射线衍射测量也将使研究Fe的液态结构变化成为可能。使用相同的综合衍射和光谱技术阵列，将在Fe-Ni与氧、硫、硅和氢的几个关键的伪二元系中研究堆芯中的轻元素的问题。视上述任务的进展情况，将审查更多元素和更复杂的核心形成化学系统。这个项目的结果将被用来了解地球深处的化学物质，从地球的陶瓷地幔到其中心富含铁的核心。特别是，我们的目标是了解那里普遍存在的极端压力和温度(高达360万个大气层，也许在地球中心的温度为6000 K)如何影响构成地球上这些难以到达的区域的物质。因此，这项研究将为解释地震、火山喷发、浮出地表的深部岩石以及各种其他地质、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作为一个整体的理解，因此将照亮地球科学以外的领域，如物理、化学、材料科学、行星科学，甚至生物学。随着新技术的发展，这项工作将扩大和加强国家实验设施(即同步加速器和中子源)的活动。此外，这项工作将展示基础科学和新技术开发之间的协同作用，新技术包括单晶钻石等新材料以及各种新的微量分析技术。该项目还将涉及对学生以及研究领域的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.