CSEDI Collaborative Research: Experimental Constraints on the Chemistry and Evolution of Earth's Core

富铁六方紧密堆积（hcp）合金的化学性质及其在元素和同位素组成、对流和地核演化中的作用将被研究。共存的富铁hcp合金和熔体的组成将在压力达到25 GPa时确定。通过将Fe与少量Os或Ru合金化，可以稳定金属的hcp结构；这一阶段被广泛认为与地核直接相关，但在之前的化学分配实验研究中一直无法实现。在高压下富铁hcp合金和熔体之间痕量元素分配的数据将提供对亲铁元素分布的深入了解，这些亲铁元素是重要的放射性同位素地球时计，并将对涉及从外核到地表的同位素特征的地球演化模型施加必要的实验约束。富铁hcp合金与熔体之间的Ni、S、O等主要元素的分配将用于约束固体内外核和液体外核的成分，并将提高我们对核心成分对流驱动机制的理解。该研究将是第一次将铁合金用于稳定hcp相在更适宜的压力和温度下的应用，并可能刺激对hcp-Fe的物理和化学特性的进一步实验研究。此外，这项工作将展示高压实验和微量元素分析技术的结合，并应促进其在地球科学中的更广泛应用。拟议研究的结果将主要通过在科学文献中发表、参加科学会议以及在必要时通过更广泛的新闻媒介传播。

The chemistry of iron-rich hexagonal close packed (hcp) alloy, and its role in the elemental and isotopic composition, convection, and evolution of the Earth's core, will be studied. The composition of coexisting iron-rich hcp-alloys and melt will be determined at pressures to 25 GPa. The hcp structure of the metal will be stabilized by alloying Fe with a small amount of Os or Ru; this phase is widely thought to be directly relevant to the Earth's core but has been inaccessible in previous experimental studies of chemical partitioning. Data on trace element partitioning between Fe-rich hcp alloy and melt at high pressures will provide insight into the distribution of siderophile elements that act as important radioisotope geochronometers, and will place needed experimental constraints on models of Earth evolution that involve isotopic signatures to be carried from the outer core to the surface. The partitioning of major elements such as Ni, S, and O between Fe-rich hcp alloy and melt will be used to constrain the compositions of the solid inner and liquid outer core, and will improve our understanding of the driving mechanism for compositional convection in the core. The proposed research will be the first application in which Fe is alloyed specifically to stabilize the hcp phase at more amenable pressures and temperatures, and it may stimulate further experimental investigations into the physical and chemical character of hcp-Fe. Additionally, this work will demonstrate a combination of high-pressure experimental and trace element analytical techniques, and should stimulate its broader application in the geosciences. Results from the proposed study will be disseminated primarily through publication in the scientific literature, by participation at scientific conferences, and when warranted, through wider-reaching news outlets.