CSEDI: Collaborative Experimental and Fluid-Dynamical Study on Core Formation of the Earth

该项目是一项合作努力，旨在研究地核的起源及其与行星吸积的时间和机制的关系。这项工作结合了实验和理论工作，并依赖于一个新的概念，即钻石晶胞中的高压-温度化学研究，多相流和行星演化的流体动力学模拟，以及结合实验参数和流体动力学模拟的地球化学模拟，以建立撞击引起的岩浆海洋的核形成和演化模型的置信度。实验计划将确定亲石-亲铁边界附近的一组关键元素和某些参与重要放射性衰变系统的高度亲铁元素的分配。地幔中这两种元素的地球化学特征提供了核形成的记录，因为这个过程有效地从地幔中提取了亲铁元素。这种提取过程的温度、压力和时间尺度是实验、理论和地球化学结果的拟议组合应限制的未知参数。拟议的实验将集中在高压实验中，使用富W、Re和Os的铁合金作为嵌入在液体硅酸盐系统中的内部金属加热器，在液体硅酸盐和金属之间分配Hf和W以及Re和Os。初始物质中不同的铁含量为硅酸盐-金属系统提供了几组铁归一化分配系数(Kd值)，然后可以从实际的实验氧化还原条件(接近各自的金属氧化物缓冲液)推断到地球核心形成的更还原的条件，从高度浓缩的实验金属硅酸盐系统到所研究元素的自然丰度。随着这一实验努力，这些研究人员将首次将在理解流体混合物乳化方面的基本进展纳入撞击、吸积和行星分化过程的流体动力学模拟方法中。

This project is a collaborative effort to study the origin of Earth's core and its relationship to the timing and mechanism of planetary accretion. This effort combines experimental and theoretical work and relies on a novel concept of high pressure-temperature chemical studies in diamond cells, on fluid dynamic modeling of multiphase flows and planetary evolution, and on geochemical modeling combining parameters from the experiments and the fluid-dynamic modeling to establish confidence limits on models of core-formation and evolution of an impact-induced magma-ocean. The experimental program will determine the partitioning of a set of key elements near the lithophile-siderophile boundary and certain highly siderophile elements that are involved in important radioactive decay systems. Geochemical signatures of both types of elements in the Earth's mantle provide the record of core-formation, because this process efficiently extracted siderophile elements out of the mantle. Temperature, pressure, and time-scale of this extraction processes are the unknown parameters the proposed combination of experimental, theoretical, and geochemical findings shall constrain. The proposed experiments will focus on partitioning of Hf and W and of Re and Os between liquid silicate and metal using W-, Re-, and Os-rich iron-alloys as internal metal heaters embedded in liquid silicate systems in high-pressure experiments. Varying bulk Fe content in the starting materials provides sets of Fe-normalized partition coefficients (kD-values) for the silicate-metal system which then can be extrapolated from the actual experimental redox conditions (close to the respective metal-oxide buffers) to the more reducing conditions of Earth's core formation and from the highly enriched experimental metal-silicate systems to natural abundances of the examined elements. Along with this experimental effort these researchers will start to incorporate for the first time fundamental advances in understanding emulsification of fluid mixtures into methods of fluid dynamic modeling of impact accretion and planetary differentiation processes.