Conditions, timescales and cosmochemical evolution during the early accretion of terrestrial planets

影响类地行星的最重要的分异事件是它们分异成富铁金属核和硅酸盐地幔。行星地幔中广泛的亲铁和亲石元素的浓度对核心形成的条件和吸积物质的组成随时间的变化提供了主要的限制。我们最近已经证明，作为原始地球和较小分化体之间碰撞的结果，核心形成逐步发生的多阶段模型最能再现地幔地球化学。在这个项目中，我们将使用多学科方法进一步开发这个初步模型，方法是：(A)将其与N体吸积模拟的结果相结合，(B)在模型中包括Hf-W同位素系统，以提供对时间和不平衡过程的额外限制，以及(C)获得新的硅、氧和挥发性元素Sb、Pb、Cu、Sn、Ge、P、Ag和As的实验分配数据。后一项研究将使大量新元素被包括在核形成/吸积模型中，并将使挥发性元素对类地行星的吸积机制和时间得以研究。

The most important differentiation event to affect the terrestrial planets was their segregation into metallic Fe-rich cores and silicate mantles. The concentrations of a wide range of both siderophile and lithophile elements in planetary mantles provide major constraints on the conditions of core formation and the composition of the accreting material as a function of time. We have shown recently that a multi-stage model in which core formation occurs progressively, as the consequence of impacts between the proto-Earth and smaller differentiated bodies, can best reproduce mantle geochemistry. In this project we will further develop this preliminary model using a multi-disciplinary approach by (a) integrating it with the results of N-body accretion simulations, (b) including the Hf-W isotopic system in the model to provide additional constraints on timing and disequilibrium processes, and (c) obtaining new experimental partitioning data for silicon, oxygen and the volatile elements Sb, Pb, Cu, Sn, Ge, P, Ag and As. The latter studies will enable a large number of new elements to be included in the core formation/accretion models and will enable the mechanisms and timing of volatile element accretion to the terrestrial planets to be investigated.