Geochemistry of Siderophile and Chalcophile Element in the Earth: Studies on the Distribution of These Elements in Natural and Synthetic Samples

地球如何分化成金属核心、岩石硅酸盐外壳和液体/气体包层的过程人们知之甚少。同位素研究表明，这一过程始于行星吸积过程，并在数千万年内结束。元素在地核和周围的硅酸盐地幔和地壳之间的分布可能发生在一系列条件(温度、压力和气体逸度)和各种环境中，包括附着在地球上的小型行星天体。这些条件的综合结果记录在地核和硅酸盐地球之间的元素当前分布中。通过表征这两个储集层的组成，并通过实验确定元素在金属和硅酸盐之间的分配方式，我们可以了解核心形成的机制。这项为期三年的研究结果将包括对地幔样品(橄榄岩和斜长岩)中亲铁元素和亲硫元素的分析，地幔岩浆(原始玄武岩、科马提岩及其某些矿物相)、陨石(特别是苍晶岩：由铁金属和橄榄石晶体混合组成的核幔边界的小行星状样品)和实验电荷的分析。橄榄岩、辉石岩和岩浆的数据将被用来确定硅酸盐地球的组成，硅酸盐地球是在分化为壳地幔系统之前的原始地幔组成。陨石的研究将有助于建立各种氧化还原条件下元素在低压和温度下的分馏行为。实验研究的数据将提供元素在矿物和熔体之间的分配系数，这将进一步限制核心形成的条件。所有这些研究都将对学生指导产生更广泛的影响，并为本科生和研究生提供研究机会。分析方法在科学、工业、医学和政府中都有应用，并将在这些学生的职业生涯中很好地服务。

The process by which the Earth differentiated into a metallic core, a rocky silicate shell, and a liquid/gas envelope is poorly understood. Isotopic studies show that this process began during planetary accretion and ended within a few tens of millions of years. The distribution of elements between the core and surrounding silicate mantle and crust likely occurred under a range of conditions (temperature, pressure, and gas fugacity) and in a variety of settings, including small planetary bodies accreted into the Earth. The integrated result of these conditions is recorded in the current distribution of elements between the core and silicate Earth. By characterizing the composition of these two reservoirs and determining how elements partition themselves between metals and silicates with experiments, we can understand the mechanisms by which the core formed.The results of this three-year study will include analyses of the siderophile (iron-loving) and chalcophile (sulfur-loving) elements in mantle samples (peridotites and pryoxenites), mantle-derived magmas (primitive basalts, komatiites and some of their mineral phases), meteorites (particularly pallasites: asteroidal samples from their core-mantle boundary that are composed of iron metal mixed with olivine crystals) and experimental charges that have been synthesized under specific pressure, temperature and redox conditions. Data for the peridotites, pyroxenites and the magmas will be used to establish the composition of the silicate Earth, which is the primitive mantle composition prior to its differentiation into a crust and mantle system. The meteorite studies will help to establish the fractionation behavior of elements at low pressures and temperatures under various redox conditions. Data from the experimental studies will provide distribution coefficients for elements between minerals and melts, which will further constrain the conditions of core formation. All of these studies will have a broader impact on student mentoring, as well as providing research opportunities for undergraduate and graduate students. The analytical methods have applications in science, industry, medicine, and government and will serve these students well into their careers.