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

地球中亲铁元素和亲铜元素的地球化学：这些元素在天然和合成样品中的分布研究

• 批准号: 0337621
• 负责人: William McDonough
• 金额: $ 26.99万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337621&HistoricalAwards=false
• 关键词: Geochemistry; Siderophile; Chalcophile; Element; Earth

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.

地球分化为金属核、岩石硅酸盐外壳和液体/气体外壳的过程知之甚少。同位素研究表明，这一过程始于行星吸积，并在数千万年内结束。地核和周围硅酸盐地幔和地壳之间的元素分布可能发生在一系列条件下（温度，压力和气体逸度）和各种环境中，包括小型行星体吸积到地球上。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分布中。通过分析这两个储层的成分，并通过实验确定元素在金属和硅酸盐之间的分配方式，我们可以了解地核形成的机制。这项为期三年的研究结果将包括亲铁体的分析。（爱铁）和亲铜地幔样品中的（亲硫）元素（橄榄岩和辉石岩），幔源岩浆（原始玄武岩、科马提岩及其某些矿物相）、陨石（特别是pallasite：来自地核-地幔边界的小行星样品，由铁金属和橄榄石晶体混合组成）和在特定压力、温度和氧化还原条件下合成的实验装药。橄榄岩、辉石岩和岩浆的数据将用于确定硅酸盐地球的组成，硅酸盐地球是在其分化为地壳和地幔系统之前的原始地幔组成。陨石研究将有助于建立在各种氧化还原条件下，在低压和低温下元素的分馏行为。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，医学和政府中有应用，并将为这些学生的职业生涯提供良好的服务。