Exploring the Effects of Light Elements on the Iron Isotope Fractionation between Metal and Silicate

探讨轻元素对金属与硅酸盐铁同位素分馏的影响

• 批准号: 1321858
• 负责人: Anat Shahar
• 金额: $ 32.22万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321858&HistoricalAwards=false
• 关键词: Exploring; Effects; Light; Elements; Iron

Differentiation is the process with which a planetary body separates into layers based on the physical and chemical characteristics of the body. Based on the temperature, pressure (or size of body), oxygen fugacity, and impact history, the body will separate into layers and the final product will be a unique planet, moon or asteroid. In this proposal we focus on the differentiation of a silicate mantle and a metallic core. This process occurred on the terrestrial planets, the moon and on many asteroids, as these objects were hot and big enough to melt the metal so it could percolate through the silicate. The iron and siderophile elements sink to the center to form a core, while the silicates and lithophile elements form a mantle. The principle of using stable isotopes to probe the bulk chemical composition of planets lies with the combination of isotope fractionation and sequestration of elements in unseen reservoirs like the core. Isotope fractionation will exist between phases with distinct bonding environments (e.g., Earth?s core and mantle), and separation of elements between reservoirs manifests this fractionation. Experiments at high pressure and temperature can reveal the equilibrium isotopic fractionation factors that cannot be directly measured in planetary materials and when combined with isotopic ratios found in natural materials provide a constraint on the formation conditions of those materials. In this proposal we focus on the equilibrium stable isotopic fractionation of iron when it is alloyed to a light element such as sulfur or carbon. There has been enormous progress in the Fe isotope community in the past 13 years an ever-increasing database has emerged however, what is missing is a more systematic understanding of how and why these seen fractionations are formed. It is the mechanisms behind the iron isotopic fractionations that we are proposing to study. In particular, we aim to understand how the bonding environment in the iron metal effects the iron isotope fractionation between metal and silicate.

分化是行星体根据其物理和化学特征分成层的过程。根据温度，压力（或身体大小），氧逸度和撞击历史，身体将分离成层，最终产品将是一个独特的行星，月球或小行星。在这个建议中，我们专注于硅酸盐地幔和金属核的分化。这一过程发生在类地行星、月球和许多小行星上，因为这些物体足够热，足够大，足以熔化金属，使其能够渗透到硅酸盐中。铁和亲铁元素下沉到中心形成地核，而硅酸盐和亲石元素则形成地幔。使用稳定同位素探测行星整体化学成分的原理在于将同位素分馏和元素封存在看不见的储层（如核心）中。同位素分馏将存在于具有不同键合环境的相之间（例如，地球？储层间元素的分离反映了这种分异作用。高温高压下的实验可以揭示行星物质中无法直接测量的平衡同位素分馏因子，当与天然物质中发现的同位素比率相结合时，可以对这些物质的形成条件进行限制。在这个建议中，我们专注于平衡稳定同位素分馏的铁合金时，轻元素，如硫或碳。在过去的13年里，铁同位素社区取得了巨大的进展，出现了一个不断增加的数据库，然而，缺少的是对这些分馏是如何形成的以及为什么形成的更系统的理解。我们建议研究的是铁同位素分馏背后的机制。特别是，我们的目标是了解如何在铁金属的成键环境的影响，金属和硅酸盐之间的铁同位素分馏。