An integral approach to reveal the identity of light elements in the Earth's core

揭示地核轻元素身份的整体方法

• 批准号: 1214990
• 负责人: Yingwei Fei
• 金额: $ 40.39万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1214990&HistoricalAwards=false
• 关键词: integral; approach; reveal; identity; light

The Earth has an iron-dominant core that consists of a liquid outer core and a solid inner core at the center. The Earth's core is the engine of the planet, generating global magnetic field and driving large-scale plate motions on the surface through mantle convection. A better understanding of its chemical composition will help us to understand how the engine works. Current knowledge of the core implies that incorporation of light elements (such as sulfur, oxygen, silicon) in the iron core is necessary to explain the observed density and velocities of the core, but there is considerable controversy over the precise identity of the light alloying elements in the core because it is experimentally challenging to precisely measure the density and sound velocity of the iron alloys under core conditions.In this study, I am outlining a new approach to narrow down the identity of the light elements in the core by combining dynamic and static compression experiments. The proposed experiments will yield new density and velocity data obtained by shock compression and static compression in the high-temperature diamond-anvil cell. Specifically, I propose four types of experiments, (1) shock compression to obtain densities of Fe-Si alloys, (2) in-situ x-ray diffraction measurements in high-temperature diamond-anvil cell to obtain P-V-T data, (3) measurements of the sound velocities of the alloys by shockwave experiments, and (4) measurements of the compressional-wave velocity of alloys in the high-temperature diamond-anvil cell by inelastic x-ray scattering technique. This is our first attempt to integrate results from dynamic and static compression experiments on the same samples, which allows us to obtain complementary data over a wide P-T range and to establish self-consistent database from two independent high-pressure experiments. The new data on Fe-Si alloys will be integrated into our existing data to make comprehensive models of the core.

地球有一个以铁为主的核心，由一个液态的外核和一个位于中心的固态内核组成。地核是地球的发动机，产生全球磁场，并通过地幔对流驱动地表大规模板块运动。更好地了解其化学成分将有助于我们了解发动机的工作原理。目前对地核的了解意味着轻元素的结合（如硫，氧，硅）在铁芯是必要的，以解释所观察到的密度和速度的核心，但是对于堆芯中轻合金元素的精确身份存在相当大的争议，因为在堆芯条件下精确测量铁合金的密度和声速在实验上具有挑战性。研究，我概述了一种新的方法来缩小身份的轻元素的核心相结合的动态和静态压缩实验。该实验将产生新的密度和速度数据，通过冲击压缩和静态压缩在高温金刚石压砧单元。具体地说，我提出了四种实验方法：（1）冲击压缩法获得Fe-Si合金的密度，（2）高温金刚石压砧中的原位X射线衍射测量法获得P-V-T数据，（3）冲击波实验测量合金的声速，（4）用非弹性X射线散射技术测量高温金刚石压砧装置中合金的纵波速度。这是我们第一次尝试整合来自相同样品的动态和静态压缩实验的结果，这使我们能够在宽的P-T范围内获得互补的数据，并从两个独立的高压实验中建立自洽的数据库。Fe-Si合金的新数据将被整合到我们现有的数据中，以制作核心的综合模型。