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，由液体外核和位于中心的固体内核组成。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。目前对铁芯的了解表明，铁芯中掺入轻元素（例如硫、氧、硅）对于解释观察到的铁芯密度和速度是必要的，但对于轻合金的精确身份存在相当大的争议核心中的元素，因为在核心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。在这项研究中，我概述了一种新方法，通过结合动态来缩小核心中轻元素的范围和静态压缩实验。所提出的实验将产生通过高温金刚石砧室中的冲击压缩和静态压缩获得的新的密度和速度数据。具体来说，我提出了四种类型的实验，（1）冲击压缩以获得铁硅合金的密度，（2）在高温金刚石砧池中进行原位X射线衍射测量以获得P-V-T数据，（3）通过冲击波实验测量合金的声速，以及（4）通过非弹性X射线散射技术测量高温金刚石砧室中合金的压缩波速。这是我们第一次尝试整合同一样品的动态和静态压缩实验结果，这使我们能够在较宽的 P-T 范围内获得互补数据，并从两个独立的高压实验中建立自洽的数据库。关于铁硅合金的新数据将集成到我们现有的数据中，以建立核心的综合模型。