High Pressure Synchrotron Radiology and Microtomography Studies of Mechanisms and Kinetics of Liquid Iron -Silicate Segregation: Implications for Formation of the Earth's Core

液态铁硅酸盐偏析机制和动力学的高压同步辐射学和显微断层扫描研究：对地核形成的影响

• 批准号: 0001088
• 负责人: Yanbin Wang
• 金额: $ 28万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-15 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0001088&HistoricalAwards=false
• 关键词: Pressure; Synchrotron; Radiology; Microtomography; Studies

Wang 0001088 All core formation models depend on knowledge of mechanisms of the liquid iron-silicate separation. The investigators propose to study the iron-silicate separation process by in-situ synchrotron X-ray radiography in the large-volume press at GSECARS and the Advanced Photon Source. Their pilot experiments have demonstrated that droplets of Fe-rich melt from a mechanical mixture of silicates and Fe (with controlled amounts of light elements) can be observed by in situ radiography during the separation process. Computed microtomography has been applied to the recovered samples to generate three-dimensional reconstructions of the size and spatial distribution of the melt droplets as a function of pressure, temperature, composition, and time. In the proposed study, the investigators will examine systems containing selected light elements, such as C, S, H, O, and Si, with various metal/silicate volume ratios at pressures up to 15 GPa and 2000K. They will start with simple compositions by selecting pure constituents but as understanding increases will work on more realistic compositions such as iron meteorite and carbonaceous meteorite. Currently a white beam is used for the radiography experiments but monochromatic radiation will be used in future experiments to enhance image resolution and contrast. In addition, the team plans to develop an X-ray transparent Drickamer-type high-pressure cell for in-situ microtomography, which will greatly enhance resolution power to the micron level. Samples will be examined at various stages of the experiment by microtomography to reconstruct the evolution of the size and spatial distribution of the Fe-rich droplets as a function of light element, pressure, temperature, and time. Recovered samples will be sectioned and examined by scanning and transmission electron microscopy to resolve metal-silicate interaction to sub-micron level. Composition analyses will be performed and element partitioning will be studied using electron microprobe and X-ray fluorescence microprobe. These experiments will provide first-hand laboratory observations on iron-silicate separation and improve our understanding of possible core formation mechanisms and dynamics of the core-mantle boundary. The results will be used to constrain existing models regarding physical and chemical processes of the formation of the core.

Wang 0001088 所有岩心形成模型都依赖于液态铁硅酸盐分离机制的知识。研究人员提议通过 GSECARS 的大容量印刷机和先进光子源中的原位同步加速器 X 射线照相技术来研究铁硅酸盐分离过程。他们的试点实验表明，在分离过程中，可以通过原位射线照相术观察到来自硅酸盐和铁（具有受控量的轻元素）机械混合物的富铁熔体液滴。计算机显微断层扫描已应用于回收的样品，以生成熔滴的尺寸和空间分布作为压力、温度、成分和时间的函数的三维重建。在拟议的研究中，研究人员将在高达 15 GPa 和 2000K 的压力下检查含有选定轻元素（例如 C、S、H、O 和 Si）的系统，以及各种金属/硅酸盐体积比。他们将从简单的成分开始，选择纯成分，但随着理解的增加，他们将研究更真实的成分，例如铁陨石和碳质陨石。目前，放射线照相实验使用白色光束，但在未来的实验中将使用单色辐射，以提高图像分辨率和对比度。此外，该团队计划开发一种用于原位显微断层扫描的X射线透明Drickamer型高压单元，这将大大提高分辨率至微米级。将在实验的各个阶段通过显微断层扫描对样品进行检查，以重建富铁液滴的尺寸和空间分布随轻元素、压力、温度和时间的变化。回收的样品将通过扫描和透射电子显微镜进行切片和检查，以将金属-硅酸盐相互作用解析到亚微米水平。将使用电子微探针和X射线荧光微探针进行成分分析并研究元素分配。这些实验将为铁硅酸盐分离提供第一手的实验室观察结果，并提高我们对可能的核心形成机制和核心-地幔边界动力学的理解。结果将用于约束有关核心形成的物理和化学过程的现有模型。