Melting Temperatures of Iron and MgO Using a New Flash Laser Heating Technique

使用新型闪光激光加热技术测量铁和氧化镁的熔化温度

• 批准号: 1248553
• 负责人: Reinhard Boehler
• 金额: $ 36.05万
• 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: 2013-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1248553&HistoricalAwards=false
• 关键词: Melting; Temperatures; Iron; MgO; Using

One of the major constraints on the temperature at the center of the Earth is the melting temperature of iron at the pressure conditions of the inner core boundary (ICB) (330 GPa, or 3.3 Mbar). Despite intensive research in this field over the last two decades, the data available from shock compression and laser-heated diamond cell experiments and from theory show considerable disagreement ranging from 4800 K to 7600 K for the ICB. Similarly ill constrained is the melting behavior of the lower mantle where one of its main components (Mg,Fe)O plays a key role for the upper bound of the melting temperature and the chemical composition of a possible partial melt. We have developed new techniques to improve the accuracy in melting experiments by combining pulsed laser-heating techniques in the diamond cell, recently developed in our laboratory, with new X-ray diffraction techniques. A more accurate knowledge of the temperature of the Earth's interior will have a profound impact on all geophysical research related to mantle geodynamics, thermal history models of the Earth, heat flux and radioactivity in the core and will put constraints on poorly known quantities such as thermal conductivity, viscosity and melting of the lowermost mantle. The technical improvements will provide new opportunities to research other physical and chemical processes in extreme environments. The development of new laser heating and synchrotron X-ray techniques will not only enlarge the scientific community in geophysics and geochemistry, but also in material science. In-situ structural and chemical analysis of matter at extreme high pressure and temperature conditions is essential for the scientific progress in these fields. Our work will help to reduce many of the previous technical problems and make these methods more easily accessible.

对地球中心温度的主要限制之一是在内核边界（ICB）的压力条件（330 GPa或3.3 Mbar）下铁的熔化温度。尽管在这一领域的深入研究，在过去的二十年中，从冲击压缩和激光加热的金刚石细胞实验和理论的数据显示出相当大的分歧，从4800 K到7600 K的ICB。下地幔的熔融行为也受到同样的限制，其中下地幔的主要成分之一（Mg，Fe）O对熔融温度的上限和可能的部分熔融的化学成分起着关键作用。我们已经开发了新的技术，以提高熔化实验的精度相结合的脉冲激光加热技术在金刚石细胞，最近在我们的实验室，与新的X射线衍射技术。更准确地了解地球内部的温度，将对有关地幔地球动力学、地球热历史模型、地核热通量和放射性的所有地球物理研究产生深远影响，并将限制对最低地幔的热导率、粘度和熔化等知之甚少的量。这些技术改进将为研究极端环境中的其他物理和化学过程提供新的机会。新的激光加热和同步辐射X射线技术的发展不仅将扩大地球物理和地球化学的科学界，而且将扩大材料科学的科学界。在极高的压力和温度条件下对物质进行原位结构和化学分析对于这些领域的科学进步至关重要。我们的工作将有助于减少许多以前的技术问题，并使这些方法更容易使用。