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

地球中心温度的主要限制之一是铁在内核边界（ICB）压力条件下的熔化温度（330 GPa，或3.3 Mbar）。尽管在过去的二十年里，这一领域进行了深入的研究，但从冲击压缩和激光加热金刚石细胞实验中获得的数据以及从理论上得到的数据表明，ICB在4800 K到7600 K之间存在相当大的分歧。同样不受约束的是下地幔的熔融行为，其主要成分之一（Mg,Fe）O对熔融温度的上限和可能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，通过将我们实验室最近开发的金刚石细胞中的脉冲激光加热技术与新的x射线衍射技术相结合，来提高熔化实验的准确性。对地球内部温度的更准确的了解将对所有与地幔地球动力学、地球热历史模型、地核热通量和放射性有关的地球物理研究产生深远的影响，并将限制鲜为人知的数量，如导热性、粘度和最下层地幔的熔化。技术的改进将为在极端环境下研究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。在极端高压和高温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获得。

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.