In Situ Study of Fe-FeS Melt System at High Pressures and Temperatures

自地核被发现以来，地核相对于纯铁成分的密度不足一直是一个长期存在的问题。对铁与其他轻元素在高压下形成的熔融合金缺乏了解，是造成这一长期困惑的原因。该项目利用国家实验室的同步加速器辐射源，开发了最先进的技术，以解决高压下熔体的密度和局部结构问题。该项目目前的目标包括：a）测量Fe-FeS熔体系统的状态方程（EOS）与硫含量的关系; B）研究高压下Fe-FeS熔体的结构。虽然许多轻元素，如S，O，Si，C和H，已被认为是考虑到密度赤字的候选者，硫是从地球化学和宇宙化学的观点来看最有利的候选者之一。然而，目前关于铁硫合金系统的可用密度数据仍然是一个巨大的不确定性。该项目应用新开发的高压原位同步加速器X射线测量技术，并继续提高高压熔体实验数据的准确性，以解决矿物物理学角度的多学科挑战。在这个项目中，多砧压机和金刚石砧室技术的集成不仅提供了不同压力范围内的补充数据，而且还为两种新开发的实验方法提供了交叉检查。这一研究的成功将为了解地核的组成和结构，以及地球外核由组成浮力驱动的对流提供非常有用的信息。该项目积极整合研究和教育培训，包括本科和研究生两个层次，这将提高大学生，特别是佛罗里达国际大学少数民族学生对现代技术的认识，并培养出新一代的科学家谁是在先进的研究前沿工作。该项目提高了国家同步加速器X射线源社区设施的实验能力，从而为地球科学界和一般材料科学的科学研究做出了更广泛的贡献。

The density deficit of Earth's core with respect to a pure iron composition has been a long-standing problem since the core was discovered. Lack of knowledge about molten alloys of iron with other light elements at high pressures is responsible for such a persistent puzzle. Taking advantage of synchrotron radiation sources at national laboratories, this project has developed state-of-the-art techniques to tackle the issue of density and local structure of melts at high pressures. The objectives for the current period of the project include a) measuring sulfur-content dependence of EOS (equation of state) of Fe-FeS melt system and b) investigating structure of Fe-FeS melts at high pressures. While many light elements, e.g. S, O, Si, C and H, have been considered as candidates to account for the density deficit, sulfur is one of the most favorable candidates from geochemical and cosmochemical points of view. However, current available density data on the iron-sulfur alloy system remain a huge uncertainty. This project applies the newly developed technique of in situ synchrotron x-ray measurement at high pressures, and continues improving accuracy of experimental data on high pressure melts to address the multidisciplinary challenge from the mineral physics point of view. Integration of multi anvil press and diamond anvil cell techniques in this project offers not only complementary data in different pressure ranges but also serves a cross check for both newly developed experimental approaches. Success of this research will provide very useful information for understanding the composition and structure of the Earth's core, and the convection driven by compositional buoyancy in the Earth's outer core. The project actively integrates research and educational training including both undergraduate and graduate levels, which will enhance the awareness of modern technology among college students, especially minority students at Florida International University, and produce a new generation of scientists who are working at the frontier of advanced research. The project enhances the experimental capability of a community facility at national synchrotron x-ray sources, and therefore generates broader contributions to the scientific research in Earth science community and general material science.