铁镍轻元素合金的高压熔融及其对外地核组份的约束

The investigation of chemical composition and the phases for the liquid outer core of the Earth has been focused on recently in high-pressure mineral physics. As the important light elements in the earth's outer core, S and P play an important role in understanding the geological processes near the core-mantle boundary, such as the geomagnetism and mantle plume evolutions, due to the S- and P-bearing phases and their stability under high-temperature and high-pressure. However, as the possible candidate of composition with S and P in outer core, Fe-Ni-S-P compounds and their melting behavior has not been paid attention to yet. This project intends, by using diamond anvil cell combination with portable laser heating system and the techniques of in-situ observation, synchrotron radiation characterization and the first principles calculations, to comprehensively study the melting behavior of Fe-Ni-S-P compounds under high pressure, in order to obtain their melting curves, partition coefficients of light element S and P, and the melting temperature as a function of S and P content in (Fe,Ni), which might provide the constraint conditions of the composition and temperature range in outer core, as well as provide the mineralogical evidences for better interpretation of the basic geological process involving the outer core.

地球液态外核的物质组成及其状态的研究是国际高压矿物物理领域研究的热点。作为外核重要轻元素硫和磷，其存在的基本状态和稳定性会影响靠近核幔边界的一些地质过程，如地磁演化、地幔热柱等。作为含硫和磷元素的铁镍合金，Fe-Ni-S-P化合物被认为是一种可能反映外核真实化学组成的样本，然而其在高压下熔融行为的研究几乎是空白。本项目拟采用金刚石压腔技术和便携式激光加温系统、原位的可视化观察仪器、大科学装置同步辐射表征技术及第一性原理计算模拟方法，综合地研究Fe-Ni-S-P化合物在高压下的熔融行为，以期得到它们的熔融曲线及轻元素硫和磷的配分系数，深入探讨硫和磷含量对（Fe,Ni）熔融温度的影响，为了解外核可能的物质组成和温度范围提供约束条件，也为更好解释涉及外地核的基础地质问题提供矿物学的依据。

本项目基于同步辐射X射线衍射（XRD）和金刚石压腔（DAC）以及相关的谱学实验技术，结合基于第一性原理的密度泛函理论的计算模拟，对地核物质Fe/Ni轻元素合金（以及部分Fe/Ni-O化合物, TbPt合金，钙钛矿型化合物以及部分含水矿物）在超高压以及高温条件下物质的结构、状态和性质进行了深入研究。研究观察到一些新现象也获得了一些新的结构和数据。这些化合物在高温高压下的结构和性质，对理解地球深部的物质组成、尤其是对地球核部物质的状态和性质的理解和认识具有重要意义，也为了解与深部物质相关的基础地质问题提供了矿物物理学方面的约束和依据。在项目基金资助下，发表英文SCI收录论文10篇、国内核心期刊论文1篇，在高压矿物物理领域产生了一定的学术影响；项目还资助了5个本科生和2个博士生的学位论文，为高压矿物物理后备人才培养做出了贡献；同时项目也资助参加了15个国内外的学术交流和会议，一定程度上扩大了矿物物理学科和所在单位的社会影响力。