Fe-S-P三元体系的高温高压相图和电阻率测量及其对月核成分和热演化的启示

前人的研究认为月核含有一部分轻元素，但轻元素的种类和含量仍然存在不确定性。硫被认为是月核中的一种重要的候选元素。磷与硫具有接近的质量，而且也具有亲铁性，被认为是另一种月核中的候选元素。本申请项目拟以Fe-S-P三元体系为研究对象，在1000~1800 K和1~6 GPa的温压条件下，采用高温高压实验装置（六面顶压机、Kawai型二级压机）开展系统的相图实验研究，并在300~1800 K和4~6 GPa条件下采用四线法测量Fe-S-P合金和熔体样品的电阻率，利用X射线衍射仪、电子探针和扫描电镜等进行物相、化学成分和结构形态等方面的分析，建立Fe-S-P三元体系在月球温压条件下的相图并约束月核的成分，揭示Fe-S-P合金和熔体在月核条件下的电阻率，计算月核的热导率及月球核幔边界的热通量，进而探讨月核的热演化历史。

Previous studies suggest that the lunar core contains some amount of light elements, but the species and contents of light elements are still uncertain. Sulfur is considered as an important candidate light element in the lunar core. Phosphorus, a siderophile element with a close mass to sulfur, is regarded as one of the candidate light elements in the lunar core. In this proposal high-pressure and high-temperature experiments will be carried out on the Fe-S-P ternary system by using large volume presses (including cubic press and Kawai-type multianvil apparatus). The phase diagram of Fe-S-P ternary system will be established under the pressure and temperature conditions of 1~6 GPa and 1000~1800 K. The electrical resistivity of Fe-S-P alloy and melt will be measured by adopting a four-wire method under the pressure and temperature conditions of 4~6 GPa and 300~1800 K covering the lunar core conditions. The recovered samples will be characterized and analyzed by X-ray diffraction, electron microprobe and scanning electron microscope to identify the phases, the chemical compositions and structural morphology. Based on the obtained Fe-S-P phase daigram, new constraints will be made on the composition of lunar core. Using the measured electrical resistivity of Fe-S-P alloy and melt, the thermal conductivity will be calculated for further estimation of the heat flux of lunar core-mantle boundary. Then the thermal evolution history of the lunar core will be discussed.