火星辉玻无球粒陨石的氧逸度研究及其对火星幔源区特征的启示

火星幔的氧逸度研究是揭示火星深部结构和物质组成的重要方法，因为氧逸度可以通过控制变价离子（铁、碳等）的赋存状态影响幔部物质的化学和物理性质。但是，目前对火星幔氧逸度的研究还未达成共识。火星辉玻无球粒陨石作为幔源岩浆活动的产物，是研究火星幔特征的关键载体。本项目拟以火星辉玻无球粒陨石为研究对象，反演火星幔氧逸度。具体方案为：利用扫描电子显微镜、电子探针、离子探针微区分析新技术等，获取辉玻无球粒陨石的岩相结构、矿物和全岩成分、同位素组成，计算氧逸度值，分析岩浆过程，剖析二者间的对应关系，并讨论导致氧逸度变化的可能因素，综合探讨火星幔氧逸度特征。本研究的创新点是：在同一样品内使用多组氧逸度指示剂，精细解析不同岩浆演化阶段的氧逸度信息。本研究将加深对辉玻无球粒陨石氧逸度特征与变化机制的新认识，为岩浆演化模型和火星幔源区特征提供新的氧逸度约束条件，对火星幔演化的研究有重要意义。

Oxygen fugacity controls the occurrence of multi-valence ions (iron, carbon, ect.), so it is a critical factor affecting the geochemical and geophysical properties of martian mantle. After dozens of years of extensive studies, there is still no consensus on the exact conditions of martian mantle oxygen fugacity. Martian shergottites are products of mantle-derived magma, so they are eligible targets to investigate both the composition of the martian mantle source and possible compositional changes during martian magmatism. Utilizing scanning electron microprobe, electron probe microanalyzer, laser ablation inductively coupled plasma mass spectrometry, and newly-developed microzone analyzing techniques for secondary ion mass spectrometry, this proposal is aimed at investigating the oxidation state of the mantle source by studying petrology, mineralogy and U-Pb isotopic composition of shergottites. Special focuses will be given on the analyses of both the magmatic process and oxygen fugacity, and potential factors that might alter the oxygen fugacity during magma evolution will be discussed. The main innovation of this proposal is that two or more sets of oxybarometers within a single shergottite will be applied to attain a detailed record of oxygen fugacity at various stages of magmatic processes. New information about the possible range and variation mechanism of oxygen fugacity in shergottites will be earned after performing this proposal, further providing constraints on magma processes and the oxidation state of the mantle of Mars.