古元古代早期大氧化事件是前寒武纪研究最重要的热点问题之一，它指示新太古代—古元古代全球表生环境发生了重大变迁，是古大气—海洋氧演化的关键事件。长期以来，大氧化事件的发生过程及机制备受关注却仍存较大分歧。条带状铁矿（BIF）作为前寒武纪特有的海洋沉积物，是地球表生环境变化的关键载体，其铁氧化物的形成过程可直接反映古海洋氧含量的变化，进而限定古大气氧的演化。本项目选择华北克拉通南部上太华群和嵩山群为研究对象，二者分别发育有记录大氧化事件期间不同阶段的BIF和碳酸盐岩，地层连续、记录齐全; 通过对铁氧化物（赤铁矿和磁铁矿）进行微观形貌、结构和成分分析，查明其成因；结合铁氧化物原位Fe同位素和单矿物Mo同位素分析，揭示BIF中铁的氧化过程，限定古海水和大气中氧的含量变化；综合分析地层从底到顶全岩Fe、Mo同位素组成，并与全球的同位素记录对比，揭示大氧化事件的精细过程，并为其发生机制提供制约。

The early Paleoproterozoic Great Oxidation Event (GOE) is one of the most important advances and hotspots of Precambrian research. The GOE presents the great changes of the Neoarchean to Paleoproterozoic surficial environment, and is the key event of oxygen evolution of atmosphere and ocean. The origin and evolution of the GOE has long been controversial. Banded iron formation (BIF), as a unique type of marine sediments in the Precambrian eon, recorded key information on the changes of surficial environment of the early Earth. Its oxidation mechanism can be used to infer the redox state of paleo-ocean, and thus constrain the changes of atmospheric oxygen contents. This proposed project plans to study the upper Taihua Group and Songshan Group in the south of the North China Craton which host continuous sediment profiles of BIFs and associated carbonates at different stages of the GOE, respectively. We will conduct mineral morphological, textural and in-situ compositional analyses on iron oxides including hematite and magnetite from BIFs to study their origins. Combined with in-situ Fe isotopic and mineral Mo isotopic analyses on these iron oxides in BIF, we could reveal oxidation mechanisms of BIF at different stages of the GOE, and further constrain the changes on oxygen contents of atmosphere and ocean. The ultimate goal is to explore the evolution and mechanism of the GOE with systematic elemental and whole-rock Fe-Mo isotopic variations of the upper Taihua Group and Songshan Group from bottom to top.