胶结壳有孔虫壳壁环境矿物学研究

建立示踪古海洋氧化还原条件的矿物学指标对地球和生命演化研究有重要意义。尽管在氧化环境中广泛存在，但铁与锰的(氢)氧化物(FMHs)因易于在埋藏和成岩过程中分解的特性，很少被用于示踪沉积环境氧化还原条件。基于胶结壳有孔虫可以固定和保存FMHs的事实，本项目联合采用基于同步辐射的微区X射线荧光光谱和X射线衍射、拉曼光谱、电子探针等分析技术，对活体胶结壳有孔虫壳壁及不同时代有孔虫壳壁化石的微区成分、物相和谱学特征开展分析，以实现对FMHs的鉴定。在此基础上阐明胶结壳有孔虫固定FMHs的机制，以及埋藏和成岩作用制约壳壁中FMHs物相转化和元素迁移的机制，最终实现“建立指示沉积环境氧化还原条件的FMHs指标”的科学目标。研究建立的新指标是传统Fe形态指标的补充，在示踪地球演化关键期古海洋氧化还原条件方面有重要应用价值。

Establishing mineralogical proxy on redox condition of sedimentary environment is important to the study of the evolution of Earth and life. Although being widespread in oxic sedimentary environment, Fe and Mn (hydr)oxides (FMHs) were rarely adopted as palaeo-redox indicators, as they are decomposed during burial and diagenesis. Based on the fact that the agglutinated foraminifera can immobilize and preserve FMHs, this project tries to identify these minerals through analyzing element, phase and spectroscopy of foraminifera tests with a combined using of synchrotron radiation-based X-ray fluorescence and diffraction, Raman spectroscopy and electron microprobe. On the base of mineral identification, this project also tries to elucidate the mechanism of FMHs immobilization by agglutinated foraminifera, and the mechanism of mineralogical transformation and element transfer in foraminifera tests during burial and diagenesis. Ultimately, this projects tries to establish FMHs proxy that can be used to trace redox condition of sedimentary environment. This new proxy is a supplement of traditional Fe-speciation proxy, and has important implication in tracing redox condition of palaeo-ocean during the critical period of the Earth’s evolution.