The evolution of free oxygen in the early Earth atmos- and hydrosphere; a paleoredox study of 3.46 - 2.48 Ga old euxinic sediments from Pibara, Australia

地球表面的氧化与气候变化、生物进化和大型金属矿体的沉积密切相关。这些事件与海洋和大气化学的基本变化有关。在整个地球历史上，环境中游离氧的数量影响着参与重要关键代谢循环的几乎所有金属的溶解度和丰度。然而，即使经过30年的科学调查，关于何时以及在多大程度上在上层海洋产生游离氧并释放到大气中的主要问题仍然存在。为了解决这个问题，拟议的研究项目将分析来自澳大利亚皮尔巴拉克拉通的太古宙和古元古代沉积物中的氧化还原敏感痕量金属。由于海洋沉积物中氧化还原敏感金属的氧依赖溶解度，其浓度和同位素组成能够记录其当代环境的氧化历史。钼（Mo）、铬（Cr）和硫(S)的同位素信息将与铀(U)和铼（Re）丰度相结合，以研究这些元素在样品形成时的氧化还原状态和迁移率。对整个岩石和矿物样本的这些氧化还原指标的新颖组合将使我们能够更精确和完整地了解早期地球在34.6亿至25亿年前这一重要时间间隔内的氧化作用。

The oxygenation of Earth’s surface is tightly coupled with climatic changes, biological evolution and deposition of large metal ore bodies. These events have been linked to essential modifications in ocean and atmospheric chemistry. The amount of environmentally free oxygen influences the solubilities and abundances of nearly all metals involved in important key metabolic cycles over the entire Earth history. However, even after 30 years of scientific investigation, major questions remain regarding when and to what extent free oxygen was produced in the upper oceans and released into the atmosphere. To address this question, the proposed research project will analyse redox sensitive trace metals in Archean and Paleoproterozoic sediments from the Pilbara craton, Australia. Due to their oxygen dependent solubilities, concentrations and isotopic compositions of redox sensitive metals stored in oceanic sediments are capable to archive the oxygenation history of their contemporary environment. The isotopic information of molybdenum (Mo), chromium (Cr) and sulfur (S) will be combined with uranium (U) and rhenium (Re) abundances to investigate the redox state and mobility of these elements at the time of sample formation. The novel combination of these redox proxies on whole rock and mineral samples will allow us to get a more precise and complete picture of the oxygenation of the early Earth within the important time interval between 3.46 and 2.5 Billion years ago.