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

地球表面的氧化作用与气候变化、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重大变化有关。在整个地球历史中，环境中游离氧的量影响着几乎所有参与重要关键代谢循环的金属的溶解度和丰度。然而，即使经过30年的科学调查，关于自由氧何时以及在多大程度上在上层海洋产生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氧化还原敏感的微量金属在太古代和古元古代沉积物从皮尔巴拉克拉通，澳大利亚。海洋沉积物中氧化还原敏感金属的溶解度、浓度和同位素组成都依赖于氧的存在，因此能够记录其现代环境的氧化历史。钼（Mo）、铬（Cr）和硫（S）的同位素信息将与铀（U）和铼（Re）丰度结合起来，以研究这些元素在样品形成时的氧化还原状态和迁移率。在整个岩石和矿物样品上的这些氧化还原代理的新颖组合将使我们能够在34.6和25亿年前之间的重要时间间隔内获得早期地球氧化作用的更精确和完整的图像。

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.