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

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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.