The elemental cycles of uranium and nickel: two highly (in)compatible bedfellows
Abstract
The Earth has witnessed a complex history of atmosphere-hydrosphere-lithosphere interaction and the geochemical cycles of many elements were additionally affected by the evolving biosphere. Many open questions regarding the Earth's surface evolution remain. In this presentation, we will follow on the tracks of two elements with fundamentally different geochemical qualities: the highly incompatible U and the very compatible Ni. Central to their geochemical cycles is whether the Great Oxygenation Event (GOE) at ca. 2.35 Ga was a one-off, irreversible event or whether it was preceded by earlier oxygenation whiffs. It will be concluded that the evidence for the GOE remains strong and that if earlier oxygenation events did occur, they were restricted to oceanic oxygen oases with limited effect on global oceanic elemental cycles. Analysis of information from sub-recent and ancient weathering profiles will be combined to argue that oceanic chemistry is and always was strongly influenced by the dominant rock type on the land surface and breakdown of primary minerals during the early stages of weathering.
Biography
Originally trained as a metamorphic petrologist in Switzerland, I have morphed into a geochemist working on understanding the elemental cycles that operate on the Earth, particularly in the surface environment. Prior to arriving at QUT in September 2018, I was Chair of Geology&Mineralogy at Trinity College Dublin and Tier 1 Canada Research Chair in Precambrian Geology at Laurentian University, Ontario. I worked as a postdoc and senior research fellow at UQ between 1998 and 2005. My research spans from the very fundamental questions of 'how did the earliest Earth look' and 'how did the atmosphere evolve' to environmental studies on the fate of pollutants in the environment and more recently, the supply of raw materials needed to support renewable technologies. Common to all these investigations is the need for quantitative chemical and isotopic data. My group is active in the development of novel analytical methods that transcend the boundaries between chemistry, geology, material science and environmental science.
