EGU24-16380, updated on 09 Mar 2024
https://doi.org/10.5194/egusphere-egu24-16380
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Linking early Earth’s internal and external reservoirs: a change in oxygen fugacity of sub-arc magmas across the Great Oxidation Event

Hugo Moreira1,2, Craig Storey2, Emilie Bruand3, James Darling2, Mike Fowler2, Marine Cotte4,5, Edgar E. Villalobos-Portillo4, Fleurice Parat1, Luís Seixas6, Pascal Philippot1,7, and Bruno Dhuime1
Hugo Moreira et al.
  • 1Géosciences Montpellier, Université de Montpellier, CNRS, Montpellier, France
  • 2School of the Environment, Geography and Geosciences, University of Portsmouth, Portsmouth, UK
  • 3Geo-Ocean, CNRS, Université de Bretagne Occidentale, Ifremer, Brest, France
  • 4European Synchrotron Radiation Facility, Grenoble, France
  • 5Laboratoire d’Archéologie Moléculaire et Structurale, University of Sorbonne, Paris, France
  • 6Departamento de Engenharia de Minas, Universidade Federal de Ouro Preto, Ouro Preto, Brazil.
  • 7Departamento de Geofísica, Astronomia e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil.

Plate tectonics exerts a first-order control on the interaction between Earth’s reservoirs. Atmospherically-altered surface materials are recycled to the mantle via subduction, while volatiles from the mantle are liberated to the atmosphere via volcanism. This cycle regulates much of Earth’s climate, ocean levels and metallogenetic processes within the continental crust. However, the interplay between Earth’s atmospheric changes and the geochemical evolution of mantle-derived magmas has remained obscure for the ancient geological history. This has led to multiple conflicting models for the crustal evolution in the early Earth.

A time-integrated evolution of the mantle-crust-atmosphere-hydrosphere interaction is yet to be fully established. For instance, secular change of the ocean and atmosphere system is evident from several proxies but the feedback of these changes to magmatic and geochemical processes in the lithosphere remain unclear. Moreover, no clear consensus has been reached on the timing of modern-style plate tectonic initiation and the evolution of net growth of the continental crust.

To explain overt and cryptic global trends in the geochemistry of magmatic rocks, a better understanding of mineral reactions and how these control trace element evolution in magmas at the lithosphere-scale is paramount. For example, the elemental and isotopic composition of apatite inclusions hosted by zircon offers a way to better understand the evolution of magmas and, to some extent, the nature of magma sources. These proxies rely on the robust data acquisition of other isotope systems with different geochemical behaviour, such as U-Pb and Lu-Hf analyses in the host zircon crystal.

A combination of methods and proxies including the elemental composition of apatite via EPMA and the oxygen fugacity based on sulphur speciation via μ-XANES of apatite inclusions was applied to ancient sub-arc magmas formed in regions akin to modern subduction zones. These magmas share a common mantle source but crystallised more than 200 million years apart (at 2.35 and 2.13 billion years ago). Importantly, they bracket the Great Oxidation Event, when atmospheric oxygen levels increased by five orders of magnitude, causing a permanent and dramatic change in Earth’s surface chemistry. As such, these sub-arc magmas were investigated as potential tracers of the interaction between Earth’s atmosphere and the mantle.

The information from several inclusions from co-magmatic rocks can then be interpreted in the light of U-Pb, Lu-Hf, trace elements and oxygen isotope analyses of the host zircon grains. Altogether, the results show a shift in oxygen fugacity of sub-arc magmas across the Great Oxidation Event. The change in oxygen fugacity is thought to be caused by recycling into the mantle of sediments that had been geochemically altered at the surface by the increase in atmospheric oxygen levels. This study opens a wide window of opportunities for the time-integrated investigation of the interaction between atmosphere and oceans with the evolving terrestrial mantle.

How to cite: Moreira, H., Storey, C., Bruand, E., Darling, J., Fowler, M., Cotte, M., Villalobos-Portillo, E. E., Parat, F., Seixas, L., Philippot, P., and Dhuime, B.: Linking early Earth’s internal and external reservoirs: a change in oxygen fugacity of sub-arc magmas across the Great Oxidation Event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16380, https://doi.org/10.5194/egusphere-egu24-16380, 2024.