The constant oxidation state of Earth's mantle since the Hadean.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39127717.
- Also identified by DOI 10.1038/s41467-024-50778-z and PMC identifier 11316782.
- Licence recorded as CC BY-NC-ND.
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Abstract
Determining the evolutionary history of mantle oxygen fugacity (fo<sub>2</sub>) is crucial, as it controls the fo<sub>2</sub> of mantle-derived melts and regulates atmospheric composition through volcanic outgassing. However, the evolution of mantle fo<sub>2</sub> remains controversial. Here, we present a comprehensive dataset of plume-derived komatiites, picrites, and ambient mantle-derived (meta)basalts, spanning from ~3.8 Ga to the present, to investigate mantle thermal and redox states evolution. Our results indicate that fo<sub>2</sub> of both mantle plume-derived and ambient mantle-derived melts was lower during the Archean compared to the post-Archean period. This increase in the fo<sub>2</sub> of mantle-derived melts over time correlates with decreases in mantle potential temperature and melting depth. By normalizing fo<sub>2</sub> to a constant reference pressure (potential oxygen fugacity), we show that the fo<sub>2</sub> of both the mantle plume and ambient upper mantle has remained constant since the Hadean. These findings suggest that secular mantle cooling reduced melting depth, increasing the fo<sub>2</sub> of mantle-derived melts and contributing to atmospheric oxygenation.