Abstract
Analysis of manganese mineral occurrences and valence states demonstrate oxidation of Earth’s crust through time. Changes in crustal redox state are critical to Earth’s evolution, but few methods exist for evaluating spatially averaged crustal redox state through time. Manganese (Mn) is a redox-sensitive metal whose variable oxidation states and abundance in crustal minerals make it a useful tracer of crustal oxidation. We find that the average oxidation state of crustal Mn occurrences has risen in the last 1 billion years in response to atmospheric oxygenation following a 66 ± 1 million-year time lag. We interpret this lag as the average time necessary to equilibrate the shallow crust to atmospheric oxygen fugacity. This study employs large mineralogical databases to evaluate geochemical conditions through Earth’s history, and we propose that this and other mineral data sets form an important class of proxies that constrain the evolving redox state of various Earth reservoirs.
Highlights
Analysis of manganese mineral occurrences and valence states demonstrate oxidation of Earth’s crust through time
We report on a revealing proxy for the redox state of Earth’s shallow crust using large mineralogical data resources and we assess implications for the co-evolution of Earth’s geosphere and biosphere
The increase in atmospheric and oceanic O2 content following the Great Oxidation Event” (GOE) led to the widespread oxidation of redox-sensitive metals[17,30], with a corresponding increase in Earth’s mineral diversity
Summary
Analysis of manganese mineral occurrences and valence states demonstrate oxidation of Earth’s crust through time. The increase in atmospheric and oceanic O2 content following the GOE led to the widespread oxidation of redox-sensitive metals[17,30], with a corresponding increase in Earth’s mineral diversity.
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