Scientists Trace 3.4 Billion Years of Earth's Mantle Oxidation

A Nature Geoscience study has documented for the first time how surface oxidation worked its way into Earth's mantle over 3.4 billion years. Sulfate from weathering, carried into the mantle wedge in subducting slabs, progressively raised its oxidation state to modern values by about 2.1 billion years ago.

• Sub-arc mantle oxidation rose from 3.4 to 2.1 billion years ago
• Mechanism: weathering sulfate carried into the mantle by subducting slabs
• Team made 337 sulfur measurements in 39 apatite inclusions from 14 samples
• Samples came from five continents, including Pilbara and Kaapvaal cratons