Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

Significance Volcanic degassing at Mauna Kea volcanoes decreases the oxidation state of both Fe and S in the magmas, consistent with recent results from Kilauea volcano. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt magmas, possibly due to plate tectonic cycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. If the degassing trend observed for Mauna Kea applies to basaltic systems more broadly, decompression does not lead to significant changes in the reducing capacity of the exsolved gases and thus cannot explain the rise of oxygen at the Archean/Proterozoic boundary.