Evidence for a dominantly reducing Archaean ambient mantle from two redox proxies, and low oxygen fugacity of deeply subducted oceanic crust.

ABSTRACT: Oxygen fugacity (ƒO₂) is an intensive variable implicated in a range of processes that have shaped the Earth system, but there is controversy on the timing and rate of oxidation of the uppermost convecting mantle to its present ƒO₂ around the fayalite-magnetite-quartz oxygen buffer. Here, we report Fe³⁺/ΣFe and ƒO₂ for ancient eclogite xenoliths with oceanic crustal protoliths that sampled the coeval ambient convecting mantle. Using new and published data, we demonstrate that in these eclogites, two redox proxies, V/Sc and Fe³⁺/ΣFe, behave sympathetically, despite different responses of their protoliths to differentiation and post-formation degassing, seawater alteration, devolatilisation and partial melting, testifying to an unexpecte

SUBMITTER: Aulbach S 

PROVIDER: S-EPMC6934757 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature