Evolution of magma redox state throughout Earth’s history revealed by zircon geochemistry

Abstract The redox state of magma provides a valuable record of significant evolutionary events on Earth, acting as a geological time capsule. Analyzing these records can illuminate key shifts in Earth’s history, including changes in atmospheric composition, the emergence of life, and major geological and tectonic events. We investigated the temporal variations of detrital zircon oxygen fugacity (fayalite-magnetite-quartz oxygen buffer, ΔFMQ), which is an igneous oxybarometer, to track magma redox states over Earth’s history. The decline in zircon ΔFMQ from 4.2 Ga to 3.8 Ga potentially corresponds to the Late Heavy Bombardment event. The significant increase in zircon ΔFMQ from 3.8 Ga to 3.0 Ga may be linked to the onset of water recycling in supracrustal materials or to thickening of the continental crust. The fluctuating trends of zircon ΔFMQ after 2.5 Ga reflect the processes of supercontinent amalgamation, namely introversion and extraversion. Introversion involves the consumption of interior oceans containing abundant reduced sediments, while extraversion involves the subduction of exterior oceans with oxidized sediments. Our study highlights that zircon ΔFMQ analysis is a potent tool for tracing magma redox evolution, offering crucial insights into significant geological events and processes.