Water-Induced Mantle Overturns Leading to the Oxidation of Archean Upper Mantle

As a consequence of the evolution of the water-bearing basal magma ocean (MO), water-induced mantle overturn can well account for many puzzling observations in the early Earth, such as the formation of the Archean continents, the Archean–Proterozoic boundary, and high Archean paleomagnetic field (Wu et al., 2023; Wang and Wu 2026). The early Earth may have experienced a deep-water cycle totally different from the current. High pressure studies suggest that the whole-mantle MO evolved into an outer MO and a basal MO. With the solidification, water in the basal MO moved toward the core-mantle boundary and the basal MO eventually became gravitationally unstable because of the enrichment of water (Fig.1). The instability triggered the massive mantle overturns and resulted in the major pulses of the thick SCLM and continental crust generations in the Neoarchean. The mantle overturns eventually got rid of the whole basal MO and the mechanism which generated the Archean-type SCLM and continents likely no more worked after the overturns. Thus, water-induced mantle overturns can account for why Archean-type SCLM and continents basically occurred in the Archean (Wu et al., 2023). The mantle overturn can substantially accelerate the cooling of the core and strengthen the geomagnetic field, which explains well the high paleointensity records from ~3.5–2.5 Ga (Wang and Wu 2026).

Besides the enrichment of water, the basal MO was enriched with ferric iron. This study shows that the ascent of ferric-rich basal MO and its mixing with the upper mantle could account for the observed shift in the redox state of the upper mantle during the Archean. Both the redox state shift and the generation of Archean continents result from these mantle overturns. Therefore, it is expected that the shift in mantle fO₂ aligns with the timing of continental generation, which is supported by the observations. The mantle overturns are rare with age > ~ 3.6 Ga, but their frequency increases with age < ~3.6 Ga and reaches the maximum in the Neoarchean. The combined effects of the ascent of the deep oxidized material, the emergence of continents, and oxygenic photosynthesis generated the broader First Redox Revolution of the Earth system, ultimately initiating the GOE shortly after the end of the Archean.

 

Wu, Z., Song, J., Zhao, G., and Pan, Z. (2023). Water-induced mantle overturns leading to the origins of Archean continents and subcontinental lithospheric mantle. Geophysical Research Letters, 50, e2023GL105178. https://doi.org/10.1029/2023GL105178

Wu, Z., and Wang, D. (2026) Water-Induced Mantle Overturn Explains High Archean Paleointensities. National Science Review. https://doi.org/10.1093/nsr/nwaf578

Figure 1. Schematic illustration of the water-induced mantle overturns (superplumes). The waterdrop is used to describe the hydrous silicate melts although hydrogen mainly exists as hydroxyls in silicate melts. (a) The solidification of a whole mantle magma ocean (MO) at the mid mantle forms an outer MO and a basal MO. (b) The basal MO eventually becomes gravity unstable and generates mantle overturns because of the enrichment of water