Oxidation of Archean upper mantle caused by crustal recycling

• Published in: Nature communications Vol. 13; no. 1; p. 3283
• Main Authors: Gao, Lei, Liu, Shuwen, Cawood, Peter A., Hu, Fangyang, Wang, Jintuan, Sun, Guozheng, Hu, Yalu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07-06-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 704/2151/209; 704/2151/213/4114; Basalt; Cratons; Earth mantle; Evolution; Fugacity; Humanities and Social Sciences; Island arcs; Isotope ratios; Isotopes; Lava; multidisciplinary; Niobium; Oxidation; Primitive Earth atmosphere; Recycling; Science; Science (multidisciplinary); Titanium; Upper mantle; Vanadium
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-30886-4

The redox evolution of Archean upper mantle impacted mantle melting and the nature of chemical equilibrium between mantle, ocean and atmosphere of the early Earth. Yet, the origin of these variations in redox remain controversial. Here we show that a global compilation of ∼3.8-2.5 Ga basalts can be subdivided into group B-1, showing modern mid-ocean ridge basalt-like features ((Nb/La)
PM
 ≥ 0.75), and B-2, which are similar to contemporary island arc-related basalts ((Nb/La)
PM
 < 0.75). Our V-Ti redox proxy indicates a more reducing upper mantle, and the results of both ambient and modified mantle obtained from B-1 and B-2 samples, respectively, exhibit a ∼1.0 log unit increase in their temporal evolution for most cratons. Increases in mantle oxygen fugacity are coincident with the changes in basalt Th/Nb ratios and Nd isotope ratios, indicating that crustal recycling played a crucial role, and this likely occurred either via plate subduction or lithospheric drips.
The basalt V-Ti redox proxy indicates that both of the Archean ambient and modified mantle exhibit a ~1.0 log unit increase in their evolution for most cratons, possibly derived by widespread crustal recycling.