Fig. 3: The evolution of sub-arc mantle fO2 and geological records over time.
From: The sub-arc mantle has remained oxidized since the Neoproterozoic oxygenation event
a The secular mean sub-arc mantle fO2 evolution since ~0.8 Ga. We first simulated arc mantle melting using a non-modal partial melting model to establish the relationship between V/Sc and fO2 (see “Data Availability”). Subsequently, we calculated the melting pressure-temperature (P-T) conditions of primitive arc basalts using the Fractionated-PT software57. By combining the V/Sc-fO2 relationship, melting P-T conditions, and mean V/Sc values, we estimated the temporal evolution of the mean sub-arc mantle fO2 relative to fayalite-magnetite-quartz (FMQ) buffer since the late Neoproterozoic (see “Methods”). The modern arc mantle fO2 was estimated from primary melt inclusions in Mariana arc basalts19. Vertical error bars in a are 1 s.d. uncertainties. The orange horizontal line and shaded orange band represent the average V/Sc since ~0.8 Ga and the 95% confidence interval, respectively. The evolution of the ambient upper mantle fO2 was estimated by Zhang et al.10. b The occurrence of blueschists and low-T, high-P metamorphic rocks since the late Neoproterozoic76. c, d Secular changes of atmospheric O2 contents13,17,89 and ocean dissolved O2 contents16,89, respectively. In a–d, the light blue shaded band indicates the time interval of the Neoproterozoic Oxygenation Event (NOE)11,12,13,14,15,16,17. e–g The secular evolution of mean Rb/La, Sr/Nd, and Th/La ratios in primitive arc basalts, respectively. Dashed lines indicate the average values of modern primitive MORBs (data extracted from the PetDB repository, n ≈ 530). The mean Sr/La, Rb/La, and Th/La ratios in primitive arc basalts are consistently higher than those in MORBs through time. Vertical error bars in e–g are 2 s.e.m uncertainties. Cen. Cenozoic, PAL Present Atmospheric Level.
