Extended Data Fig. 5: Variation in oxygen fugacity for the intrinsic model.

Intrinsic deserpentinization oxygen fugacity conditions (a) relative to the FMQ buffer, Δlog₁₀fO₂[FMQ] and in absolute values (b) for a representative metaserpentinite (sample Al98-05a, see Supplementary Table 1) in a pressure-temperature space. Yellow dots are pressure-temperature deserpentinization conditions at the slab surface for a worldwide compilation of subduction zones^83,84, geographically located in (c). (d) Difference between the slab surface intrinsic deserpentinization and the mantle wedge oxygen fugacity (expressed as Δlog₁₀fO₂[FMQ]) along the 1000 °C isotherm for the DMM (solid line) and ultradepleted mantle (red dashed line), see also Extended Data Fig. 7, right panels.