The Fe‐FeO buffer at lower mantle pressures and temperatures

As a constraint on oxygen fugacity of the lower mantle, the iron‐wüstite (IW) oxygen buffer has been calculated for temperatures to 3000 K and pressures to 135 GPa using available thermochemical and thermophysical data for Fe, FeO, and O2. At conditions corresponding to the coremantle boundary and 670 km depth, respectively, the oxygen fugacity of this buffer is 1020 and 10³ Pa; oxygen activities referenced to these conditions are 10−9 and 10−13.