Formation of humite-group minerals and hydrous olivine by redox decarbonation of subducted peridotites: implications for the deep water cycle

In this work we investigated the influence of the redox decarbonation of peridotites on the stability of fluorine-free HGM and the H₂O storage capacity of olivine at pressures of 5.5–7.8 GPa, temperatures of 850–1100 °C, and a range of redox conditions from fO₂ values near the Ni–NiO (NNO) to Fe–FeO (IW) buffer. The formation of HGM in the decarbonation products and the abrupt increase in the water storage capacity of the newly formed olivine allowed us to substantiate a new mechanism that can significantly increase the efficiency of water transport into the mantle during slab subduction.