Influence of majorite on hot plumes

The influence of MgSiO₃ majorite on mantle convection has been investigated via 2-D numerical simulations that incorporate the stability field of majorite. According to a recent first principles study, wadsleyite decomposes into an assemblage of majorite plus periclase with a large negative Clapeyron slope. Since the stability field of majorite is limited to be greater than ~2200 K in a depth range of 500-660 km for Mg₂SiO₄, very hot upwelling plumes are expected to be strongly influenced by the phase transitions related to majorite. These hot upwellings are occasionally observed in simulations, even though the average temperature of hot plumes is far less than the stability field of majorite. The dynamics of these upwellings are controlled by the release and the absorption of latent heat induced by majorite's phase transitions as well as by the interruption of currents due to the large negative Clapeyron slope related to majorite. Key Points We find strongly heated hot plumes when temperature of mantle is highHot plumes in Archean could be affected by transitions related to majoriteHigh temperature plumes intermittently form at the present mantle temperature