Insights into the nature of plume-ridge interaction and outflux of H2O from the Galápagos Spreading Centre

Approximately one-third of the global mid-ocean ridge system is influenced by the transfer of compositionally distinct material from nearby, upwellings of anomalously-hot mantle. Transfer of this plume material to the oceanic spreading centres might represent an important mechanism of volatile loss from Earth’s mantle, but there are limited constraints on the quantities of H₂O and other volatile degassing from these regions of plume-influenced oceanic spreading centres. In this study, we evaluate the mechanism of plume-ridge interaction between the Galápagos mantle plume and the nearby Galápagos Spreading Centre (GSC) using new analyses of volatiles in basalts erupted on the ridge. The results from our new numerical models demonstrate that the geochemical and geophysical signatures of plume-ridge interaction along the GSC are best explained if the transport of deep sourced mantle material between the Galápagos mantle plume and GSC occurs as a melt rather than a solid phase. In addition, our new analyses  enable us to constrain the flux of H₂O out of the GSC and demonstrate that melt channelization can account for up to 50% of the H₂O flux out of plume-influenced ridges.