Uptake of dissolved oxygen during marine diagenesis of fresh volcanic material

Convergent plate volcanism typically occurs close to the oceans, hence a high proportion of fresh, highly reactive, volcanogenic material is rapidly deposited onto the seafloor. Previous studies (Haeckel et al., 2001) have shown that dissolved oxygen (O2) is extensively depleted in the pore waters of ash deposited in the South China Sea from the 1991 Pinatubo eruption. Here, we report the results of an extensive field, laboratory and modelling study of dissolved O2 concentrations and ancillary geochemical data (pore water NO2 + NO3 and solid phase FeII/FeIII and organic carbon) in the sediments surrounding the volcanic island of Montserrat, Lesser Antilles. Dissolved O2 is depleted to zero within 0.3 cm of the sediment–water interface in sites containing the thickest layers of volcanogenic material (35 cm), compared to a penetration depth of ∼6 cm in sites with minimal ash loading of