Beryllium in marine pore waters: Geochemical and geochronological implications

DIAGENETIC remobilization and hydrothermal inputs have been invoked as possible explanations for the discrepancy between the theoretical and measured temporal decrease of the non-detrital ¹⁰Be/⁹Be ratio observed in sediments. Remobilization is also consistent with water-column profiles of beryllium, which indicate a significant benthic flux from sediments. To evaluate the impact of diagenetic recycling on the beryllium isotopic composition of marine waters and the effects of this process on the beryllium geochronometer, we have analysed the ⁹Be content of interstitial waters from different environments. Here we report the first pore-water profiles for ⁹Be in oxic and suboxic pore waters as well as some preliminary results from hydrothermal sediments collected in the Guaymas Basin. Our results suggest that the use of the beryllium isotopes as a geochronometer is not affected either by sedimentary diagenesis at oxic and suboxic sites or by input of hydrothermally derived ⁹Be more than a few kilometres from vent sites.