Boron isotopic fractionation during clay adsorption from sea-water

Sea-water is enriched in11B with respect to terrestrial and volcanic inputs. It is proposed that this is due to an isotope effect during adsorption of boron by clay minerals from sea-water. An experimental test of this hypothesis using illite indicates a fractionation of about 30–40 per mile, enriching10B in the clay. This is in approximate agreement with a value calculated assuming that the ocean is at an isotopic steady state.