The oceanic chemistry of the rare-earth elements

Abstract

Because of the unique chemical characteristics of the rare-earth elements (REES), they provide information as oceanic tracers of element source and reactivity. The absolute and relative concentrations of the REES in ocean waters reflect their input from rivers, by aeolian transport and from hydrothermal vents; their interaction with the bio-geochemical cycle involving removal from surface waters by adsorption and oxidation at particle surfaces (probably with organic coatings) and deeper regeneration; and the effects of advective transport. Within the REE group, Ce anomalies occur in response to oceanic redox conditions; Eu anomalies in response to aeolian and hydrothermal input; and Nd isotopic variations reflect element sources. Both REE concentration patterns and Nd isotopic variations allow the effects of the vertical particle flux and of lateral advection to be separated.