Fathoming sequestration and enrichment of rare-earth elements in marine deposits

Rare earth elements (REE) are essential to modern life, yet we know little about how they concentrate at Earth’s surface, especially on the seafloor, which holds vast reserves. The underlying mechanistic pathways leading to some of the highest elemental enrichments in supergene ores is a long-standing geochemical and crystallochemical enigma. To advance the field, we propose to determine how light (LREE = Ce-Nd), medium (MREE = Gd-Dy), and heavy (HREE = Er-Yb) REE are incorporated in apatite-rich sediments at the atomic scale. The structural results will inform atomistic calculations that will be employed to model the thermodynamics and kinetics of the chemical reactions at the seawater-apatite interface. The Long Term Proposal is supported by an ERC Advanced Grant awarded to the ESRF and the Ecole Normale Supérieure of Lyon.