Mechanism of enrichment and sequestration of neodynium (Nd) in natural apatite

Rare earth elements (REE) are essential to modern life, yet we know little about how they concentrate at Earth’s surface, especially on phosphatized marine deposits, which hold vast reserves. We propose to study the crystal chemistry of neodymium in natural apatites from marine and terrestrial deposits. We hypothesize that the site occupation of Nd is indicative of its geochemical enrichment processes. If enrichment occured via diffusion-substitution in the apatite nanopores, then the REE should occupy the Ca2 site. If the enrichment results from precipitation of authigenic apatite, then the REE is expected to occupy the Ca1 and Ca2 sites. The results will inform atomistic calculations aimed at modeling the scavenging kinetics of Nd in ore deposits.