Carbonatite hosted residual REE deposits

Abstract

Rare earth elements (REEs) occur in magmatic rocks but are especially enriched in carbonatite and alkaline silicates. If these rocks are chemically weathered, then the REEs may become further enriched within the regolith developed from these rocks. Primary magmatic REE minerals, as well as the various carbonate minerals and apatite, provide the REEs which, under pervasive chemical weathering are incorporated within low temperature REE minerals forming within the regolith. Many of these minerals, as well as their textures are characteristic of this mode of formation. Lateritic conditions of weathering are instrumental in producing a thick weathered or regolith profile and the roles of sulfide oxidation, fluctuating groundwater tables and downward mass wasting due to carbonate dissolution are identified as the most important controls on REE enrichment in the regolith.