Biogeochemical expression of rare earth element and zirconium mineralization at Norra Kärr, Southern Sweden

Biogeochemical samples were collected from the Norra Kärr Alkaline Complex, a rare earth element (REE) and zirconium enriched deposit in Southern Sweden, to determine which sample medium is the most effective grassroots exploration tool for delineating concealed REE mineralization. The fern species Dryopteris filix-mas and Athyrium filix-femina were found to be widespread in the study area and surrounding countryside, and particularly efficient at concentrating high levels of REEs in their leaf tissue.There was distinct elemental fractionation in all three fern species. Each species showed enrichment in the LREEs (light rare earth elements), especially A. filix-femina. D. filix-mas showed the most enrichment in HREEs (heavy rare earth elements); Pteridium aquilinum had lower levels of REEs than the other two species.The best contrast was observed in D. filix-mas samples from areas over mineralization compared to samples taken over barren Växjö granites, which suggests that D. filix-mas is the preferred biogeochemical sample medium for REE exploration in this environment.

► Three fern species are collected over known rare earth element (REE) mineralization.
► All fern species fractionate light REEs more than heavy REEs.
► Dryopteris filix-mas is the most efficient sample medium for biogeochemical exploration.