Rare earth element detection from near-field to space - samarium detection using the REEMAP algorithm

Hyperspectral rare earth elements detection in space borne and near-field acquired images becomes more and more important for global exploration. In comparison to classic exploration methods, the benefit of hyperspectral surveys is the fast and in-situ generation of spatial information. Current hyperspectral investigations do more and more include rare earth element mappings - one new tool for hyperspectral rare earth mapping is the REEMAP algorithm. So far it is trained for five rare earth elements (erbium, dysprosium, holmium, neodymium and thulium). Previous versions of REEMAP did not map samarium. The here presented study focusses on the extension of REEMAP to identify samarium and presents a detailed mapping of the samarium and dysprosium occurrences of a two-carbonatite units containing outcrop (rauhaugites - dolomitic carbonatites and rodbergites - hematitic carbonatites) at Fen Complex, Norway. Four absorption bands of samarium were scrutinized for their shape characteristics in order to extend REEMAP for the detection of samarium. REEMAP was extended with these newly defined filter parameters. The mapping result for the investigated outcrop show that two absorption bands proved to be robust enough to be used in the REEMAP algorithm. The two remaining absorption bands are superimposed by H2O absorptions and are therefore not recommended for space borne or near-field hyperspectral analyses. However, the resulting samarium map shows the two-rock units represented by different samarium concentration levels and revealed a gradual increase of samarium towards the top of the rauhaugites rock unit. This study shows that REEMAP can be trained for the detection of samarium, especially for two of the investigated absorption bands (1250 and 1567 nm), and that REEMAP helps for in-situ interpretations of REE ore distributions.