Mineralogical and Geochemical Study of Rare Earth Elements from a Carbonatite Deposit

Five samples coming from a carbonatite deposit were characterized and rare earth element (REE) grades were measured. Mineralogical examination by SEM-EDS shows the following observations: (i) The rare earths are associated with carbonates, (ii) all analysed minerals contain preferably light REE (La, Ce, Pr, Nd, Sm and Eu), (iii) the sum of LREE in each analysed mineral varies between similar to 3 and 10 wt%, (iv) the only heavy REE identified are Gd and Yb with a content lower than 0.4 wt%, and (v) three groups of carbonate minerals were observed containing variable concentrations of Ca, Na, and F. The leachability of rare earth elements was tested using normalized kinetic testing (humidity cells with 64 weekly cycles). The geochemical results obtained indicate that the highest sum of light rare earth leached is recorded in the ferro-carbonatite (HG) (42 mu g/l), while the lowest sum (8.8 mu g/l) is from in the ferro-carbonatite (LG). For heavy rare earths, the leaching is between 0.27 and 1.5 mu g/l with the maximum in the breccia and the minimum in the ferro-carbonatites (HG).