Rare Earth Elements (La, Ce, Pr, Nd, and Sm) from a Carbonatite Deposit: Mineralogical Characterization and Geochemical Behavior

Abstract

Geochemical characterization including mineralogical measurements and kinetic testing was completed on samples from the Montviel carbonatite deposit, located in Quebec (Canada). Three main lithological units representing both waste and ore grades were sampled from drill core. A rare earth element (REE) concentrate was produced through a combination of gravity and magnetic separation. All samples were characterized using different mineralogical techniques (i.e., quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), X-ray diffraction (XRD), and scanning electron microscopy with X-ray microanalysis (SEM-EDS)) in order to quantify modal mineralogy, liberation, REE deportment and composition of REE-bearing phases. The REE concentrate was then submitted for kinetic testing (weathering cell) in order to investigate the REE leaching potential. The mineralogical results indicate that: (i) the main REE-bearing minerals in all samples are burbankite, kukharenkoite-Ce, monazite, and apatite; (ii) the samples are dominated by REE-free carbonates (i.e., calcite, ankerite, and siderite); and (iii) LREE is more abundant than HREE. Grades of REE minerals, sulfides and oxides are richer in the concentrate than in the host lithologies. The geochemical test results show that low concentrations of light REE are leached under kinetic testing conditions (8.8-139.6 µg/L total light REE). These results are explained by a low reactivity of the REE-bearing carbonates in the kinetic testing conditions, low amounts of REE in solids, and by precipitation of secondary REE minerals.

Anaerobic reduction of europium by a Clostridium strain as a strategy for rare earth biorecovery

“…The complex is located in North-Eastern Limpopo region (South Africa) and mines a world unique deposit of copper carbonate 62,63 . The mining of copper generates large amounts of carbonatite rock waste with significant rare earth concentrations 64,65 that leach into nearby streams. Stream sediment was collected aseptically in degassed 150 ml sterile serum bottles with Teflon-coated septa (Wheaton, USA).…”

Mine Waste Rock: Insights for Sustainable Hydrogeochemical Management

“…Indeed, they are found in many ARD cases [142,143] but most REE deposits are within geological settings that are not prone to ARD generation, such as pegmatites, carbonatites, and peralkaline igneous deposits, as well as within placers and clays ( [144] and references therein). Upon their release in near-neutral mine waters, REE concentrations are mostly controlled by secondary precipitation and sorption phenomena (Section 2.4) [145][146][147][148]. However, significant knowledge gaps remain as to the fate of REE released from mine wastes.…”

Nb and REE Distribution in the Monte Verde Carbonatite–Alkaline–Agpaitic Complex (Angola)

“…Although some authors propose a magmatic origin for these elements and barite in other carbonatites (e.g., [70]), the textural evidence and the mineral association with quartz suggest a hydrothermal origin for them, as it was also suggested in Tchivira [25]. Other carbonatites worldwide, for instance, Italian carbonatites [56,57]; the Amba Dongar complex, India [71][72][73]; the occurrences from Sichuan Province, China [74][75][76]; or the Montviel deposit, Canada [77][78][79][80]; may display similar late REE mineral associations. This interpretation poses a problem since it is difficult to deduce how hydrothermal processes distribute REE minerals within carbonatite.…”