Rare earth element trends and their relationship to mineralogy in iron oxide-apatite (IOA) mine waste: a case study of the Jan-Matts stamp sand repository (Grängesberg, Sweden)

Övrigt konferensbidrag, 2026

With the inception and implementation of the European Commission’s Critical Raw Material Act, the interest in re-evaluating formerly subeconomic raw material resources has drastically increased to boost the production of critical raw materials (CRMs). One such type of non-traditional CRM source is historic mine waste facilities (MWFs), as previously discarded gangue mineral phases can host elements which are today classified as CRMs. The latter is the aim of this study. When the Grängesberg iron-oxide apatite (IOA) deposit was mined, only the iron oxide minerals were targeted for extraction, leaving concentrated amounts of apatite in the waste material – the Jan-Matts stamp sand repository being one such MWF. Apatite can incorporate significant portions of rare earth elements (REEs) in its crystal lattice, making the apatite in mine waste a tempting target as a source of REEs. F-Apatite and Ce-monazite are the most abundant REE-associated minerals identified in the mine waste material. With detailed laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) trace element analyses, the distribution of REEs within apatite and monazite found in the mine waste material is explored. Apatite is commonly found within the mine waste material as separated grains, whilst monazite predominantly occurs as micro-inclusions within the apatite. Independent monazite grains are only found in trace amounts (i.e., sporadic grains). The LA-ICP-MS analyses of apatite and monazite clearly show that monazite contains higher contents of all REEs, except for Lu. Measured apatite contains, on average 4,972 ppm light REEs (LREEs), 823 ppm medium REEs (MREEs), and 3,134 ppm heavy REEs (HREEs). Monazite contains, on average, 60 wt% LREEs, 2.5 wt% MREEs, and 1.2 wt% HREEs. Chondrite-normalized REE patterns demonstrate the presence of multiple apatite populations within the mine waste. Relatively to the total ∑REE+Y of each mineral, apatite contains more HREEs compared to monazite, and would thus be particularly significant for the recovery of HREEs. Average contents of ∑REE+Y, ∑LREE, ∑MREE, and ∑HREE+Y of whole rock, apatite, and monazite data indicate that apatite, not monazite, is the most prominent mineral controlling REE contents in this mine waste. This is also evident through the comparison of the shares of the individual REEs (e.g., Pr, Nd, Tb, and Dy) when normalized to the total sum of rare earth elements including yttrium (∑REE+Y). By combining whole rock data and previously published mine waste tonnage estimates, the total REE resource of the Jan-Matts MWF can be estimated and put into context with active REE mining operations. The combined results of this study will aid in the evaluation of other, both historic and active, IOA MWFs, where REE-bearing apatite and monazite are left behind as waste.