Comparison of XRF and ICP Techniques for Geochemical Characterization of a Celestite Deposit

The digital transformation and the transition towards low-carbon energy systems have intensified global demand for mineral resources, particularly those classified as Critical Raw Materials (CRM) by the European Union (EU). In this context, strontium (Sr), included in the EU CRM list since 2020, has gained strategic relevance during the last years. Spain plays a key role in the European strontium supply chain, with the Montevive celestite deposit (Granada, southern Spain) representing the largest strontium reserve in the EU. However, the progressive exploitation of lower-grade ores and the potential presence of hazardous trace elements raise concerns regarding both resource efficiency and occupational health.

This study, developed within the framework of the ROTATE project, aims to characterize the elemental composition of the Montevive celestite deposit, evaluate the presence of CRMs and rare earth elements (REEs), and assess the potential health risks to mine workers. A total of 22 soil samples were collected from five distinct mining areas (CDS, FDM, PIS, LAN, and D) and analyzed using X-ray fluorescence (XRF) and inductively coupled plasma techniques (ICP-MS/ICP-OES). Method validation was evaluated through certified reference materials and duplicate sample analyses.

Accuracy assessment demonstrated that ICP techniques significantly outperformed XRF, allowing reliable quantification of 34 elements contained in the certified reference materials, compared to only 20 elements detected by XRF. Precision assessment based on duplicate ICP analyses showed high analytical precision, with coefficients of variation below 5 % for 40 analytes, which exhibited concentrations above the quantification limit.

The average mineralogical composition was dominated by celestine, calcite, quartz and magnesite. Spatial variability within the deposit was evaluated using statistical analyses (Tukey’s HSD tests), revealing marked compositional differences in the LAN area relative to the remaining zones, with strong negative correlations between silicate phases (SiO₂ and Al₂O₃) and sulphate minerals (SrSO₄ and BaSO₄). Similarly, LAN sector exhibited higher total rare earth element concentrations than the other areas, dominated by Ce, La, Nd and Y, indicating a potential secondary CRM resource.

Finally, a quantitative occupational health risk assessment was conducted considering inhalation of airborne particulate matter as the sole relevant exposure pathway, under a conservative worst-case scenario assuming the absence of personal protective equipment. For this exposure route, both non-carcinogenic and carcinogenic risks remained well below accepted regulatory thresholds for all evaluated elements considered individually, as well as for the aggregated risk (Hazard Quotient < 1; Carcinogenic Risk < 10^-5). Considering the dust control measures and personal protective equipment currently implemented at the site, occupational exposure levels and associated health risks for workers are expected to be negligible.

Overall, this study provides an integrated assessment of resource potential, analytical reliability, and occupational health risks in a strategic European strontium deposit, supporting informed decision-making for sustainable mining and critical raw material supply in the EU.