Prospecting for Strategic Raw Materials in stream sediments through geochemical and mineralogical analyses: Case studies from Northern Italy

Strategic Raw Materials (SRMs) are fundamental to the development of energy‑transition technologies, and the European Union promotes domestic exploration through the Critical Raw Materials Act. In this context, the Emilia Romagna region (Northern Apennines) represents a promising area for SRM prospection owing to the presence of ultramafic ophiolitic sequences and volcanogenic massive sulfide (VMS) deposits associated with the External Ligurides Formation [1].

This study investigates SRM enrichment in river sediments influenced by variable mafic detrital contributions, integrating geochemical, mineralogical, and magnetic separation techniques. Bulk sediment characterization was carried out using X‑ray fluorescence (XRF) on glass beads and pressed powders, and inductively coupled plasma mass spectrometry (ICP‑MS) on acid‑digested samples to quantify major and trace elements.

Fine sand fractions were processed using a Frantz isodynamic magnetic separator to isolate magnetic and paramagnetic mineral concentrates. These separates were subsequently examined through scanning electron microscopy (SEM) to characterize ore minerals, identify SRM‑bearing phases, and evaluate their textural and compositional variability.

Trace‑element analyses of magnetic heavy‑mineral fractions were performed via ICP‑MS, with specific attention to elements of strategic relevance in this geological setting—namely chromium, nickel, manganese, zinc, and boron. These elements represent key targets due to their association with ultramafic lithologies, hydrothermal systems, and industrial applications linked to the energy transition.

Dragone Creek, Taro River, Nure River, and Trebbia River were selected to represent different mafic inputs and sediment‑transport dynamics. Preliminary results reveal distinct SRM concentration patterns across the catchments, with higher Cr and Ni contents in basins draining ophiolitic units (bulk concentrations up to 1000 ppm), and variable Mn, Zn, and B enrichments reflecting both lithological sources and sedimentary processes. Magnetic separation proved effective in enhancing the concentration of SRM‑bearing minerals, while SEM analyses provided crucial insights into mineral phases and potential ore associations.

These findings highlight the potential of fluvial sediments as secondary sources of SRMs and demonstrate the value of integrating magnetic separation, SEM mineral characterization, and geochemical proxies in regional exploration frameworks. Finally, this approach provides an effective preliminary exploration tool to delineate sediment provenance domains and identify high‑potential exploration targets at the basin scale.

 

[1] Kiss G., Molnàr K., Skoda P., Kapui Z., Garuti G., Zaccarini F., Palcsu L. and Czuppon G. 2023. Tracing the Source of Hydrothermal Fluid in Ophiolite-Related Volcanogenic Massive Sulfide Deposits: A Case Study from the Italian Northern Apennines. Minerals, 13 (1).