Geochemical assessment of a closed tailings storage facility as part of a mine closure plan

Authors: Robinson, J; Colston, R Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2615_81

Cite As:
Robinson, J & Colston, R 2026, 'Geochemical assessment of a closed tailings storage facility as part of a mine closure plan', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-10, https://doi.org/10.36487/ACG_repo/2615_81



Abstract:
Boliden Mineral AB appointed SLR Consulting Limited (SLR) to provide geochemical advice regarding a closed tailings storage facility (TSF) associated with a former Pb/Zn mine in Vassbo, Sweden. SLR conducted the sampling of tailings to undertake detailed geochemical characterisation to identify the mineralogy, risk of acid production and leachability of contaminants of concern. This included Bureau Communautaire de Référence (BCR) leaching and upflow kinetic leaching analysis to enable modelling of elemental source depletion rate. The mineralogy of the tailings was dominated by quartz, with minor components of albite, calcite and feldspar, and trace levels of cerussite, a Pb carbonate. Acid base accounting confirmed that tailings material is non-acid forming (NAF) and has some buffering capacity. The pH sequential leaching and BCR sequential extraction results were used to assess the dominant controls on the solubility of metals/metalloids within the tailings material. They have shown that 89 to 98% of the Pb is in an easily liberated form in carbonates (cerussite), sorbed to metal hydroxides and/or organic compounds. Most of the Pb is in the carbonate form, which aligns with the mineralogical analysis. Cd and Zn both show similar solubilities, controlled by carbonate phases and phases sorbed to metal hydroxides. The upflow study results informed the derivation of kappa values to model the metal source term rate of decline. The study showed that leaching of Pb, Zn and Cd could fall below the related environmental quality standards (EQS), potentially within a 50–1,600-year period. Given the predicted metal concentration in the tailings leachate, the incorporation of passive treatment is considered an option which requires further investigation as a potential mitigation scheme to treat the groundwater at the site.

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