Volcanogenic massive sulfide (VMS) deposits belong to the most significant sources of base and precious metals such as Zn, Cu, Pb, Ag, and Au, as well as critical elements such as In, Ga, Ge, Sb, and Bi. Deformation and metamorphism of VMS deposits complicate their exploration and beneficiation. Examples are found in the Skellefte district, northern Sweden, where VMS deposits formed and underwent polyphase deformation (D1, D2, D3) during the 2.0–1.8 Ga Svecokarelian orogeny, imparting structural and mineralogical complexity at various scales. Presence of highly conductive graphitic strata in the host succession complicates direct detection using conventional electromagnetic geophysical techniques, necessitating a larger emphasis on geological and geochemical criteria to guide exploration. This study addresses these challenges by providing an integrated mineralogical, chemical, and textural characterisation of the Rävliden North Zn–Cu–Pb–Ag VMS deposit in the Skellefte district. 

Rävliden North is hosted at the transition between 1.89–1.88 Ga metavolcanic rocks of the Skellefte group and overlying 1.88–1.87 Ga, predominately metasedimentary rocks of the Vargfors group. Massive to semi-massive sphalerite, pyrrhotite, galena, pyrite occurs structurally and stratigraphically above chalcopyrite, pyrrhotite, pyrite-dominated mineralisation. Petrographic and structural analysis reveals textural evidence of sulfides hosted in ductile to brittle structures (e.g. foliations, boudinage, durchbewegt ore, piercement veins, tension gashes, breccia, and veinlets), indicative of polyphase remobilisation. Microanalysis show that sphalerite and chalcopyrite retain a zonation comparable with unmetamorphosed VMS, with enrichment of Cu, Co, and In in chalcopyrite-rich mineralisation. Limited syn-metamorphic redistribution of trace elements occurred beyond partitioning between coexisting sulfides. In-situ δ34S analyses indicate limited isotopic fractionation, with δ³⁴S values tightly constrained at 0 ± 2‰, consistent with a volcanic sulfur source. Meanwhile, variable δ114Cd, δ66Zn, δ56Fe and Zn/Cd ratios in sphalerite suggest an importance of mass-dependent kinetic fractionation with lighter isotopes precipitating near a high-temperature source, albeit volcanic source rocks akin to the Skellefte group can be pinpointed based on Pb isotopes. 

Overprinting, late-Svecokarelian sulfide assemblages (sphalerite, galena, Ag-rich sulfosalts) occur in quartz veins and sulfide-cemented breccia that crosscut ductile fabrics in the hanging wall. These host sphalerite and galena enriched in Cd, Ag, and Sb, and exhibit δ34S values consistent with recycling of syn-sedimentary sulfides, originally formed via sulfate reduction under anoxic deep-ocean conditions. Post-Svecokarelian mineralisation associated with calcite or zeolite (laumontite, heulandite and wairakite) veins and breccia crosscut all ductile fabrics. Distinctive colour-zoned sphalerite with oscillatory trace-element distribution in twins (enriched in Ga, Ge, Cu, Sb) together with δ114Cd, δ66Zn, δ56Fe, Zn/Cd, δ34S, δ15C and δ18O indicate a low-temperature (~150 °C) system involving reduced meteoric to connate water. Mineralogical and Pb isotopic similarities to nearby vein- and breccia-type Zn-Pb deposits indicate derivation from a juxtaposed mineral system at c. 0.5 Ga, linked to far field effects during opening of the Iapetus Ocean or the Timanian orogeny. Future research should test exploration vectors derived from hanging wall mineralisation, perhaps by correlating bulk-rock geochemical proxies with mineral-scale chemistry.

The classification of Rävliden North’s VMS mineralisation based on dominant sulfides, host lithology, and textures allowed the investigation of mineral processing performance. Massive sphalerite-rich mineralisation hosted in amphibole and mica rich rocks differ markedly in grindability and flotation response compared to chalcopyrite-rich veinlets in more quartz-rich rocks. Recovery and concentrate quality for Zn, Cu, and Pb are controlled by mineralogy, liberation and grain size, while trace and critical elements (Ag, Sb, Bi, Cd, Hg, Tl, As) recovery depends on liberation and inter-locking associations with sulfides and sulfosalts. The results allow optimisation of blending protocols that could help enhance recoveries, mitigate deleterious elements, and facilitate exploitation of future by-products such as Bi and Sb. Future research should develop geometallurgical models that capture deposit-scale variability and strategies to recover critical metals as by-products.