Isotopic fingerprinting of remobilized and superimposed mineralization in orogenic terrains: Rävliden North VMS deposit, Skellefte District, Sweden

Abstract Stable and radiogenic isotopes trace fluid and metal sources in volcanogenic massive sulfide (VMS) deposits and discriminate between superimposed mineral systems in ancient terrains. Despite their application in many VMS districts, isotopic studies remain limited for the Skellefte district. This study presents the first in-situ sulfur isotope (δ 34 S) data for pyrite, pyrrhotite, sphalerite, and chalcopyrite from the metamorphosed Rävliden North Zn-Pb-Cu-Ag VMS deposit. The δ 34 S (Vienna Canyon Diablo Troilite, V-CDT) values ranging from -2.67 to 3.68 ‰ indicate a primordial sulfur source for the c. 1.88 Ga mineralization, derived from hydrothermal fluids leaching volcano-sedimentary rocks. In contrast, sulfide minerals in the stratigraphic hanging wall record heavier δ 34 S values (up to 5.3 ‰ in sphalerite) reflecting syn-diagenetic incorporation of Paleoproterozoic seawater sulfur under anoxic conditions. Pyrite from overprinting Svecokarelian quartz veins and sulfide-cemented breccia demonstrates progressive 34 S isotope enrichment during syn-metamorphic growth, from near-zero hydrothermal δ 34 S in grain cores to ~ 5 ‰ in grain margins. Post-Svecokarelian Zn-Pb minerals hosted in calcite- and zeolite-bearing veins and breccias display stable isotope ratios (δ 13 C, δ 18 O, δ 114 Cd, δ 66 Zn, δ 56 Fe) consistent with a meteoric or connate fluid source and precipitation under reducing conditions at approximately 150°C. Lead isotopes show a typical Skellefte VMS signature for Rävliden North, whereas the post-Svecokarelian mineralization exhibits a more radiogenic composition, similar to ~ 0.5 Ga Pb–Zn veins of the Lycksele–Storuman area, constituting a superimposed mineral system, which formed due to far-field effects of the Timanian orogeny or the opening of the Iapetus Ocean. Our results demonstrate that distinguishing between remobilized and superimposed mineral systems in orogenic terrains requires integration of detailed paragenesis with isotope analyses.