Rhenium-osmium geochronology of gersdorffite and skutterudite-pararammelsbergite links nickel–cobalt mineralization to the opening of the incipient Meliata Ocean (Western Carpathians, Slovakia)

Abstract

AbstractThe multi-orogenic crustal segment of the Central Western Carpathians comprises a Variscan basement that is host to small nickel–cobalt (Ni–Co) arsenide and sulfarsenide mineralizations at Ľubietová-Kolba and Čierna Lehota (Slovakia). Here, we constrain the timing of Ni–Co mineralization by using rhenium-osmium (Re–Os) isotope geochemistry of (1) gersdorffite (NiAsS) after krutovite (NiAs2) at Ľubietová-Kolba, and (2) a mixture of skutterudite-pararammelsbergite (CoAs3–NiAs2) from the Čierna Lehota deposit, hosted by metamorphosed carbonaceous rocks. Gersdorffite, which is bereft of common Os, returns a Re–Os model age of 238.2 ± 1.0 (2σ) million years (Ma). Four aliquots of the skutterudite-pararammelsbergite mixture define a robust model 1 isochron at 238.2 ± 12.7 (2σ) Ma (mean square weighted deviates – MSDW = 0.95). A crustal source of Os, and by inference other metals, is inferred from the initial 187Os/188Os ratio of 0.90 ± 0.01 of this isochron. We conclude that studied Ni–Co mineralizations are related to an extensional tectonic regime and hydrothermal fluid flow in connection with the opening of the Meliata ocean in the Middle Triassic (Ladinian).