Geochemistry of oil inclusions in sulfide-related calcites—fingerprinting the source of the sulfate-reducing hydrocarbons of the Pb–Zn carbonate-hosted Jubilee deposit of Nova Scotia, Canada

Abstract Sulfide precipitation in the context of carbonate-hosted base metal deposits has been previously explained by numerous processes including SO 4 reduction in the presence of hydrocarbons. This model has been suggested for numerous deposits although clear criteria to support the model have not been systematically provided. Numerous oil-inclusions are encompassed by fibrous calcite crystals in finely laminated Carboniferous limestone at the base of the Windsor Group, a unit that hosts numerous base metal occurrences in Nova Scotia, particularly the hydrocarbon-rich Jubilee Pb–Zn deposit in Cape Breton Island. Oil from two inclusion-rich samples from this deposit have been characterised by gas chromatography, gas chromatography–mass spectrometry, gas chromatography–isotope ratio mass spectrometry and bulk stable C isotopes. As established in the authors' former publications, the Jubilee deposit is a clear metallogenic case for which the ground preparation and mineralisation stages involved reduction of SO 4 by hydrocarbons. Here, the question of potential sources of these hydrocarbons is addressed. It is postulated that the hydrocarbons that were trapped in the sulfide-related calcites at the deposit, correlate with previously characterised oil seeps, and it is demonstrated that their source is not the marine host-carbonates but stratigraphically deeper lacustrine formations of the Horton Group.