Rhenium–osmium geochronology and oil–source correlation of the Duvernay petroleum system, Western Canada sedimentary basin: Implications for the application of the rhenium–osmium geochronometer to petroleum systems

Abstract

The Re–Os geochronometer has been applied to many petroleum systems worldwide. However, it is debated if the Re–Os systematics in petroleum actually record the timing of oil generation. Here, we investigate the Re–Os isotope systematics of the Duvernay petroleum system in the Western Canada sedimentary basin, which has been shown to be a relatively simple petroleum system that is associated with oil generated during the Late Cretaceous–early Eocene Laramide orogeny from a single source. The organic geochemistry of the Duvernay oils (pristane/phytane ratios of ∼1.5, smooth homohopane profile, C29 > C27 > C28 regular sterane distribution, and predominance of diasteranes over regular steranes) strongly suggests the oil source to be that of type I–II marine organic matter of the Upper Devonian Duvernay Formation. The asphaltene fraction Re–Os isotope data of the Duvernay oil yield an age of 66 ± 31 Ma, which is in excellent agreement with the timing of the main-stage hydrocarbon generation of the Duvernay Formation based on basin models. Further, the similarity between the 187Os/188Os compositions of the Duvernay Formation source rock (0.46–1.48) and the oil (0.55–1.06) at the time of oil generation supports the hypothesis that the 187Os/188Os composition of an oil is inherited from the source unit at the time of oil generation and therefore shows no, or limited, influence from interaction with basin fluids. This study supports that the Re–Os isotope systematics of an oil can yield the timing of oil generation and be used to trace its source.