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oa Stable Carbon and Nitrogen Isotope Measurements of Individual Alkylcarbazole in Crude Oils and its Geochemical Implications
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IMOG 2025, Sep 2025, Volume 2025, p.1 - 2
Abstract
Geoporphyrins and carbazoles in crude oils are mostly investigated due to its importance of nitrogen sources and geochemical applications. Compared with geoporphyrins, sources and formation pathway of carbazoles are ongoing debates and remain controversial. Here, we developed a new method to separate and purify nitrogen-containing fractions from crude oils, and conducted d13C and d15N measurements of individual alkylcarbazole to probe these issues. Preliminary results show that d13C values of individual alkylcarbazole are enriched in 13C compared with those of whole oils, in agreement with a 12C-enriched trend as decreasing polarity of fractions in crude oil. A flat pattern of d13C profiles could be suggestive of a common carbon source and/or the same mechanism for the formation of alkylcarbazoles. Significant nitrogen isotopic fractionation among alkylcarbazole homologues in one given oil probably indicates multiple nitrogen sources and/or formation mechanisms upon diagenesis. One possibility is incorporation of inorganic nitrogen during sedimentary diagenesis and consolidation in heterocyclic molecules. Future studies on samples from diverse geological settings could provide deep insight into the nitrogen sources and formation pathway of alkylcarbazoles in crude oils and extracts, especially by integrating d15N values of geoporphyrins that exhibit distinct signal of biological origin.
