Geochemical identification of coal-sourced oils and interbedded shale-sourced oils as revealed by compound specific carbon isotopic analysis

To date, questions remain as to how to differentiate between coaland interbedded shale-sourced oils in coal measures. Based on the hypothesis that δ¹³C value of sedimentary organic matter is controlled by the depositional environment and productivities of biota grown in such depositional setting, this note examines compound specific carbon isotopic profiles from coal and interbedded shale extracts using the gas chromatography-isotope ratio mass spectrometry technique (GC/IRMS). The results show that compound specific carbon isotope values from coal extracts are enriched in¹³C relative to that of interbedded shale extracts, and provide useful information in characterizing coal- and interbedded shale-sourced oils in coal measures. An example for its successful application from the Turpan Basin, Northwestern China is presented.