Sulphur K edge spectroscopy was used to differentiate types of sulphur present in petroleum asphaltenes and kerogens. A simplified model of the near edge structure enabled quantification of the different sulphur forms. The evolution of the sulphur edge following pyrolysis of kerogens confirms that thiophenic sulphur is more stable than organic sulphide forms. Pyrite retained in the kerogens may partially transform to iron sulphate during air storage. During pyrolysis FeS2 is regenerated and subsequently converted to FeS, contributing to the release of H2S. The results show that exchange between organic and mineral forms of sulphur is limited.

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