Elucidating Sulfurization Processes in Sulfur-Rich Mudstones: An X-Ray Absorption Spectrometric Study

Preservation through sulfurization of organic matter (OM) is an important process in the formation of hydrocarbon reserves, but this process remains poorly understood (Amrani 2014), despite the attention given to understanding how sulfurization of OM and pyrite (FeS2) precipitation occur (Werne et al. 2008). It is conventionally thought that FeS2 precipitation outcompete sulfurization. However, recent analyses suggest that sulfurization of OM might start in the water column (i.e. on timescale of days; Raven et al. 2016). This implies that sulfurization of OM precedes FeS2 formation, contrary to the convention that iron sulfide formation is favoured over OM sulfurization in iron-rich oceans and porewater (Raiswell et al. 1994; Canfield et al. 1996). To the best of our knowledge, Raven et al. (2016) is the only study documenting sulfurization of OM outcompeting FeS2 formation. Moreover, there is a lack of data on the micron/nano/molecular-scale necessary to fully comprehend these complex processes. The aims of this study are to use synchrotron-based techniques to nondestructively spatially resolve (map), and provide detailed information about, oxidants and reductants critical in sulfurization and FeS2 precipitation processes, using sulfur-rich mudstones as a model system.