| Initially it was hypothesized that chemical exchange processes occur in sedimentary organic matter (OM) during diagenesis, modifying the biologically-derived chemical structure of the macerals intimately associated within a given coal or kerogen. This hypothesis was tested through the application of battery of microanalytical techniques, performed upon macerals separated from a variety of coals and kerogens using density gradient centrifugation (DGC) method. Introduction of treatment with liquid N{dollar}sb2{dollar} prior to DGC, allowed for particle size minimization. The dominant maceral in most of the samples was concentrated in high purity ({dollar}>{dollar}90%). Pyrolysis-GC/MS was chosen as the principal analytical tool.; Samples used for the study came from the Green River Formation, Tasmanian Tasmanite, Lower Toarcian Shale of the Paris Basin, Duwi Fm., New Albany Shale, Monterey Fm., Herrin No. 6 coal, and an Eocene coal and a Miocene lignite from Kalimantan.; Chemical differences between the Herrin No 6 coal DGC fractions were pronounced. The liptinite fraction was dominated by aliphatic compounds, vitrinite showed a characteristic phenolic signature and inertinite was rich in polyaromatic hydrocarbons. Chemical differences between the DGC fraction pyrolyzates of the marine shale from the Paris Basin were subtle. Amorphinite fractions separated from marine kerogens of the Duwi and the Monterey Formations samples were rich in thiophenic sulfur ({dollar}>{dollar}7%) and, in the case of the Monterey, pyrrolic nitrogen as well. Both amorphinites, from Duwi and Monterey showed similar preferential concentration of sulfur, as well as comparable FTIR spectra. The results obtained support a bacterially-mediated, degradative origin for Type II-S amorphous OM.; The vitrinite pyrolyzate from an Eocene coal showed abundant n-alkene/n-alkane pairs. The Miocene lignite's huminite exhibited almost exclusively phenolic signature. Resinite separated from an Eocene coal was enriched in the aliphatics, while resinite from the Miocene lignite showed abundant resin-markers. Assuming a strictly (methoxy)phenolic structure of the vitrinite precursors, it is suggested that enrichment in aliphatic moieties might occurred during early coalification. The interactions between macerals might have employed a "migration-impregnation" mechanism.; The study as a whole demonstrated a new approach to the separation of macerals and described the optical and chemical properties of numerous macerals not investigated in such details before. Based on the chemical and optical characterization of the investigated macerals, we conclude that overall (1) diagenetically-driven interactions between macerals do indeed occur on the molecular level, leading to the alteration of the original biologically-derived signatures, and (2) chemical differences between macerals in the same sample diminish with increasing extent of diagenesis. |
