Stepwise chemical degradation of immature S-rich kerogens from Vena del Gesso (Italy)

Stepwise chemical degradation involving cleavage of ester bonds (KOH/MeOH), sulfide and remaining ester bonds (Li/EtNH2), ether bonds (HI/LiAlH4) and sub-units linked to aromatic moieties (RuO4) has been carried out on the ke rogens of two immature sulfur-rich marls (IV-1.4 and 1.8, TOC ca. 1.5%) Fro m evaporitic cycle IV of the Gesosso-solfifera Formation (Messinian, Vena d el Gesso, Italy). Up to 80% of the organic matter was converted to solvent- soluble material, with the greatest proportion released by Li/EtNH2. The ma jority by far of the extracts comprises polar macromolecular material which is thought to correspond to high molecular weight sub-units of the kerogen . Quantification of the small amounts (<1%) of the released GC-amenable com ponents indicates that diagenetic sulfurization was more important in the c ase of kerogen IV-1.4 but that the extent of oxygen sequestration was simil ar in both cases; the distributions of biomarkers released by ether cleavag e of the desulfurized residue and polar fraction showed differences which r eveal heterogeneity in the building blocks making up different macromolecul ar fractions. (C) 1998 Elsevier Science Ltd. All rights reserved.