Sulphur and oxygen sequestration of n-C{sub 37} and n-C{sub 38} unsaturated ketones in an immature kerogen and the release of their carbon skeletons during early stages of thermal maturation
- Netherlands Institute for Sea Research (NIOZ), Den Burg (Netherlands); and others
Sedimentary rock from the Gessoso-solfifera Formation (Messinian) in the Vena del Gesso Basin (northern Italy) containing immature (R{sub o} = 0.25%) S-rich organic matter was artificially matured by hydrous pyrolysis at temperatures from 160 to 330{degrees}C for 72 h to study the diagenetic fate of n-C{sub 37} and n-C{sub 38} di- and tri-unsaturated methyl and ethyl ketones (alkenones) biosynthesised by several prymnesiophyte algae. During early diagenesis, the alkenones are incorporated into the kerogen by both sulphur and oxygen cross-linking as indicated by chemical degradation experiments with the kerogen of the unheated sample. Heating at temperatures between 160 and 260{degrees}C, which still represents early stages of thermal maturation, produces large amounts (up to 1 mg/g TOC) of S-bound, O-bound, and both S- and O-bound n-C{sub 37} and n-C{sub 38} skeletons, saturated n-C{sub 37} and n-C{sub 38} methyl, ethyl, and mid-chain ketones, C{sub 37} and C{sub 38} mid-chain 2,5-di-n-alkylthiophenes, C{sub 37} and C{sub 38} 1,2-di-n-alkylbenzenes, and C{sub 37} and C{sub 38} n-alkanes. With increasing thermal maturation, three forms of the n-C{sub 37} and n-C{sub 38} skeletons are relatively stable (saturated hydrocarbons, 1,2-di-n-alkylbenzenes and saturated ketones), whereas the S- and O-bound skeletons are relatively labile. These results suggest that in natural situations saturated ketones with an n-C{sub 37} and n-C{sub 38} skeleton can be expected as well as the corresponding hydrocarbons. 58 refs., 8 figs., 2 tabs.
- OSTI ID:
- 576321
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 61, Issue 12; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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