Geochemistry of the alginite and amorphous organic matter from type II-S kerogens

B.A. Stankiewicz; M.A. Kruge; Maria Mastalerz; G.L. Salmon

doi:10.1016/0146-6380(96)00048-4

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Geochemistry of the alginite and amorphous organic matter from type II-S kerogens

B.A. Stankiewicz·M.A. Kruge·Maria Mastalerz·G.L. Salmon

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Abstract

Maceral fractions of the Type II-S kerogens from the Monterey Formation (Miocene. California. U.S.A.) and Duwi Formation (Campanian/Maastrichtian, Egypt) were separated by density gradient centrifugation. The Monterey Fm. kerogen sample was comprised chiefly of light red-fluorescing amorphous organic matter (AOM), the flash pyrolyzate of which was characterized by a predominance of alkylbenzenes, alkylthiophenes and alkylpyrroles. In contrast, the pyrolyzates of its alginite concentrate showed a highly aliphatic character, typical of this maceral, with the series of n-alkenes and n-alkanes (C6- C26) predominating. The pyrolyzate of the dominant light brown-fluorescing AOM of the Duwi Fm. kerogen had a relatively high concentration of alkylbenzenes and alkylthiophenes, while its elginite concentrate showed a more aliphatic character upon pyrolysis. There was a marked enrichment of thiophenic sulfur in the light-colored AOM of both samples (and also pyrrolic nitrogen in the case of the Monterey) relative to the alginite. The results support a bacterially-mediated, degradative origin for Type II-S amorphous organic matter, with algal remains as the primary source of the kerogen.

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B.A. Stankiewicz, M.A. Kruge, Maria Mastalerz, G.L. Salmon. 1996. Geochemistry of the alginite and amorphous organic matter from type II-S kerogens. https://doi.org/10.1016/0146-6380(96)00048-4

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