Kerogens isolation

Durand, B., and Nicaise, G. (1980). Procedures for kerogen isolation. In Kerogen. ed. Durand,... 

Kerogens isolated from the Fig Tree cherts produced very complex mixtures of pyrolysis products, dominated by a series of methyl branched alkenes with each member of the series having 3 carbon atoms more than the previous member. At each carbon number a highly complex mixture of branched alkanes and alkenes plus various substituted aromatic compounds was found. The highly branched structures may have actually incorporated isoprenoids originally present in the Precambrian microorganisms (Philp Van DeMent, 1983)6>. 

It has been recently shown that the most abundant sulfur-containing pyrolysis products of kerogens isolated from immature organic-rich... 

The samples from the North Sea were analysed as extracted whole rocks. The low TOC content of these samples prevented analysis by dual FID/FPD. Descriptions of maturity-related changes in kerogens isolated from these shales will be given elsewhere. 

Table III. EPR Parameters of Kerogens Isolated from Core Samples in Proximity of Dibase Sill, Site 368, Leg 41...

Figure 8. Mass chromatogram of fragment ion m/z 97 in pyrograms of kerogens isolated from samples Cal, D8, and ULL Pyrolysis and GC conditions as in Figure 5. GC interfaced to VG 70-70H mass spectrometer. Numbers represent hydrocarbon chain lengths, and T3, T4, etc, represent a thiophene substituted with a Cy C4, etc, alkyl...

Figure 6 indicates the position of the Ontario shales on the van Krevelen diagram. Atomic 0/C ratios are considered to be overstated because of the presence of minor amounts of silicate mineral matter in the kerogen isolates. Therefore, the kerogens may have lower atomic 0/C ratios than shown and so could be type I or type II. 

Elemental analyses. Elemental (C,H,N, and 0) analyses of the kerogen isolates, and analyses of the total carbon content of the whole shale were obtained, directly, using a Carlo Erba Model 1106 Elemental Analyzer(any use of trade names in this publication are for descriptive purposes only and does not constitute indorsement by the U. S. Geological Survey. Elemental analyses (C,H, and N) of the coal samples were accomplished using a Perkin-Elmer Model 240 Elemental Analyzer, with oxygen contents calculated by difference. The ash content of the whole shale was determined by combustion of 10-20 mg aliquots in a muffle furnace at 750°C. All samples (coal and kerogen) were... 

Very heavy oils have similar sulfur concentration to the kerogens. Isolation of kerogens is as described by Tannenbaum and Aizenshtat (1984) oil analysis from Baskin and Peters (1992). 

Fig. 1. Flow chart for bitumen and kerogen isolation and separation for samples after thermal...

The samples were obtained from the working cores of the DSDP repository. The samples were freeze-dried, powdered in a glass mortar and pestle, composited, heated, and treated in the same manner for extraction, kerogen isolation, thin-layer chromatography (TLC) of the extracts, and analysis by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) as reported earlier (Simoneit et al, 1981 Fig. 1). 

C2 to Cg acids of this type are also generated from sedimentary organic matter by hydrous pyrolysis at temperatures from 250 °C for 72 h to 330 °C for 168 h (Eglinton et al. 1987). These experiments used kerogen isolated... 

Fig. 4. Modified van Krevelen diagram after Tissot et al. (1974) showing the three major kerogen types based on their atomic hydrogen/carbon and oxygen/carbon ratios. Labeled points refer to kerogens isolated from rocks used to study organic acid generation by hydrous pyrolysis in the authors laboratory...

---