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A thermal and chemical degradation approach to decipher pristane and phytane precursors in sedimentary organic matter

Organic Geochemistry

By:
, , , , ,
DOI: 10.1016/S0146-6380(99)00088-1

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Abstract

A thermal and chemical degradation approach was followed to determine the precursors of pristane (Pr) and phytane (Ph) in samples from the Gessoso-solfifera, Ghareb and Green River Formations. Hydrous pyrolysis of these samples yields large amounts of Pr and Ph carbon skeletons, indicating that their precursors are predominantly sequestered in high-molecular-weight fractions. However, chemical degradation of the polar fraction and the kerogen of the unheated samples generally does not release large amounts of Pr and Ph. Additional information on the precursors of Pr and Ph is obtained from flash pyrolysis analyses of kerogens and residues after hydrous pyrolysis and after chemical degradation. Multiple precursors for Pr and Ph are recognised in these three samples. The main increase of the Pr/Ph ratio with increasing maturation temperature, which is associated with strongly increasing amounts of Pr and Ph, is probably due to the higher amount of precursors of Pr compared to Ph, and not to the different timing of generation of Pr and Ph.A thermal and chemical degradation approach was followed to determine the precursors of pristane (Pr) and phytane (Ph) in samples from the Gessoso-solfifera, Ghareb and Green River Formations. Hydrous pyrolysis of these samples yields large amounts of Pr and Ph carbon skeletons, indicating that their precursors are predominantly sequestered in high-molecular-weight fractions. However, chemical degradation of the polar fraction and the kerogen of the unheated samples generally does not release large amounts of Pr and Ph. Additional information on the precursors of Pr and Ph is obtained from flash pyrolysis analyses of kerogens and residues after hydrous pyrolysis and after chemical degradation. Multiple precursors for Pr and Ph are recognised in these three samples. The main increase of the Pr/Ph ratio with increasing maturation temperature, which is associated with strongly increasing amounts of Pr and Ph, is probably due to the higher amount of precursors of Pr compared to Ph, and not to the different timing of generation of Pr and Ph.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A thermal and chemical degradation approach to decipher pristane and phytane precursors in sedimentary organic matter
Series title:
Organic Geochemistry
DOI:
10.1016/S0146-6380(99)00088-1
Volume
30
Issue:
9
Year Published:
1999
Language:
English
Publisher:
Elsevier Science Ltd
Publisher location:
Exeter, United Kingdom
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1089
Last page:
1104
Number of Pages:
16