Extraction of bound porphyrins from sulphur-rich sediments and their use for reconstruction of palaeoenvironments
Article Abstract:
Porphyrins are molecular fossils found in sediments and crude oils, and help in understanding the palaenvironmental conditions during their formation. Standard analytical methods cannot identify all the porphyrins present in a geological sample, as a substantial fraction of the porphyrins may be bound to kerogen or to solvent-extractable macromolecules or may be degraded by the oxidative extraction procedures. Sulphur was also responsible for binding 'biomarker' molecules at an early stage of sediment diagenesis and desulphurization using Raney nickel liberates small molecules bound to sulphur containing species. This technique results in large amounts of porphyrins being released from the total organic extract of a sulphur-rich marl.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1993
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Sulphur isotope fractionation in modern microbial mats and the evolution of the sulphur cycle
Article Abstract:
High sulphate concentrations lead to sulphides with highly depleted sulphur isotope (34S) in modern microbial mats. This indicates that increase in seawater sulphate concentrations occurred only after the initial accumulation of oxygen into the atmosphere in post-Archean times. This increase is represented by the high negative isotope shift in shale-hosted sedimentary sulphides at between 2.2 to 2.3 Gyr. The timing of this event coincides with the beginning of a high early Proterozoic burial pulse of organic carbon which released oxidants to the Earth surface.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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Sulphur-radical control on petroleum formation rates
Article Abstract:
The presence of sulphur radicals, rather than the relative weakness of C-S bonds, controls petroleum formation rates. It seems that the rate of petroleum formation is strongly determined by the concentration of sulphur radicals produced during the initial stages of thermal maturation. A proposed mechanism for the overall composition of petroleum emphasizes the concentration of sulphur radicals, rather than bond strengths. This mechanism has implications for natural gas formation through thermal cracking of migrated petroleum in reservoirs.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1998
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