Geochemical and petrographic properties of some Spitsbergen coals and dispersed organic matter

Abstract

This paper presents the characteristics of selected parameters of organic matter of the Tertiary coal samples and organic matter of Carboniferous rock samples from the Spitsbergen. The coal samples were taken from Central Coal Basin (the Longyearbyen region) and from the Forlandsundet Basin (Oscar II Land, the Kaffioyra region). Samples of dispersed organic matter were collected from Suffolk Pynten and Sergeijevfjellet area in Sorkapp Land. The optical properties of coal samples are different from properties of dispersed organic matter. Macerals of vitrinite group dominate in all of the samples. The average content of vitrinite group macerals is much lower in dipersed organic matter samples than it is in coals. The average content of liptinite group macerals is a little lower, and inertinite group macerals is much higher. The average content of mineral matter is higher in organic matter samples than in coal samples. The average value of vitrinite reflectance and standard deviation of organic matter is higher in comparison with coals. The coal samples are generally classified as orthobituminous, medium rank type C. There are samples from very low- to middle-grade coal. The values of vitrinite reflectance and standard deviation of coals investigated are similar and are lower than they are in dispersed organic matter. Gas chromatography–mass spectrometry (GC-MS) was applied to assess organic matter source and rank with use of several biomarker parameters. Primary organic matter of the Tertiary coals contained predominantly material from conifers, among them, Cupressaceae and/or Taxodiaceae and Podocarpaceae families were identified by their characteristic biomarkers. Dispersed organic matter of rocks does not show features indicating input of vascular plants into its primary material, and its origin is assumed to be algal/bacterial. Samples with Calamites fossils contained organic matter with only low terrestrial input. Results of rank assessment by thermal maturity parameters based on biomarkers agree with vitrinite reflectance data: the Kaffioyra and the Longyearbyen coals are in the range of high volatile bituminous coals. The dispersed organic matter samples seems to be more mature than that of both coals and can be assessed as late catagenetic. The organic matter of the Sergeijevfjellet Formation was formed in basins with higher fluctuation of water level; lower amount of water caused oxidation of organic matter in a basin. The mire plants contained less of resins and essential oils than Hornsundneset Formation mire plants. The deposits of organic matter in a Tertiary basin were formed with faster subsidence and higher water level. The plants of Oligocene age (Kaffioyra region) contain more resins and essential oils than plants of Paleocene age (Longyearbyen region), while coalification degree is similar. However, technological parameters of Paleocene coals are better. The organic matter of Kaffioyra region was formed in basins with higher fluctuation of water level than from the Longyearbyen region.