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Diversities in biomarker compositions of Carboniferous-Permian humic coals in the Ordos Basin, China.
- Source :
-
Australian Journal of Earth Sciences . Jul2018, Vol. 65 Issue 5, p727-738. 12p. - Publication Year :
- 2018
-
Abstract
- The molecular composition of Carboniferous-Permian coals in the maturity range from 0.66 to 1.63% vitrinite reflectance has been analysed using organic geochemistry to investigate the factors influencing the biomarker compositions of humic coals. The Carboniferous-Permian coal has a variable organofacies and is mainly humic-prone. There is a significant difference in the distribution of saturated and aromatic hydrocarbons in these coals, which can be divided into three types. The Group A coals have biomarker compositions typical of humic coal, characterised by high Pr/Ph ratios, a lower abundance of tricyclic terpanes with a decreasing distribution from C19 tricyclic terpane to C24 tricyclic terpane and a high number of terrigenous-related biomarkers, such as C24 tetracyclic terpane and C29 steranes. The biomarker composition of Group B coals, which were deposited in a suboxic environment, have a higher abundance of rearranged hopanes than observed in Group A coals. In contrast, in Group C coals, the Pr/Ph ratio is less than 1.0, and the sterane and terpane distributions are very different from those in groups A and B. Group C coals generally have abnormally abundant tricyclic terpanes with a normal distribution maximising at the C23 peak; C27 steranes predominates in the m/z 217 mass fragmentograms. The relationships between biomarker compositions, thermal maturity, Pr/Ph ratios and depositional environments, indicate that the biomarker compositions of Carboniferous-Permian coals in Ordos Basin are mainly related to their depositional environment. This leads to the conclusion that the biomarker compositions of groups A and B coals collected from Shanxi and Taiyuan formations in the northern Ordos Basin are mainly related to their marine-terrigenous transitional environment, whereas the biomarker compositions for the Group C coals from Carboniferous strata and Shanxi Formation in the eastern Ordos Basin are associated with marine incursions. [ABSTRACT FROM AUTHOR]
- Subjects :
- *CARBONIFEROUS Period
*GEOLOGICAL basins
*PERMIANS
*VITRINITE
*ORGANIC geochemistry
Subjects
Details
- Language :
- English
- ISSN :
- 08120099
- Volume :
- 65
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Australian Journal of Earth Sciences
- Publication Type :
- Academic Journal
- Accession number :
- 130773243
- Full Text :
- https://doi.org/10.1080/08120099.2018.1467342