25th International Meeting on Organic Geochemistry IMOG 2011

P-047
Characterization of lignites from the Drmno field, Kostolac Basin,
Serbia, based on biomarker composition
Dragana Ņivotiš 1 , Ksenija Stojanoviš 2 , Aleksandra Ńajnoviš 3 , Olga Cvetkoviš 3 , Hans
Peter Nytoft 4 , Georg Scheeder 5
1 University of Belgrade, Faculty of Mining and Geology, 1100 Belgrade, Serbia, 2 University of Belgrade,
Faculty of Chemistry, 11000 Belgrade, Serbia, 3 Center of Chemistry, IChTM, 11000 Belgrade, Serbia,
4 Geological Survey of Denmark and Greenland, DK-1350 Copenhagen, Denmark, 5 Federal Institute for
Geosciences and Natural Resources, 30655 Hannover, Germany (corresponding
author:xenasyu@yahoo.com)
The Kostolac lignite basin of Upper Miocene age is
located about 90 km east of Belgrade. It is divided
into three coal fields: Drmno in the eastern, Širikovac
in the central, and Smederevsko Podunavlje in the
western part of the basin. Coal from the Drmno field is
typical humic coal with huminite concentrations
between 50.8 and 90.3 vol.%, liptinite less than 6
vol.% and inertinite between 1.5 and 21.6 vol.%.
Saturated and aromatic hydrocarbons were analyzed
by GC-MS. The relative proportions of hydrocarbons
in the SOM are low (< 11 %), consistent with the low
maturity of the organic matter. The n-alkane patterns
of the coal samples are dominated by long-chain nalkanes
(C27-C33) with a marked odd over even
predominance (CPI 3.1-5.6), indicating a significant
contribution of epicuticular waxes. The
pristane/phytane (Pr/Ph) ratio varies in range 0.24 to
1.74. Based on the maceral composition, it could be
concluded that Pr and Ph most probably originated
from chlorophyll in land plant-dominated organic
matter. Therefore, the values of Pr/Ph could imply
anaerobic to slightly oxic conditions during
sedimentation, consistent with maceral composition.
In all samples, aromatic sesquiterpenes are observed
in low quantities. Cadalene predominates over
cuparene, calamenene and 5,6,7,8-tetrahydrocadalene.
Diterpenoids are main constituents of
saturated and aromatic fractions of investigated coals.
16�(H)-phyllocladane and pimarane are dominant by
far in the saturated fractions, whereas norpimarane,
kaurane and beyerane are present in minor amounts.
The aromatic diterpenoids consist of norabietatetraenes,
norabieta-trienes, dehydroabietane,
bisnorsimonellite simonellite, retene, sempervirane,
totarane, bisnordehydroabietane, hibaene, ferruginol,
with 18-norabieta-triene, dehydroabietane, simonellite
and retene predominating. Due to the fact that in all
samples totarane was identified, the precursor of
which is totarol [1], it was assumed that ferruginol, 18norferruginol
and 12-hydroxysimonellite may be
subjected to the same diagenetic transformations as
totarol, specially in anoxic conditions, forming
dehydroabietane, 18-norabieta-triene and simonellite,
which are dominant compounds in aromatic fraction
(Fig. 1). Almost all of the samples contain nonhopanoid
triterpenoids in very low amounts,
consisting of de-A-ring degraded triterpenoids (des-Aolean-enes,
des-A-urs-enes, des-A-lupane,
tetramethyl-octahydro-chrysenes and trimethyltetrahydro-chrysenes).
Strong domination of
diterpenoids over triterpenoids implies that the coalforming
plants were mostly gymnosperms (conifers).
A high amount of 16α(H)-phyllocladane and presence
of pimarane, ferruginol, totarane, hibaene, and
cuparene indicates that the coal forming plants
belonged to the conifer families Taxodiaceae,
Podocarpaceae, Cupressaceae, Araucariaceae and
Phyllocladaceae [1,2].
The hopanoid patterns are characterized by the
occurrence of C2713,18-hop-ene, 17α,21β(H)- and
17β,21β(H)- hopanes from C27 to C32 with the C28
being absent. Domination of ββ-isomers in range C27 -
C30 over αβ-hopanes confirms an immature stage of
the organic matter. Steroid biomarkers in Drmno
samples consist of C29 Δ 2 -, Δ 4 - and Δ 5 -sterenes. Low
steroids/hopanoids ratio (0.07-0.22) indicates a more
bacteria-influenced facies and argues the role of
bacteria in degradation of plant tissue.
Fig. 1. Proposed diagenetic pathways for the
degradation of ferruginol.
References
[1] Otto et al., 1997. Org. Geochem. 26, 105-115.
[2] Otto, A., Wilde, V., 2001. Bot. Rev. 67, 141-238.
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