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| Titel |
Petrological, geochemical and isotopic characteristics of lignite and calcified lignite from mining area Pesje, Velenje Basin, Slovenia |
| VerfasserIn |
Mirijam Vrabec, Milos Markic, Marko Vrabec, Radojko Jaćimović, Tjaša Kanduč |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091537
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| Publikation (Nr.) |
 EGU/EGU2014-5837.pdf |
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| Zusammenfassung |
| Lignite (organic rich) and calcified lignite (inorganic rich) samples from excavation field -50c
mining area Pesje, Velenje Basin, Slovenia were investigated. During geological and
structural mapping lignite and calcified lignite samples were systematically taken for
determination of their petrological, geochemical and isotopic characteristics. Lignite is
composed of fine detritical gelified matrix. At least five different types of calcified lignite
were recognized forming laminations, calcifications after wood, petrified wood and complete
replacements of lignite with carbonate. All measured parameters so far indicate geochemical
processes during sedimentation of the Velenej Basin. After macroscopic description samples
were split to organic and inorganic component (Ward, 1984) and powdered in an agate mortar
for geochemical and isotopic analyses. Major and trace elements (As, B, Ba, Cd,
Co, Cr, Cu, Hg, Mn, Mo, Sb, Se, Th, U, Zn) in these samples were determined by
instrumental neutron activation analysis (INAA) using k-0 standardization method
(Jaćimović et al, 2002). The isotopic composition of carbon and nitrogen was determined
using a Europa 20-20 continuous flow IRMS ANCA-SL preparation module. A 1
mg amount of a sample was weighed in a tin capsule for carbon and 10 mg for
nitrogen analysis. Samples for carbon analyses were pretreated with 1 M HCl to
remove carbonates. Carbonate samples from carbonate-rich strata and calcified
xylite were first roasted at 450 deg C (Krantz et al., 1987). Three miligrams of
carbonate sample was transformed into CO2 by reaction with anhydrous H3PO4 at 55
deg C under vacuum (McCrea, 1950) and measured with GV 2003 isotope ratio
mass spectrometer. Measured isotopic composition of oxygen as VPDB values was
recalculated to the VSMOW reference standard to enable the comparison with data
from other coal basins. SEM/EDXS of carbonate rich sediments was performed
with JEOL JSM 5800 electron microanalyzer scanning electron microscope energy
dispersive X-ray spectroscopy at the Department of Ceramics at the Jožef Stefan
Institute.
Geochemical characteristics of major and trace elements indicate that the values of major
and trace elements are comparable to world average coal (Zhang et al., 2004). Isotopic
composition of carbon and isotopic composition of nitrogen of investigated samples indicate
values from to -29.4oto -23.7oand 1.8oto 5.9o respectively. Lower value of isotopic
composition of carbon indicates higher gelification (values up to -29.4) and higher value of
isotopic composition of nitrogen (values up to 5.9) indicate higher mineralization.
The results of SEM/EDXS microscopy revealed that in calcified lignite chemical
composition of calcite prevails. Traces of diagenetic pyrite were also found, indicating
localized anoxic conditions during sedimentation. Values of isotopic composition of
CCaCO3 range from -2 to +13 and indicate temperature of precipitation from 17.3 to
35 deg C, which is similar to results obtained in previous studies (KanduÄ et al.,
2012).
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