| Abstrakt: |
The Troyanovo-3 Mine occupies the SE part of the Maritsa Iztok Basin (MIB). The mean thickness of the coal-overlying sediments is on average 70-80 m but southwards, close to the basin rim, it is often 8-10 m. Carbonaceous mudstone and lignite of high ash yield were deposited in the dump area of the Troyanovo-3 Mine. Samples collected at the Trojanovo-3 Mine represent coals (lignite) and coal wastes stored 6-10 years after excavation and underwent mild heating, smoldering. Organic matter (OM) is dominated by huminite macerals. Macerals of liptinite and inertinite are relatively rare. Huminite macerals sometimes contain cracks and/or are paler in colour. Rarely signs of plasticity or devolatilisation pores occur indicating a low heating rate. The reflectance of unaltered OM is 0.19-0.25%; the reflectance of altered OM can reach 0.53% but in the case of individual particles it might exceed 1%. Organic matter co-occurs with dominating clay minerals and pyrite usually occurring as framboidal particles. Pyrite content varies from 0.2-8.8% and its oxidation might contribute to self-heating of coal and coal wastes. The bituminous fraction of gangue rocks comprised a wide range of compounds from aliphatic and aromatic hydrocarbons and polar derivatives. Two populations of samples can be distinguished, (i) lignite and wastes corresponding to the common level of thermal maturity of the early geochemical diagenetic stage, (ii) much more mature samples that were exposed to self-heating/smoldering. The (i) set samples contained only small amounts of n-alkanes, high concentrations of diterpenoids such as 16α(H)-phyllocladane. kauren-15-ene, and abietane derivatives. Pentacyclic triterpanes and aromatic hydrocarbons, both substituted and unsubstituted, were mostly absent. Among polar compounds ferruginol, benzoic aldehyde derivatives, and fatty acids predominate. The second group (samples SN1, SN2, SN7, SN8, SN9, SN14, and SN6) showed the obvious signs of higher temperature impact such as high concentrations of n-alkanes with a pyrolytic Gaussian peaks outline, presence of alkyl aromatic hydrocarbons including C1-C5 naphthalenes and C1-C2 phenanthrenes, absent in the first sample set. Their distribution is mature and does not conform with the generally immature organic matter of rocks investigated. Lighter pheno He compounds that comprised phenol, cresols, and xylenols were present only in the samples of the (ii) set whereas absent in (i) samples. Opposite, higher pheno he compounds derived from lignin weathering such as guiacol were found in the (i) set. Altogether the features suggest thermal stress during self-heating that affected the (ii) samples. [ABSTRACT FROM AUTHOR] |
