Geochemistry of brown coal organic matter in Barzassky field, Kuznetsk basin

The authors present the results of studies the Devonian barzassky brown coal (Rovt = 0.48-0.49 %, ПК3 stage) in the Barzassky field (the Kuznetsk Basin). According to Organic Carbon isotope composition (δ13С ranges from -24 to -18 ‰), the coal belongs to Type III kerogen that consists of higher ground vegetation remains. Pyrolytic parameters of the coal do not accord with this conclusion as the high Hydrogen Index (average HI is about 450 mg HC/g Corg) corresponds mainly to Type II kerogen having marine genesis. The kerogen elemental composition (hydrogen content is 8 to 8,5 %) of the coal is also typical of immature aquatic Organic Matter. In about half of the coal samples, other geochemical data are also indicative of the same: n-alkanes in bitumoids have n-C27/n-C17 0.5, Pr/Ph mostly 5. At the same time, the coals demonstrate sterane (C29/C27 >> 1) and tricyclane (2C19-20/C23-26 > 1) distributions typical of terragenous Organic Matter, and contain biomarkers of coniferous plants (phyllocladanes and kauranes). As for genetic origin of these coals, geochemical data show the contradicting results. However, based on the combination of isotopic and pyrolytic characteristics, elemental composition of kerogen, and maceral composition of coal, the barzassites can be attributed to cuticular liptobiolites, and the first protomorphic higher plants were the source material for them