Change in Maturity of Coals of the Same Genotype Occurring at Different Depths, as Determined by Saturated Hydrocarbon Biomarkers

Abstract

Saturated hydrocarbon biomarkers have been determined in chloroform extracts of coals occurring at different depths (190, 205, and 322 m) of the Vinogradovskii open-pit mine (Belovo, Kuzbass), using gas–liquid chromatography and gas chromatography–mass spectrometry. The relative distribution of hydrocarbon (HC) biomarkers—n-alkanes, isoprenanes, steranes, and terpanes—shows that the coals are genetically uniform. In terms of hydrocarbon composition, they are weakly mature, although they relate to long-flame D-type coals by the degree of metamorphism. With an increase in the coal occurrence depth, the HC biomarker ratios that reflect the degree of maturity of organic matter slightly increase. As coal occurrence depth increases, the carbon preference index of n-alkanes decreases, the maturity coefficients $$K_{{{\text{mat}}}}^{1}$$ and $$K_{{{\text{mat}}}}^{2}$$ by C29 steranes and the dia/reg ratios of C27 steranes increase; the terpane Ts/Tm ratio and S/R epimer ratio of C31 and C32 homohopanes increase, and the moretane/hopane ratio decrease.