A comparison of geochemical features of extracts from coal-seams source rocks with different polarity solvents

There exists a great difference in group-type fractions and biomarker distributions of chloroform extracts from coals and coal-seams oils, which makes the source identification of coal-seams oils in sedimentary basins rather difficult. The experiment, in which four different polarity solvents, n-hexane, benzene, dichloromethane and chloroform, were used to extract 9 coal-seams source rocks and 3 typical lacustrine source rocks, showed that the yield of extracts increased gradually with increasing solvent polarity, among which obviously the proportion of n-alkanes gradually decreased and the composition of the n-hexane extract was the most similar to that of coal-formed oils. Although some obvious differences existed in yields and compositions of the extracts obtained by different solvents, the entire distribution features of their n-alkanes, isoprenoids and sterane and terpane biomarkers remained, in general, similar, showing no distinct enrichment or depletion for a certain fraction by any solvent. The c...