Saturated hydrocarbon characteristics of superhigh-organic-sulfur coals in Heshan Shicun mine, Guangxi

A superhigh-organic-sulfur (SHOS) coals were chosen to study the environmental causes of Heshan coal origin. Based on routine analysis such as scanning electron microscope (SEM-EDX) observation, gas chromatograph (GC) and gas chromatograph-mass spectrometry (GC-MS), the composition and molecular geochemical features of organic matter were analyzed to deeply reveal the organic matter sources, sedimentary environments and provenance inputs. The results indicate that the average vitrinite reflectance of the samples is 1.76%, and the average total sulfur is 6.01%, among which the organic sulfur content accounts for 94.3%, belonging to a high-maturation super high organic sulfur coal. Unresolved Complex Mixtures(UCM) bulge is obvious in the saturated hydrocarbon chromatogram, both front and bimodal peaks are found. The main carbon peaks of the front peak type are C₁₆, C₁₈, C₂₁ and the bimodal is C₁₈ and C₂₇. Meanwhile, these compounds norpristane, dehydroabietane, cadalene have been found in samples, and regular sterane C₂₇, C₂₈, C₂₉ show a "V" type distribution, which indicates that sedimentary parent material is affected by the double input of lower aquatic organisms and high plants. The distribution of hopane in C_31-35 decreases stepwise, and the ratio of pristane to phytane shows that there are certain oxidation conditions in the coal-forming zone of marine carbonate platform. Fe (Si, Al)-oxysulfate and cell-filled pyrite observed by SEM indicate that the sedimentary diagenesis is affected by hydrothermal process to some extent in the diagenetic stage of late sedimentary facies.