Shenjun Qin

Coal petrological and coal facies characteristics of the No. 2 seam from Huangling mine, Shanxi Province, China

Twenty-two coal samples and six parting samples of two sections of seam 2 from Huangling mine in Shanxi Province were collected and then were analyzed by using optical microscopy. The coal petrological characteristics indicate that vitrinite, with an average content of 77%, is the dominant maceral. The average content of inertinite is only 19%. Liptinite shows only in trace contents. All GWI, VI, GI, TPI values and a ternary diagram of indicator macerals indicate that the main coal facies were formed in moist forest moors, which are the main moor types of the No. 2 coal seam. The evolution of the moors can be divided into 5 stages: I, II, III, IV and V, which evolved from moist forest-moor to open moor, and then became moist forest-moor again.

Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin

The North China Basin is the largest coal-bearing basin in China, and has an areal extent of 800,000 km 2 . We analyzed 138 coal samples and in situ pillar coal samples of the middle Permian from this basin by macropetrography, microscope, scanning electron microscope, gas chromatography, and gas chromatography–mass spectrometer in order to study wildfires. High contents of inertinite (charcoal) and natural coke particles observed in coal samples indicate that vegetation in precursor mires and peats of the middle Permian coal from north China was exposed to far-ranging wildfires. In addition, high-molecular-weight polycyclic aromatic hydrocarbons were detected in the coal samples. These aromatic compounds were formed under high temperatures and provide further evidence of wildfire. These wildfires would have discharged significant CO and CO 2 gases into the atmosphere and affected the paleoclimate and paleoecosystem.

Organic geochemical characteristics of source rocks in the Mizhi region of Ordos Basin

To study the distribution relationship between salt rocks and oil-and-gas in Mizhi region of the Ordos Basin, a detailed research was conducted to assess the organic geochemical characteristics of the source rocks. The results show that the Pr/Ph (pristane/phytane) ratios are higher than 1 and that the content of chloroform bitumen “A” is lower in the Triassic and highest in the Carboniferous strata. From the Triassic to the Ordovician, the maturity is increased but the ratio of aliphatic to aromatic hydrocarbons is decreased with the depth, which is possibly related to the high salinity levels in the region. Long-chain n-alkanes are absent in the Carboniferous, whereas they are observed in the Ordovician. The aromatic chromatograms show that the naphthalene content increases with depth and is consistant with maturity. β-carotene and dehydrovitamin E were detected, which may indicate the presence of marine and reducing environments. The Triassic, Permian and Carboniferous sediments can be classified as source rocks.

Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

The enrichment and geochemical significance of elements associated with Late Permian coals in Southwest China have always gained widespread interest in the field of coal geology. The present study focuses on the geochemical characterization of Late Permian coal in the Zhongliangshan mine. Twenty-three samples were collected from the K1a coal seam of the Zhongliangshan mine, and the major and trace elements in the coal were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry. The composition of minerals in the Zhongliangshan coal, and the modes of occurrence of coal-associated elements, especially those with elevated contents, were studied through a combination of microscopic analyses, X-ray powder diffraction, and scanning electron microscope – energy dispersive X-ray spectrometer. The minerals in coal mainly consist of kaolinite, pyrite, calcite, and quartz, as well as small amount of gypsum and anatase. Compared with the average elemental concentrations in world coal, the Zhongliangshan coal is enriched in Cr, and slightly enriched in Li, U, Sr, V and Ag. Combining the correlation analysis and sequential chemical extraction experiments, it can be inferred that many trace elements in the Zhongliangshan coal have both inorganic and organic affinities. The elements Cr, Li, and V mainly occur in clay minerals, and also are related to organic matter in the coal. Uranium presents firstly in the organic and then silicate states. Strontium shows multiple modes of occurrence including carbonate, silicate, and exchangeable ion states, and Ag primarily occurs in sulfides followed by silicates. The terrigenous debris input from the Emeishan basalt is the major reason for the enrichment of above elements in the Zhongliangshan coal.

Organic geochemistry of the Late Permian coals from the Huoshaopu and Jinjia Mines, Liupanshui Coalfield, China

Four coal samples from the Huoshaopu Mine and six coal samples from the Jinjia Mine, Liupanshui Coalfield, China were collected and analyzed, focusing on their petrological and organic geochemical features. The microscopic results show that the vitrinite random reflectance (Ro) of all samples is 0.97%, which is classified as high-volatile A bituminous coal. The maceral groups are dominated by vitrinite followed by inertinite. The low ratios (0.07–0.42) of saturated to aromatic hydrocarbons indicate a terrestrial plant input for the coals. Gas chromatography and gas chromatography/mass spectrometry were employed to analyze the composition of organic matter in the samples. The gas chromatography chromatograms of saturates display a monomodal outline of n-alkanes with a predominance of short chains. The odd-even preference values around 1 reflect the thermal maturity of the coals. Based on the different pristine/phytane ratios and dibenzofuran contents, we infer a relatively weak oxic coal-forming environment for Huoshaopu coals and a relatively anoxic environment for Jinjia coals. Among the aromatics, thermodynamically stable compounds, including 2-methylnaphthalene, 2,6 + 2,7-dimethylnaphthalenes, 3 and 4-methylbiphenyls, 4,4′-dimethylbiphenyl, methylphenanthrene, 2 and 3-methyldibenzofurans, were the dominant isomers in the respective homologs. The occurrence of dibenzothiophenes and benzonaphthothiophenes may confirm the paralic depositional environment of Late Permian coals from the Huoshaopu and Jinjia mines.