Abstract:Total 138 coal samples and 14 parting samples were taken from the No. 6 Seam of the Jungar Coalfield, Inner Mongolia. These samples were analysed by optical microscopy, sequential chemical extraction procedure (SCEP), inductively coupled plasma mass spectrometry (ICP–MS), X–ray powder diffraction (XRD), and scanning electron microscope in conjunction with an energy–dispersive X–ray spectrometer (SEM–EDX) analysis. The results indicate that the Li contents have reached the industrial grade of the coal associated Li deposit, and the total Li reserves have reached 2406600 tons, that is, 5157000 tons Li2O in the No. 6 seam in the Jungar Coalfield. The sequential chemical extraction procedure results suggest that the Li concentration is mainly related to inorganic matter. The minerals in the coals consist of kaolinite, boehmite, chlorite–group mineral, quartz, calcite, pyrite, siderite and amorphous clay material. Some Li could be absorbed by clay minerals in the Li–bearing coal seam. The chlorite phase could be most likely the host for a part of Li. The Yinshan Oldland should be the most possible source of Li of the coal.

In order to study the relationship between trace element concentrations and coalforming environment in the No. 6 Coal, Haerwusu Mine, Inner Mongolia, China, 39 bench samples were taken from the opencast mine, following Chinese Standard Method GB/T 482-2008. The samples were analyzed by an optical microscope, a scanning electron microscope in conjunction with an energy-dispersive X-ray spectrometer (SEM-EDX) analysis, inductively coupled plasma mass spectrometric (ICP-MS). The results indicate that the average contents of vitrinite, inertinite, liptinite are 54.59%, 34.84% and 5.8%, respectively. The concentrations of Li and Ga in the No. 6 coal are higher than those of in world coals, and most of trace elements in the No. 6 coal are correlated with minerals, which are mainly clay minerals, carbonate minerals and sulfide minerals. Two samples were identified as dry forest swamp facies (FtM I), 19 samples as shallow water forest swamp facies (FtM II), and 13 samples as reed swamp facies (RM). Compared with the average contents of world coals, trace elements in No. 6 coal of Haerwusu mine are rich in Li and V, while contents of the other elements are close or lower than the average contents of world coals. However, the variations of CC (Concentration Coefficients) among each swamp type are small and irregular, which may indicate that the concentration of the selected trace elements in the coal is mainly dominated by regional coal-forming environment, not coal-forming microenvironment.

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Haerwusu Surface Mine of the Jungar Coalfield is a large coal mine. Its coal formation environments have not been reported in detail. In order to reconstruct the paleoenvironment of the peat formation, nine samples were collected, and were analyzed using microscope, column chromatography, gas chromatography (GC), and gas chromatography–mass spectrometry (GC–MS). According to the results of the microscopic analysis, the average random vitrinite reflectance ( Rr) is 0.73%, indicating a low rank bituminous coal. Vitrinite group is the predominant macerals with an average content of 54.54%, followed by inertinite group with an average of 35.99%. The higher inertinite contents indicate widespread wildfire events during the peat formation. The distribution pattern of n-alkanes, the cross plot between Pr/ n-C17 and Ph/ n-C18, the lower saturated/aromatic hydrocarbon ratios (0.22–0.68) and the presence of cadalene, retene, simonellite indicates that the organic matter is predominantly terrestrial higher plants with a small amount of aquatic organisms. The ternary diagram of Pr/Ph, Pr/ n-C17 and Ph/ n-C18 and the relative abundance of fluorene, dibenzofuran and dibenzothiophene indicate a continental–oceanic alternative facies. The higher contents of combustion-derived PAHs are also indicative of widespread wildfire events during peat formation.