Mineralogical Characteristics of Late Permian Coals from the Yueliangtian Coal Mine, Guizhou, Southwestern China

Abstract

This paper reports the mineralogical compositions of super-low-sulfur (Yueliangtian 6-upper (YLT6U)) and high-sulfur (Yueliangtian 6-lower (YLT6L)) coals of the Late Permian No. 6 coal seam from the Yueliangtian coal mine, Guizhou, southwestern China. The mineral assemblages and morphology were detected and observed by X-ray diffractogram (XRD), optical microscopy and field-emission scanning electron microscope (FE-SEM) in conjunction with an energy-dispersive X-ray spectrometer. Major minerals in the coal samples, partings and host rocks (roof and floor strata) include calcite, quartz, kaolinite, mixed-layer illite/smectite, chlorite and pyrite and, to a lesser extent, chamosite, anatase and apatite. The Emeishan basalt and silicic rocks in the Kangdian Upland are the sediment source for the Yueliangtian coals. It was found that there are several modes of chamosite occurrence, and precursor minerals, such as anatase, had been corroded by Ti-rich hydrothermal solutions. The modes of occurrence of minerals present in the coal were controlled by the injection of different types of hydrothermal fluids during different deposition stages. The presence of abundant pyrite and extremely high total sulfur contents in the YLT6L coal are in sharp contrast to those in the YLT6U coal, suggesting that seawater invaded the peat swamp of the YLT6L coal and terminated at the YLT6U-9p sampling interval. High-temperature quartz, vermicular kaolinite and chloritized biotite were observed in the partings and roof strata. The three partings and floor strata of the No. 6 coal seam from the Yueliangtian coal mine appear to have been derived from felsic volcanic ash. Four factors, including sediment-source region, multi-stage injections of hydrothermal fluids, seawater influence and volcanic ash input, were responsible for the mineralogical characteristics of the Yueliangtian coals.

Geochemistry of Toxic Elements and Their Removal via the Preparation of High-Uranium Coal in Southwestern China

“…Mo and U are enriched, while V According to the enrichment classification proposed by Dai et al [7], elements V, Cr, Mo, and U in the Ganhe coals are all significantly enriched (i.e., 10 < concentration coefficient (CC) < 100, CC referring to the ratio of a given trace element in an investigated sample versus the corresponding average for world hard coals reported by Ketris and Yudovich [46] The results of our EMPA analysis of Rongyang coal are shown in Figure 5 and Table 3 These data show that U-bearing minerals include anatase, clay minerals, guadarramite, and pyrite ( Figure 5), and that anatase coexists with clay minerals (Figure 5a). There are also traces of corrosion in anatase, indicating that coal has been subjected to hydrothermal fluids during syngenetic or early diagenetic stages [55]. Anatase also contains traces of Na, Mg, P, S, K, Ca, Fe, and, to a lesser extent, Cl, I, Nb, and U, and have a UO 2 content of 2.76% ( Table 3: spot 1).…”

“…The results of our EMPA analysis of Rongyang coal are shown in Figure 5 and Table 3 These data show that U-bearing minerals include anatase, clay minerals, guadarramite, and pyrite ( Figure 5), and that anatase coexists with clay minerals (Figure 5a). There are also traces of corrosion in anatase, indicating that coal has been subjected to hydrothermal fluids during syngenetic or early diagenetic stages [55]. Anatase also contains traces of Na, Mg, P, S, K, Ca, Fe, and, to a lesser extent, Cl, I, Nb, and U, and have a UO2 content of 2.76% ( Table 3: spot 1).…”

“…It is known that peat swamps formed in reductive environments, so the elements V, Cr, Mo, and U react with aluminum silicate minerals and coexist with clay minerals. Wang et al [56] and Xie et al [55] found that the coals from the Yueliangtian Coalfield, adjacent to the Rongyang Coalfield, were subjected to volcanic ash, hydrothermal fluids, and seawater during syngenetic or early diagenetic stages. The elements V and U occur in syngenetic minerals and coexist with clay minerals ( Figure 5).…”

Mineralogical and Geochemical Compositions of the Lopingian Coals in the Zhongliangshan Coalfield, Southwestern China

“…Pyrite is a common mineral in the Lopingian coal seams in southwestern China [8,39,[42][43][44]. From the K1 to K10 coal LTA residues, the proportion of pyrite increases gradually, from 2.7% (K3-1) to 20.4% (K10-5) and with an average of 10.5%.…”

Mineralogical and Geochemical Compositions of the Lopingian Coals and Carbonaceous Rocks in the Shugentian Coalfield, Yunnan, China: with Emphasis on Fe-Bearing Minerals in a Continental-Marine Transitional Environment

“…A number of studies showed that hydrothermal fluids have significantly influenced the geochemical and mineralogical composition of Lopingian coals in southwestern China (e.g., [26,48,86,[93][94][95]). The evidence for the No.…”