Origin of Minerals and Elements in the Late Permian Coal Seams of the Shiping Mine, Sichuan, Southwestern China

Abstract

Volcanic layers in coal seams in southwestern China coalfields have received much attention given their significance in coal geology studies and their potential economic value. In this study, the mineralogical and geochemical compositions of C19 and C25 coal seams were examined, and the following findings were obtained. (1) Clay minerals in sample C19-r are argillized, and sedimentary layering is not observed. The acicular idiomorphic crystals of apatite and the phenocrysts of Ti-augite coexisting with magnetite in roof sample C19-r are common minerals in basaltic rock. The rare earth elements (REE) distribution pattern of C19-r, which is characterized by positive Eu anomalies and M-REE enrichment, is the same as that of high-Ti basalt. The concentrations of Ti, V, Co, Cr, Ni, Cu, Zn, Nb, Ta, Zr, and Hf in C19-r are closer to those of high-Ti basalt. In conclusion, roof sample C19-r consists of tuffaceous clay, probably with a high-Ti mafic magma source. (2) The geochemical characteristics of the C25 coals are same as those reported for coal affected by alkali volcanic ash, enrichment in Nb, Ta, Zr, Hf, and REE, causing the C25 minable coal seams to have higher potential value. Such a vertical study of coals and host rocks could provide more information for coal-forming depositional environment analysis, for identification of volcanic eruption time and magma intrusion, and for facilitating stratigraphic subdivision and correlation.

Concentration and Distribution of Cadmium in Coals of China

“…The Southern area had the highest value, with a particularly high arithmetic average reaching to 1.21 µg/g, nearly five times as high as the value reported by Dai et al [7]. The coalfields (mines) with abnormally high concentrations of cadmium in coal, such as the Moxinpo Coalfield in Chongqing (31.19 µg/g) [11], the Chenxi Mine in Hunan (5.01 µg/g) [10], the Shiping Mine in Sichuan (5.91 µg/g) [84], are located in this coal-distribution area. In the other coal-distribution areas, cadmium concentrations were all lower than that estimated by Dai et al [7].…”

Abundance, Distribution, and Modes of Occurrence of Uranium in Chinese Coals

“…Significant uranium enrichment in coals only occurs in Shanxi, Yunnan, Guizhou, Guangxi, Xinjiang, Inner Mongolia, Sichuan, and Chongqing Provinces of China (Table 1), e.g., the Datong coal (averaging 38.2 mg/kg and 28.8 mg/kg uranium [31]), the Dazhai coal (52.5 mg/kg [32] and 56.0 mg/kg [33]), the Yanshan coal (167 mg/kg [34] and 153 mg/kg [35]), the Luquan coals (34.1 mg/kg [36]), the Guiding coal (229 mg/kg [34] and 200 mg/kg [30]), the Puan coal (32.4 mg/kg [37]), the Zhijin coal (49.6 mg/kg [38]), the Heshan coal (10.2 mg/kg to 326 mg/kg [39][40][41][42]), the Yishan coal (71.7 mg/kg [43]), the Sawabuqi coal (365 mg/kg [44]), the Yili coal (320 mg/kg [45] and 147 mg/kg [46]), the Shenli coal (25.9 mg/kg [47]), the Shiping coal (39.8 mg/kg [48]), and the Moxinpo coal (376 mg/kg [49]). …”

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

“…It is suggested that the dominant terrigenous material of the Lopingian coals in southwestern China is the basaltic Kangdian Upland, which is typically enriched in Sc, V, Cr, Co, Ni, Cu and Zn [10,45,64,[68][69][70][71]. For example, the dominant terrigenous material for the coals in the Xinde Mine, Yunnan Province, southwestern China is identified as the Kangdian Upland, with high concentrations of Sc, V, Cr, Co, Ni, Cu and Zn in the coals [45].…”