Geochemical and mineralogical anomalies of the late Permian coal in the Zhijin coalfield of southwest China and their volcanic origin |
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Authors: | Shifeng Dai Deyi Ren Xiaoqiang Hou Longyi Shao |
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Institution: | a China University of Mining and Technology, Box 1, D11, Xueyuan Road, Haidian District, Beijing 100083, China;b The Key Laboratory of Coal Resources, Ministry of Education, Beijing 100083, China;c Department of Geology, University of Illinois at Urbana-Champaign, 245 NHB, 1301 West Green Street, Urbana, IL 61801, USA |
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Abstract: | This paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the Zhijin Coalfield in western Guizhou Province, China. Our studies reveal that the No. 9 coal seam in the Zhijin Coalfield has very high content of Fe (4.34%), Cu (369.90 μg/g), U (49.6 μg/g), Mo (63.10 μg/g), Zn (33.97 μg/g), and Zr (841.80 μg/g). The studies have also found that elements, such as Fe and Cu, do not occur as sulfides in this coal seam, in sharp contrast to many other coal seams in China. The geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash. In addition to normal macerals and minerals in coal, a volcanic-influenced material (VIM) derived from volcanic ash, detrital material of terrigenous origin and organic matter was identified under polarized-light reflectance microscopy and scanning electron microscopy equipped with energy-dispersive X-ray (EDX) analyzer. The volcanic-influenced material is the main carrier of the above elements in this coal. Six types of the volcanic-influenced material (VIM-1, VIM-2, VIM-3, VIM-4, VIM-5, and VIM-6) are further distinguished on the basis of their structures and compositions. To the best of our knowledge, this is the first report that presents a detailed classification of coal components with a high content of volcanic ash. |
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Keywords: | Coal Volcanic-influenced material Volcanic ash Associated elements Geochemical anomaly Late Permian age |
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