The Relationship between Trace Element Concentrations and Coal-Forming Environments in the No. 6 Coal Seam, Haerwusu Mine, China

Abstract

In order to study the relationship between trace element concentrations and coal-forming 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.