Occurrence and geological genesis of pyrite in permian high sulfur coal in Guizhou Province,China

Mineralogy characteristics and 12 potentially toxic elements( PTEs) of the Late Permian high sulfur coal from middle-western Guizhou Province were investigated using optical microscopy,powder X-ray diffraction and scan- ning electron microscopy with energy dispersive X-ray spectrometer. This study focused on the occurrences of pyrite and the geologic process responsible for pyrite formation at various stages of the coal deposition. Minerals in the coals mainly included kaolinite,pyrite,quartz. The average concentrations of PTEs in the high sulfur coals were relatively lower than Chinese and Guizhou coals,except for the enriched Cr and Zn. However,the No. 5 coal from Dahebian Coal Mine in Shuicheng district was enriched in Hg,Cd,Cr,Cu,Mn,Sr and Zn. Different forms of pyrite occurred in high sulfur coal,included framboidal,euhedral,massive,colloidal,cleat and pore cell filled,nodular pyrites. Pyrite was often associated with kaolinite,siderite,quartz in high sulfur coal. Sometimes kaolinite could be subjected to chloritization and siderite subjected to pyritization in the No. 5 coal from the Dahebian Coal Mine in Shuicheng district. The formation processes of pyrite in high sulfur coal are complicated,and pyrite was formed during different stages of coal forma- tion. Seawater invasion and balsalt terrigenous input provided stable materials supply. Further more,the occurrence of epigenetic pyrite indicated that high sulfur coal seams had been influenced by hydrothermal fluids.