贵州晚二叠世高硫煤中黄铁矿的赋存特征及其地质成因

采用光学显微镜、XRD,SEM-EDX等方法,研究了贵州晚二叠世5号,7号,16号,32号高硫煤层的矿物学特征和12种有害微量元素的含量特征,重点探讨了黄铁矿的赋存特征以及控制黄铁矿形成的地质因素。结果表明:贵州高硫煤中矿物主要为高岭石、黄铁矿、石英;与中国煤及贵州煤相比,高硫煤中有害微量元素含量较低,仅Cr和Zn富集,其中水城大河边5号煤中富集Hg,Cd,Cr,Cu,Mn,Sr和Zn;高硫煤中黄铁矿赋存形态多样,包括莓球状、自形晶体状、块状、胶状、充填状、结核状;黄铁矿常与高岭石和石英互相伴生,水城大河边5号煤中高岭石发生绿泥石化,并且黄铁矿部分交代菱铁矿;高硫煤中黄铁矿成因复杂,经历多个期次形成,海水入侵与玄武岩陆源碎屑输入为高硫煤的形成提供了稳定的物源供给,同时后生黄铁矿的发育,表明多层高硫煤均受到后期热液的叠加作用。

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 scanning 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 formation.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