大同煤田白洞矿区5号煤层煤相特征

采用光学显微镜、X射线荧光光谱（XFS）和电感耦合等离子体质谱（ICP-MS）等方法测定了大同煤田塔山井田太原组5号煤的宏观煤岩类型、显微煤岩类型和地球化学参数,探讨了煤的煤岩学、煤地球化学及煤相特征,系统地分析了煤层的原始成煤泥炭沼泽环境及演化规律。研究结果表明,5号煤层有4种煤相类型,即湖沼相、泥炭沼泽相、潮湿森林沼泽相和较干燥森林沼泽相,相应表现为湖泊、障壁岛后潟湖、上三角洲平原和洪泛盆地含煤沉积体系特征。煤层自下而上存在5次比较明显的沉积旋回韵律,与之相随的水介质环境也发生了相应的海陆、咸水、淡水交替变化,从而形成了一套以陆相为主、海陆交互的成煤泥炭沼泽环境,沉积环境逐渐从海相、海陆过渡相向陆相演化。

Coal Facies Characteristics of No.5 Coal Seam in Baidong Mine Area,Datong Coalfield

Methods of optical microscope,X-ray fluorescence spectrometry（XFS） and inductively coupled plasma mass spectrometry（ICP-MS） have been used to determine macrolithotype and microlithotype of coal,geochemical parameters of the No.5 coal seam in the Taiyuan Formation,Tashan minefield,Datong coalfield;coal petrology,geochemical and coal facies characteristics discussed;and coal seam primary coal-forming peat bog environment and evolutionary pattern systematically analyzed as well.The results have demonstrated that： No.5 coal seam has four facies types,namely limnetic facies,peat bog facies,humid and rather dry forest-swamp facies,correspondingly shown as lacus,back-barrier lagoon,upper delta plain and flood basin coal-bearing systems characteristics.From bottom to top,coal seams show 5 distinct sedimentary cyclic rhythms,correspondingly environment aqueous media vary from oceanic-continental,brine-fresh water alternatively.Accordingly,a set of mainly terrestrial and transitional marine to limnic facies coal-forming peat bog environment formed,and gradually evolved from marine,marine-limnic to terrestrial facies.