永城煤田石炭二叠纪煤系成因分析与聚煤特征

GENETIC ANALYSIS AND COAL ACCUMULATING FEATURES IN COAL—BEARING STRATA OF CARBONIFEROUS—PERMIN,YONGCHENG COALFIELD

根据成因地层分析和沉积环境分析的方法,在永城煤田石炭二叠纪煤系识别出三种沉积体系、11个生长层序。重点分析了陆表海潮下碳酸盐岩沉积和碎屑潮坪沉积特征,认为灰岩在微观特征、微相类型上由上而下的有规律变化,符合向上变浅的缓坡型陆表海沉积模式。潮坪沉积物以潮道发育、砂泥混合坪标志明显为特征。三角洲则表现为浅水沉积性质。有价值的煤层形成于废弃碎屑潮坪泥炭沼泽和下三角洲平原泥炭沼泽。泥炭沼泽几乎不受咸水和活动碎屑体系的影响是主要煤层低硫低灰的原因。

According to the methods of genetic stratigraphy and depositional environments analysis,threekinds of depositional systems and eleven genetic sequences have been recognized in the coal-bearing strata ofYongcheng Coalfield.The paper mainly discusses the depositional characteristics of subtidal carbonate of epicon-tinental sea and clastic flat.The microcharacteristics and microfacies of carbonate regularly change upward.Thisis the results of sediments filling to the basin and it conforms to the depositional models of shallowing-upwardcarbonate-sillisiclastic sequences of epicontinental sea.Tidal channels in the tital flat are dominated and sand-mud mixed tidal flat marks are obvious.The most economic coal beds were formed from the swamp types whichdeveloped on the abandoned clastic tidal flat and lower delta plain.The major reasons for low ash and sulfur incoal beds are that saline water and active clastic systems were nearly no influence upon the swamps when peatswere accumulated.