陆相煤系聚煤环境及聚煤特征——以青海祁连山和柴北缘含煤区侏罗系为例

Coal-accumulating environments and characteristics of inland coal measures: a case study of Jurassic coal-bearing area in Qilian Mountains and north Caidamu basin in Qinghai

通过对青海祁连山和柴北缘含煤区侏罗系沉积体系的研究,系统总结了陆相地层的主要聚煤环境,即冲积扇、辫状河、曲流河、扇三角洲、曲流河三角洲和滨湖聚煤环境,其中曲流河、曲流河三角洲及滨湖为陆相地层中最有利的聚煤环境。研究显示:曲流河的岸后沼泽为重要的聚煤环境,平面上煤层呈带状产出,垂向上往往形成较厚的煤层,且横向延伸较远;曲流河三角洲平原分流河道间洼地中发育泥炭沼泽,形成的煤层成带性好,具有沿湖岸线广泛分布的特点;滨湖聚煤环境中湖岸线延深较远,煤层在平面上呈带状展布,同时由于湖平面变化的多旋回性,在垂向上可形成多套碳质泥岩与煤层的互层。这些研究成果,为研究煤系赋存规律和准确预测煤层提供了依据。

By the detailed study of Jurassic depositional systems in coal-bearing area in Qilian Mountains and the north Caidam basin in Qinghai Province, the paper systematically summed up the main coal-accumulating environments of continental strata. The coal-accumulating environments of alluvial fan, meandering river, braided river, fan delta, meandering delta, braided delta and coastal lake had been mainly developed. The most favorable coal-accumulating environments in continental strata were systems of meandering river, meandering delta and coastal lake. The main features were as follows： the swamp behind bank in meandering river was important coal-accumulating environment, coal seams were presented as strip on plane, accumulated thickly vertically, extended far distance horizontally. The peat swamp developed in low-lying land between split streams of meandering river＇s delta plain had good tapability, wide distribution along lake shoreline. In coastal lake coal-accumulating environments lakeshore line stretched far distance, on the plane coal was distributed as strip, vertically several sets of carbonaceous mudstone and coal seam were interbeded because of multi-cycle of the lake level changes at the same time. The research results provided the basis for accurate forecasts of the coal measures and the law of occurrence of coal and rocks.