白布勘探区龙潭组沉积环境及成煤条件分析

贵州大方县白布勘探区煤系地层龙潭组为海陆交互相沉积，厚度177～211m，含煤21～36层，煤层总厚18.04～30.29m，可采煤层6层。根据岩性、岩相特征自下而上分为3段，下段为潟湖—潮坪相沉积，并在大部分地区形成泥炭沼泽，形成了可采的33、28号煤层；中段为三角洲相，泥岩沼泽相多在三角洲分流河道间的湖沼区及湖波浪带基础上发育而成，煤层层位稳定，厚度不大；上段为潮坪三角洲相，该期构造活动趋于平稳，形成的煤层层位稳定，厚度大，6中煤0.39～6.88m，7号煤0～3.09m。三段厚度比较接近，反映该区晚二叠世期间地壳沉降均衡。沉积环境差异是本区成煤条件的主要控制因素。

Longtan Formation Depositional Environment and Coal-forming Condition in Baibu Exploration Area

The Longtan Formation in coal measures strata of Baibu exploration area, Dafang County, Guizhou Province is a continental-marine interactive deposits with thickness of 177-211m, 21-36 coal seams, total coal thickness 18.04-30.29m, 6 mineable coal seams. Based on lithology and lithofacies from bottom to top can be divided into 3 members： lower member is lagoontidal flat facies deposit, formed peat bogs in most part of the area and mineable Nos.33 and 28 coal seams; middle member is delta facies, peat bog facies developed on limnic and limnic wave zones between deltaic interdistributaries, coal seams have not thick but stable horizons; upper member is tidal flat-delta facies, tectonic movements were placid during this stage, thus stable and thick coal seams were formed, No.6m coal seam 0.39-6.86m, No.7 coal seam 0-3.0m, thickness of the three members are rather similar, thus reflected homogenous crust subsidence during Late Permian. Different depositional environment is main controlling factor of coal- forming condition in the area.