构造作用与沉积环境对聚煤作用的地质约束--以柴北缘东部北大滩地区侏罗系石门沟组为例

摘要

Shimengou Formation is a set of middle Jurassic coal-bearing strata in the east of Qaidam northern margin of Beidatan area.This paper analysed coal accumulation rule of Shimengou Formation by the field outcrop,core drilling and regional geological data.The result shows that spreading and growth of coal bed constrainted by tectonism and sedi-mentary environment.With affection of I andⅡcurtain of Yanshan movement,Beidatan area accepted deposition in Mid-dle Jurassic and experienced reform by lake-fan delta sedimentary system.In the early of Shimengou deposition,Beidatan area had lake facies deposition with coal forming in lakeshore swamp;Two large fan delta sedimentary bodies develop-ment in the study area in the late of Shimengou deposition and coal forming in Fan delta plain and front.Beidatan area ex-perienced movement stacking such as Ⅲ curtain of Yanshan movement,Himalayan movement and Neotectonic move-ment with multiple syncline formed in Beidatan area at last.With affection of thrust faults,all Jurassic layers in Beidatan area uplifted as a whole with lower buried depth,which are benefit for exploration.%位于柴北缘东部北大滩地区的石门沟组为一套中侏罗统含煤地层，通过野外露头、钻井岩心及区域性地质资料对北大滩地区聚煤规律进行了研究。结果表明，煤层的发育和展布受构造作用和沉积环境的双重约束。受燕山运动I、II幕的影响，北大滩地区在中侏罗世接受沉积，经历了湖泊-扇三角洲两大沉积体系的改造。石门沟组沉积早期，北大滩地区为湖泊相沉积，滨湖沼泽成煤；石门沟组沉积晚期，研究区内发育两个大型的扇三角洲沉积体，扇三角州平原和扇三角州前缘成煤。石门沟组成煤期后，北大滩地区经燕山运动III幕、喜山运动及新构造运动的叠加，形成大规模的复式向斜构造。受逆冲断层影响，侏罗系整体抬升，使埋藏深度变浅，有利于煤层的勘探。