伊犁盆地南缘中侏罗统西山窑组沉积环境讨论  

Discussion on the Sedimentary Environment of the Middle Jurassic Xishanyao Formation in the Southern Margin of the Yili Basin

作　　者：吴斌 朱莉娟 侯明才[1,2] 晁晖[1,2] 江文剑[4] 石鑫 罗宏谓 曹海洋[1,2] 何佳伟 WU Bin;ZHU LiJuan;HOU MingCai;CHAO Hui;JIANG WenJian;SHI Xin;LUO HongWei;CAO HaiYang;HE JiaWei(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;Nuclear Industry Geological Bureau of Jiangxi Province（Brigade 266）,Nanchang 330038,China;School of Earth Science,East China University of Technology,Nanchang 330013,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室(成都理工大学),成都610059 [2]成都理工大学沉积地质研究院,成都610059 [3]江西省核工业地质调查院(江西省核工业地质局266大队),南昌330038 [4]东华理工大学地球科学学院,南昌330013

出　　处：《沉积学报》2018年第3期456-467,共12页Acta Sedimentologica Sinica

基　　金：国家重点基础研究发展计划(“973”计划)项目(2015CB453001)

摘　　要：伊犁盆地南缘是中国重要的煤和砂岩型铀矿富集区,中侏罗统西山窑组是主要的赋矿层位。基于对野外剖面的实测、室内岩矿鉴定、碎屑粒度统计分析和钻测井等资料的解释,明确了伊犁盆地南缘中侏罗统西山窑组的沉积环境类型、砂体成因、展布及其煤系地层分布的耦合关系。研究结果表明:伊犁盆地南缘西山窑组为曲流河三角洲平原—前缘沉积环境,分流河道微相的砂岩以高含煤屑或碳质、中粗结构、富岩屑和长石、分选性较差、中等磨圆为特征,具有较低的成分成熟度和结构成熟度。粒度曲线以三段式为主,显示了三角洲平原水道跳跃、滚动和悬浮搬运的特征。电阻率曲线纵向上表现为粒度向上变粗的逆粒序。砂体厚度多在20~40 m之间,砂地比值在0.3~0.8之间。分流河道砂岩与分流河道间沼泽相的煤层或泥炭在平面上毗邻、剖面上交互产出,古植物茎干化石和植物印痕多处存在。曲流河三角洲沉积环境和三角洲砂岩与煤系地层共生耦合关系的提出,对伊犁盆地南缘煤铀富集规律的深入研究提供了沉积学支持。The southern margin of the Yili Basin is an important area with enrichment of coalmine and sandstone-typeuranium deposits in China and the Middle Jurassic Xishanyao Formation is the main ore-bearing strata. Based on fieldgeological section, indoor microscopical identification, grain size analysis, and drilling data, the sedimentary environ-ment types, genesis and distribution of sand bodies, and its relation with coal-bearing stratum distributions in the Mid-dle Jurassic Xishanyao Formation at the southern margin of the Yili Basin were identified. Results show that the Xish-anyao Formation on the southern margin of the Yili Basin is dominated by meandering-stream delta plain-delta front.The sandstones of the distributary channel microfacies are highly coal-bearing or carbonaceous, medium-coarse size,rich in debris and feldspar, poor selection and moderate roundness, with relatively low compositional maturity andstructural maturity. The three-stage particle-size curve is the main feature, showing the characteristics of the jumping,rolling, and suspension transport in the delta plains. The resistivity curve appears in the longitudinal direction as aninverse grain size with a coarser grain size. Moreover, the thickness of the sand body is mostly between 20-40 m, withthe sand ratio between 0.3-0.8. The coal seam or peat in the marsh facies between the distributary channel sandstoneand the distributary river channel is adjacent to each other in the plane and alternant vertically. There are many fossilsof ancient plant stems and plant imprints. The symbiotic coupling relationship between the depositional environment ofthe meander river delta, the delta sandstone and the coal-bearing strata has provided sedimentary support for the in-depth study of coal and uranium enrichment in the southern margin of the Yili Basin.

关 键 词：伊犁盆地南缘 中侏罗统 西山窑组 沉积环境 曲流河三角洲 

分 类 号：P512.2[天文地球—地质学]