松辽盆地大庆长垣南端四方台组含铀砂岩岩石学特征及地质意义

Petrology characteristics of the uranium-bearing layer of Sifantai Formation in Daqing placanticline of Songliao basin and their geological implications

研究区位于松辽盆地北部大庆长垣南端构造区,其含矿目的层主要为上白垩统四方台组下段砂体。通过野外地质调查、岩芯编录,岩矿鉴定、X衍射及扫描电镜等方法,详细研究了目的层砂岩碎屑组分、结构以及矿物特征,并初步对其物源及源区构造背景进行了分析。结果表明研究区含铀砂岩类型为长石岩屑砂岩,其成分及结构成熟度中等,成岩作用较弱,表现为较弱的压实作用、胶结作用、溶蚀作用以及部分重结晶作用,对铀成矿作用较为有利;呈薄膜状或蜂窝状的蒙脱石等粘土矿物大量分布在颗粒表面,对铀的吸附具有重要作用。物源及源区构造背景分析结果表明蚀源区与岩浆活动区和再旋回造山带等不稳定的构造区有关,物源可能来自于研究区东部张广才岭一带的太古-元古宙变质岩系、中生代火山岩及花岗岩。

The study area is located in the south of Daqing placanticline structure area in Songliao basin.The sandbody from the lower member of Sifantai Formation in Late Cretaceous is the metallogenichost rock.Through methods of field geological survey,core logging,combining the rock-mineral determination,the analysis of Xdiffraction,and scanning electron microscope,this paper has detailed studied the characteristics of detrital grain composition,structure and mineral.In the end,it has made some discussion about the provenance and tectonic background of source region.The results show that the types of uraniferous sandstone are mainly feldspathic litharenite.Both the compositional maturity and textural maturity are poor,the diagenesis is also weak.It shows the weak compaction,cementation,dissolution and partial recrystallization.The source area is related to the unstable tectonic zone,such as magmatic activity zone and recycle orogenic beltits.And the provenance of study area is likely to come from the Zhangguangcai mountains,where develop the Archaean-Proterozoic metamorphic series and Mesozoic volcanic rocks and granites.