鄂尔多斯地区中元古界蓟县系沉积特征研究

Study on sedimentary characteristics of the Meso Proterozoic Jixianian System in Ordos Area

利用野外剖面考察、岩心观察和薄片鉴定等方法对鄂尔多斯地区蓟县系沉积特征进行研究。研究表明,蓟县系岩石类型主要为各种白云岩,可见厚层块状泥晶-微晶、粉晶、细晶白云岩,层状、纹层状叠层石白云岩,硅质条带团块白云岩,内碎屑白云岩和球(团)粒白云岩等几种类型;其沉积主要发育在研究区南缘、西南缘和西缘,在西北缘及北缘等地区仅有小面积分布,东缘基本缺失;其沉积环境主要为潮坪沉积,可分为潮上带、潮间带和潮下带3种类型。研究认为,研究区自古陆向外缘依次分为砂坪、云坪、燧石云坪、开阔台地和开阔海等5个相区,具典型的陆表海沉积特征;其沉积时的水体较浅,并向西、向南逐渐变深,沉积厚度也随之逐渐增大。

Based on investigation of outcrops and cores in the field,observation of thin sections by microscop,the sedimentary characteristics of the Meso Proterozoic Jixianian System have been studied in Ordos Area.The research shows that the lithology of the Jixianian System are mainly dolomites,which are mainly thick-massive dolomicrite,silty dolomite,stratiform,lamellar stromatolitic dololaminite,banded and lumped siliceous dolomite,intraclast dolomicrite and algal pellet dolomite.The sedimentation developed in the southern margin,southwestern margin and western margin of Odors Area,and only occurred in small areas in the northwestern margin and northern margin,while there is basically no deposition in the eastern margin of there.It is mostly in tidal flat sedimentary environment,which can be divided into three types:supratidal zone,tidal zone and subtidal zone.From the center to the edge of Odors Basin,there are sand flat,dolomitic flat,flint dolomitic flat,open platform and open sea facies with the characteristics of epeiric sea.It also shows that the water body was relatively shallow and gradually deepened westward and southward and the sediment thickness also increased gradually when deposition occurred.