鄂尔多斯盆地西缘山西组沉积物源及源区大地构造属性分析

Sediment provenance analysis and tectonic setting discrimination of Shanxi Formation on west edge of Ordos Basin

利用碎屑岩骨架组分、含量分布、古水流方向、砂岩岩石学特征、常量与微量元素及沉积构造特征等,对鄂尔多斯盆地西缘二叠纪山西组母岩类型、物源方向及大地构造属性进行了研究。砂岩岩石组分表明,物源主要以再旋回造山带为主,源区主要由花岗岩、浅变质岩及片麻岩类组成。砂岩百分含量图也表明,山西组沉积时的主物源区在盆地以北的阴山地区,南部仅为次物源区。古水流参数也证明物源方向为SSW。另外,沉积岩常量与微量元素分布特征显示,当时该区的大地构造环境为被动大陆边缘环境。因而可推知,二叠世山西组沉积时,鄂尔多斯盆地西缘的沉积以北方物源为主,且可能来自北部的阴山地区和西北方向的阿拉善地块。

The sandstone framework detrital composition characteristic, the ratio map of sandstone, directions of palaeo-flow, sandstone petrography,constant elements,trace elements and sedimentary structure feature were used to analyze source rock,source direction and tectonic discriminent of Shanxi Formation in the west edge area of Ordos Basin. The petrographic characteristics of sandstone show that the sediments are mainly carried from the North of the basin, where occurred granite, metamorphic rocks, gneiss and other rocks. According to the data of constant elements and trace elements, the tectonic environment is the passive continental margin. It is indicated that as Permian Shanxi Formation deposited, the sediments were carried from northern Yinshan area and northwestern Mashan mass.