鄂尔多斯盆地乌审旗地区上古生界砂岩碎屑锆石U-Pb年龄及其地质意义

Zircon U-Pb Dating of Clastic Sandstone in the Upper Paleozoic from Wushenqi Area,Ordos Basin and Its Geological Significance

通过LA-ICP-MS碎屑锆石的U-Pb测年和U、Th元素含量分析,结合邻区年龄数据和岩性特征,对鄂尔多斯盆地乌审旗地区上古生界山西组1段和下石盒子组8段砂岩进行了同位素定年物源示踪研究。研究揭示,盒8段和山1段源区母岩形成年龄属于太古代、古元古代、中元古代、晚古生代,分别与华北块体的形成、增生和克拉通化相关,是华北克拉通演化多阶段地质事件作用下的产物。沉积物源区主要为华北克拉通内部或盆地北缘,物源主要来自华北地台东部的早太古代基底古老变质岩系和新太古代的变质岩系、乌拉山和东部集宁地区的新太古代晚期的片麻状花岗岩、早元古代早期的古老的TTG片麻岩及麻粒岩和早元古代晚期的孔兹岩带,此外,阴山地块390~310 Ma岩浆岩也是重要物源之一。该项成果不仅查明了乌审旗地区上古生界山西组1段和下石盒子组8段碎屑锆石年龄与华北克拉通地质事件在时间上的对应关系,指明了年龄区间碎屑物质成分来源的归属性,而且对研究区可能存在的华北克拉通地质事件首次从岩性上提供了重要信息。

Research result of provenance tracing and geological events setting for clastic sandstone deposit in the first member of Shanxi Formation and the eighth member of Shihezi Formation of the Upper Paleozoic in Wushenqi area,Ordos Basin,using LA-ICP-MS in situ U-Pb dating and U,Th element content,combined with adjacent areas age and lithology data analysis of the detrital zircons from the sandstones reveals that the age of source rock in the first member of Shanxi Formation and the eighth member of Shihezi Formation from Archean,Proterozoic,Proterozoic,Late Paleozoic,respectively,with relationship about the formation,proliferation and cratonization of the North China block,and is the product of a multi-stage evolution of the North China Craton geological events. By comparative study of isotopic chronology with the potential parent rocks,it can be concluded that the provenance of the clastic sandstone deposit in Wushenqi area mainly came from the environment of within the North China Craton and the northern edge of the Ordos Basin,and the basement metamorphic rocks and the metamorphic rocks,which it exposed in the environment of eastern North China Platform in the Early Archean and the new Archean,the gneissic granite and TTG genesis or granulites bodes from the northern edge of the Ordos Basin and the West of the Ural Mountains-Jining area in the Late Archean and the Late Paleoproterozoic,In addition,magmatic rocks bodes of Yinshan block formed in continental crust is one of the important areas of provenance in Wushenqi area between 390 ~ 310 Ma. The new results is of very important significance for deeply corresponding to the time between the age of detrital zircon in the Upper Paleozoic from Wushenqi area and the North China Craton geological events,but it is the first time to provide important information from the source rock on the geological events of the North China craton,which it may exist in Wushenqi area.