内蒙古林西地区上二叠统林西组砂岩碎屑锆石的年龄及其大地构造意义  

Detrital zircon U-Pb dating from sandstone of the Upper Permian Linxi Formation,Linxi area,Inner Mongolia,China and its tectonic implications

作　　者：韩杰[1] 周建波[1] 张兴洲[1] 邱海峻[2] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]国土资源部油气资源战略研究中心,北京100034

出　　处：《地质通报》2011年第2期258-269,共12页Geological Bulletin of China

基　　金：国土资源部油气专项(编号:2009GYSQ12-01);大学生创新计划项目(编号:2008A61035);国家自然科学基金项目(批准号:40739905;40872121)

摘　　要：林西地区林西组的主体岩性以碎屑岩为主,对其中代表性岩石组合——长石石英砂岩进行了年代学研究。50粒碎屑锆石样品的LA-ICP-MS U-Pb年代学测试结果显示2个主要年龄区间:(256±2～322±3)Ma,峰值年龄为279Ma±2Ma;(357±7～497±4)Ma,峰值年龄为441Ma±3Ma。另有3颗锆石的年龄分别为797Ma±6Ma、1413Ma±38Ma、1661Ma±24Ma。其中256 Ma±2Ma的年龄限定了林西组原岩年龄应为晚二叠世;第二组年龄(357±7～497±4)Ma,峰期年龄441Ma±3Ma,与东北地区的主要泛非期事件年龄一致,表明主要的物源区为东北地块(佳蒙地块)。而797Ma±6Ma、1413Ma±38Ma、1661Ma±24Ma等年龄反映了东北地块基底年龄的信息。这些年龄数据表明,林西组应为东北地块的一部分,并进一步限制了华北与西伯利亚两大板块的缝合线应位于林西组发育地区的南部,即西拉木伦河断裂,而拼合时代应晚于晚二叠世,可能为早三叠世。Linxi Formation is mainly consist of clastic rocks. New research from Linxi detritial zircon by the LA-ICP-MS U-Pb dating showed that the 50 zircons analyses gave two age populations： 256±2～322±3Ma with the peak age at 279Ma and 357±7～497±4 Ma with peak age at 441 Ma. In addition, three analyses yielded ages of 797±6 Ma, 1413±38 Ma, and 1661±24 Ma. Detrital zircon age from this study indicated that 256±2 Ma limited the depositional age of the Lixin Formation and 441±3 Ma represented the main source area （from NE China blocks） age. 797±6 Ma, 1413±38 Ma, and 1661±24 Ma represented the basement rocks in the NE China blocks. New date from this study suggest that Linxi Formation belongs to NE China blocks. Therefore the suture zone between the Siberia and North China is situated in the southern of Linxi Formation, which locates along the Xar Moron suture, and the timing for the final collision should be later than Late Permian, probably at Early Triassic.

关 键 词：内蒙古 碎屑锆石年龄 林西组砂岩 构造意义 

分 类 号：P534.46[天文地球—古生物学与地层学] P597.3[天文地球—地质学]