温都尔庙群锆石的LA-MC-ICPMS U-Pb年龄及构造意义  

LA-MC-ICPMS U-Pb geochronology of zircons from the Wenduermiao Group and its tectonic significance

作　　者：李承东[1] 冉皞[2] 赵利刚[1] 王惠初[1] 张阔[1] 许雅雯[1] 谷永昌[1] 张永清[3] 

机构地区：[1]天津地质矿产研究所,天津300170 [2]中国地质大学,北京100083 [3]内蒙古自治区地质调查院,呼和浩特010020

出　　处：《岩石学报》2012年第11期3705-3714,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40972037);地质大调查项目(1212010811004)联合资助

摘　　要：温都尔庙群分布在内蒙古中部地区,分下部桑达来呼都格组和上部哈尔哈达组,通常被认为属于蛇绿岩套组合,形成时代也一直存在争论。详细的野外调查表明,温都尔庙群不完全是蛇绿岩组合,还发育洋内弧的玄武岩-玄武安山岩-安山岩组合。所以,温都尔庙群为一套包含大洋洋壳、洋内弧等不同时代和成因的增生杂岩。对温都尔庙群洋内弧变质安山岩及变质碎屑岩进行锆石LA-MC-ICPMS法U-Pb同位素测年表明:桑达来呼都格组上部洋内弧变质安山岩年龄为470±2Ma。哈尔哈达组两个样品(10NM142、10NM143)的碎屑锆石年龄主要集中在445～480Ma范围内,其中10NM143样品中最年轻谐和年龄多在424～438Ma之间,表明至少有一部分地层形成于中志留世。考虑温都尔庙群蛇绿岩形成时代(497～477Ma)、高压变质时代(446±15Ma～453±1.8Ma)及晚志留世西别河组不整合覆盖其上的事实,桑达来呼都格组可能形成于寒武纪-晚奥陶世,哈尔哈达组形成于晚奥陶世-中志留世。因此,温都尔庙群是形成于寒武纪-中志留世的变质增生杂岩。Wenduermiao Group is located at central section of Inner Mongolina of China, which may be subdivided in ascending order into the Sangdalaihuduge Formation and Haerhada Formation. It has been usually considered to be an ophiolite suite, but there has been a controversy on its era. According to filed investigation, Wenduermiao Group includes not only ophiolite but also lithological association of intra-ocean island arc：basalt, andesite-basalt and andesite. Therefore Wenduermiao Group is a suit of complex including ocean-crust slices,intra-ocean island arc and otherwise with different ages and geneses. Based on recent dating of the LA-MC-ICPMS U-Pb zircons from Wenduermiao Group, the intra-ocean island arc metamorphic andesite from upper part of Sangdalaihuduge is dated at 470±2Ma, and the main ages of detrital zircons from two samples（10NM142,10NM143）of Haerhada Formation range from 445Ma to 480Ma and the youngest age of detrital zircons from 10NM143 is mainly 424～438Ma, indicating that there are at least some Middle Silurtion strata in the Haerhada Formation. Our results, in conjunction with the available geological data including ophiolite age （497～477Ma）, metamorphic times（446±15Ma～453±1.8Ma） of high-pressure metamorphic rocks and evidence that Late Silurian Xibiehe Formation overlies unconformably Wenduermiao Group, suggest that times of Sangdalaihuduge Formation is possibly from Cambrian to Late Ordovician and times of Haerhada Formation from Late Ordovician to Middle Silurtion. It is thus concluded that Wenduermiao Group is a suit of metamorphic complex formed in Cambrian to Middle Silurtion.

关 键 词：U-PB年龄 增生杂岩 温都尔庙群 

分 类 号：P597.3[天文地球—地球化学]