内蒙古西部温都尔庙群的时代及其在中亚造山带中的位置

内蒙古西部的温都尔庙群下部为含铁石英岩、变质火山岩与绢云石英片岩，上部由各类绢云石英片岩、石英岩组成，局部夹碳酸盐沉积。利用SHRIMP和ICP-MS定年方法，获得该群下部的变质火山岩时代为(460±4) Ma，上部绢云石英片岩中最年轻的峰值年龄为417 Ma和444 Ma。结合已有的锆石年龄分析结果，本文认为温都尔庙群的发育时代可能为500~415 Ma。根据温都尔庙群的物质组成，推测其形成于松辽-浑善达克地块周围的大陆边缘海域并命名为温都尔庙洋，代表我国境内早古生代时期的古亚洲洋。根据碰撞造山带理论探讨了温都尔庙群的构造位置，提出在早-中古生代时期，以温都尔庙群为代表的古亚洲洋发生了向南部华北地块和向北部兴安-艾力格庙地块的双向俯冲，其主体部分形成南、北两个加积楔，而其边缘部分卷入南、北混杂岩带成为基质，因此温都尔庙群的褶皱及变质历史记录了中亚造山带东段的演化过程。对碎屑锆石年龄分布的研究表明，温都尔庙群的前寒武纪物源特征与蒙古国下古生界的相似，而与华北陆块显著不同，表明温都尔庙群的物源很可能来自华北陆块之外的前寒武纪古陆。

Age of the Ondor Sum Group in western Inner Mongolia and its position in the Central Asia Orogenic Belt

The Ondor Sum Group (OSG) in western Inner Mongolia can be divided into two parts: the lower part consists of ferrian quartzites, meta volcanic rocks and sericite quartz schists; the upper part includes sericite quartz schists and quartzites mixed with localized carbonate rocks. In SHRIMP and ICP MS geochronometric determination, one SHRIMP peak age of 460±4 Ma and two detrital zircon peak ages of 417 Ma and 444 Ma were acquired from the meta volcanic rocks in lower part and sericite quartz schists in upper part, respectively. These new data, combined with previous zircon dating indicate OSG developed from 500 Ma to 415 Ma. Composition of OSG suggests that it formed in the continental margins of the Songliao Hunshandake block, which is called the “Ondor Sum Ocean” (OSO) in this paper, representing the Paleo Asian Ocean in China during the early Paleozoic. During the early middle Paleozoic, OSO was subducted beneath the north China block in the south and Xingan Angin Sum block in the north, respectively; its main part formed the northern and southern accretionary wedges whereas its marginal part became the matrix of northern and southern mélanges. Deformation and metamorphism in OSG recorded the evolution process of the eastern Central Asia Orogenic Belt. Detrital zircon analyses of OSG demonstrate that its Precambrian source area is similar with the lower Paleozoic in Mongolia and different from that in the North China Craton (NCC), indicating there were other provenances for OSG.