摘要
内蒙古温都尔庙地区有一套统称为温都尔庙群的变质岩系，该岩系主要由两种不同的岩石组合组成：一套是出露于乌兰沟一带的浅变质岩系，主要由变玄武岩、硅质岩、火山碎屑岩、碎屑岩组成的基性火山岩－碎屑岩组合；另一套是出露于德言其庙一带的深变质岩系，主要由斜长角闪岩、斜长片麻岩组成。这两套岩石组合在变形变质、岩石化学和形成环境等方面都有很大的差异，前者主要表现出弧后盆地的特征，后者则是拉张过程中板底垫托的产物，它们分别代表了华北板块北缘中段新元古代不同构造演化阶段的产物。
There is a set of metamorphic rocks in Ondor Sum region, Nei Mongol, which was named as Ondor Sum Group and its age was considered as Paleozoic before. Tow major assemblages of the Group can be recognized. One is outcropping at Wulangou and consists of metamorphic pillow basalt,clastic rocks, silicalite and other epimetamorphic rocks. The other is outcropping at Deyanqimiao and consists of plagioamphibole, plagiogneiss and other hypometamorphic rocks. The assemblages are different from each other in metamorphism,deformation and petrologic chemistry as well as the tectonic settings. The results of this study demonstrated that the volcanoclastic assemblage was formed in backarc basin, and the hypometamorphic assemblage was the underplatting prouduct during extention in the region. Recognization of the two assemblages has an important significance for the tectonic evolution of the northern margin of North China Plate.According to the recent isotopic chronological data, the ages of two assemblages are all NeoProterozoic. The SmNd isotopic age of the volcanoclastic assemblage is 807 ～ 961Ma,and the hypometamotphic assemblage is about 638Ma.The rifting began in the MesoProterozoic at northern margin of North China Plate[11,12].At the beginning of the NeoProterozoic,there was a series of island arcs separated from the North China Plate and backarc basin occurred at the sametime. The volcanoclastic assemblage were formed in this period. Another extensional cycle began at the end of the NeoProterozoic .The hypometamorphic assemblages were formed in the magmatic passive margin during underplating.Since the major assemblages of the Ondor Sum Group are the products of different stages in tectonic evolution of North China Plate in NeoProterozoic,the tectonic evolution in the Paleozoic must be reconsidered.
出处
《高校地质学报》
CAS
CSCD
1998年第2期168-176,共9页
Geological Journal of China Universities
基金
国家自然科学基金
关键词
内蒙古
温都尔庙群
岩石组合
形成环境
构造意义
Inner Mongolia, Ondor Sum Group, different assemblage, tectonic setting.
