内蒙古大青山北石兰哈达石英闪长岩构造环境讨论

Discussion on Tectonic Setting of the Quartz Diorite in Shilanhada,Northern Daqingshan Mountain in Inner Mongolia

内蒙古大青山北石兰哈达地区的晚古生代黑云石英闪长岩,1∶20万区域地质调查时将其置于华力西中期第二次侵入体(δο42(2)),现经岩石学、地球化学、同位素年代学研究,认为该石英闪长岩为早二叠世岩浆活动的产物。岩石具高铝、高钾、高钙的特点,A/CNK<1.1,σ在2.05～2.83之间,为高钾钙碱性岩,属I型花岗岩类,产于碰撞后的抬升构造环境。岩石稀土总量偏低,LREE富集,δEu=0.8～1.0,稀土曲线呈右倾平滑型,其物质来源很可能是源于软流圈的玄武质岩浆与元古宙地壳物质混合作用的结果。

Based on the study of petrology, geochemistry and isotope, it is suggested that the Neopaleozoic quartz diorites distributed in Shilanhada area, northem Daqingshan of Inner Mongolia should be the intrusives in early Permain. The rocks have the characteristics of high Al, K, Ca. A / CNK〈 1.1, a = 2.05 ～ 2.83. And they belong to high-K calcalkali series and Ⅰ-type granites. The tectonic setting of the rocks might be the upliit of post collision. Those rocks also have relative low REE content, high L/HREE, 6 Eu = 0.8 ～1.0, which imply that they may be the mixture of the basaltic magma and Proterozoic crust.