内蒙古扎鲁特旗嘎达苏早三叠世A型花岗岩的发现及其地质意义

The discovery of the Early Triassic A-type granite in Gadasu,Jarud Banner,Inner Mongolia,and its geological significance

内蒙古扎鲁特旗嘎达苏A型花岗岩具晶洞构造,文象、蠕英结构,其化学成分富硅铝而贫铁,属高钾钙碱性过铝质系列;轻稀土元素曲线右倾,富Ga、Nb、U,贫Ba、Sr、Ti,10~4Ga/Al值为2.64~3.18,Y/Nb值为1.72~2.03,Nb/Ta值为5.99~8.33,属A2型花岗岩。锆石U-Pb测年结果显示,该岩体侵位年龄为249.0±2.7Ma,推测属古亚洲洋在三叠纪闭合后,兴蒙造山带的后期伸展拉张环境的产物。

Gadasu A-type granite has the miarolitic structure and graphic and creep textures as well as chemical characteristics of rich silica and alumina and poor iron, thus belonging to high potassium calc-alkaline series aluminum. Light rare earth curve is included to the right. The rock has rich Ga, Nb, U, poor Ba, Sr, Ti, 104Ga/Al ratios of 2.64-3.18, Y/Nb ratios of 1.72-2.03, and Nb/Ta ratios of 5.99 - 5.99, indicating A2 type granite. Zircon U - Pb emplacement age shows that the rock mass has the age of 249.0±2.7 Ma. The authors thus infer that the granite was formed in the environment of late stage stretching and pull-apart of the Xing-Meng orogenic belt after the closure of the paleo-Asia Ocean in Triassic.