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

摘要: 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，10⁴Ga/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。

Abstract: 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 calcalkaline 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.