内蒙古呼伦贝尔地质公园阿敦础鲁花岗岩锆石U-Pb年龄及其构造意义

Zircon U-Pb dating of Adunchulu granite in Hulun Buir Geopark of Inner Mongolia,and its tectonic significance

通过对内蒙古呼伦贝尔地质公园阿敦础鲁花岗岩进行的锆石U-Pb同位素年代测定和岩石样品主要地球化学特征分析,结合野外地质调查成果,综合分析表明,阿敦础鲁花岗岩锆石U-Pb年龄为158.0±2.7Ma,为晚侏罗世岩浆活动的产物;岩石具有富硅、高钾钙碱性和过铝质特征,富集大离子亲石元素Rb、Th、K等,轻微亏损高场强元素Ta、Nb、Zr等。结合区域地质研究成果,初步确定阿敦础鲁正长花岗岩是晚侏罗世蒙古-鄂霍茨克洋闭合造山后伸展作用下地壳挤压增厚局部熔融的产物。

Researches on the isotopic dating of the zircon U - Pb and rock geochemistry of the Adunchulu Granite in the HulunBuir Geopark of Inner Mongolia, together with the geological field trip results and the comprehen-sive analysis proved that the zircon U -Pb was formed in （158.0±2.7 ）Ma, the result of intense magmatic activity in late Jurassic. These granites are rich in silicon, high -k calc -alkaline and peraluminous, which contains abundant heavy iron lithophile elements like Rb, Th, K, and minor loss high field - strength elements like Ta, Nb, Zr, and other elements. The research results of the regional geology indicate that the syengranite of the Adunchulu Granite was the result of the thickened diatexis by the earth crust extrusion after the closed orogenic event of the Mogolia - Ehuocike Ocean in the Late Jurassic.