Zircon U-Pb ages and its significance of the Mesozoic granites in the Wulanhaote region, central Da Hinggan Mountain
大兴安岭中部乌兰浩特地区中生代花岗岩的锆石U-Pb年龄及地质意义

The timing and stages of the Mesozoic granites in the Da Hinggan Mountain is the key to the tectonic and magmatic evolution of Northeast China. In this paper, we present new zircon U-Pb age data of granites using laser ablation ICP-MS technique. The result shows three stages of granites in the Wulanhaote-Suolun region, central Da Hinggan Mountain, i. e. , Middle to Late Triassic granites (235 -225 Ma) , Early to Middle Jurassic granites (182 - 175 Ma) and Early Cretaceous granites (140 - 125 Ma) , which are consistent with the stages of volcanic rocks. This geochronological framework is also comparable to that in the Zhangguangcai-Lessor Hinggan Mountain in the east to the Songliao Basin. The identification of - 800 Ma inherited zircons, consistent with Neoproterozoic granites in Eguna block, suggests that there existed Precambrian basement in this region. Considering their petrography and geological data of adjacent regions, we propose that the formation of Triassic granites is related to post-orogenic lithospheric extension after closure of the Paleo-Asian Ocean, Jurassic granites are results of subduction of oceanic plate in the western Jiamusi block and assembly of Jiamusi and Songnen blocks, while, Early Cretaceous granites are product of intra-plate extension.