1. College of Earth Sciences��Jilin University��Changchun 130061��China; 2. No. 240 Institute of Nuclear Industry��Shenyang 110032��China; 3. State Key Laboratory of Continental Dynamics��Northwest University��Xi'an 710069��China

The granites in southern Manzhouli region of Inner Mongolia are composed mainly of alkaline-feld- spar��orthoclase and adamellite granite�� We present new zircon U--Pb dating of granites using ablation LA--ICP--MS technique�� The result shows that three stages of granites in the southern Manzhouli region: Middle to Late Triassic (208 ��239 Ma)��Early Jurassic (179 ��185 Ma)��Late Jurassic to Early Cretaceous (137 ��151 Ma)��which are consistent with all of the Da Hinggan Mountain��and this geochronological framework is also comparable to that in the Zhangguangcai-Lessor Hinggan Mountain in the East�� Zircon Hf analyses conducted by LA--MC--ICP--MS show that these granites have εHf(t) values of +0. 7 �� +9. 5 with Hf modal ages of 0. 6 ��1. 2 Ga��indicating that thecrust in the Ergun block was extracted from mantle during Meso-Neoproterozoic��which is different from the Xing'an block to the south��where the crustal accretion was aged in the Neoproterozoic-Phanerozoic��