Ϊ�˽⸻��¡��Ĺ����ݻ����о��˼�ľ˹�ؿ鶫��������¡�����һ�׺�����ɰ��- -ʯӢɰ�뻨��Ƭ���Ҳ������档LA��ICP��MS �ʯ U��Pb ���ѧ�������������Ƭ���ҵļ�Ȩƽ������Ϊ 495 ±5 Ma��ʯӢɰ���е���м�ʯ����� ��480 Ma�������� 480 ��520 Ma ��������Ϊ���壬�������������� ��800 Ma ���ʯ���ǶȲ����ϼ����ѧ֤�ݳ�ֱ���������¡���Ǽ�ľ˹�ؿ����ɲ��֡����ڼ�ľ˹�ؿ�ȱʧ���ռ�—־���ͳ������Ʋ����׺�����ɰ�ң�ʯӢɰ�ҵ��γ�ʱ��Ϊ����͡�����������ϣ���Ϊ��ľ˹�ؿ�ı��ʽᾧ�����γɺ󣬾����˳��ڵ�¡����ʴ���������������䶫������תΪ������½��Ե��

In order to understand the tectonic evolution of Fujin uplift�� the authors studied the unconformity of conglomeratic sandstone- quartz sandstone with its underlying granitic gneiss in Fujin uplift of northeastern Jiamusi Massif�� Based on the LA��ICP��MS zircon dating�� granitic gneiss weighted mean age is 495 ±5 Ma�� The U�� Pb ages for zircons from quartz sandstone are all more than 480 Ma��of which are mainly concentrated in the age of 480 �� 520 Ma��and just a small amount of ages are more than 800 Ma�� The evidence of unconformity and geochronology indicates that the Fujin uplift is a part of Jiamusi Massif�� Due to the Jiamusi Massif lacking of the Ordovician and Silurian sediments��it suggested that the forming time of the conglomeratic sandstones and quartz sandstone is Devo- nian�� Combined with the regional research data��it is considered that after the formation of metamorphic crystalline basement��the Jiamusi Massif was undergone long- time uplift and erosion until Early Devonian��then the eastern part of the Massif was whole turning into passive continental margin��