�������澮����λ�ڻ�������ͨ��Ե����ʯӢ��������ɡ�Ϊ��̽�ֻ�������ͨ��Ե��������ݻ���ʷ������LA--MC--ICP--MS �ʯU--Pb ���귨�����ʯӢ������206Pb /238U ����Ϊ471 ± 2 Ma��ʱ��Ϊ�а���������ʯΪ�Ƽ���ϵ�У���ϡ��������΢��Ԫ��Nb��P��Ti��Y��Yb ���𣬣�b��Th��K�� Ba��Sr ��Ԫ�ظ������������γ��ڵ�������½��Ե�������ʯHf ͬλ�ط����������ʯεHf ( t) ֵΪ+ 8. 3 �� + 10. 1�����׶�ģʽ����Ϊ679 �� 753 Ma�����׶�ģʽ����Ϊ807 �� 921 Ma����TDM1��TDM2 �������γ�ʱ�����ϴ�����Դ�ڿ����᣻�ӿ�����������������ؿ����ʵIJ������ڣ���ʾ�˻�������ͨ��Ե������Ԫ�Ŵ��ؿ������¼����������������Ϸ��������澮������γɿ�������������¶���������򻪱�����֮ͨ�µĸ��������йء�

Sanmianjing pluton from northern Hebei was located in the northern margin of North China Craton�� which consisted of quartz diorite�� With the aim of constraining the tectonic evolution of the northern margin of North China Craton in Early Paleozoic��the quartz-diorite206Pb /238U age was gained by LA-MC-ICP-MS zircon U-Pb dating as 471 ± 2 Ma��showing the Middle Ordovican�� The pluton has calc-alkaline characteristics��enriched in L��EE�� The trace elements are depleted in Nb��P��Ti��Y and Yb��but enriched in ��b��Th��K��Ba and Sr��showing Sanmianjing pluton formed in island arc or active continental margin settings�� Zircon εHf ( t) values ranged from + 8. 3 to + 10. 1��their single-stage ( TDM1 ) and two-stage ( TDM2 ) model ages varied from 679 Ma to 753 Ma and from 807 Ma to 921 Ma��respectively��implying that the quartz diorites could be derived from partial melting of a depleted mantle source or a newly accreted crust�� Combined with the regional geological data��it is suggested that the quartz diorites formed under an active continental margin setting related to the Early Paleozoic subduction of the Onduermiao oceanic crust subducted the northern margin of the North China Craton��