�����뻨����������ʯ����ѧ���������� SiO2�����ϸߣ�Ϊ 71. 3% �� 73. 28%��K2O = 2. 14% ��4. 29%�����ڸ߼ظƼ���--�Ƽ��� I �ͻ����ҡ��ʯ LA--ICP--MS U--Pb ������ʾ�����뻨�������������Ϊ 127. 9 ±1. 3 Ma���������������ʯ�� ��b/Sr �� Nb/Ta ��ֵ���Լ���ɫ�����ʰ����о����������뻨��������Ϊ��᣻��Դ���ҽ�Դ��Ϊ�����Դ����������þ�����µؿǡ����������ʷ�����Ϊ�����뻨�������ҵ��γ���̫ƽ���鸩������Ĵ�½����չ���������С�

The Guojialing grandiorite was characterized by high SiO2content of 71. 3% �� 73. 28%��K2O of 2. 14% ��4. 29%��which belongs to high potassium calc alkaline to calc alkaline I-type granite�� The result of the zircon LA--ICP--MS U--Pb dating shows that the grandiorite formed in Early Cretaceous with the age of 127. 9 ±1. 3 Ma�� The ratio of the ��b/Sr and Nb/Ta and the study of the dark dioritic inclusions indicate that the Guojialing grandiorite had a mixed source of the crust and mantle��and the magma source region was the newborn mafic lower crust with features of the mantle source�� Combined with the analysis of the regional geology��it is suggested that the formation of the Guojialing grandiorite is closely related to the extension of the continental arc caused by the subduc- tion of the Pacific Plate��