�����о���СĪ���ɵ���������ҵ��ʯ LA-ICP-MS U-Pb ������������ѧ��������������򼰹������������̽�֡���Ʒ�е��ʯ��ʰ����ξ������������������ͽϸߵ� Th/U ��ֵ (0. 38 ��0. 68)����ʾ��Ϊ�ҽ����򡣲�������ʾ��������������γ�����ʯ̿�� ( (348. 9 ± 2. 1) Ma)����ʯ����ѧ������������������Ԫ�ؾ��и߹� (SiO 2 = 75. 78% �� 77. 01%)������ (K₂O =4. 58% ��4. 76%)��ƶ�� (Al₂O₃ =11. 80% ��12. 37%)��ƶ�� (CaO =0. 28% ��0. 31%)����þ (MgO =0. 05% ��0. 09%) ������; ΢��Ԫ�ؾ��п��� Ba��Sr��P��Ti ��Ԫ�أ����� ��b��Th��U��K �ȴ�������ʯԪ�ص�����; ϡ��Ԫ�س��� Eu ���쳣���ԡ���ϡ��Ԫ����ȸ����� “��Ÿ”ʽ���䣬���е��͵� A �ͻ�����������ͨ�� Eby �Ĺ��컷���б�ͼ�⣬��һ���б���Ϊ A2 �ͻ����ң��������γ�����ײ��չ��ת������֮�С���������о����ϣ���Ϊ�����˰��ؿ������۵ؿ����ײƴ����ϵ�йء�

The authors studied the zircon LA-ICP-MS U-Pb dating and geochemical characteristics of alkali- feldspar granites in Xiaomoeke area��and discussed their petrogenesis and tectonic significance�� Most zircons of the selected samples are subhedral in shape��display distinctly oscillatory zoning structures with high values of Th/ U (0. 38 �� 0. 68)��implying a magmatic origin�� The dating results show that the alkali- feldspar granites are formed in the Early Carboniferous ( (348. 9 ±2. 1) Ma)�� The geochemical data indicate that the major elements of alkali- feldspar granites are characterized by high SiO₂ (75. 78% �� 77. 01%) and K₂O (4. 58% �� 4. 76%)�� and low Al 2 O 3 (11. 80% ��12. 37%)��CaO (0.28% ��0.31%) and MgO (0. 05% ��0. 09%)�� The trace ele- ments are characterized by depletion of Ba��Sr��P��Ti and enrichment of LILE such as ��b��Th��U��K�� The ��EE are characterized by the typical sea- gull lines with obvious negative Eu and enrichment of L��EE�� Geochemis- try shows that the alkali- feldspar granites are quite similar to the A- type granite�� On the base of the classification diagrams proposed by Eby��the alkali- feldspar granites can be classified into A2��and were formed under a trans- forming tectonic setting from collision to extension�� Combining with the regional research data��the authors consid- ered that it is probably related to the system of collision and merging of Xing’an terrane and Songnen terrane��