�����в���Ͳɽ�����Գ����������ʯ��������-������, ���о��ȵ������������ͽϸߵ� Th /U��ֵ(0.63��1.49) , ��ʾ������ҽ������ʯ��LA-ICP-MS U-Pb����������, 206 Pb /238U ����Ϊ(118 ±1)��(125 ±1) Ma ( n = 24) , ���Ȩƽ������Ϊ( 122 ±1) Ma (MSWD = 415) , �������������λ�ᾧ����—��������������SiO2����Ϊ52.41% ��53.38% , TiO2 = 1.27% ��1.95% , MgO��TFe₂O₃�����ֱ�Ϊ3.34% ��4.27%��8.42% ��9.48% , Mg#ֵΪ44��47��Na₂O����Ϊ3.99% ��4.31% , K₂O����Ϊ1.54% ��1.97% , Na₂O /K₂OΪ2.05��2.75, Al₂O₃ = 16.87% ��19.60% , ������Ը��ơ��������ص㡣ϡ��Ԫ��������ʯ��׼��������ʾ����и�����ϡ��Ԫ��(LREE) ��ƶ��ϡ��Ԫ��(HREE) �Լ�΢����Eu�������쳣���ص㡣΢��Ԫ��ԭʼ��ᣱ�׼������ͼ��, ����߸�����������ʯԪ��(Rb��Ba��Th) , ���Կ���߳�ǿԪ��(Nb��Ta��Zr��Hf��Ti) ���ص㡣��Ͳɽ�Գ������ҵ�ԭʼ�ҽ���Դ���ܸ������彻���ĵ��Ш�IJ�������, ���γ�Ӧ���̫ƽ���鸩�������γɵ����ƻ���������ʵ���չ�����йء�

Gabbro-diorite zircons from Yantongshan in central Jilin Province are euhedral-subeuhedral in shape, and display homogeneous growth zoning and high Th /U ratios (0.63��1.49) , suggesting theirmagmatic origin. LA-ICP-MS zircons U-Pb dating indicate that ²⁰⁶ Pb /²³⁸U ages of 24 spots ranging (118 ±1) to (125 ±1) Ma with a weighted mean age of (122 ±1) Ma (MSWD = 4.5) , implying the crystallization of this rock body as Early Cretaceous in age. The contents of SiO₂ are 52.41% ��53.38% , TiO₂ 1.27% ��1.95% , MgO 3.34% �� 4.27% (Mg# = 44��47) , TFe₂O₃ 8.42%��9.48% , Na₂O 3.99%��4.31% , K₂O 1.54%��1.97%, Na₂O /K₂O 2.05��2.75 and Al₂O₃ 16.87% ��19.60%, characterizing high Na and Al. The gabbro-diorites have high light rare earth elements (LREEs) , low heavy rare earth elements (HREEs) and weakly positive Eu anomalies in chondrite- normalized rare earth element curves, and with high L ILEs (Rb, Ba and Th) and relative low HFSEs (Nb, Ta, Zr, Hf and Ti) in p rimitive mantle-normalized trace element spider diagram. The primary magma of gabbro-diorite in Yantongshan derived from the partialmelting ofmantle wedge which metasomatized by subduction fluids, and formed under an extensional environment similar to back-arc basin during the subduction of the Paleo-Pacific Plate.

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