����—������������������һ�������Ի�ɽ�ҽ��죬��ҪΪ��ɽ�ҡ������ҡ�Ӣ���ң�ͬʱ�����������䰲ɽ�ң��������ڸƼ���ϵ�С�����Ʒ�ĵ���ѧ��������������K₂O ( 1. 3% �� 5. 27%) �����ϸߣ�ȫ��K₂O + Na₂O ( 43. 45% �� 9. 97%) �����еȣ�TiO₂ ( 0. 26% �� 1. 3%) �����ϵͣ�ϡ��Ԫ������ΣREE ( 81. 68 × 10^-6 �� 172. 89 × 10^-6 ) �����еȡ�������ʯ��׼����REE ������߱���Ϊ��ϡ��( LREE) �������ϡ��( HREE) ����������( La /Yb) N �仯��ΧΪ5. 37 �� 11. 73������ϡ���������ԣ�ȫ����Ʒ��Eu �ʹ󲿷���Ʒ��Ce ����Ϊ���ĸ��쳣����������ʯԪ��( LILE) Rb��Ba��K ������Pb ǿ�Ҹ������߳�ǿԪ��( HFSE) Nb��Ti��Ta ���𡣻�ɽ����Ʒ���컷���б�ͼ�����������—����������������ɽ�Ҿ��л��½��Ե��������鸩�������γɵĻ�����չ�����ǻ�ɽ�ҵ��γɱ�����

Sunwu --Jiayin Basin developed a intermediate-acidic volcanic formation in Early Cretaceous�� The volcanic rocks include andesites��rhyolite and dacite with a few basaltic andesites��belonging to calc-alkalic series�� The geochemical analyses on the volcanic rock samples revealed the K₂O ( 1. 3% �� 5. 27%) relatively high��K₂O + Na₂O ( 43. 45% �� 9. 97%) moderate��TiO₂ ( 0. 26% �� 1. 3%) relatively low��and earth element ( 81. 68 × 10^-6 �� 172. 89 × 10^-6 ) medium rare in contents�� Chondrite normalized REE pattern showed that LREE were enrichment compared with HREE��and ( La /Yb) N ranged from 5. 37 to 11. 73��with weak Eu and Ce anomalies�� These samples were enriched in LILE ( Rb��Ba��K) and Pb��but relatively depleted in HFSE ( Nb��Ti��Ta) �� According to tectonic environment discrimenation diagrams��Sunwu --Jiayin Basin was active in continental margin characteristics in Early Cretaceous��and back-are extensional environment formed by plate subduction was the formation background of volcanic rocks��