胶东郭家岭花岗闪长岩U--Pb年代学、地球化学特征及地质意义

U--Pb dating,geochemical characteristics and geological significance of Guojialing grandiorite in Jiaodong Peninsula

郭家岭花岗闪长岩岩石地球化学特征表明其SiO2含量较高,为71.3％～73.28％,K2O=2.14％ ～4.29％,属于高钾钙碱性-钙碱性I型花岗岩.锆石LA-ICP-MS U-Pb年龄显示郭家岭花岗岩体成岩年龄为127.9±1.3 Ma,属早白垩世.岩石的Rb/Sr和Nb/Ta比值,以及暗色闪长质包体研究表明郭家岭花岗闪长岩为壳幔混合源,岩浆源区为具有幔源特征的新生镁铁质下地壳.结合区域地质分析认为郭家岭花岗闪长岩的形成与太平洋板块俯冲引起的大陆弧伸展作用最密切.

The Guojialing grandiorite was characterized by high SiO2 content 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 Rb/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 subduction of the Pacific Plate.