延边地区青龙村群斜长角闪岩中锆石U-Pb同位素年龄及地质意义

青龙村群岩石类型主要为片岩类、斜长角闪岩类、粗细粒片麻岩类和大理岩夹层。岩石地球化学特征表明，青龙村群的原岩属于钙碱性安山岩-流纹岩组合，这套组合是岛弧区玄武质岩浆分异的产物，推测它是一个较宽阔的大陆边缘拼贴缝合带中的一个岛弧地体。LA-ICP-MS颗粒锆石U-Pb法同位素年龄测定表明，青龙村群斜长角闪岩中锆石年龄为(274±6) Ma，梨树沟花岗岩体中的锆石年龄为(187±3) Ma，这一事实说明青龙村群的变质作用时代为二叠纪末期，代表华北板块北缘的碰撞造山事件。而周边大面积花岗岩的侵位时间为燕山早期，属青龙村群碰撞造山后伸展事件产物。

Zircon U - Pb Isotopic Ages of Amphibolite of Qinglongcun Group in Yanbian Area and Its Geological Significance

Qinglongcun Group consists mainly of gneiss, amphibolite, fine-to coarse-grained schist and laminated marble. The geochemical features of Qinglongcun Group show their protolith belongs to calc-alkalic andesite-rhyolite series that were formed during crystallization differentiation of island arc basalt magma. It is suggested that the rock series constitute an island arc terrane within a rather wide accretion-collision zone along continental margin. The zircon U-Pb dating shows that the age from amphibolite of Qinglongcun Group is (274±6) Ma while the age of Lishugou granite is (187±3) Ma. It indicates that Qinglongcun Group metamorphosed at the end of Permian during the collision orogen event of northern margin of North China plate and the granite intruded into Qinglongcun Group at early Yanshan movement, which belongs to the results of postorogenic extension event.