摘要
对延边地区侵入五道沟群的辉长岩岩脉进行了单颗粒锆石的CL图像分析和SHRIMPU-Pb年龄测定,结果表明:该脉岩中的锆石大多呈内部结构均匀的半自形粒状,少量为条带结构的长柱状。11个单颗粒锆石中有(387.0±11.8)Ma、292.0～251.1Ma加权平均值为(270±10)Ma,n=10,两组谐和年龄,初步确定前者为其侵位过程中捕获的围岩中的锆石,而后者代表辉长岩就位过程中形成的岩浆锆石。结合该区呼兰群变质作用和花岗岩的年代学研究的新成果,认为延边地区兴蒙造山作用晚期的地壳由挤压向伸展环境转化的时间应在270Ma±。
By analyzing CL image and SHRIMP U-Pb dating for single-grain zircons in the studied area, the results show that the most zircons are half-euhedral granular with homogeneous inner structures, a few zircons are long cylindrical with streaky structures; there are two group concordia ages for the 11 single-grain zircons, one is 387.0 ± 11.8 Ma and the other is 292. 0 -251.1 Ma （weighted mean =270 ± 10 Ma, n = 10）. The former age is the time for the zircons in the wall rock; the latter is the age of gabbro emplacement. Combined with the latest achievements of chronological study of the granite and metamorphism in Hulan Group, it is considered that the transform time was ca. 270 Ma for the lithosphere from compression to extensional environment during late Xingmeng orogeny in Yanbian area.
出处
《世界地质》
CAS
CSCD
2008年第2期150-155,共6页
World Geology
基金
国家自然科学基金(40472050)
国家油气中心项目(XQ-2004-07)
