藏北羌塘地块中部蓝片岩中捕获锆石SHRIMP U-Pb定年及其意义

SHRIMP U-Pb dating of zircons from blueschist in the central part of the Qiangtang block,northern Tibet,China,and its implications

羌塘中部2个蓝片岩样品中锆石的SHRIMp U-Pb定年结果表明,锆石属于残留锆石,不是蓝片岩相变质作用形成的新生锆石,这些年龄代表源区原岩的年龄或原岩捕获锆石的年龄,是不同构造-热事件的响应。首次在藏北羌塘地区获得了锆石SHRIMP U-Pb年龄2533Ma,说明这颗锆石来自新太古代,虽然不一定源自本地,但至少暗示羌塘地区新太古代曾经可能发生过构造-热事件。

SHRIMP U-Pb dating of zircons from two blueschist samples in central Qiangtang, northern Tibet, suggests that the zircons in blueschist are relict ones rather than neogenic ones formed by blueschist facies metamorphism. These ages stand for those of protoliths in source regions or those of zircons captured by protoliths and are responses to different tectonothermal events. The SHRIMP U-Pb zircon age of 2533 Ma obtained for the first time in the central Qiangtang area, northern Tibet, indicates that the zircon originated from the Late Archean rocks, and although the zircon may not necessarily have originated in the study area, its age at least implies that a tectonothermal event may have occurred in the Qiangtang area in the late Archean.