西藏谢通门地区中侏罗世花岗岩的地球化学特征及时代依据

Geochemical characteristics and age evidence of Middle Jurassic granite in Xietongmen area, Tibet

西藏谢通门县一带区域上属于冈底斯花岗岩带南亚带,侵入岩极其发育,目前填绘有白垩纪、古近纪和新近纪岩体。通过同位素年代学研究,获得12个锆石的U-Pb同位素年龄数据,在原划归白垩纪、古近纪和新近纪岩体中解体出侏罗纪侵入体,按其岩石类型特征,归并为早侏罗世东热村序列和中侏罗世东嘎乡序列。其中,在约拉嘎莫岩体中获得锆石U-Pb同位素年龄166.9±2.8Ma,时代为中侏罗世巴柔期。

Xaitongmoin County belongs regionally to southern subbelt of Gandise granite belt and possesses extremely developed intrusive rocks. In geological map, there are Cretaceous, Paleogene and Neogene rock masses. Through isotopic chronologic study, the authors obtained 12 zircon U-Pb age data and, on such a basis, separated a Jurassic intrusive body from the previously-assigned Cretaceous, Paleogene and Neogene rock masses. According to its rock type, this Jurassic intrusive body is incorporated into the Early Jurassic Dorecun series and Middle Jurassic Donggaxiang series. Zircon U-Pb isotopic age of Yuelagamo rock body within the Jurassic intrusive body is 166.9±2.8Ma, suggesting Middle Jurassic Barou period.