坦桑尼亚乌本迪带内花岗岩类的LA-MC-ICP-MS锆石U-Pb年龄及地质意义

Zircon U-Pb LA-MC-ICP-MS Dating and Geological Significance of the Granitoids in the Ubendian Belt, Southwestern Tanzania

乌本迪带位于坦桑尼亚西南部,由8个地质单元构成,早期被认为是一条古元古代活动带,而后期研究发现该带经历了多阶段的构造岩浆活动,为一条复杂的活动带。本次通过对地质调查期间在乌本迪带采集的花岗岩类进行LA-MC-ICP-MS锆石U-Pb同位素测年,得到不同地质体内花岗岩类的年龄分别为2 549±20 Ma、2 662±33 Ma及2 744±11 Ma,为新太古宙时期的岩浆作用。所有岩体年龄都位于太古宙坦桑尼亚克拉通地壳生长的主要阶段范围内,暗示乌本迪带早期可能为坦桑尼亚克拉通的一部分。根据上述研究成果,综合区域地质背景,认为乌本迪带自古元古代以来的构造演化是在太古宙地壳基础上进行的,为坦桑尼亚克拉通大陆边缘遭受不同阶段的俯冲作用和伸展作用的结果。

Ubendian Belt is mainly located in southwest of Tanzania and composed of 8 blocks. In the early days,the belt was considered as a Paleoproterozoic belt, but later studies have shown that the belt experienced a series of tectonic thermal events in different stages. Through LA-MC-ICP-MS zircon U-Pb dating of the granitoids collected during the geological survey, this paper gets the ages of the granitoids are 2 549±20 Ma, 2 662±33 Ma and 2 744±11 Ma, which indicates that these granitoids are Archean. All ages are within the main stage of crustal growth of the Tanzania Craton, suggesting that the early Ubendian belt may be part of the Tanzania Craton.According to the above research results and comprehensive regional geological background studies, it can be concluded that the evolution of the Ubendian Belt since the Paleoproterozoic was based on the Archean crust,which is the result of the subduction and extension of the continental margin of Tanzania Craton.