肥东杂岩锆石U-Pb年龄和Lu-Hf同位素:对扬子克拉通统一结晶基底的限制  

Zircon U-Pb Dating and Lu-Hf Isotope Results for Feidong Complex:Implications for Coherent Basement of the Yangtze Craton

作　　者：涂城 张少兵[1] 苏克 梁婷 Tu Cheng;Zhang Shaobing;Su Ke;Liang Ting(Key Laboratory of Crust-Mantle Materials and Environments,Chinese Academy of Sciences,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]中国科学院壳幔物质与环境重点实验室,中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《地球科学》2021年第5期1630-1643,共14页Earth Science

基　　金：国家自然科学基金项目(Nos.41772187,41572168)。

摘　　要：扬子克拉通广泛存在太古宙-古元古代的结晶基底,但关于扬子克拉通早前寒武纪基底形成和演化的基本问题尚未完全解决,特别是基底是由多个块体拼合而成还是一个统一的结晶基底尚无定论.对扬子北缘张八岭隆起内肥东杂岩的片麻岩、斜长角闪岩及侵入其中的花岗岩进行了同位素地质年代学和地球化学研究,发现片麻岩具有相似的原岩年龄,分别为2 449±17 Ma、2 444±15 Ma、2 495±23 Ma、2 478±24 Ma,斜长角闪岩和A型花岗岩的原岩年龄分别为2 032±35 Ma和747±4 Ma,表明肥东杂岩出露有扬子克拉通晚太古-古元古代的结晶基底.片麻岩锆石Hf同位素组成相似,εHf(t)平均值为-3.6±0.5,两阶段Hf模式年龄(T_(DM2))范围主要在3.3~3.0 Ga,平均值为3 185±31 Ma,说明这一期约为2.45~2.50 Ga的岩浆活动主要是对扬子北缘古-中太古代地壳的再造.扬子北缘的鱼洞子群和陡岭杂岩都经历了相同性质的岩浆事件,同时扬子克拉通广泛出现约2.50 Ga的碎屑锆石和捕获锆石,表明扬子克拉通结晶基底是统一的.Archean-Paleoproterozoic basement is widespread in the Yangtze craton. However,many essential problems about the formation and evolution of the Precambrian basement of the Yangtze craton are still open, especially whether the basement of the Yangtze craton is coherent or composed of multiple blocks. A geochronological and geochemical study was carried out for the felsic gneiss, amphibolite and intrusive granite from the Feidong complex in the Zhangbaling uplift at the northern margin of the Yangtze craton. Zircon U-Pb dating gives similar protolith ages of 2 449±17 Ma, 2 444±15 Ma, 2 495±23 Ma and 2 478±24 Ma for the felsic gneisses. The ages of the amphibolite and A-type granite are 2 032±35 Ma and 747±4 Ma, respectively. This indicates that the Late Archean-Paleoproterozoic crystalline basement of the Yangtze craton cropped out in this area. The zircon εHf(t) values of the ca. 2.45-2.50 Ga gneisses are negative with an average value of-3.6±0.5 and the corresponding two-stage Hf model ages(T_(DM2)) range from 3.3 to 3.0 Ga with an average of 3 185±31 Ma, which shows that the 2.45-2.50 Ga magmatic event is mainly the reworking of Paleo-Mesoarchean crust. The occurrence of similar magmatic rocks in other terranes, including the Yudongzi Group and Douling complex in the northern Yangtze craton, as well as detrital zircons and volcanic xenocrystals with similar ages widespread in the Yangtze craton, suggests that the basement is coherent throughout the whole Yangtze craton.

关 键 词：太古宙-古元古代 肥东杂岩 扬子克拉通 结晶基底 地球化学 

分 类 号：P597[天文地球—地球化学]