北大别燕子河片麻岩的锆石U-Pb年龄:印支期变质事件的确定  

Zircon U-Pb ages of Yanzihe gneiss from Northern Dabie, China: evidence for Jurassic metamorphism.

作　　者：葛宁洁[1] 夏群科[1] 吴元保[1] 侯振辉[1] 秦礼萍[1] 柏林 

机构地区：[1]中国科学技术大学地球和空间科学学院,合肥230026 [2]安徽省地质学会,合肥230001

出　　处：《岩石学报》2003年第3期513-516,共4页Acta Petrologica Sinica

基　　金：中国科学院知识创新重点项目(KZCX2-107);国家重点基础研究发展规划(G1999075503);国家自然科学基金(49673197)

摘　　要：本文对北大别燕子河地区英云闪长质片麻岩中的锆石进行了单颗粒U-Pb年龄测定。该片麻岩中存在两种类型的锆石,一种是片麻岩原岩中的岩浆锆石,在后期的变质事件中经历了不同程度的Pb丢失;另一种是变质作用过程中的新生锆石。5个分析点拟合出一条很好的不一致线,得到上下交点的年龄分别为880±110Na和228±13Ma(MSWD=1.1),其中上交点的年龄代表了片麻岩原岩的形成时代,下交点的年龄代表了变质作用发生的时间。变质锆石给出了238Ma的一致年龄,与不一致线给出的下交点年龄在误差范围内相同。这一结果表明北大别片麻岩也经历了印支期变质作用。北大别地体为扬子板块的北缘,华北与扬子板块的缝合线应位于北大别以北。U-Pb ages of zircons from Yanzihe gneiss of Northern Dabie have been determined by single-grain TIMS method. There are two types of zircon: one is the magmatic zircon from protolith which had undergone different degree of Pb loss, and the another is metamorphic zircon. Five points give a good concordia line with lower intercept at 228 +/- 13 Ma and upper intercept at 880 +/- 110 Ma (MSWD = 1.1). The upper intercept point represents the protolith age and the lower intercept point represents the metamorphic age. One metamorphic zircon gives concordant U-Pb age of 238 Ma, which is similar to the lower intercept age. The result demonstrates that the Northern Dabie gneiss also underwent Jurassic metamorphic event. The suture of North China Block and Yangtze Block should be north of the North Dabie.

关 键 词：北大别 片麻岩 锆石U-PB定年 印支期 

分 类 号：P597.3[天文地球—地球化学] P588.346[天文地球—地质学]