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大别造山带白垩纪花岗岩的多期侵位与地壳结构变化的关系,是研究大别造山带演化的热点和前沿问题之一.北大别造山带产出三期白垩纪花岗岩,通过对石鼓尖岩体、天堂寨岩体和薄刀锋岩体进行锆石U-Pb年龄和Sr-Nd同位素研究,探讨了北大别白垩纪三期花岗岩的侵位时间和造山带地壳结构的演化.石鼓尖石英二长岩年龄为142±4Ma,(87Sr/86Sr)t比值范围为0.707 801~0.707 870,εNd(t)值范围为-17.94~-17.09;天堂寨斑状二长花岗岩年龄为132±4Ma,(87Sr/86Sr)t比值范围为0.708 390~0.708 934,εNd(t)值范围为-16.89~-13.86;薄刀锋细粒花岗岩的年龄为130±4Ma,(87Sr/86Sr)t比值范围为0.711 424~0.714 972,εNd(t)值范围为-14.88~-12.97.这样的同位素组成显示花岗岩的多期侵位与地壳结构演化的密切关系,第一期花岗岩形成于增厚的基性下地壳部分熔融,第二期花岗岩来源于大别造山带伸展垮塌过程的中酸性中下地壳的部分熔融,晚期无变形花岗岩形成于造山带伸展垮塌后,酸性中上地壳的部分熔融.
The relationship between the multi-stage emplacement of the Cretaceous granites and the crustal structure changes in the Dabie orogenic belt is one of the hot and frontier issues in the study of the evolution of the Dabie orogenic belt.Because the Cretaceous Granite was produced in the North Dabie orogenic belt, U-Pb ages and Sr-Nd isotope studies of zircons from Jianping, Jiaozuo, Tiantangzhai, and thin-blade rock bodies, and discussed the emplacement time of the Cretaceous III granitoid and the evolution of crustal structure in the orogenic belt. The age of spike quartz mantle is 142 ± 4Ma, the range of (87Sr / 86Sr) t is 0.707 801 ~ 0.707 870, the range of εNd (t) is -17.94 ~ -17.09. The age of the Tiantangzhai porphyritic monzonite is 132 ± 4Ma , (87Sr / 86Sr) t ranged from 0.708 390 to 0.708 934, and εNd (t) ranged from -16.89 to -13.86. The age of the thin-blade fine granite is 130 ± 4Ma and the ratio of (87Sr / 86Sr) t is 0.711 424-0.714 972, and εNd (t) values ranged from -14.88 to -12.97. Such isotopic composition shows the close relationship between granitic multi-stage emplacement and crustal structure evolution. The first stage granite was formed under thickening basement The crust is partially melted. The second stage of granite is derived from middle-to-lower crust in the extensional collapse process of the Dabie orogen Part of the melting, late stage of the formation of non-deformable granite in the orogenic belt stretching collapsed, acidic melting of the upper crust.