大别造山带发育大量早白垩世侵入体,前人对北大别岳西岩体和飞旗寨岩体的形成时代的认识存在差异。选取岳西岩体和飞旗寨岩体为研究对象,对其进行全岩主元素分析和LA-ICPMS锆石U-Pb定年。锆石的高 Th/U 比值特征及典型岩浆锆石环带显示其为岩浆成因。岳西岩体的26个测点的加权平均年龄为(128.5±1.4) Ma,飞旗寨岩体的15个测点的加权平均年龄为(127.4±1.7) Ma,说明岳西岩体和飞旗寨岩体均形成于早白垩世。结合目前大别造山带高精度火成岩年代学数据,大别造山带腹地侵入岩可以划分为早晚两期,分别为143~130 Ma和130~119 Ma。早期火成岩具有高钾钙碱性和埃达克质地球化学属性,而晚期火成岩具有向碱性岩过渡的性质,在120 Ma左右出现少量A型花岗岩,暗示130 Ma为本地区深部过程转换的重要时期。%Early Cretaceous intrusive plutons are distributed extensively in the Dabie orogen. How to identify the formation ages for the Feiqizhai and Yuexi plutons remains a topic of controversy. We choose the Yuexi and Feiqizhai plutons as the study object, and carried out LA-ICPMS zircon U-Pb dating. The high Th/U ratios and typical magmatic oscillatory zoning of zircons indicate their magmatic origin. The 206Pb/238U weighted average age of 26 analyses for the Yuexi pluton is (128.5±1.4) Ma, the 206Pb/238U weighted average age of 15 analyses for the Feiqizhai pluton is (127.4±1.7) Ma. These results indicate that both Yuexi and Feiqizhai plutons are formed in early Cretaceous. Based on high precision geochronology data of magmatic rocks in the Dabie orogen, the intrusive rocks can be categorized into two stages:the early stage (143~130 Ma) rocks exhibit the characteristics of high-K calc-alkaline series and show adakitic affinity, whereas the late stage (130~119 Ma) rocks show the characteristics of alkaline rocks with occurrence of small amount of A-type granite at~120 Ma. This may suggest that 130 Ma is an important period for deep process transformation in the Dabie orogen.
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