中文摘要：

北大别岳西地区广泛分布燕山期侵入岩和火山岩。14个岩浆岩样品中锆石LA-ICP-MS U-Pb定年结果显示，这些岩浆岩形成于134~125 Ma之间。以130 Ma为界，岩浆岩可以分为两个期次：早期以石英闪长岩—石英二长闪长岩—似斑状二长花岗岩组合为主；晚期以二长花岗岩—钾长花岗岩组合及脉岩为主。早期岩浆岩含有古元古代（1900~2120 Ma）、新元古代（670~800 Ma）和三叠纪继承锆石；晚期岩浆岩中缺少古元古代继承锆石，以新元古代、三叠纪及140~160 Ma时期的继承锆石为主。高Sr低Y地球化学特征仅出现在早期岩浆岩中，结合继承锆石的年龄特征，表明早期岩浆岩物质来源于加厚的基性下地壳，下地壳的拆沉和岩石圈的减薄发生在约130 Ma；而晚期岩浆岩为以新元古代年龄的中—下地壳在减薄后的环境下发生深熔作用形成。

英文摘要：

Mesozoic intrusive rocks and volcanic rocks are widely distributed in Yuexi area, North Dabie orogenic belt. Zircon U Pb dating were carried out using LA ICP MS method for fourteen samples, resulting a forming age of 134~125 Ma. These rocks can be divided into two stages by 130 Ma. The first stage magmatic rocks （〉 130 Ma） mainly consist of quartz diorite, quartz monzodiorite and porphyritic monzogranites; while the second stage ones （〈 130 Ma） are mostly monzogranites, K feldspar granites and dyke rocks. The inherited zircons ages in the first stage rocks are made up of Middle Paleoproterozoic （1900~2120 Ma）, Neoproterozoic （670~800 Ma）, and Triassic; while the second stage rocks are short of inherited zircons of Middle Paleoproterozoic, and have an inherited zircon age composition of Neoproterozoic, Triassic and 140~160 Ma. Combined the inherited zircon ages composition with the character that magmatic rocks with geochemical features of high Sr, low Y occur only at the early stage, we conclude that the early stage rocks were originated from thickened lower crust, and delamination of the lower crust and thinning of lithosphere happened at ~130 Ma; while the late stage rocks results from anatexis of middle to lower crust aged of Neoproterozoic at an after thinning background.