【摘要】 浙江神仙居濒临西太平洋火山岩带,晚中生代构造—岩浆活动频繁,堆积了巨厚的火山沉积地层,是研究晚中生代大陆边缘形成演化动力学过程的重要窗口之一。区内主体为一套流纹质熔结凝灰岩,岩石SiO₂含量为74.17%⁷8.38%,Al₂O₃含量为11.16%¹3.14%,全碱（K₂O+Na₂O）含量为6.44%⁸.76%,属高钾钙碱性系列;稀土总量（ΣREE）介于144.5×10^-6247.1×10^-6之间,ΣLREE/ΣHREE=5.58⁶.81,LaN/YbN=5.17⁸.59,δEu为0.17⁰.23,弱富集K、Rb,亏损Ba、Sr等大离子亲石元素,相对富集U、Th,亏损Nb、Ta、Ti等高场强元素。LA-ICP-MS锆石U-Pb定年表明,神仙居流纹质熔结凝灰岩同位素年龄集中于（113.4±1.4）Ma^114.4±1.5Ma,是早白垩世晚期区域伸展拉张的构造背景下玄武质岩浆底侵作用诱发的地壳部分熔融的产物,层位归属小平田组。更多还原

【Abstract】 Thick rhyolitic volcanic-sedimentary rocks in the Shenxianju area of Zhejiang Province are an important component to understand the evolution of the active Mesozoic continental margin of eastern China. Geochemical analysis indicates that the rhyolitic volcanic rocks have SiO₂ contents ranging from 74.17% to 78.38%, whereas the total alkali range from 6.44% to 8.76%, and Al₂O₃ from 11.16% to 13.14%, suggesting that they are high-K calc-alkalic rocks. The rhyolitic volcanic rocks are rich in K, Rb, Th, U, and relatively depleted in Sr, Ba, Nb, Ta, Ti. The total REE contents are relatively low(ΣREE =144.5×10^-6-247.1×10^-6), and the rocks show obvious LREE and HREE fractionation（ΣLREE/ΣHREE=5.58-6.81, LaN/YbN=5.17-8.59） and moderately negative Eu anomalies（δEu= 0.17-0.62）. Zircon LA-ICP-MS U-Pb dating results show that the rhyolitic volcanic rocks are 114.4±1.5 Ma to 113.4±1.4 Ma in age, and they were derived from felsic magmas generated from partial melting of crust materials with underplating of mantle-derived basaltic magma in late Early Cretaceous. These rocks belong to the Xiaopingtian Formation.更多还原