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福建永泰云山破火山石帽山群第三旋回顶部的霏细流纹岩含有霓石、钠铁闪石等碱性铁镁矿物。化学成分富硅、富碱,碱性指数(AKI值)大于0.90,Rb、Th、Nb、Zr、Ga等元素的含量高,Ga/Al值大;贫钙、镁、铝和过渡族元素,轻、重稀土比值较小,并具有显著的负铕异常。在K_2O-Na_2O及以Ga/Al值为基础的多种判别图上均投影在A型花岗岩区。上述特征与其邻近的魁歧典型碱性花岗岩相似,也可与国外有关典型碱性流纹岩相对比,据此将该层流纹岩厘定为碱性流纹岩。这一流纹岩与魁歧碱性花岗岩均形成于拉张的构造环境,两者的Nd同位素组成十分接近,ε_(Nd)(t)值分别为—3.62～—4.29和—3.45～—5.21,显示它们具有相同的岩浆源区,均为壳幔混源岩浆作用的产物。
Fujian Yongtai Yunshan volcanic rock cap mountain group third spin top of the fine fine rhyolite contains aegirine, sodium iron iron ore and other alkaline iron magnesium mineral. The chemical composition is rich in silicon, rich in alkali and has an alkaline index (AKI value) of more than 0.90, high contents of elements such as Rb, Th, Nb, Zr and Ga and large Ga / Al values; Light and heavy rare earth ratio is small, and has a significant negative Eu anomaly. In the K 2 O-Na 2 O and Ga / Al values based on a variety of discriminant maps are projected in the A-type granite area. The above features are similar to those of Kuiqi typical alkaline granite in the adjacent area, and can also be compared with the typical alkaline rhyolites abroad. Therefore, the rhyolite of this layer is determined as basic rhyolite. The rhyolite and Quiqi basic granite are all formed in a tensioned tectonic setting. The Nd isotope compositions of the two are very close, the values of ε Nd Nd are -3.62 ~ -4.29 and -3.45 ~ -5.21 respectively, It shows that they have the same magmatic source area, which are the products of crust-mantle mixed source magmatism.