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永泰云山早白垩世石帽山群第Ⅰ、Ⅱ旋回岩石组合由沉积岩、基性熔岩、酸性火山岩构成，缺乏中性成分的岩石单元，为典型的双峰式岩石组合。其玄武岩富碱（尤其富钾）、富铝、富铁，贫镁，富轻稀土元素和大离子亲石元素，贫高场强元素及亲铁元素，并具偏高的ＩＳｒ值和显著偏低的εＮｄ（Ｔ）值［ＩＳｒ＝０．７０６８２～０．７０７７０，εＮｄ（Ｔ）＝－７．４２～－３．２２］。流纹质岩石总体具富碱、富硅、富铝，贫钙、贫镁特征，其Ｒｂ、Ｔｈ等元素的含量较高，而Ｂａ、Ｓｒ、Ｔｉ、Ｐ等元素含量则明显偏低，并具显著的铕负异常（δＥｕ＝０．１６～０．４４），岩石的εＮｄ（Ｔ）值变化于－５．９３～－２．２２。Ⅰ、Ⅱ旋回玄武岩和流纹岩在地球化学特征上均具明显变异。根据对火山岩地球化学特征的综合分析表明，玄武岩主要为幔源岩浆与下部地壳岩石相互作用的产物，而流纹岩则为玄武岩浆与上部地壳物质进行热及成分交换的结果，不同旋回的玄武岩和流纹岩有不同的源区，为多次脉动分层部分熔融的产物。
The volcanic units I and II of the Early Cretaceous Shiamishan Group in the Yongtaiyu area are composed of sedimentary rocks, basic lavas and acidic volcanic rocks. The rock units lacking neutral compositions are typical bimodal rock assemblages. The basalts are rich in alkali (especially potassium), rich in aluminum, rich in iron, poor in magnesium, rich in light rare earth elements and large ion lithophile elements, poor in high field strength elements and pro-iron elements, and have high ISr values and significant Low εNd (T) values [ISr = 0.70682 ~ 0.70770, εNd (T) = -7.42 ~ -3.22]. Rhyolitic rocks are generally rich in alkali, silicon-rich, aluminum-rich, poorly-calcined and poorly-depleted, with higher contents of elements such as Rb and Th, while elements such as Ba, Sr, Ti and P are significantly lower With a significant negative Eu anomaly (δEu = 0.16 ~ 0.44), the εNd (T) value of rocks varied from -5.93 to -2.22. The basalts Ⅰ, Ⅱ and the rhyolites have obvious variation in the geochemical characteristics. Based on a comprehensive analysis of the geochemical characteristics of volcanic rocks, basalt is mainly a product of the interaction between mantle magma and lower crustal rocks, whereas rhyolite is the result of thermal and compositional exchange between basaltic magma and the upper crustal material. Different cycles of basalts And rhyolite have different source areas, for multiple pulsation stratified partial melting of the product.