根据 TAS图解 ,北京市北部凤鸵梁 -四海地区东岭台组火山岩属于流纹岩 -粗面岩 -粗安岩组合。该套火山岩既不属于钾玄岩系列 ,也不是典型的高钾钙碱性系列或碱性橄榄玄武岩系列 ,在总体上应属于钾质碱性系列和富钾质拉斑系列相混合的过渡岩石组合。该套火山岩轻稀土元素明显富集。粗安岩类岩石没有负铕异常或负铕异常不明显 ,而流纹岩和粗面岩存在明显的负铕异常。凤鸵梁 -四海地区东岭台组酸性火山岩形成于造山晚期或后造山期初始阶段。 According to the TAS diagram, the Donglingtai volcanic rocks in the Fengli Beam - Sihai area in the northern part of Beijing belong to the rhyolite-rapithian-gabbro combination. The suite of volcanic rocks neither belong to the series of potash, nor the typical series of high-K calc-alkaline or basic olive basalt, but should generally be the transitional rock that is a mixture of potassic alkaline series and potassium-rich protractor series combination. The set of volcanic rocks of light rare earth elements significantly enriched. There are no negative europium anomalies or negative europium anomalies in the intrusive rocks, while there are obvious negative europium anomalies in rhyolite and trachyte. Fengliang Bei - The Ordovician volcanic rocks of the Donglingtai Formation in the four seas are formed in the early orogenic or post-orogenic stages.