华北板块北缘东段分布的构造混杂岩带为研究古亚洲洋的演化提供了重要的依据,下二台岩群作为该构造混杂岩带的重要组成部分,其形成时代和构造属性仍存在争议。详细的研究表明下二台地区变质火山岩原岩包括流纹岩、英安岩、安山岩,为一套钙碱性火山岩,属于准铝质-弱过铝质岩石,根据岩相学和地球化学特征将其分为变质酸性火山岩和变质中性火山岩;二者均相对富集轻稀土元素,亏损重稀土元素,轻重稀土元素分馏明显,Eu负异常不明显,但变质中性火山岩稀土总量低于变质酸性火山岩,变质酸性火山岩明显亏损Sr、P元素,结合野外产出面积和高场强元素相关性特征,认为二者不是同一基性岩浆分异的产物。变质火山岩锆石LA-ICP-MS U-Pb年龄为341~348Ma,代表其原岩结晶年龄。变质酸性火山岩原始岩浆来自于地壳物质的部分熔融,变质中性火山岩原始岩浆来自于俯冲带附近岩石圈地幔,并遭受了地壳物质的混染,二者均形成于活动大陆边缘火山弧环境。最新研究成果表明下二台岩群由不同时代、不同构造环境下形成的地质单元叠置混杂而成,称其为下二台构造杂岩更为准确。下二台地区变质火山岩表明在早石炭世初,古亚洲洋板块已经南向俯冲,在华北板块北缘形成活动大陆边缘弧环境,早石炭世变质火山岩原岩为这一俯冲阶段的产物。;The tectonic mélange belt distributed in the eastern segment of the northern margin of the North China Block provides an important evidence for studying the evolution of the Paleo-Asian Ocean. The Xia’ertai Group is located in this belt, its formative age and tectonic properties have also been controversial. The detailed research indicates that the protolith of meta-volcanic rocks in the Xia’ertai area includes rhyolite, dacite and andesite, they are calc-alkaline series and metaluminous-weak peraluminous rocks. The meta-volcanic rocks in the Xia’ertai area can be divided into metamorphic acid volcanic rocks and metamorphic intermediate volcanic rocks according to the petrography and trace element characteristics. The trace elements of them all show that LREEs are relatively enriched, while HREEs are relatively deficient and obvious REEs fractionation, meanwhile, negative Eu anomalies is not obvious, but the total amount of REEs in metamorphic intermediate volcanic rocks is lower than that in metamorphic acidic volcanic rocks, and the metamorphic acid volcanic rocks are depleted in Sr and P, combined with the distribution area and the correlation of HSFEs, we believe that they are not the product of the same basic magma differentiation. The zircon LA-ICP-MS U-Pb ages of the meta-volcanic rocks are 341~348Ma, represents the crystallization age of their protolith. The primordial magma of the metamorphic acidic volcanic rocks came from partial melting of material in the crust, but the primordial magma of the metamorphic intermediate volcanic rocks was originated from the lithospheric mantle near the subduction zone with the mixing of crustal materials, meanwhile, they were all formed in the volcanic arc environment of an active continental margin. The material composition of the Xia’ertai Group is characterized by different times and different tectonic backgrounds, we suggest to the Xia’ertai Group as a tectonic complex. The meta-volcanic rocks in the Xia’ertai area indicate that the Paleo-Asian Ocean was subducted southward no later than the early Early Carboniferous, the active continental marginal arc environment was formed at the northern margin of the North China Block, and the protolith of meta-volcanic rocks in the Xia’ertai area were the products of this subduction stage.