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分布于华北陆块南部的熊耳群火山岩由玄武质到流纹质火山岩组成,并以玄武安山岩、安山岩为主,次为英安-流纹岩,SiO2=62％±的岩石较少,显示双峰特点。中基性熔岩的主要造岩矿物是辉石和斜长石,没有角闪石和黑云母,表明熊耳群火山岩形成于相对无水的环境。岩石地球化学上的显著特点是,富K2O、FeO,低Al2O3、MgO、CaO;富含大离子亲石元素(LILE,如K、Rb、Ba)和轻稀土元素(LREE),相对亏损高场强元素(HFSE,Nb、Ta、Ti),表现出岛弧型火山岩的地球化学亲合性。文中详细的岩石地球化学证据表明,熊耳群火山岩具有岛弧型地球化学特征的主要原因是其地幔源区遭受俯冲带组分的改造,而岩浆在上升到地表的过程中混染地壳物质是次要的。基于熊耳群及下伏结晶基底的地质学和地球化学特征,表明熊耳群形成于夭折的三叉裂谷环境,推断俯冲带组分的改造和富集事件发生在华北陆块南部古元古代大陆壳的形成和 拼贴过程中,由于洋壳和地壳物质再循环到上地幔中,使陆下岩石圈地幔源区富集LILE、LREE并亏损HFSE。熊耳期岩浆作用正是源于这样的保留有早期俯冲带组分改造特征的陆下岩石圈富集地幔。
The Xiong’er Group volcanic rocks distributed in the southern part of the North China terrane consist of basaltic to rhyolitic volcanic rocks. Basalt andesite and andesite are the main types, and the second is Yingan-rhyolite. There are few rocks with SiO2 = 62% ±, Peak characteristics. The main rock-forming minerals of the mafic lava are pyroxene and plagioclase, with no amphibole and biotite, indicating that the Xionger volcanic rocks are formed in a relatively anhydrous environment. The petrogeochemical characteristics of rocks are rich in K2O, FeO, low Al2O3, MgO, CaO and rich in LILE such as K, Rb, Ba and LREE, Strong elements (HFSE, Nb, Ta, Ti) show the geochemical affinity of island-arc volcanic rocks. The detailed geochemical evidence in this paper shows that the main reason for the Xiong’er Group volcanic rocks having island arc geochemical characteristics is that the mantle source area is subject to subduction zone component transformation. The magma mixed up with crustal material in the process of rising to the surface need. Based on the geology and geochemistry of the Xiong’er Group and the underlying crystalline basement, it shows that the Xiong’er Group formed in an aborted trigeminal rift environment, and the remodeling and enrichment events of the subduction zone components were inferred to occur in the Paleoproterozoic continental crust During the formation and collage process, the oceanic crust and crustal materials are recycled into the upper mantle, enriching LILE and LREE and depleting HFSE in the mantle source area of the submarine lithosphere. The ear-ear period magmatism is precisely due to such a submarine lithosphere-enriched mantle that retains the characteristics of early subduction zone remodeling.