摘要
熊耳群火山岩系以熔岩为主,其岩石学、岩石化学及地球化学特征表明为双模式火山岩套:下、上熊耳群的主要岩石类型为钾细碧岩及细碧岩、钾角斑岩及角斑岩,属碱性玄武岩浆系列,其源岩浆来自地幔,在上升过程中曾在中间岩浆房停顿并与壳层物质混染。中熊耳群的主要岩石类型为钾石英角斑岩,属拉斑玄武岩浆系列,岩浆来源于下地壳的熔融。火山岩系的岩石地球化学特征及区域分布特征表明熊耳群火山岩系产于活动大陆边缘裂谷带,豫西-陕西这一裂谷带从下熊耳群至上熊耳群火山活动从北向南移动,从东向西扩展,上熊耳群形成时裂谷深度最大,东西范围也最广。中熊耳群形成时期裂谷带为相对闭合阶段,壳层熔融物质上升喷发。
The volcanic series of Xlonger Group, located in the common boundary area of three provinces:Henan, Shaanxi and Shanxi, is distributed in the southern margin of north China plate and formed in Middle Proterozoic Era. The major minerals of these volcanic rocks are albite(An<8), alkali-feldspar, chlorite, biotite, clinopyroxene, epidote et al. and they belong to spilite-keratophyre. The characteristic of petrography, chemical composition and trace elements of volcanic rocks show that the volcanic series of Xionger Group is a bimodal volcanic suite. The main rock types in Lower and Upper Xionger Group are potassium spilite, spilite, potassium keratophyre and keratophyre and they belong to alkali-basaltic magma series. The initial magma was formed by partial melting of the upper mantle. In the course of ascending the magma stagnated in an intermediate magma chamber and was contaminated by the crustal materials. The main rock type of Middle Xionger Group is potassium quartz-keratophyre and belongs to tholeiitic magma series. The magma was derived from the fusion of lower crustal materials. The volcanism of Xionger Group occurred in a rift zone in margin of mobile continent. From Lower to Upper Xionger Group the volcanic activity transfered from north to south and developed from east to west. During Upper Xionger Group the rift zone was deepest and the rang of east-west was broadest. During Middle Xionger Group the rift zone relatively dosed and the magma which was generated by the fusion of lower crustal materials then ascended and erupted.
