辽西兴城地区新太古代花岗质杂岩特征与成因

Characteristics and genesis of Neoarchean granitic complex in Xingcheng of western Liaoning

辽西兴城台里地区新太古代花岗质杂岩主要分为黑云长石片麻岩和花岗闪长质片麻岩两类,是华北克拉通新太古代花岗质地壳的重要组成部分。花岗闪长质片麻岩类均为"模糊的"渐变过渡,没有侵入体的一般特点,与黑云长石片麻岩类相互混杂伴生,显示协调的变形或过渡关系。显微组构研究发现两类片麻岩均可分为两种不同的结构相类型:原生结构相及新生结构相。从黑云长石片麻岩类到花岗闪长质片麻岩类具有新生结构相逐渐增多、原生结构相逐渐减少的变化规律。在常量元素上,两类片麻岩SiO2与MnO、CaO、TiO2、Fe2O3、MgO的变化特征具有线性分布的趋势;在微量及稀土元素含量变化特征上,两类片麻岩具有相似的特点。花岗闪长质片麻岩类在成因上属于深熔型花岗岩,其源岩可能为一套副变质的硬砂岩。

Neoarchean granitic complex in Taili area of Xingcheng in western Liaoning,was an important part of Neoarchean granitic crust in North China craton,and divided into two types： the biotite-feldspar gneiss and granodioritic gneiss.All granodioritic gneiss was ＂fuzzy＂ in gradual transition without general characteristic of intrusive body.Granodioritic gneiss and biotite-feldspar gneiss mixed with eath other,indicating coordinated deformation or transitional relationship.Micro fabric research showed that the two types of gneiss can be divided into two different types of structural phase for each：native structure phase and neonatal structure phase.The content of neonatal structure phase was increasing and the native structure phase was decreasing gradually from biotite-feldspar gneiss to granodioritic gneiss.In major elements,the two types of gneiss had linear distribution trend in SiO2 with MnO,CaO,TiO2,Fe2O3 and MgO with similar characteristics in trace and rare earth elements.The granodioritic gneiss belongs to anatectic granite in genesis,and their source rocks might be a metamorphosed greywacke.