内蒙古杜尔基构造混杂岩物质组成及构造属性研究  

Study of material composition and tectonic properties of the Duerji tectonic melange, Inner Mongolia

作　　者：金松[1,2] JIN Song(Geological Institute of China Chemical Geology and Mine Bureau,Beijing,100101;College of Resources,China HeBei GEO University,Shijiazhuang,050031)

机构地区：[1]中化地质矿山总局地质研究院,北京100101 [2]河北地质大学资源学院,石家庄050031

出　　处：《地质学报》2020年第8期2227-2242,共16页Acta Geologica Sinica

基　　金：中国地质调查局项目内蒙古1∶5万兴安敖包(L51E016004)、查干保好(L51E016005)、塔拉布拉克(L51E017004)、杜尔基(L51E017005)幅区域地质调查(编号DD20160048-14)资助成果。

摘　　要：杜尔基构造混杂岩是一套由"基质"和"岩块"构成的混杂堆积地质体。通过岩石学、岩石地球化学特征研究,查明其"基质"主要为一套强变形浅变质的海相碎屑岩,局部具有复理石沉积建造的特点,形成于活动大陆边缘构造环境;"岩块"岩石类型为辉石角闪岩、角闪石岩、玄武岩、辉绿岩、闪长岩,其中玄武岩、辉绿岩具有低Ti、高Mg和Al的特点,为一套富钠贫钾岩系,具有洋中脊和岛弧拉斑玄武岩的双重构造属性,形成于洋内初始俯冲背景下的弧前构造环境,属"外来岩块";闪长岩SiO2均值53.41%,MgO均值5.57%,Mg#均值51,FeO/MgO均值1.08,属镁闪长岩(MA),相比玄武岩、辉绿岩更加富集Ti、Ta、亏损Nb,形成于俯冲消减背景下活动大陆边缘构造环境,与基质大地构造环境基本一致,应属"原地岩块"。通过对杜尔基构造混杂岩的物质组成及其构造属性的研究,结合其各组成物质的同位素年龄信息、区域地质背景及区域构造演化史研究成果,认为杜尔基构造混杂岩可能反映了晚石炭世洋内俯冲-早二叠世洋陆俯冲-中二叠世洋盆关闭的过程。The Duerji tectonic melange is composed of "matrix" and "blocks". Based on petrological and geochemical studies, the "matrix" is considered to be a set of marine debris rocks formed in the tectonic environment of active continental margins. The "blocks" include pyroxene amphibolite, amphibolite, basalt, diabase, diorite. Basalt and diabase are Na-rich and K-poor rock system with low Ti, high Mg and Al. They have the dual tectonic properties of MORB and IAT, and are allochthonous blocks that formed in the tectonic forearc when the ocean began to initially subduct. Diorite is the Mg diorite(MA) which has the characteristic of SiO2(53.41%), MgO(5.57%), Mg#(51), FeO/MgO(1.08). Compared with basalt and anthracite, diorite has the characteristic of high Ti, Ta and low Nb, and is an autochthonous block formed in the tectonic environment of active continental margins with subduction. The conclusion of the study on the material composition and tectonic properties of the Duerji tectonic melange is that it may reflect the process of late Carboniferous Ocean Subduction-Early Permian Ocean Land Subduction-MiddlePermianoceanBasin Closing.

关 键 词：构造混杂岩 基质 岩块 镁闪长岩 俯冲作用 杜尔基 

分 类 号：P587[天文地球—岩石学]