辽北法库变质杂岩的组成、变形与变质特点及构造属性

The deformation and metamorphic features of Faku metamorphic complex the composition and tectonic affinity in the northern Liaoning Province

辽北法库变质杂岩的形成时代、大地构造属性及其与长春-延吉缝合带的形成过程一直以来都是众多地质学者关注的重要科学问题。本文试图通过U-Pb年代学以及物质组成分析、变形变质作用特点分析和区域对比的方法来建立法库变质杂岩的时空格架,大地构造归属及区域构造演化。通过详细的野外工作和镜下分析得到法库变质杂岩存在至少两期变形作用特点及角闪岩相-高绿片岩相至低绿片岩相的变质作用特点。通过对杂岩体中不同类型变质岩的锆石SHRIMP U-Pb年代学研究得到中志留世糜棱岩化黑云母花岗闪长岩原岩年龄为433±3Ma;晚志留世绢云长英质糜棱岩原岩年龄为423±5Ma;早二叠世绢云绿泥方解斜长糜棱岩原岩年龄为292±2Ma;早三叠世长英质糜棱岩原岩年龄为250±3Ma。通过区域对比,笔者认为法库变质杂岩为索伦-西拉木伦缝合带东延的一部分是长春-延吉缝合带的重要组成,其形成演化具有复合型造山的特点,具有复杂的构造演化史。

The age and tectonic affinity of Faku metamorphic complex in the northern Liaoning Province and Changchun-Yanji suture zone their forming process always is a significant scientific problem of many geologists focused.This paper tried to use U-Pb chronology,analysis of material composition,analysis of the deformation and metamorphic features and the approach of regional correlation to establish the time and space framework,the tectonic affinity and regional structure evolution of Faku metamorphic complex.Through detailed field work and microscopic analysis,we found that Faku metamorphic complex had at least two stage deformation effect features and the metamorphic effect features of amphibolites facies to high greenschist facies and low greenschist facies.Through zircon SHRIMP U-Pb dating research of different types of metamorphic rocks in the complex we obtained Middle Silurian mylonitize biotite granodiorite which protolith age was 433±3Ma,Late Silurian epoch sericite felsic mylonite which protolith age was 423±5Ma,Early Permian epoch sericite chlorite calcite plagioclase mylonite which protolith age was 292±2Ma and Early Triassic epoch felsic mylonite which protolith age was 250±3Ma.Using the way of regional comparison the writer believed that Faku metamorphic complex was an eastern extension of Solonker-Xar Moron suture zone,which Faku metamorphic complex was also an important constitute of Chang-Yanji suture zone.The formation and evolution of Faku metamorphic complex had composite type orogenic features,which Faku metamorphic complex possessed an complicated tectonic evolution history.