阿尔金断裂剪切过程中定向生长锆石的发现及其意义——来自于显微构造和锆石内部矿物包裹体的证据  

Discovery of oriented zircon growing in the shear process of the Altun(Altyn)fault and its significance:Evidence from microstructure and mineral inclusions in zircon

作　　者：李海兵[1] 杨经绥[1] 吴才来[1] 宋述光 刘福来[1] 史仁灯[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《地质通报》2002年第6期298-303,共6页Geological Bulletin of China

基　　金：国家重点基础研究发展规划项目(编号:G1998040800);中法"阿尔金山-祁连山构造演化及岩石圈剪切作用"合作项目资助。

摘　　要：阿尔金断裂带中段出露一套走滑过程中形成的花岗质和角闪质糜棱岩。从糜棱岩中分选出3种类型的锆石:岩浆成因的长柱状锆石、柱状锆石和变质成因的次浑圆状锆石。这3种锆石的显微结构和构造特征以及它们内部的矿物包裹体均有所区别。其中长柱状锆石在岩石中定向排列,晶体长轴方向与拉伸线理方向一致,并且内部的所有矿物包裹体的长轴方向均与锆石的长轴方向平行,即与拉伸线理方向平行;拉曼研究表明包裹体矿物具熔融相特征;阴极发光图像中反映出这种锆石具有相对均一的内部结构。因此,该长柱状锆石是在韧性剪切过程中部分熔融环境下快速定向生长的,不仅代表了走滑剪切过程中的剪切应变方向,而且其生长年龄代表了走滑剪切的时代。A suite of granitic and amphibolitic mylonite formed in the process of strike-slip shear is ex-posed in the central segment of the Altun(Al tyn)fault belt.Three types of zircon are identified from the mylonite:long-prismatic zircon,prismatic zircon of magmatic origin and subrounded zircon of metamor-phic zircon.The three types of zircon are more or less different in respect to their microstructural features and mineral inclusions therein.Of these types,long-prismatic zircon grains are oriented in the rock,with their long axis oriented in the same direction as the stretching lineation and the long axes of all the miner-al inclusions therein being parallel to that of the zircon,i.e.to the direction of stretching lineation.Raman spectrum study indicates that the inclusion minerals show the melting phase feature,and cathodolumines-cence images show that this type of zircon has a relatively homogeneous internal structure.Therefore,the long-prismatic zircon resulted from rapid oriented growth in a partial melting regime in the ductile shear process.It not only denotes the direction of shear strain in the strike-slip shear,but the growth age(crys-tallization age)of this type of zircon denotes the age of strike-slip shear.

关 键 词：走滑剪切 糜棱岩 定向生长锆石 矿物包裹体 阿尔金断裂 

分 类 号：P542.3[天文地球—构造地质学]