东天山花岗岩与造山带演化

Granites and evolution of orogenic belt in Eastern Tianshan moutain

文章通过建立花岗岩类类型与地球动力学之间的联系,试图利用分类清楚、测年准确的花岗岩解决本区地壳及造山带演化过程。根据K2O等地壳成熟度的指标,得出了该地区地壳性质由不成熟→半成熟岛弧→成熟陆壳演变;构造环境由不成熟岛弧→成熟的"大陆化"岛弧→大陆碰撞带演化。总结了东天山地区经历了三大地壳演化时期,分别为前寒武纪基底演化阶段陆核及超大陆形成期;古生代古亚洲洋形成演化期和中生代特提斯―印欧板块碰撞阶段板内演化期。反演出了东天山造山带经历了俯冲汇聚及不成熟陆壳形成阶段→弧―陆碰撞及半成熟陆壳形成阶段→碰撞造山及成熟陆壳形成阶段→陆内造山及陆壳改造阶段→中生代板内演化阶段。

Based on the link between types of granites and geodynamics established in this paper,the author attempts to understand the evolution process of crust and orogenic belt in this area by utilizing clearly classi-fied and accurately dated granites.According to K2 O and other indexes of the degree of crustal maturity,it i-dentified that the development of crust is from immaturity to half-mature island arc to mature continental crust.The development of tectonic environment is from immature island arc to mature “continentized”island arc to continental collision zone.It is concluded in this paper that Eastern Tianshan moutain area experiences three major crustal evolution periods which are formation period of continental nucleus and supercontinent in Precambrian basement evolution stage,formation and evolution period of Paleo-Asian Ocean in Palaeozoic Era as well as intraplate evolution period of Tethys-Indo-European plate collision stage in Mesozoic Era.It is also reconstructed that the Eastern Tianshan moutain orogenic belt undergoes a process which in sequential order consists of a period of subduction and convergence as well as formation of immature continental crust, a period of arc-continent collision and formation of half-mature continental crust,a period of collision orogen-esis and formation of mature continental crust,a period of intracontinental orogenesis and reconstruction of continental crust,as well as a period of introplate evolution in Mesozoic Era.