中天山东段澄江期片麻状花岗岩特征和成因——以天湖东岩体为例  

Characteristics and genesis of the Chengjiangian gneissic granites in the east section of the Middle Tianshan Mountain areas:Taking the Tianhudong granite as an example

作　　者：张遵忠[1] 顾连兴[1] 杨浩[1] 吴昌志[1] 王银喜[1] 闵茂中[1] 

机构地区：[1]内生金属矿床成矿机制国家重点实验室(南京大学)南京大学地球科学系,南京210093

出　　处：《岩石学报》2004年第3期595-608,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(编号:2001 CB409802)成果

摘　　要：本文以天湖东岩体为例,探讨中天山澄江期片麻状花岗岩的特征及其形成机制。岩相学、岩石化学、稀土元素、微量元素和同位素研究表明,天湖东岩体是岛弧钙碱性火山—沉积岩系经原地改造的产物,其Rb-Sr等时线年龄为707.7±4.9Ma。花岗岩形成作用的动力、热力来源可能与向塔里木大陆俯冲的天山岩石圈的拆沉有关。在造山过程晚期-期后的挤压向拉张转变过程中,拆沉导致的底侵和内侵引发了地壳岩石的脱水和熔融,所产生的熔体-流体上升并将较浅层次的变质岩改造为片麻状花岗岩。变质峰期以后形成的韧性剪切带为熔体-流体的运移提供了通道。Taking the Tianhudong granite as an example, this paper investigates characteristics and genesis of the Chengjiangian gneissic granites in the Middle Tianshan Mountain areas. Studies in petrography, petrochemistry, rare earth elements, trace elements and isotopes indicate that the Tianhudong granite, with a Rb-Sr isochron age of 707.7 +/- 4.9 Ma, was formed by essentially in situ transformation of metamorphosed island arc calc-alkaline volcanic-sedimentary rocks. Dynamics and heat might have been derived by delamination of the Tianshan lithosphere which had subducted beneath the Tarim continent. In the course of tectonic conversion from compression to extension at late- or post-orogenic stage, underplating and intraplating induced by delamination triggered dewatering and partial melting of crustal rocks. The resultant melts and fluids ascent and transformed the metamorphic rocks at higher levels into gneissic granites. Ductile shear zones that were formed after peak metamorphism might have provided pathways for upward transport of melts and fluids.

关 键 词：片麻状花岗岩 底侵 内侵 韧性剪切 天湖东 天山 新疆 

分 类 号：P588.121[天文地球—岩石学]