新疆东天山秋格明塔什—黄山韧性剪切带^(40)Ar/^(39)Ar年代学研究  

^(40)Ar/^(39)Ar Geochronology of the Qiugemingtashi—Huangshan Ductile Shear Zone in East Tianshan,Xinjiang,NW China

作　　者：陈文 孙枢[2] 张彦[1] 肖文交[2] 王义天[3] 王清利[1] 姜立丰 杨俊涛 

机构地区：[1]国土资源部同位素地质重点实验室 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国地质科学院矿产资源研究所,北京100037 [4]新疆地质矿产局第一地质大队,新疆昌吉832111

出　　处：《地质学报》2005年第6期790-804,共15页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划项目(编号2001CB409807);国家自然科学基金项目(编号49973003);国土资源大调查项目(编号2000020190118)资助的成果。

摘　　要：秋格明塔什—黄山巨型韧性剪切带产出在东天山北部,其活动时期的系统厘定对东天山大地构造演化极为关键,因而对揭示中亚造山带南部晚期的历史有着重要意义。系统的Ar-Ar同位素年代学研究表明,该剪切带的活动在时间上具有多期性:剪切带早期为挤压推覆剪切作用,发生于300Ma之后,至少延续到了283.7Ma,但在280.2Ma时已经终止;晚期为右行走滑剪切变形作用,主活动期的时代为262.9～242.8Ma,历时近20Ma。在右行走滑剪切变形阶段,秋格明塔什—黄山韧性剪切带出现差异抬升现象,导致剪切带不同区段糜棱岩的同位素年龄有较大差别:剪切带中—西段(康古尔地区)走滑剪切变形作用产生的糜棱岩的时代为262.9～256.1Ma,快速抬升发生在262.9～261.5Ma,冷却速率>100℃/Ma。剪切带东段(土屋—延东地区)走滑剪切变形作用产生的糜棱岩的时代为247.1～242.8Ma,快速抬升发生在247.1～246.9Ma期间,冷却速率>200℃/Ma。结合区域地质资料,笔者认为早期的挤压推覆剪切作用可能与东天山晚古生代板块俯冲—碰撞过程有关,而晚期的走滑剪切变形则可能反映了东天山北部地区碰撞后陆内变形特征。The Qiugemingtashi--Huangshan ductile shear zone in the east Tianshan Mountains is located between the Tuha basin and the ridge of the middle Tianshan Mountains with a length of 600 km from Xiao Requanzi in the west to Huangshan Mountain in the east and a width of 20-40 km from south to north. The study of ^40Ar/^39Ar isotope chronology reveals that the activity of Qiugemingtashi--Huangshan ductile shear zone shows different features in different periods of time. In the early stage, the shear zone was characterized by nappe shearing, starting later than 300 Ma and lasting at least to 283.7 Ma. However, it can be sure that the activity ended at 280.2 Ma. In the late stage, it was characterized by strike-slip shear deformation, occurring mainly during 262.9--242.8 Ma and lasting 20 Ma. During the strike-slip shear deformation, lifting of different areas in the Qiugemingtashi--Huangshan ductile shear zone was not in the same time, resulting in different isotope ages of mylonites from different areas in this ductile shear zone. In the middle--western shear zone （Kanggur area）, the age of mylonites from the shear deformation is 262.9-256.1 Ma and the time of rapid lifting is 261.5~262.9 Ma, with a cooling rate over 100℃/Ma. In the east part of the zone （Tuwu--Yandong area）, the age of mylonites is 247.1-242.8 Ma and the time of rapid lifting is 247.1-246.9 Ma, with a cooling rate over 200℃/Ma. Because the metallic deposits in the east Tianshan region are mostly located in this shear zone, the above results not only deepen the study on the tectonic history of the east Tianshan Mountains, hut also provide new age evidence for further understanding the control of the shear deformation on mineralization.

关 键 词：AR-AR年龄 变形时代 韧性剪切带 东天山 

分 类 号：P597.3[天文地球—地球化学]