红柳峡韧性剪切带形成时代及其对准噶尔洋盆闭合时限的约束  

Geochronology of the Hongliuxia ductile shear zone and its constraint on the closure time of the Junggar Ocean

作　　者：吴琪[1,2] 屈迅[3] 常国虎[1,2] 张永[4] 董连慧[3] 徐兴旺[1] 

机构地区：[1]中国科学院矿产资源研究重点实验室 中国科学院地质与地球物理研究所,北京100029 [2]中国科学院研究生院,北京100049 [3]新疆维吾尔自治区地质矿产勘查开发局,乌鲁木齐830000 [4]中国地质调查局天津地质矿产研究所,天津300170

出　　处：《岩石学报》2012年第8期2331-2339,共9页Acta Petrologica Sinica

基　　金：“十二五”国家科技支撑计划项目专题(2011BAB06B03-3);中国科学院知识创新工程主要方向项目(KZCX-EW-LY03);国家自然科学基金项目(41072060)联合资助

摘　　要：东准噶尔卡拉麦里蛇绿岩带是新疆一条重要的蛇绿岩带,地质学家对其所代表的准噶尔洋的闭合时限一直存在不同看法。我们在开展东准噶尔区域构造研究的过程中,发现红柳峡地区近东西向的片理带为韧性剪切带、且截切卡拉麦里蛇绿岩带。宏微观构造特征显示其为右旋韧性剪切带,形成于野马泉弧与准噶尔地块的碰撞过程。对韧性剪切带中的博尔羌吉糜棱岩化花岗岩和花岗质超糜棱岩开展了锆石SIMSU-Pb定年研究,结果显示糜棱岩化花岗岩锆石的谐和年龄为348.1±2.8Ma、206Pb/238U年龄的权平均年龄为348.2±2.7Ma,花岗质超糜棱岩锆石谐和年龄为343.2±2.6Ma、206Pb/238U年龄的加权平均年龄为为343.5±2.6Ma。超糜棱岩中的锆石多为新生锆石,其年龄可代表韧性剪切带的形成时间,即该韧性剪切带形成于343.2Ma。这意味着以卡拉麦里蛇绿岩带为代表的准噶尔洋在343Ma前已关闭、东准噶尔地区在早石炭世末期已进入碰撞造山阶段。The Kalamaili ophiolitic belt in East Junggar is one of the important ophiolitic belts in Xinjiang, the closure time of Junggar Ocean represented by the Kalamaili ophiolitic belt is still argued and unclear. Recently, we discovered that the Hongliuxia EW-trending schistosity zone cut the Kalamaili ophiolite belt is a dextral ductile shear zone, which was formed in collision process between the Yemaquan arc and the Junggar block. The foliated granite and granitic uhramylonite in the ductile shear zone in the Boerqiangji area are selected for zircon SIMS U-Pb dating. New results show that the foliated granite has a concordia age of about 348.1 ±2. 8Ma with a 206Pb/238U weight average age of about 348. 2 ±2. 7Ma, and the granitic ultramylonite has a concordia age of 343.2 ± 2. 6Ma with a 206pb/238 U weight average age of about 343.5 ± 2. 6Ma. Zircons from the granitic ultramylonite axe new formed by metamorphic recrystallization; their ages may represent formation time of the ductile shear zone. This indicates that the Hongliuxia ductile shear zone was formed at about 343Ma BP, and that the Junggar ocean should be closed before 343Ma BP, and the East Junggar was involved in collisional orogen at the end of Early Carboniferous.

关 键 词：卡拉麦里蛇绿岩带 红柳峡韧性剪切带 准噶尔洋 锆石U-PB年龄 

分 类 号：P597.3[天文地球—地球化学]