准噶尔北部蛇绿岩形成时限新证据及其东、西准噶尔蛇绿岩的对比研究

New constraints on formation ages of ophiolites in northern Junggar and comparative study on their connection

准噶尔北部出露有塔尔巴哈台库吉拜蛇绿岩、洪古勒楞-和布克赛尔蛇绿岩及扎河坝-阿尔曼太蛇绿岩。洪古勒楞蛇绿岩中的堆晶辉长岩样品进行SHRIMP U-Pb定年,结果为472±8.4Ma(MSWD=1.4),限定洪古勒楞-和布克赛尔蛇绿岩形成于早奥陶世。对扎河坝蛇绿岩中斜长花岗岩采用SHRIMP U-Pb方法测定年龄为495.9±5.5Ma(MSWD=2.7),证实扎河坝蛇绿岩形成于晚寒武世-早奥陶世。塔尔巴哈台蛇绿岩、和布克赛尔-洪古勒楞蛇绿岩以及扎河坝-阿尔曼太蛇绿岩均在早奥陶世已经形成,大部分以断层侵位的形式侵位于泥盆纪-石炭系火山-沉积地层中。准噶尔北部东西三段蛇绿岩在形成时代、区域地质以及地球物理特征等方面具有可对比性,认为它们构成一条贯穿东、西准噶尔的蛇绿岩带,这为新疆北部及邻区古生代构造格局的重建以及区域构造的对比连接提供了重要信息。

There exist Kujibai ophiolite in Taerbahatai,Hongguleleng-Hebukesaier ophiolite and Zhaheba-Aermantai ophiolite in northern Junggar.The SHRIMP zircon U-Pb dating of cumulate gabbro in Hongguleleng ophiolite is 472±8.4Ma(MSWD = 1.4) and the zircon U-Pb age of plagioclase granite in Zhaheba ophiolite is 495.9±5.5Ma(MSWD =2.7).Taerbahatai ophiolite, Hongguleleng-Hebukesaier ophiolite and Zhaheba-Aermantai ophiolite had been formed before Early Ordovician and mostly emplaced in Devonian-Carboniferous volcanic sedimentary strata along faults.A comparative study on formation age,regional geology and geophysical characteristics of these three segments of ophiolites in northern Junggar indicates that they are correlated as a unique ophiolite belt passing through from east to west in northern Junggar.This study is significant for the reconstruction of Paleozoic tectonic framework and regional tectonic evolution.