新疆西准噶尔北部谢米斯台山南坡蛇绿岩带的发现及其意义

Discovery and its tectonic significance of the ophiolite in the south of Xiemisitai Mountain,West Junggar,Xinjiang

新疆西准噶尔和什托洛盖谷地以北,沿谢米斯台山南坡出露一套蛇绿混杂岩(查干陶勒盖蛇绿岩),岩石组合自下而上包括蛇纹石化橄榄岩、变质辉长岩、玄武岩、细碧岩及伴生的硅质岩、同源火山碎屑岩等,基质为蛇纹石化橄榄岩和绿片岩相变质玄武岩。蛇绿岩中辉长岩的LA-ICP-MS锆石U-Pb定年结果为517Ma±3Ma和519Ma±3Ma,代表了蛇绿岩的形成年龄。蛇绿岩中不同组分(橄榄岩、辉长岩和细碧岩)的稀土元素和微量元素特征,以及细碧岩的Nb/Yb-Th/Yb图解均显示该蛇绿岩为洋中脊(MOR)型。查干陶勒盖蛇绿岩与西准噶尔北部的塔尔巴哈台(库吉拜)蛇绿岩、洪古勒楞蛇绿岩,邻区东哈克斯坦北部的扎乌尔-塔金蛇绿岩和巴尔克别克蛇绿岩可以很好地进行对比连接,为成吉斯-塔尔巴哈台构造带在西准境内的时空特征提供更多的约束。

Chagantaolegai ophiolite was discovered from the south of Xiemisitai Mountain, north to Heshituoluogai valley in West Junggar, Xinjiang. The ophiolite is represented by a ca. 18km long, north-northeast-striking serpentinite-matrix m61ange, which en- closes serpentinized peridotite, gabbro, basalt, spilite, chert blocks and homologous pyroclastic rocks. The LA-ICP-MS zircon U-Pb datings of gabbro in Chagantaolegai ophiohte are 517Ma±3Ma and 519Ma±3Ma, suggesting Early-Middle Cambrian. The REE pat- terns, trace element variation diagram and Nb/Yb-Th/Yb diagram show geochemical characteristics of Mid-ocean ridge ophiolite. Chagantaolegai ophiolite could be correlated well with Tarbagatai （Kujibai） ophiohte, Hongguleleng ophiolite in northern part of West Junggar and Zhaur ophiolite, Barkbek ophiolite in northern part of East Kazakhstan, thus providing more constraints for spafiotemporal characteristics of Chingiz-Tarbagatai Belt.