新疆布尔根蛇绿混杂岩的发现及其大地构造意义

Discovery of the Buergen ophiolitic mélange belt in Xinjiang and its tectonic significance

新发现的出露于新疆北部额尔齐斯板块缝合带的布尔根蛇绿混杂岩带位于西伯利亚板块与哈萨克斯坦—准噶尔板块的结合带,呈北西向展布。主要表现为糜棱岩化的基质中混杂着大小不一、性质各异的蛇绿岩各组分的岩块。基质主要有糜棱岩化的火山岩、凝灰岩和破碎强烈的火山碎屑岩。蛇绿岩岩块主要有碳酸盐化的超镁铁岩(?)、玄武岩、辉长岩和硅质岩岩块等。玄武岩具有OIB和IAB特征。拉斑玄武岩SHRIMP锆石年龄352Ma,说明蛇绿岩的形成可持续到晚泥盆世—早石炭世。这一发现对于认识中国准噶尔盆地以北地区的晚古生代蛇绿岩带及其向境外的延伸具有重要的意义。

The Buergen ophiolitic mélange belt found recently by the authors is exposed in the Ertix （Irtys） suture zone between the Siberian plate and Kazakhstan-Junggar plate in northern Xinjiang and extends in a NW direction. The rock is chiefly marked by mixing of blocks of various ophiolite components of varying size and nature in mylonized matrix. The matrix consists dominantly of mylonized volcanic rocks, tuff and strongly tragmented pyroclastlc rocks, l he ophiolite blocks are mainly carbonatazed ultramalates （？）, basalt, gabbro and cherts. Basalt has the OIB and IAB features. Tholeiite has a zircon SHRIMP U-Pb age of 352 Ma, suggesting that the formation of the ophiolites may have continued till the Late Devonian-Early Carboniferous. This discovery is of great significance for understanding the late Paleozoic ophiolitic mélange belt in the area north of the Junggar basin of China and its extension beyond China.