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

Abstract：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 fragmented pyroclastic rocks. The ophiolite blocks are mainly carbonatized ultramafites (?), 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.