Arc-ophiolite obduction in the Western Kunlun Range (China): implications for the Palaeozoic evolution of central Asia

The nature of the ‘Kudi ophiolite’ in the Western Kunlun Range is hotly debated. Our new structural–geochemical data reveal that it is actually an arc ophiolite comprising: (1) arc- or ophiolite-derived turbidites of two generations containing Late Ordovician–Silurian and Late Devonian–Early Carboniferous radiolarians; (2) a central intra-oceanic (Yixieke) arc with basalt–andesite–tuff–agglomerate; (3) lower (Buziwan) oceanic crust containing dunite–harzburgite–gabbro. We propose the following tectonic evolution. South-dipping subduction in Late Cambrian to earliest Ordovician time generated the Yixieke arc on top of the Buziwan oceanic crust–mantle. This subduction led to emplacement of the arc northwards onto the North Kunlun terrane (Tarim block), creating an active continental margin with northward subduction below it. The Kudi ophiolite was thrust southeastward over the incoming Kudi continental (gneiss) terrane in mid-Ordovician–mid-Devonian time. During a tectonic hiatus in the Kudi region Late Devonian–Carboniferous subduction further west led to development of the Oytag arc, formerly regarded as an equivalent of the Kudi ophiolite. Lower Permian arc lavas and Upper Triassic granites in the Xiananqiao arc south of Kudi mark the resumption of north-dipping subduction before final collision with the incoming Qiangtang block. Comparison with the Lapeiquan ophiolite in the Eastern Kunlun assists regional correlation along this Palaeozoic orogen and constrains Cenozoic displacement of the Altyn Tagh fault.