Material composition, age and significance of the Dong Co Melange in the Bangong Co-Nujiang suture zone

The Dong Co Melange, which contains various Ophiolitic blocks, ocean island fragments, flysch deposits, and continental marginal sediments, is an ideal object for restoring the evolution of the Bangong Co-Nujiang Ocean. In this paper, the authors present a detailed review and in-depth analysis of previous studies about the Dong Co Melange with the purpose of clarifying the material composition and age of the Dong Co Melange and discussing the significance of the Dong Co Melange. The authors hold that the ophiolitic blocks, ocean island fragments and flysch deposits in the Dong Co Melange are all multi-stage tectonic mélange, with their earliest age probably being the latest Late Permian and the latest age being the Early Cretaceous, indicating that the Bangong Co-Nujiang Ocean was continuous from the latest Late Permian to Early Cretaceous. The unconformity between the Early Cretaceous continental marginal sediments and the flysch deposits in the Dong Co Melange is only a record of fore-arc basin located on the accretion wedge.