Constraining the obduction process of the Dongqiao ophiolite in the Bangongco-Nujiang suture zone by the sedimentary record

The Bangongco-Nujiang suture zone separates the Qiangtang terrane to the north and the Lhasa terrane to the south, representing the once-disappeared ocean—the Bangongco-Nujiang ocean. The ophiolite, which is distributed intermittently from Ritu in the west to Dingqing in the east, is important for recording the evolution of Bangongco-Nujiang Ocean. For a long time, little has been known on when and where the Bangongco-Nujiang ophiolite formed and how it was obducted. The study of stratigraphy, sedimentology and provenance of terrestrial-marine siliciclastic-cabonate deposits (the Dongqiao Formation) above the Dongqiao ophiolite in this paper suggests that the Dongqiao ophiolite was obducted onto a passive Lhasa-affinity continental margin before Oxfordian- Kimmeridgian (Late Jurassic). The process of Dongqiao ophiolite from crystallization to obduction is reconstructed, and the dynamic mechanism of Dongqiao ophiolite obduction and its tectonic implications are discussed on the basis of the ophiolite age and geochemical data.