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The Bangong-Nujiang suture zone (BNSZ) separates the Lhasa terrane from the Qiangtang terrane and contains remnants of the Bangong-Nujiang oceanic lithosphere (ophiolites). Despite decades of research, when and how the Bangong-Nujiang ophiolites were emplaced remains enigmatic. In the Gerze area (western segment of the BNSZ), the geochemistry and provenance discrimination of chromian spinels (Cr-spinels) from the precollisional subduction complex (Mugagangri Group) and syn-collisional peripheral foreland basin succession (Wuga Formation) can help us solve this fundamental problem in the BNSZ evolution. This study compares the geochemistry of Cr-spinels from the Mugagangri Group and Wuga Formation with those from the BangongNujiang ophiolites. Cr-spinels in the Bangong-Nujiang ophiolites have either low TiO2 (0.01-0.15%) and low Al2O3 (11.74-26.76%), indicating an SSZ peridotite origin, or high Al2O3 (4528-49.15%), indicating a MORB peridotite origin. Cr-spinels from the ultramafic fragments within the Mugagangri Group have extremely low TiO2 (<0.06%) and geochemically overlap with those from the Dong Co ophiolite, suggesting that these ultramafic fragments were sourced from the Dong Co ophiolite above the subduction zone rather than off-scrapped remnants from the subducting oceanic lithosphere. Compositional fingerprints of detrital Cr-spinels from the Wuga Formation indicate provenance either derived from the Bangong-Nujiang ophiolites or recycled from the Mugagangri Group in the north, with minor input possibly from the Lhasa terrane in the south, consistent with the depositional pattern of a peripheral foreland basin. Provenance data reveals that the Bangong-Nujiang ophiolites in the Gerze area had been emplaced and exposed to erosion during northward oceanic subduction prior to the Lhasa-Qiangtang collision. Contrasting the Tethyan-type Yarlung-Zangbo ophiolites in southern Tibet, the Bangong-Nujiang ophiolites in central Tibet are Cordilleran-type in terms of emplacement mechanism, which were uplifted above sea-level by progressive growth of the subduction complex structurally beneath ophiolite. The emplacement of the Cordilleran-type ophiolites in the western segment of the BNSZ is divided into two stages: (1) infra-oceanic subduction initiation at similar to 177-179 Ma based mainly on zircon U-Pb dating of plagiogranite from the SSZ-type Laguo Co ophiolite; (2) accretionary emplacement of the ophiolites at similar to 151-168 Ma constrained by the depositional age of the Mugagangri subduction complex. Final dosure of the Bangong-Nujiang Tethyan Ocean may convert the ophiolite emplacement mechanism from "accretionary" to "collisional" at similar to 150-152 Ma, evidenced by the first development of a peripheral foreland basin. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.