Microcontinent collision triggered Jurassic subduction transference in central Tibet

Subduction transference occurs when an existing subduction zone is choked by the arrival of buoyant crust, and a new subduction zone is generated on the down-going plate to accommodate continuing convergence. Although subduction transference triggered by microcontinent collision was conceptually proposed as a viable tectonic mechanism across several Tethyan oceanic branches, evidence remains controversial, and geodynamic controls are unclear. Here, we report geological data from central Tibet documenting the Early Jurassic northward subduction initiation of the Bangong-Nujiang Ocean, followed by collision with a presently ∼70-km-wide microcontinent, ophiolite obduction, foreland-basin development, and initiation of a new north-dipping subduction zone to the south of the microcontinent in the late Middle to Late Jurassic. According to numerical geodynamic simulations, such a process can be triggered by an increase in buoyancy and/or lithospheric mantle strength of the collided microcontinent. Our study provides a geological example of subduction transference triggered by a narrow microcontinent collision, able to explain the progressive suturing of microcontinents in the Tethyan realm.