Where and when the Palaeo-Asian Ocean was closed: new evidence from the Tuquan ophiolite

The Solonker Suture marks the location of the final collision in the southeastern Central Asian Orogenic Belt, but is obscured at the western margin of the Songliao Basin. The recently discovered Tuquan ophiolite is an important fragment within the Solonker Suture. The analysis of samples from the Tuquan ophiolite using laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating gave chronological data with weighted mean ²⁰⁶Pb/²³⁸U ages from 279 ± 6 to 265 ± 5 Ma, which we interpret to represent the formation age of the Tuquan ophiolite from the late Cisuralian to Guadalupian. The geochemistry of the Tuquan ophiolite shows the characteristics of a supra-subduction zone. We suggest that it represents an important bidirectional subduction event involving the oceanic crust of the Palaeo-Asian Ocean beneath the Mongolia Block and the North China Craton during the early to late Permian. Integrating these findings with previous research indicates that the final subduction of the Palaeo-Asian Ocean persisted until at least the late Permian. Our study provides further insights indicating that the Tuquan ophiolite could be regarded as the eastern extension of the Solonker Suture, providing new constraints on the evolution of the southeastern Central Asian Orogenic Belt.