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

The Solonker suture marks the location of the final collision in southeastern Central Asian Orogenic Belt (CAOB). However, it is observed that the suture is obscured at the western margin of the Songliao Basin. Fortunately, the recently discovered Tuquan ophiolite is one of the important fragments within the Solonker suture. Testings of samples from the Tuquan ophiolite yielded LA-ICP-MS zircon U–Pb chronological data with weighted mean of 206 Pb/ 238 U ages from 265 ± 5 Ma to 279 ± 6 Ma which were interpreted to represent the formation age of the Tuquan ophiolite from the late Cisuralian to Guadalupian. The geochemical characteristics of the Tuquan ophiolite is related to supra-subduction zone features. We suggest that it represents an important bidirectional subduction event involving the oceanic crust of the Paleo-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 Paleo-Asian Ocean persisted until at least the late Permian. Our study provides further insights, indicating that the discovery of the Tuquan ophiolite could be regarded as the eastern extension of the Solonker suture. This finding will provide new constraints on the evolution of the southeastern CAOB.