Abstract: The final closure of the eastern segment of the Paleo-Asian Ocean remains a hotly debated topic in geological research. However, the eastward extension of the Solonker suture and its exact closure location are further complicated by thick Mesozoic cover on the western margin of the Songliao basin. The recent discovery of the Tuquan ophiolite, which constitutes an important component of the ophiolitic fragments within the Solonker suture, provides key constraints on the eastward extension of the suture. LA-ICP-MS zircon U-Pb dating yields ages of (265.5 ± 3.5) Ma for serpentinized peridotite and (276.5 ± 4.6) Ma for gabbro are, indicating formaion of the Tuquan ophiolite from the late Early Permian to Middle Permian. Combined with the geochemical characteristics, it suggests that the Tuquan ophiolite originated in a forearc tectonic setting during the Early to Middle Permian, coinciding with bidirectional subduction and consumption of the Paleo-Asian Ocean. These findings further reveal that the final subduction and collision of the Paleo-Asian Ocean persisted at least until the late Permian. Collectively, the Tuquan ophiolite serves as direct geological evidence for the eastward extension of the Solonker suture and provides new constraints on the Late Paleozoic tectonic evolution of the southeastern Central Asian orogenic belt.

Key words: Paleo-Asian Ocean, Solonker suture, Tuquan ophiolite, Middle Permian, forearc basin