The Mongolia Block (MOB), which is now sandwiched by the Siberia Craton (SIB) and the North China Craton (NCC), plays an essential role for understanding the late stage evolution of the Paleo‐Asian Ocean and the early stage evolution of the Mongol‐Okhotsk Ocean. Here, a paleomagnetic study is performed for the first time on the Early Permian volcanic strata in the Bayandun region of northeastern Mongolia and the data are used to uncover the late Paleozoic paleoposition of the MOB and better understand the evolution of both oceans. Zircon U‐Pb dating results reveal an emplacement age of 283 ± 3 Ma for the studied volcanic strata. Rock magnetic analyses identify that titanium‐poor magnetite is the main magnetic carrier. Characteristic remanent magnetization isolated from seven sites shows consistent reverse polarity, corresponding to the Permo‐Carboniferous (Kiaman) Reverse Superchron. Site‐mean directions pass fold tests, and an Early Permian paleomagnetic pole is calculated for the MOB at λ/φ = −14.9°N/76.8°E (A95 = 5.7°) with N = 7 sites. Comparison with published Permian paleomagnetic poles from surrounding blocks indicates that (1) the MOB should have welded with the NCC before the Early Permian or was at least very close to it. (2) The welded MOB‐NCC was separated from the SIB by the Mongol‐Okhotsk Ocean with ~30° latitudinal difference during the Early Permian. (3) Significant vertical‐axis strike‐slip related rotations occurred within and along the margins of the unified MOB‐NCC due to the far‐field stress effect produced by posterior orogenic events.

To better constrain the evolution of the Mongol‐Okhotsk suture, we carried out new paleomagnetic studies on Sharilyn Formation (~155 Ma) and Tsagantsav Formation (~130 Ma) in southern Mongolia, Amuria Block (AMU), and Tuchengzi Formation (~140 Ma) and Dadianzi/Yixian Formation (~130 Ma) in the Yanshan belt, North China Block (NCB). A total of 719 collected samples (from 100 sites) were subjected to stepwise thermal demagnetization. After a low‐temperature component of viscous magnetic remanence acquired in the recent field was removed, the stable high‐temperature components were isolated from most samples. The high‐temperature components from each rock unit passed a fold test and a reversal test, indicating their primary origins. The corresponding paleomagnetic poles were thus calculated. For AMU, the ~155 Ma pole is at 74.7°N/232.5°E (A95 = 3.7°), the ~130 Ma pole at 74.6°N/194.7°E (A95 = 2.9°); for the NCB, the ~140 Ma pole is at 82.7°N/208.6°E (A95 = 4.3°), the ~130 Ma pole at 80.5°N/197.4°E (A95 = 2.3°). By combining our new results with the published data, we refined the 155–100 Ma segment of the apparent polar wander paths for AMU and NCB, which can demonstrate that these two blocks have been tectonically coherent (AMU‐NCB) during 155–100 Ma. Comparison of the apparent polar wander paths, however, revealed a latitudinal plate convergence of 14.3° ± 6.9° and ~19.0° relative rotation between Siberia and the AMU‐NCB after ~155 Ma. Large‐scale latitudinal convergence likely ceased by ~130 Ma, although some relative rotation between them continued along the Mongol‐Okhotsk suture until ~100 Ma.

The Mongolian Altai Zone of the Central Asian Orogenic Belt has been traditionally interpreted as a mosaic of Paleozoic magmatic arcs, back‐arcs, and Precambrian continental terranes. In order to define its architecture and its tectonic evolution, three domains previously interpreted as terranes were investigated. The findings show that the Northern and Central domains are formed by a metamorphic sequence characterized by Barrovian S1 fabric transposed by recumbent folds and dominant sub‐horizontal amphibolite facies S2 schistosity. The latter is associated with the intrusions of late Devonian syntectonic granite sheets and anatexis in the south. The Southern domain is formed by early Permian migmatites and anatectic granites separated from the metamorphic envelope by amphibolite to green‐schist facies D3 shear zone cross‐cutting S2 fabrics. All domains have been reworked by E‐W upright folds associated with axial‐planar greenschist facies cleavage, reflecting the final mid‐Permian to Triassic D4 shortening. Lithological, geochemical, and U‐Pb zircon analyses of metasediments of all domains indicate that they are formed by Ordovician mature quartzite derived from Precambrian basement intruded by Cambrian‐Ordovician continental arc and Silurian immature graywacke which originated through erosion of an oceanic arc. Altogether, the whole sequence represents a fore‐arc basin in front of a migrating arc affected by thickening and late Devonian extension. The Southern domain is interpreted as an early Permian core complex amplified by mid‐Permian to Triassic compression. The apparent “terrane” architecture of the Mongol Altai Zone originated due to Devonian and Permian heterogeneous reworking of a giant Ordovician to Silurian fore‐arc basin.