Absolute reconstruction of the closing of the Mongol‐Okhotsk Ocean in the Mesozoic elucidates the genesis of the slab geometry underneath Eurasia

Abstract

Understanding the present‐day fast seismic velocity anomalies in the mantle requires an accurate kinematic reconstruction of past convergent tectonics. Using the paleomagnetism‐based absolute reconstruction method from Wu and Kravchinsky (2014), we present here the restoration of the closing of the Mongol‐Okhotsk Ocean (MOO) that existed between Siberia and North China‐Amuria (NCA) during the Mesozoic. Three stages, i.e., 250–200 Ma, 200–150 Ma, and 150–120 Ma, are identified from the time‐varying convergence rates of Siberia and NCA. The spherical distance between the suture margins was reduced by approximately 66.7% at an average convergence rate of 8.8 ± 0.6 cm/yr during the first stage at 250–200 Ma, when approximately 62.5–76.1% of the slabs associated with the MOO lithosphere were formed primarily through intraoceanic convergence. In the second stage at 200–150 Ma, the spherical distance was reduced by another 21.1% with a convergence rate of 3.6 ± 0.3 cm/yr. During this stage, approximately 14.2–30.9% of the MOO slabs were formed and continental‐oceanic convergence outpaced intraoceanic subduction. In the last stage at 150–120 Ma, the convergence rate dropped to approximately 0.4–0.6 cm/yr with the formation of approximately 4.6–9.8% slabs associated with the MOO lithosphere. The final closure of the remnant MOO basin could have been accomplished by 130–120 Ma, which explains the origin of the fast‐velocity anomalies inside the restored continents at 120 Ma near the suture margins.

New Late Jurassic to Early Cretaceous Paleomagnetic Results From North China and Southern Mongolia and Their Implications for the Evolution of the Mongol‐Okhotsk Suture

“…For Europe, although the APWPs of Torsvik et al () have been used for discussion (e.g., Van der Voo et al, ; Wu, Kravchinsky, Gu, et al, ), they included Cretaceous data from Mongolia that are unfit to compare with our new Early Cretaceous AMU and NCB paleomagnetic results. Therefore, we continue to choose the frequently‐used Europe APWP of Besse and Courtillot (), which was cited by Metelkin et al () and Ren et al ().…”

“…The Mongol‐Okhotsk suture (MOS) is widely accepted as an important tectonic boundary between Siberia and the Amuria (AMU)‐North China Block (NCB; Figure a), and thus bears important information to understand the amalgamation of the eastern part of the Eurasian continent (Cogné et al, ; Enkin et al, ; Halim et al, ; Kravchinsky, Cogné, et al, ; Metelkin et al, ; Ren et al, ; Tang et al, ; Tomurtogoo et al, ; Van der Voo et al, ; Wu, Kravchinsky, Gu, et al, ; Wu, Kravchinsky, & Potter, ; Zonenshain et al, ; Zorin, ). Regarding this issue, paleomagnetism remains the most powerful tool for studying plate motion and has provided a great deal of independent evidence for paleogeographic reconstruction.…”

“…Regarding this issue, paleomagnetism remains the most powerful tool for studying plate motion and has provided a great deal of independent evidence for paleogeographic reconstruction. The current kinematic models supported by paleomagnetic data are mainly based on comparisons between the paleomagnetic databases from each side of the MOS (e.g., Cogné et al, ; Enkin et al, ; Gilder & Courtillot, ; Halim et al, ; Kravchinsky, Cogné, et al, ; Metelkin et al, ; Ren et al, ; Van der Voo et al, ; Wu, Kravchinsky, Gu, et al, ; Wu, Kravchinsky, & Potter, ; Zhao et al, ). However, although the apparent polar wander path (APWP) of the Siberia craton on the north side of the MOS has been updated (Metelkin et al, , ), that of the south side still has problems.…”

“…Some areas have been intensively deformed since the Late Jurassic by episodic folding, thrusting, and regional extension, whereas others have been fairly stable (Cogné et al, ; Davis et al, ; Ren et al, ; Y. Wang et al, ). Most paleomagnetic data from the south side of the MOS are from the North China craton (Figure b; e.g., Gilder & Courtillot, ; Ren et al, ; Van der Voo et al, ; Wu, Kravchinsky, Gu, et al, ), and would benefit from more precise age constraints, wider spatial comparison and averaging, and recent advances in paleomagnetic technologies, such as testing for inclination shallowing (Van der Voo et al, ; Wu, Kravchinsky, Gu, et al, ; Wu, Kravchinsky, & Potter, ) and secular variations (Ren et al, ). Therefore, our new investigations were extended into the remote desert of southern Mongolia, part of the AMU, focused on well‐dated successions, and added data from both volcanic and clastic rocks.…”

Decoding stratigraphic evolution of the Hailar Basin: Implications for the late Mesozoic tectonics of NE China

“…The northern NCMT possibly developed as an active margin as a result of southward subduction of the Mongol–Okhotsk Oceanic plate in the early Mesozoic (Liu, Li, He, Huangfu, & Liu, ). It was postulated that the Siberia–NCMT collision took place progressively from west to east during the period from the Middle to Late Jurassic and resulted in crustal shortening and thickening in NE China (Pei et al, ; Wu, Kravchinsky, Gu, & Potter, ). The NCMT then underwent widespread extension in the Early Cretaceous as a consequence of gravitational spreading of the thickened crust, creating a wide rift system (Liu et al, ; Meng, ).…”