SS04 – THE GEOLOGIC EVOLUTION OF NE ASIA

Thu-02 Jul 2020 | 13:30 – 15:30 | Tower B, Lavender II Alexei IVANOV Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences “Timing of the Mongolia-okhotsk Ocean Closure, Collision and Post-collisional Extension”

Alexei IVANOV^#+, Elena DEMONTEROVA, Anastasia ARZHANNIKOVA, Sergey ARZHANNIKOV

Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences

The Mongolia-Okhotsk Ocean started to form between Siberian and Amurian continental blocks in the Middle Devonian. However, the extent of the ocean and the timing of its closure are debated. Most researchers agree that the ocean was once ~2000 km wide and closed step by step from the west to the east (in modern coordinates). Today, the evidence of the ocean is along a narrow Mongolia-Okhotsk suture zone (MOSZ), which is continuous for a few thousand km from Central Mongolia to Okhotsk Ocean. The remnants of the slab subducted beneath Siberia are still visible in seismic tomography images. In this presentation, we consider the state of the art geological, geochemical and geochronological information about the central part of the MOSZ and regions to the north from it. We argue that the central part of the Mongolia-Okhotsk Ocean closed at the boundary of the Early and Middle Jurassic with the collision of the two continental blocks. The collision was quickly followed by the post-collisional extension, which culminated in the Early Cretaceous.The study is supported by the Russian Science Foundation and the Ministry of the Russian Federation (projects 16-17-10068 and 075-15-2019-1883, respectively).

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