Deformation patterns and timing of the thrust‐nappe structures in the Mohe Formation in Mohe Basin, Northeast China: Implication of the closure timing of Mongol–Okhotsk Ocean

Abstract

The Mohe Basin, to the south of the eastern Mongol–Okhotsk suture belt, contains important stratigraphic records and thrust‐nappe structures for understanding the closure of the eastern Mongol–Okhotsk Ocean. Meso‐micro structures in the Mohe Formation indicate a low‐temperature deformation/metamorphism (ca. 400°C) under an N‐S compression related to the southward thrusting faulting. The S‐L‐tectonites record strain similar or close to flattening/compressional strain and denote sinistral shearing in analogously N‐S‐trending thrusting. Our new detrital zircon U–Pb ages exhibit that maximum depositional ages of the Mohe Formation were conservatively estimated as latest Middle Jurassic (ca. 165 Ma). The Northeast China and Erguna Block to the south of the Mohe Basin, and Siberian Block to the north were the sources for the Mohe foreland basin's sediments throughout the deposition of the Mohe Formation, which derived from the basement uplift where erosion cuts deep into the dissected arcs. In the latest Jurassic to earliest Cretaceous, the southward collision and indentation of the Siberian Block (final closure of Mongol–Okhotsk Ocean) led to intense thrust nappe structures, syn‐collisional folds, and low‐temperature metamorphism occurred along the northwestern margin of Mohe Basin.