The Yanshanian Movement in Western Liaoning, northeastern North China Craton

Abstract

The Yanshanian Movement (or Yanshanian Orogeny) has been a topic of study for nearly a century, with ongoing interests. This study reviews its origin, tectonic subdivision, development and dynamic mechanisms, and associated magmatic-tectonic activity in Western Liaoning, northeastern North China Craton (NCC). By analyzing rock assemblages, petrogenesis, and magma sources of Mesozoic volcanic rocks, and combining with available data on deformation, basin formations, mineralization, and evolution of biota, we propose a new dynamic mechanism of the Yanshanian Movement in Western Liaoning, particularly during its initial stage and pulsation pattern. The initial stage (Early to Middle Jurassic, 190–165 Ma) is defined by abundant magmatism, mineralization and compressional structures, likely associated with the multi-plate (Mongol-Okhotsk, Paleo-Pacific, and Meso-Tethys) convergence around the East Asian continent. The pulsation pattern is characterized by alternating tectonic settings in the northeastern NCC during the Jurassic to Early Cretaceous, featuring stages of both compression and extension. The first N(W)–S(E) compression stage (165–160 Ma) is marked by an unconformity above the Jiulongshan/Haifanggou Formation and associated (N)E–(S)W fold-and-thrust structures, influenced by WNW-directed subduction of the Paleo-Pacific Plate (PPP) and the far-field effect of the N–S closure of the Mongol-Okhotsk Ocean (MOO). The subsequent first extension stage (160–145 Ma) is small-scale and local, dominated by NE–SW and NW–SE structural trends, with NE–SW extension indicated by magnetic lineations of granitic plutons and top-to-the-NE ductile shear zones in the northern NCC, likely correlating with short-term stress relaxation from the MOO regime. This NW–SE extension is confirmed by the Late Jurassic basin-and-range-type tectonics in the northeastern NCC, possibly linked to the localized high-angle subduction and rollback of the PPP. The second N(W)–S(E) compression stage (145–135 Ma) corresponds to the Yanshanian B-episode, illustrated by the syn-tectonic deposition and the unconformity from Upper Jurassic to lowermost Cretaceous. The NE–SW-trending compressional structures were controlled by rapid low-angle NNW-directed subduction of the PPP, alongside with subordinate E–W-trending structures associated with the final N–S closure of the MOO. The following second NW–SE extension in the late Early Cretaceous (135–100 Ma) is recorded by metamorphic core complexes, extensional domes and rift basins, and large-scale magmatic-tectonic activity, driven by asthenospheric material upwelling, lithospheric delamination, and thinning of the NCC lithosphere due to the rapid retreat and rollback of the PPP.