Triassic magmatism in Northeast China: Implications for spatiotemporal distribution, continental crustal accretion, and geodynamic evolution.

Triassic magmatism in Northeast (NE) China was geodynamically controlled by the Mongol–Okhotsk Ocean (MOO), Palaeo-Asian Ocean (PAO), and Palaeo-Pacific Ocean (PPO) tectonic regimes. To define the mechanisms of crustal accretion and geodynamics, the magmatic processes generated by ocean closure and plate subduction must be determined. In the present study, we assembled geochronological, geochemical, Cu (Mo)-porphyry deposit, and zircon Hf isotopic data from magmatic rocks throughout NE China. Central-NE China harbours more reworking of juvenile continental crustal material than the NE China margin. The widespread Triassic felsic magmas in NE China are primarily due to the recycling of juvenile and ancient crustal components during the tectonic evolution of the PAO. During the Triassic, NE China was subjected to a syn- to post-collisional orogenic regime accompanied by scissor-like basin closure and bidirectional subduction of the eastern PAO, before transitioning to the PPO tectonic regime in the latest Triassic. Magmatism in the Erguna and the central–northern Xing'an blocks was more affected by the MOO tectonic regime. Magmatism in the central–southern Xing'an Block, the southwestern Songliao Basin, and northern Lesser Xing'an–Zhangguangcai Range was linked to the closure of the PAO. Triassic magmatic rocks along the eastern Songliao Basin are extensional and formed during the opening of the Mudanjiang Ocean. The NE margin of Eurasia was a passive continental margin in the Late Triassic. [ABSTRACT FROM AUTHOR]