Multistage evolution of the Keluo Complex in the northern Da Hinggan Mountains: Implications for the Mesozoic tectonic history of the eastern Central Asian Orogenic Belt

Abstract

The Da Hinggan Mountains (DHM) are located in the eastern segment of the Central Asian Orogenic Belt (CAOB) and represent a prominent geomorphic marker of NE China, although its evolution history and exhumation/uplift mechanisms remain equivocal. Here, we present results from a comprehensive study on the field and micro-structures, kinematics, rheology, quartz EBSD fabrics, geochemistry and geochronology of the Keluo Complex (KC) exposed in the northern DHM. The KC is dominated by deformed Early Carboniferous to earliest Permian rocks (337–297.1 Ma) and is invaded by Early Mesozoic multi-stage granitic intrusions (219.8–175.5 Ma). These were further overprinted by magmatism, metamorphism, and deformation during the Late Jurassic (152.0–157.7 Ma) and late Early Cretaceous (118.3 Ma). The latest Carboniferous/earliest Permian rocks formed in a post-collisional extensional environment that might be related to the collision of the Xing'an and Songnen massifs. The Early Mesozoic rocks were derived from magma generated by partial melting of the lower continental crust within an active continental margin setting related to the subduction of the Mongol-Okhotsk Ocean. Two prominent deformation events (D1 and D2) were recognized in the KC, which occurred in Late Jurassic and late Early Cretaceous. The D1 is dominated by SW-trending sinistral ductile shearing accompanied by moderate to high-temperature deformation (500–600 °C) resulting from NW–SE compression. The D2 is a bi-directional extensional and detachment deformation corresponding to a low temperature (300–400 °C) deformation developed at a shallow-level ductile regime resulting from NW–SE extension. The D1 deformation was influenced by subduction and closure of the Mongol-Okhotsk Ocean, whereas the D2 deformation is correlated to the superposition of the extension after the closure of the Mongol-Okhotsk Ocean and the rollback of the Paleo-Pacific Plate. Our results provide new insights into the tectonic history of the DHM domain of the CAOB.