Structural and Geochronological Constraints on the Collision Between the Chinese Altai and the West Junggar in Central Asia: Implication for Deformation Response and Geodynamic Evolution of Arc-Arc Collision in 4D

Arc-arc collision represents one of crucial geological processes to shape mountain belts on the Earth. The deeply-eroded Central Asian Orogenic Belt (CAOB) is characterized by the collision of multiple arc systems and provides a natural laboratory to understand arc-arc collision in 4D given the exposure of crustal rocks at different levels. Here we focus on the similar to NW-SE Irtysh fault zone, which represents a major suture zone within the CAOB to bound arc systems of the Chinese Altai and the West/East Junggar in NW China. Our structural work, for the first time, delineates the spatial position of the western segment of the Irtysh Fault between the Chinese Altai and the West Junggar, and demonstrates a phase of brittle strike-slip deformation with sinistral kinematics in the Permian. An earlier episode of similar to NE-SW shortening event affected both southern Chinese Altai and northern West Junggar, forming similar to NW-SE fold structures. Both similar to NE-SW shortening and sinistral strike-slip faulting overlap in time with the collision of the Chinese Altai and the West Junggar during the latest Carboniferous to Permian as constrained by new detrital zircon data, thus indicating a transition from orthogonal collision to oblique convergence between the Chinese Altai and the West Junggar. A comparison with ductile deformation at deep structural levels along the eastern segment of the Irtysh Fault between the Chinese Altai and the East Junggar allows for investigation of arc-arc collision in 4D, which highlights deformation decoupling across different crustal levels, with an intermediate episode of orogen-parallel flow recorded within deep crustal rocks.