From early Paleozoic subduction to end-Carboniferous post-orogenic collapse: New constraints on the tectonic evolution of the Central and South Tianshan (NW China)

Recognition of extensional events during orogenesis is critical for the reconstruction of geodynamic evolution of orogens, but is also a challenge due to multi -stage tectonic superimpositions. The South Tianshan is the southern margin of the Paleozoic Central Asian Orogenic Belt (CAOB) and a key for understanding the geodynamic evolution of the CAOB. Here we present new structural, geochronological and geochemical data for the Paleozoic sedimentary, igneous and metamorphic rocks in the Central and South Tianshan (NW China). Based on our new results and published data, we suggest that a neritic to terrestrial back -arc basin existed to the south of the Central Tianshan magmatic arc during the Early-Middle Devonian. We document a crustal anatectic event (-304 Ma) associated with peraluminous granitic magmatism (-305-295 Ma) in the South Tianshan. Multi -stage ductile deformation events witnessed the Paleozoic evolution from subduction-accretion to post-orogenic collapse of the Tianshan Orogen: (1) Late Devonian-Carboniferous regional top -to -the -north ductile shearing is related to the southward subduction of the South Tianshan back -arc basins; (2) late Carboniferous south -verging folds and brittleductile axial -plane cleavages correspond to back-thrusting resulted from the collision between Central Tianshan and Tarim; (3) latest Carboniferous ductile normal faults developed in migmatites define a dome-like structure linked with syn-anatectic exhumation of the middle crust during the postcollisional extension; and (4) regional dextral strike-slip faulting attributed to Permian lateral extrusion. Therein, two stages of crustal extension are key puzzle pieces to reconstruct the accretionary orogenic processes of the Paleozoic Tianshan. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.