Episodic provenance changes in Middle Permian to Middle Jurassic foreland sediments in southeastern Central Asian Orogenic Belt: Implications for collisional orogenesis in accretionary orogens

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The final collisional orogenesis in accretionary orogens is crucial for reconstructing the whole orogenic circle and understanding the material and energy recycling along convergent margins. However, it is always not straightforward to be addressed, particularly when the final suturing following the ocean closure occurred softly, for instance, the Central Asian Orogenic Belt (CAOB). In this study, a comprehensive dataset of detrital zircon U-Pb ages and Hf isotopes for the Middle Permian to Middle Jurassic foreland sediments from the Linxi region, southeastern CAOB, is synthesized. We observed multiple abrupt changes in sedimentary provenance over time from this dataset: (1) the ca. 275 Ma sediments (Upper Zhesi Fm.) were entirely sourced from the local NAO, whereas the ca. 270–258 Ma sediments (Middle-Upper Linxi Fm.) received an additional detritus contribution from the northern NCC, (2) the ca. 257–236 Ma sediments (Lower-Middle Xingfuzhilu Fm.) returned to a pure NAO source, but the slightly postdated ca. 227 Ma sediments (Upper Xingfuzhilu Fm.) show provenance affinities of both NAO and northern NCC, (3) the ca. 171 Ma sediments (Middle Xinmin Fm.) were exclusively derived from the Late Paleozoic to Early Mesozoic magmas in the NAO and northern NCC with no Early Paleozoic and Precambrian detritus. The above episodic shifts in sedimentary provenance observed in the Linxi region, in conjunction with other regional geological evidence, provide key constraints on the pre- to post-collisional evolution in the southeastern CAOB, including the transition from waning subduction to initial collision, subsequent slab break-off and intracontinental contraction, and the post-collisional extension before the superposition of the Paleo-Pacific tectonic regime. Our results show that understanding the spatio-temporal changes of sedimentary provenance of the foreland basins systems during the plate convergence and orogenic evolution can aid in exploring the final collisional dynamics and evolutionary history in ancient accretionary orogens.