Provenance and depositional history of the Mesozoic Sanjiang Basin (northeastern China): implications for the uplift history of the northeastern Asian continental margin. (3rd March 2022) - Luan, Jin-Peng
Abstract: The uplift history of northeastern Asian continental margin has been the subject of much debate. The Sanjiang Basin is an ideal area to investigate the uplift history of this margin. We present new data from sandstone petrology, whole-rock geochemistry, U–Pb geochronology and Hf isotopy of detrital zircons to trace the provenance of the basin and to unravel the uplift history of the northeastern Asian continental margin. We investigated the chemical and plagioclase indices of alteration and index of compositional variability (CIA, PIA and ICV, respectively) in samples from two formations. The geochemical proxies indicate that source rocks were subjected to an intensified weathering process. Based on the high SiO2 /Al2 O3 values and low K2 O, we infer that the two basinal strata experienced silicification and insignificant potassium metasomatism. Sandstone petrography is indicative of low degrees of sedimentary sorting, suggesting a proximal deposition. The provenance fingerprints of light rare earth, high-field-strength and transition metal elements indicate that parts of the provenance included recycled sediments, and that first-cycle sediments were derived mainly from felsic rocks with a minor contribution from intermediate and mafic rocks. The combined detrital zircon U–Pb ages and Hf isotopic results constrain the contributions of different source terranes over time. The provenance results, in combination with seismic profile interpretations from the Sanjiang Basin, suggest that the northeastern Asian continental margin experienced at least three stages of uplift, which were driven by subduction initiation of the Paleo-Pacific Ocean during the Jurassic Period, a plate motion change during the Early Cretaceous Epoch, and a shallowing of the slab dip angle during the Late Cretaceous Epoch.