Carboniferous-Triassic rise and fall of continental arc recorded by retro-arc shifts of basin-infill and climate in the Hexi Corridor

Abstract. The Hexi Corridor inboard the Andean-type North China Continental Arc preserves pivotal records of basin transition and dynamic change in Carboniferous-Triassic. This work provides an integrated study on strata in the Eastern Hexi Corridor Belt (EHCB) and western Ordos. Provenance analyses show that Carboniferous strata in the southern EHCB were sourced from the Central Qilian, evidenced by north-direct paleoflow data and age profiles mainly of Paleozoic and Neoproterozoic clusters. The northern EHCB samples have age spectra with dominance of ca. 2700–1700 Ma ages, implying sources from the Ordos basement, which is compatible with south-direct paleoflow. Crustal thinning and mantle-derived magmatism indicate an extension setting for the EHCB. Shallow-water deposition in the EHCB was terminated at ca. 295 Ma. The late Permian strata were fed by the intensely raised Nuru-Langshan Continental Arc (NLCA), given occurrence of >80 % number of Paleozoic-age zircons in forearc and retroarc samples. Crustal thickening and negative ε(Hf) values for plutons demonstrate raising of the NLCA, cratonward expansion of which constructed a retroarc foreland system in the western Ordos and EHCB. The ~3±0.5 km high relief of the IMCA triggered orographic rain shadow and retroarc aridification, expressed by changing of mudstone color from black to red. The Paleo-Asian Ocean closure at early Triassic induced uplift of the NLCA basement and left-lateral strike-slip of the Bayanwula Fault, providing a swath of zircons of ca. 2700–1700 Ma ages to the retroarc. Paleodrainage reorganized, as fluvial-delta systems in the western Ordos commenced routing to the southeast.