Provenance analysis of Nanyinger Group in the North Qilian Belt: constraints from zircon U–Pb geochronology

LA–ICP–MS U–Pb dating has been performed on detrital zircons from the Nanyinger Group in the eastern section of the north Qilian orogenic belt in Jingyuan County, Gansu Province. The results show five major age groups: 3.1–2.0, 1.8–1.4, 1.4–0.8, 0.6–0.4, and ~0.26 Ga. Archean to Neoproterozoic zircons were derived from the central Qilian belt. The early Paleozoic grains are considered to have been derived from the magmatic arc related to ocean closure. The youngest age may be derived from the recycling of sediments prior to the Nanyinger Group. The youngest detrital zircon age (262 ± 5 Ma) is close to the depositional age of the strata, suggesting rapid uplift of the Qilian Mountains. In the early Indosinian, the palaeo-Qilian Mountains uplifted rapidly and provided the main source for the Hexi Corridor basins. The North Qilian Belt is the southern boundary of the Hexi Corridor basins. From the Ordovician to the Triassic, the depocenter gradually moved to the Qilian Mountains and was very close to the Qilian Mountains in the Late Triassic. By comparing with previous research, we infer that the Hexi Corridor basin may not connect with the Ordos Basin in the Triassic.