Provenance of Middle-Upper Permian Sandstones in Lintan and Jiangligou Areas, West Qinling, China: Insights from Geochemistry, Detrital Zircon Chronology, and Hf Isotopes

The provenance of the Middle-Upper Permian in the Lintan and Jiangligou areas, remnants of rift basin sedimentation within the West Qinling, remains controversial, hindering understanding of the basin-range coupling evolution of the Qinling Orogenic Belt and its periphery. Heavy minerals, major and trace elements, rare earth elements, detrital zircon U-Pb dating, and in situ Lu-Hf isotopes were analyzed to determine the provenance of the Middle-Upper Permian sandstones. Results were integrated with previous studies to investigate basin-range coupling processes. The results reveal the following: (1) The Upper Member of the Shilidun Formation in the Lintan area was deposited during the Late Permian. Heavy minerals are dominated by moderately to highly stable species. Source rocks were derived from intermediate-acidic magmatic rocks and low- to medium-grade metamorphic terrains. The provenance was primarily situated in a continental island arc tectonic setting. Diverse source rock types were identified, including materials from felsic igneous, quartzose recycled, and mafic igneous provenances. Detrital zircon U–Pb age spectra display two major peak ages at 285 Ma and 442 Ma, along with five subordinate peaks at 818 Ma, 970 Ma, 1734 Ma, 1956 Ma, and 2500 Ma. The εHf(t) values range from –44.95 to 42.67, and TDM2 ages vary from 367 Ma to 4106 Ma. It is concluded that the sedimentary materials were mainly derived from the North Qinling Orogenic Belt, with minor contributions from the basement of the North China Craton. (2) In the Jiangligou area, the Shiguan Formation is characterized by highly and stable heavy minerals. The provenance is dominated by intermediate-acidic magmatic rocks, within an oceanic island arc tectonic setting. Detrital zircon U–Pb age spectrum displays a prominent peak at 442 Ma. The εHf(t) values range from –0.5 to 10.55, with TDM2 ages ranging from 744 Ma to 897 Ma. These results indicate that the sedimentary materials were derived from the North Qilian Orogenic Belt. (3) The Permian in the Western Qinling exhibit multi-provenance supply, dominated by the North Qinling Orogenic Belt and the North China Craton basement, with local contributions from the North Qilian Orogenic Belt. Significant regional variations in provenance contributions were identified. This study further constrains the closure of the Shangdan Ocean to pre-Late Permian. It reveals that the Western Qinling was situated in a back-arc rift basin setting during the Late Paleozoic. Key sedimentary evidence is provided for understanding the tectonic evolution of the Paleo-Tethys Ocean and the collision between the North China and Yangtze cratons.