Geochemistry and Geochronology of Late Permian–Middle Triassic Sandstones in the North Qiangtang Terrane, Tibet: Implications for Paleoenvironmental and Provenance Reconstruction

ABSTRACT The Late Permian sedimentary sequences of the Northern Qiangtang Terrane are closely related to the formation of late Palaeozoic basins and the sub‐duction of the Paleo‐Tethys Ocean. Here we present new insights into the paleoenvironment and provenance of the southern margin of the Northern Qiangtang Terrane (NQT) during the Late Permian to Middle Triassic, integrating existing petrological, geochemical and detrital zircon U–Pb age data. The Chemical Index of Alteration (CIA) and Ln (Al 2 O 3 /Na 2 O) ratio indicate that the Late Permian sediments experienced moderate chemical weathering under warm and humid conditions, while the Early to Middle Triassic sediments underwent weak chemical weathering under cold and arid conditions. Paleo‐salinity indicators (Sr/Ba, CaO/(CaO + Fe)), suggest that the Northern Qiangtang Terrane transitioned from brackish to saline marine environments. Redox‐sensitive indicators, including V/(V + Ni) and Ce/La, reveal that the anoxic conditions persisted from the Late Permian to the Middle Triassic, with a significant increase in the degree of anoxia. Provenance‐sensitive geochemical indicators (La/Th vs. Hf, La/Sc vs. Co/Th, TiO 2 /Al 2 O 3 vs. TiO 2 /Zr), along with tectonic setting discrimination diagrams based on zircon trace elements, indicate that the clastic contributions to the Northern Qiangtang Basin during the Late Permian to Middle Triassic were dominated by felsic volcanic arc‐derived sources. Detrital zircon age spectra show a notable shift in provenance from the Late Permian to Early Triassic, with Late Devonian to Early Carboniferous volcanic rocks from the western Northern Qiangtang Terrane contributing partially to the southern Northern Qiangtang Terrane, while Late Permian to Early Triassic continental arc magmatism provided proximal volcanic sources. We conclude that the development of the Late Permian to Middle Triassic sedimentary sequences in the southern Northern Qiangtang Terrane was closely linked to the subduction of oceanic crust beneath the Northern Qiangtang Terrane and subsequent closure of the Paleo–Tethys Ocean. These findings provide an improved understanding of the climatic, depositional and tectonic evolution of the NQT during the Permian–Triassic transition and have significant implications for further exploration of the early evolution of the Paleo‐Tethys Ocean and regional tectonic frameworks.