Petrography, geochemistry, and detrital zircon geochronology of Zongzhuo Formation sandstones in southern Tibet: insights into the tectonic evolution and provenance model of the Tethys Himalaya during the Late Cretaceous

Abstract

Upper Cretaceous Zongzhuo Formation sandstones in the Tethyan Himalaya record critical provenance shifts linked to the India–Asia collision. Petrographic, geochemical, and detrital zircon U-Pb data classify sandstones into three types: Type I (high maturity, quartz/feldspar-rich, passive margin), derived from the Indian craton, with REE patterns mirroring Jurassic passive margin sediments, indicating long-distance transport during ongoing Neo-Tethys subduction; Type II (mixed felsic-mafic composition), reflecting dual sourcing from the Indian craton and the Lhasa Terrane, marking the end of Neo-Tethys subduction and transition to initial collision; and Type III (low maturity, lithic/OIB-type REE, high TiO2), near-source Lhasa arc volcanics with young zircons (~100–70 Ma), signaling active collision and foreland basin development via India underthrusting. Provenance evolution – from purely Indian (Type I) to mixed (Type II) and dominantly Lhasa-derived (Type III) – constrains the collision onset to ~70–66 Ma. This shift coincides with the Tethyan Himalaya’s transformation from a passive margin to a foreland basin, driven by India–Asia convergence. The data challenge Paleogene collision models, emphasizing Late Cretaceous tectono-sedimentary responses as the key markers of collision initiation. These findings provide robust sedimentological evidence for reconstructing collision dynamics and refining regional tectonic timelines.