The Bangong–Nujiang Ocean played an important role in the formation of the Tibetan Plateau prior to the Cenozoic India–Eurasia collision. However, there are still uncertainties about the subduction polarity and timing of the Lhasa–Qiangtang collision. We conducted sandstone petrologic and detrital zircon U–Pb–Hf isotopic analyses on the Cretaceous Wada mélange, trench-fill strata and Duoni Formation in the Basu area in the eastern Bangong–Nujiang Suture Zone. The Wada mélange (∼114 Ma) exhibits block-within-matrix features and a detrital zircon U-Pb age spectrum characterized by multiple peaks at 114–180 Ma, 200–300 Ma, and 1800–2000 Ma. The trench-fill strata consist of coherent chert, sandstone, and mudstone, with a detrital zircon age spectrum dominated by a single peak at ∼120 Ma. The ε(t) values of the 110–300 Ma detrital zircon grains in the Wada mélange and trench-fill strata range from −20 to +10 and are consistent with those of the South Qiangtang Terrane. The ε(t) values of the ∼120 Ma detrital zircons are all negative, and these grains were likely derived from a remnant Cretaceous arc in the South Qiangtang Terrane to the north. These data suggest that the accretionary wedge was derived from the South Qiangtang Terrane during the northward subduction of the Bangong–Nujiang Ocean. The Duoni Formation (∼113 Ma) represents peripheral foreland basin deposits with the Lhasa Terrane as the basement. Provenance analysis indicates that these deposits received clastic material mainly from the South Qiangtang Terrane and to a lesser degree from the North Lhasa Terrane. Our results suggest that the Lhasa–Qiangtang collision occurred in the Early Cretaceous (∼113 Ma) in the eastern segment of the Bangong–Nujiang Suture Zone.

中文翻译：

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八宿地区班公湖东部—怒江洋白垩纪缝合过程

班公湖-怒江洋在新生代印度-欧亚大陆碰撞之前的青藏高原形成过程中发挥了重要作用。然而，拉萨-羌塘碰撞的俯冲极性和时间仍存在不确定性。我们对班公湖缝合带东部巴苏地区的白垩系瓦达混杂岩、沟充填地层和多尼组进行了砂岩岩石学和碎屑锆石U-Pb-Hf同位素分析。 Wada 混杂岩（~114 Ma）表现出基体内块体特征和碎屑锆石 U-Pb 年龄谱，其特征在于 114-180 Ma、200-300 Ma 和 1800-2000 Ma 处有多个峰。沟渠充填地层由连贯的燧石、砂岩和泥岩组成，碎屑锆石年龄谱主要由约 120 Ma 处的单峰组成。和田混杂岩和沟充填地层中110~300 Ma碎屑锆石颗粒的ε(t)值范围为-20~+10，与南羌塘地体一致。 ～120 Ma碎屑锆石的ε(t)值均为负值，这些颗粒很可能源自南羌塘地体北侧的白垩纪遗迹弧。这些数据表明，增生楔源自班公湖-怒江洋向北俯冲期间的南羌塘地体。多尼组（∼113 Ma）代表以拉萨地体为基底的外围前陆盆地沉积。物源分析表明，这些矿床接收的碎屑物质主要来自南羌塘地体，少量来自北拉萨地体。我们的研究结果表明，拉萨-羌塘碰撞发生在班公-怒江缝合带东段的早白垩世（~113 Ma）。