Provenance of Late Triassic-Early Jurassic forearc basin in southern Tibet and its tectonic significance

The Late Triassic-Early Jurassic tectonic setting that produced arc magmatism in the southern Gangdese region and the timing of the initial Yarlung Zangbo Ocean sub-duction remain controversial. Arc-related basin records can provide sedimentological constraints on these con-troversial events. In this study, the sedimentary tectonic setting of the Liuqiong Formation and the tectonic evolu-tion of the Yarlung Zangbo Ocean in the southern Gang-dese were investigated using detrital zircon U-Pb chronology and Hf isotope data. The Liuqiong Formation mainly comprises intercalated clastic and volcanic rocks, locally developed limestone blocks, and is characterized by deep -water gravity flow deposits. The detrital zircon U-Pb ages were concentrated at 202-249 Ma, with highly positive epsilon Hf(t) values (+10.3-+14.4). Provenance analyses indi-cate that the sedimentary detritus in the Liuqiong Forma-tion was sourced from Late Triassic-Early Jurassic arc magmatic rocks in the southern Gangdese region. Based on comprehensive investigations of the regional geology, the Late Triassic-Early Jurassic Liuqiong Formation was deposited in a forearc basin setting, and contains a basin record of the northward subduction and southward accre-tion of the Yarlung Zangbo Ocean.