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Models of in situ oceanic subduction and underthrusting is proposed to explain the formation and exhumation of the central Qiangtang mélange belt. Some studies have suggested that continental subduction occurred in central Qiangtang, but there is a lack of definitive evidence. Thus, the role of continental subduction in the formation and evolution of the central Qiangtang mélange belt has not been fully considered. We therefore studied the origin and structural evolution of the central Qiangtang mélange belt. Detrital zircon research indicates that the continental blocks in the Gangma Co mélange are part of the Carboniferous-Permian strata of the South Qiangtang terrane and have a Gondwanan affinity. Structural studies and geologic observations in the Gangma Co area show a change in the structural style and a pressure difference between the lower mélange and the upper Carboniferous-Permian strata. Structures in the Gangma Co mélange include D1 layer-parallel ductile structures, D2 horizontal contractional structures, D3 flattening structures, and D4 slightly horizontal contractional structures. According to our analysis, the newly proposed in situ continental subduction model best explain these findings. [ABSTRACT FROM AUTHOR]

The Upper Triassic Langjiexue Group, which lies immediately south of the Yarlung-Tsangpo Suture Zone in the Shannan area of southeastern Tibet, represents an important part of the Tethyan Himalayan Sequence (THS). Its provenance and palaeogeography have been the subject of debate. We present new data on petrographic composition, whole-rock geochemistry, and detrital zircon U-Pb geochronology to constrain the provenance of the Langjiexue Group. The dominance of quartz grains and felsic volcanic lithic fragments suggests that the sandstones are litho-quartzose. The trace element geochemical signatures (V-Ni-Th*10, Co/Th-La/Sc, Eu/Eu*-Th/Sc) suggest derivation from felsic igneous sources. The detrital zircon age spectra display three major peaks: a Meso-to-Neoproterozoic peak (1200-900 Ma, 7-18%), a Neoproterozoic-to-Late Cambrian peak (750-500 Ma, 32-65%), and a Late Carboniferous-to-Late Triassic peak (300-200 Ma, 11-33%). The maximum depositional age of early Carnian (236-235 Ma) is obtained by calculating weighted average ages of the youngest zircons (≤250 Ma). The youngest age cluster (300-200 Ma) is incompatible with sources from neighbouring terranes, including the South Qiangtang terrane, Lhasa terrane, THS, and Higher Himalayan Crystalline. Correlations of the Permian-Triassic zircons with those of time-equivalent strata in northwest Australia, west Burma, and the Banda Arc unveil a potential connection to the Tasmanides along the convergent margin of eastern Australia. The New England Orogen (300-230 Ma) could have supplied the Langjiexue Group with magmatic materials via continent-scale drainage systems or a submarine fan complex. This scenario provides a new perspective into the transport of detritus from distal orogens to sedimentary basins thousands of kilometres away. [ABSTRACT FROM AUTHOR]