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The widespread Linzizong volcanic successions (LVS) in the Lhasa Terrane was a magmatic response to the tectonic transition from Neo‐Tethyan oceanic subduction to the India–Asia collision, which has been the subject of many studies; however, studies on the LVS in the western Lhasa Terrane are scarce compared to those in the east, limiting our understanding of the tectonic transition. Zircon U–Pb ages of two rhyolitic samples from the Shiquanhe region in the west of the Lhasa Terrane indicate that at least part of the Zenong Group, previously thought to have formed during the Early Cretaceous, was actually erupted during the Late Palaeocene (ca. 54 Ma) and belongs to the LVS. The rhyolites are characterized by high SiO2 and Al2O3, moderate K2O and Na2O, and low MgO, CaO, and FeO contents, enrichment in Rb and Th, depletion in Sr, Ba, Eu, Nb, and Ta, and have relatively uniform whole‐rock εNd(t) (−1.90 to −0.89) and zircon εHf(t) (+0.95 to +5.03) values. These geochemical characteristics indicate that they were formed by the partial melting of juvenile continental crust with subsequent plagioclase, biotite, amphibole, and Fe–Ti oxide fractionation. Combined with the results of previous studies, our data show that the western Lhasa Terrane underwent intensive Early Cenozoic crustal growth, similar to what occurred in the east, due to underplating of mantle‐derived magma resulting from the roll‐back and eventual break‐off of the Neo‐Tethys slab after the initial continental collision. [ABSTRACT FROM AUTHOR]

An integrated investigation of Lower Jurassic Jialapu Formation (including U-Pb dating of igneous and detrital zircons, geochemical analysis of igneous rocks, and analysis of detrital modes of sandstone interbeds) in the southern margin of the Lhasa terrane, Tibet, provides new constraints on the early evolution of the Neo-Tethyan Ocean. Our new data reveal a stage of silicic magmatism, with an arc affinity along the southernmost Eurasian margin at 193-190 Ma, which is characterized by high SiO2 (76.5-80.0 wt%), Na2O (5.30-7.22 wt%) and low K2O (0.07-0.55 wt%), MgO (0.16-0.54 wt%), Cr (1.44-4.37 ppm), and Ni (0.67-1.62 ppm) contents with low εNd(t) values of + 1.21 to + 2.33. These silicic volcanic rocks are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and can be classified as highly fractionated I-type rhyolites. They show a wide range of zircon εHf(t) values from − 11.7 to + 9.4, suggesting variable contributions from both juvenile and ancient crustal sources. It is concluded that the Jialapu Na-rich rhyolites were derived by the partial melting of a highly differentiated residual melt separated from the K-rich magma, triggered by upwelling asthenospheric mantle. Detrital zircons in the sandstones from the Lower Jurassic Jialapu Formation are dominantly the Mesozoic ones, which are likely derived from Lhasa terrane sources. Considering the associated sedimentary records as well as literature data, it is suggested that an Early Jurassic back-arc basin developed along the southern Lhasa terrane in response to the northward subduction of the Neo-Tethyan Ocean. [ABSTRACT FROM AUTHOR]

The absence of a fully preserved foreland basin system in the central-eastern Yarlung-Zangpo Suture Zone (YZSZ) of Tibet has hindered the understanding of the initial timing of the India-Asia collision along strike. To address this issue, remnant foredeep and wedge-top deposits of the foreland basin system are described from the Tethyan Himalaya sequence and the YZSZ in the Xigaze area. The foredeep is defined by the olistostrome of the Zongzhuo Formation, which consists of matrix and blocks, including chert, limestone, sandstone and volcanic rocks. Based on the matrix properties, the Zongzhuo Formation is divided into two units: a lower member (Zhilong unit) with a matrix composed of black shale and thin layers of siltstone and an upper member (Yongla unit) with a matrix composed of distinctly red shale or yellow-green siliceous mudstone with interbedded siltstone and limestone. The Zongzhuo Formation is dated to 65–57 Ma by detrital zircon U - Pb chronology and radiolarian assemblages. In the YZSZ, the Puxia and Jiabi units are interpreted as wedge-top deposits consisting of mudstone matrix and exotic blocks, such as sandstone, chert and limestone. The maximum depositional ages (MDAs) of the sandstone blocks from both units are ca. 65–59 Ma. Detrital zircon provenance analysis and trace element data exclude an intraoceanic arc origin and point to a source from the Gangdese arc and recycled accretionary wedge in the suture zone. Therefore, we propose that the initial collision between India and Asia occurred at 65 Ma in the central-eastern YZSZ. • We report a remnant peripheral foreland basin at the Yarlung-Zangpo Suture Zone. • The foredeep consists of the Zongzhuo Formation on the Tethyan Himalaya. • The wedge-top, exposed on the accretionary wedge, contains Jiabi and Puxia units. • The foredeep implies the India-Asia collision is no later than 65 Ma. • The ages and provenance of wedge-top and foredeep support a single-stage collision. [ABSTRACT FROM AUTHOR]