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The history of volcanic activity of the Gangdese arc in southern Tibet during the Cretaceous remains poorly known due to the intense erosion of the arc. Here we present zircon U–Pb ages, trace element and Hf isotopic data of tuffs and volcanic conglomerates from the Chongdoi and the Ngamring Formation in the Xigaze forearc basin. Three tuff samples from the Chongdoi Formation yield zircon U–Pb ages around 112 Ma. Such ages could be taken as their depositional ages, indicating that detrital clasts of the Chongdoi Formation were deposited at that time. One andesitic conglomerate sample from the Ngamring Formation was dated at ca. 105 Ma, the other rhyolitic conglomerate sample and one tuff sample were dated to be ca. 95 Ma and 91 Ma, respectively, suggesting that this formation was formed during the late Albian–late Turonian. All zircons illustrate I-type granitoid characteristics and possess low Ti-in-zircon temperatures (< 800 °C). Zircon ε Hf (t) values of tuffs from the Chongdoi Formation define two groups: (1) the first group of 117–110 Ma displays large positive ε Hf (t) values (+ 12.1 to + 17.1), larger than those of the tuff from the Ngamring Formation (+ 6.0 to + 10.2); (2) the second group of 119–111 Ma yields negative to small positive ε Hf (t) values (− 4.5 to + 1.1). All above observations indicate that their host rocks were derived from the juvenile materials with significant input of fluids. Combined with extant data, the first group and the tuff, volcanic conglomerates from the Ngamring Formation are mostly likely derived from the eroded Cretaceous volcanic rocks in the Gangdese arc, while the second group is likely sourced from the late Early Cretaceous volcanic rocks in the central Lhasa terrane. Our data confirm the presence of Cretaceous volcanism in the Gangdese arc, suggesting that the Neo-Tethyan Ocean lithosphere was most likely subducted northerly in a normal angle rather than in a manner of low-angle subduction. [ABSTRACT FROM AUTHOR]

Abstract: The distribution of peraluminous granites in Tibet is treated on the basis of the tectonic zones in which they occur, their spatial and temporal distribution, the peak of magmatic activity and the volume of magma intruded. Magmatic activity, with the intrusion of peraluminous granites, was initiated during the Early Jurassic and culminated in the middle Miocene, especially between 20 and 10Ma. Rock types include tourmaline, muscovite and two-mica granites. Magmatic activity in the Gangdise Belt migrated from the east to west and from the south to the north. Episodes of tectonic evolution for the lithosphere of the Qinghai–Xizang (Tibet) Plateau, deduced from peraluminous granite intrusion are: (1) Latest Triassic to Early Jurassic (208–157Ma), representing the subduction phase of the Bangong Co–Nu Jiang oceanic zone; (2) Late Jurassic to Early Cretaceous (157–97Ma), representing the subduction and collision phases of the Bangong–Nu Jiang oceanic zone; (3) Late Cretaceous to early Paleocene (97–65Ma), representing the subduction and initial collision phases of the Yarlung Zangbo oceanic zone ; (4) Paleocene to Eocene (65–40Ma), representing the major collisional stage of the Yarlung Zangbo Oceanic zone and the formation of crust-derived granites; and (5) Oligocene to Recent, representing an intense intracontinental convergence phase. [Copyright &y& Elsevier]