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• A new Neoproterozoic stratum is determined in North Lhasa terrane. • The stratum is an intercontinental rift sedimentation (∼875 Ma). • Detrital zircons of the stratum exhibit both Australian and Indian characteristics. • North Lhasa originated from Western Australia. • North Lhasa experienced the Precambrian evolution of "rift–drift–emplacement". Constraining the origin and Paleogeographic positions of ancient continental fragments plays a crucial role in reconstructing and validating supercontinent cycles. The Lhasa terrane in southern Tibet is the key to revealing the early formation and evolution of the Himalayan–Tibetan orogen. Although previous origin models of the Lhasa terrane are supported by Phanerozoic evidence, Precambrian geological records have not been comprehensively considered. The U–Pb age and Hf isotope data on detrital zircons from newly discovered Precambrian basement in the North Lhasa terrane define two distinctive age populations of ca. 1170 Ma with ε Hf (t) values identical to the coeval detrital zircons from Western Australia, and ca. 950 Ma with a similar ε Hf (t) range to the contemporaneous detrital zircons from South Qiangtang and Tethyan Himalaya terranes. The ca. 1170 Ma detrital zircons were most likely derived from Western Australia, whereas the ca. 950 Ma detrital zircons might have been sourced from the norther Indian margin. Compiled detrital zircon data shows that in the early Neoproterozoic, the affinity between northern Lhasa and Western Australia decreased, while the predilection between northern Lhasa and northern India increased. Combined with ca. 930–870 Ma rift, ca. 870–700 Ma arc igneous rocks and ∼650 Ma high-pressure granulites, we propose that the North Lhasa terrane was a ribbon continent that rifted from Western Australia in the early Neoproterozoic (ca. 930–870 Ma), drifted westward along the northern edge of Rodinia in the middle Neoproterozoic (ca. 870–700 Ma), and was emplaced in the Northern East African Orogen during the late Neoproterozoic (∼650 Ma). [ABSTRACT FROM AUTHOR]

The timing and mechanisms of collapse of the middle and western segments of the Lhasa–Qiangtang orogenic belt in central Tibet are poorly constrained. Here, we report whole-rock geochemical, and zircon U–Pb age and Hf-isotopic data for the Asa-intrusive rocks located at the southern edge of the northern Lhasa subterrane. The Asa-intrusive rocks include the Namujeler granite porphyry (NGP), the Gernicamdro granodiorite porphyry (GGDP), and the Neeze granodiorite porphyry (NGDP). The NGP and GGDP have adakitic geochemical characteristics, such as high Sr (317–511 ppm), Sr/Y (57.8–96.8), and (La/Yb)N (13.1–16.0), and low Y (4.68–5.49 ppm) and heavy rare-earth element contents (e.g., 0.44 ≤ Yb ≤ 0.57 ppm). In situ zircon U–Pb dating of three samples yielded Late Cretaceous ages (NGP = 88.7 Ma; GGDP = 89.7 Ma; NGDP = 90.1 Ma). Zircon εHf(t) values vary over a wide range (NGP = − 11.5 to + 9.3; GGDP = + 4.6 to + 7.6; NGDP = − 21.2 to + 7.6). Our results suggest that the Asa adakitic rocks (NGP and GGDP) are most likely generated by partial melting of thickened mafic lower crust under a garnet-bearing amphibolite facies. The presence of the Asa adakitic rocks indicates that the crust beneath the Lhasa–Qiangtang collision zone had experienced thickening and the crustal thickness remains quite large (> 40 km) at ca.90 Ma. On the basis of evidence from the Asa-intrusive suite and coeval igneous rocks, along with some stratigraphic and tectonic constraints, we proposed that the middle and western segments of the Lhasa–Qiangtang orogenic belt was collapsed by lithospheric delamination during the early Late Cretaceous (ca. 94–82 Ma), and the thickened lithospheric keel did not delaminate as a wholly, it delaminated piece by piece. From east to west, the time of the lithospheric delamination is getting younger. [ABSTRACT FROM AUTHOR]