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Slab rollback is one of the primary processes in shaping tectonic framework. However, in the Tibet–Himalaya orogen, the timing of the Neo-Tethyan slab rollback remains controversial. In this contribution, we investigated an early Paleocene (ca. 62 Ma) A1-type granitic intrusion (South Gongshan) from the Gaoligong–Tengliang–Yingjiang (GTY) area, SE Tibet. It is mainly characterized by high 10,000*Ga/Al ratios (4.0–9.1) and extremely high HFSEs contents (Zr + Nb + Ce + Y = 669–3146 ppm), with relatively low Y/Nb ratios (0.8–1.1). The samples collected from the intrusion exhibit high zircon εHf(t) (+1.1 to +5.7) and whole-rock εNd(t) values (− 0.8 to − 3.1). Geochemical data indicated that it was probably produced by extreme FC of asthenospheric mantle-derived basaltic magmas. Together with results from convergence rate between India and Asia, the emplacement of the South Gongshan intrusion was likely to be associated with a transition from flat to steep subduction triggered by the Neo-Tethyan slab rollback. We proposed that the Neo-Tethyan slab rollback beneath the GTY area might have occurred at ca. 62 Ma. [ABSTRACT FROM AUTHOR]

This paper investigates the Jigede gabbros from the Shalazhashan tectonic belt, Alxa Block. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb dating reveals that they were emplaced in the Middle Permian (ca. 262 Ma). All the gabbro samples collected from the intrusion exhibit low contents of TiO2 (0.24–0.37 wt %) and (4.87–5.41 wt %), but high levels of MgO (11.15–12.15 wt %), CaO (11.45–12.75 wt %), Al2O3 (14.18–17.08 wt %) and high Mg# (0.81–0.83). Relative to HREEs and LILEs, the gabbros are enriched in LREEs and depleted in Th, Nb, Ce, Zr, Hf, and Ti, with positive Eu, Sr and U anomalies. In contrast to MORB, the Jigede intrusion has higher initial 87Sr/86Sr values of 0.7046 to 0.7054 and lower εNd(T) of + 1.8 to + 4.8. Elemental and isotopic data suggest that the intrusion was likely to have been produced by partial melting of a shallow lithospheric mantle source modified by slab-derived fluids, with subsequent cumulation of plagioclase. Thus, the Jigede intrusion was emplaced in a back-arc setting, in response to the Paleo-Asian oceanic subduction. In addition, the final closure of the Paleo-Asian Ocean did not occur prior to the Middle Permian. [ABSTRACT FROM AUTHOR]