Paleocene Neo-Tethyan slab rollback constrained by A1-type granitic intrusion in the Gaoligong–Tengliang–Yingjiang belt of the Eastern Himalayan Syntaxis, SE Tibet
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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.
KeywordsA-type granite Neo-Tethys Slab rollback Paleocene SE Tibet
We are grateful to Wolf-Christian Dullo (editor in chief), J.F. Moyen (topic editor), Bernard Bonin, and other anonymous reviewers for their thoughtful reviews and constructive comments. This study is financially supported by the National Natural Science Foundation of China (Grants 41703022), Fundamental Research Funds for the Central Universities (lzujbky-2018-52), Joint Foundation Project between Yunnan Science and Technology Department and Yunnan University (Grants C176240210019) and Geology Discipline Construction Project of Yunnan University (Grants C176210227).
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