Origin of Tibetan post-collisional high-K adakitic granites: Anatexis of intermediate to felsic arc rocks

Abstract Potassium-rich adakitic rocks have been used to infer high-pressure (HP) melting of thickened or foundered mafic lower crust in post-collisional settings. However, their origin remains debated because potassic rather than sodic nature. We address this debate by investigating the source Oligocene high-K granites southern Tibet, which are widely attributed overthickened crust. Our new data provide evidence for generation these anatexis exposed migmatitic intermediate felsic arc orthogneisses. These contain high-Th/U magmatic zircons (30?22 Ma), and inherited (66?48 Ma) with same ?Hf(t) (0 +12) as coeval migmatites. The migmatites turn low-Th/U metamorphic zircon rims around 66?48 Ma cores recording anatectic event at 29?25 Ma. Phase equilibrium modeling yields an temperature ~740 °C pressure (P) ~0.9 GPa shows that garnet is stable P > 0.7 melt-present field. results indicate magmas derived from older pressures, stability field, without any involvement HP metabasaltic rocks. propose hybridization between such purely crustal subcontinental lithospheric mantle–derived shoshonitic hybridized Oligocene–Miocene microgranular enclave–bearing granitic Tibet.