Post-collisional extension of the South Altun subduction-collision belt, northern Tibetan Plateau: Insight from phase equilibria modeling and zircon geochronology of pelitic migmatites

•Continental collision led to the burial of pelitic rocks in the South Altun.•Pelitic migmatites were formed under the conditions of ∼850–870 °C and 0.6–0.7 GPa.•High-T/P type metamorphism and migmatisation lasted for ∼10 Myr (457–447 Ma)•Continental subduction to post-collisional extension took place in ∼50 Myr.