On the origin of high-pressure mafic granulite in the Eastern Himalayan Syntaxis: Implications for the tectonic evolution of the Himalayan orogen

•Mafic granulites from the Eastern Himalaya underwent long-lived HP and HT metamorphism and intensive partial melting.•The generated voluminous granitic melts with distinct compositions provided the source for the Himalayan granites.•The Himalayan orogen has a gradual decreasing metamorphic pressure but increasing temperature from west to east.•The Indian plate has a subduction angle that flattens from west to east after the Indo-Asian collision at the Early Cenozoic.•The melts derived from the underthrusted Indian crust contributed to the Early Cenozoic magmatism of the Gangdese arc.