Geochemistry and zircon U–Pb geochronology of granitic rocks in the Buqingshan tectonic mélange belt, northern Tibet Plateau, China and its implications for Prototethyan evolution

•The intrusive is divided into adakitic rocks and normal arc rocks chemically.•The magmas formed by partial melting of subduction slab in Early Silurian.•This intrusive formed in late stage of oceanic crust subduction.•The East Kunlun Ocean crust subducted from Middle Cambrian until Early Silurian.