关键词: 冈底斯弧岩浆作用, 新特提斯洋俯冲, 印度亚洲大陆碰撞, 青藏高原南部

Abstract: The Gangdese magmatic arc, located in southern Tibet, was formed during the long-lasting subduction of the Neo-Tethyan oceanic lithosphere and subsequent collision between the Indian and Asian continents, typical of composite continental magmatic arc. Therefore, the arc is a natural laboratory for studying subduction-related magmatism and continental crust growth. Based on a synthesis of available research results, we propose that the Gangdese arc experienced five stages of tectonic-magmatic events during its formation and evolution. The first stage of magmatism occurred before the Late Cretaceous, characterized by normal subduction of the Neo-Tethyan oceanic lithosphere and formation of subduction-related magmatic rocks. The second stage is related to subduction of an active Neo-Tethyan mid-oceanic ridge, featuring extensive Late Cretaceous magmatism and juvenile crustal growth. The third stage of the latest Late Cretaceous arc magmatism occurred during subduction of the residual Neo-Tethyan oceanic lithosphere. The fourth stage of Paleocene to middle Eocene magmatic flare-up resulted from slab roll-back and break-off of subducted Neo-Tethyan ocean during the Indo-Asian collision, marked by significant thickening and partial melting of juvenile and old crusts. And the fifth and latest post-collisional magmatism involved formation of thickened lower crust-derived adakitic rocks and mantle-derived potassic to ultrapotassic volcanic rocks during the late Oligocene to middle Miocene, induced probably by the roll-back and break-off of the deeply subducted Indian lower crust and mantle lithosphere or by convective removal of the thickened Gangdese arc mantle lithosphere. The systematic temporospatial variations of magmatic events and magmatic compositions of the Gangdese arc provide an excellent record of tectonic evolution from the Neo-Tethyan ocean subduction to India-Asia continental collision.

Key words: Gangdese arc magmatism, Neo-Tethyan oceanic subduction, India-Asia continental collision, southern Tibet