Subduction Erosion Revealed by Late Mesozoic Magmatism in the Gangdese Arc, South Tibet

Subduction of oceanic lithosphere can cause crustal growth and destruction, but whether this balancing act is common in a single fossil convergent system has been unclear. Here we report geochronologic‐geochemical‐isotopic data on Mesozoic igneous rocks in the central‐eastern Gangdese arc. Our results reveal: (a) A coupling of magmatic arc migration toward the continent interior with a marked incompatible enrichment of sub‐arc mantle magma sources; (b) numerous Late Cretaceous adakites were generated via combined partial melting of both eroded forearc crust debris and subducted oceanic crust; (c) the truncation of forearc crust and extremely short arc‐suture distance. Our work demonstrates that although there was significant vertical growth of juvenile crust throughout the Gangdese arc during the Late Mesozoic, a large amount of continental crust was returned back into the mantle through lateral subduction erosion at the same time. This study provides important insights into long‐term material recycling on Earth. Plain Language Summary Arc magmatism plays a significant role in the formation of new crust, tectonic erosion has also been suggested to represent a major process associated with the destruction of continental crust. Crust generation and destruction triggered by subduction sustain the volume of the continental crust in some modern arcs, but subduction erosion is difficult to identify in fossil convergent systems and whether or not this balancing act is a common process over long geological period has been unclear. Here we report geochronologic‐geochemical‐isotopic data on Mesozoic igneous rocks in the central‐eastern Gangdese arc, which is widely considered to have been a very important area for Phanerozoic crustal growth. We consider magmatism along with integrated tectonic and sedimentological evidence to constrain the subduction erosion history of the Gangdese arc. We propose that the southern part of Eurasia was a typical erosive plate margin during the Late Mesozoic comparable to modern Andean arc. Although there was significant vertical growth of juvenile crust throughout the Gangdese arc during the Late Mesozoic, a large amount of continental crust was returned back into the mantle through lateral erosion at the same time. This study provides important insights into long‐term material recycling and crustal evolution on Earth. Key Points The Late Mesozoic Gangdese arc suffered extensive tectonic erosion triggered by the subduction of Neoteth