The crustal juvenile and reworking in eastern Tibet due to tectonism and magmatism.

Crustal thickening in Tibet results from the collision of India and Eurasia. The fine structure of the crust is vital information to detect the tectonic genesis of crustal growth and reworking. Here, we constructed the crustal structure of eastern Tibet and its neighboring areas using depth-domain receiver function imaging. The imaging results reveal widespread low-velocity layers in the mid-crust, alternating high- and low-velocity structures in the lower crust, and regional variations in the velocity at the bottom of the lower crust and the thickness of the entire crust. We propose that the lower crust is juvenile crust, formed by multiphase magmatism and tectonic activity during continental collision. The regional variations in crustal structure can be attributed to differences in the tectonic position of subduction-collision system and the distinct crustal-derived materials that contribute to the formation of the juvenile crust. The low-velocity layers in the mid-crust are more likely to be the product of arc magmatism during the assembly of micro-continents. Based on the constraints of the unique crustal structure, we suggest that tectonic compression and magmatism caused the juvenile and reworking of the Tibetan crust.