Petrogenesis of Late Cretaceous magmatic rocks in the Zhongcang area of northern Tibet and their implications for early up lift of the plateau

During the late Cretaceous, extensive magmatic activity erupted in the central Tibetan Plateau. accompanied by rapid surface uplift. However, the deep dynamical mechanisms behind this phenomenon have been a subject of considerable debate. This study conducts U-Pb zircon dating, as well as analyses of whole-rock major and trace elements and Sr-Nd-Hf isotopes on the diorite and rhyolite developed in the Zhongcang area of northern Tibet, aiming to provide new constraints on regional tectonic-magmatic evolution. The U-Pb zircon dating results indicate that both the diorite and rhyolite formed in the Late Cretaceous (90 - 85 Ma). The geochemical characteristics of the diorite show high Sr. low Y content- and high Sr/Y ratios, indicating an affinity to adakite. Combined with its high Mg~, it is proposed to be a product of the mixing of underplated eclogite-facies lower crustal melts with mantle materials. The geochemical and isotopic characteristics of the rhyolite are similar to those of the diorite. reflecting a common magmatic source. However, its significant depletion in Rb. Ba. Sr. and other easily altered elements suggests it underwent intense alteration during the late diagenesis. Coupled with the contemporaneous eruption of high-Mg adakitic magma and large-scale molasse deposition in the region* this study posits that the tectonic-magmatic activity in the central Tibetan Plateau during the Late Cretaceous was a result of the thickening and detachment of the lower crust following the collision of the Bangong Lake -Nujiang suture zone. This deep detachment simultaneously triggered rapid surface uplift, forming a Cretaceous paleo-plateau and laying the foundation for the modern plateau's formation. © 2024 Science Frontiers editorial department. All rights reserved.