The role of Indian and Tibetan lithosphere in spatial distribution of Cenozoic magmatism and porphyry Cu-Mo deposits in the Gangdese belt, southern Tibet

We suggest that this difference reflects the variable extent of underthrusting of the Indian plate continental lithosphere beneath Tibet in the Oligo-Miocene, and diachronous breakoff of the Greater India slab. In the absence of underthrust Indian lithosphere to the east of ~ 89° E in the Oligo-Miocene, slab breakoff triggered asthenospheric upwelling and partial melting of previously subduction-modified Tibetan lithosphere, generating hydrous, oxidized calc-alkaline magmas with the potential to generate porphyry Cu-Mo deposits. In contrast, underthrusting of the Indian plate to the west at this time limited the involvement of asthenospheric melts and the extent of partial melting of subduction-modified lithosphere, with the result that melts ± fluids derived from the underthrust lithosphere were infertile.