New Constraints on Cenozoic Subduction between India and Tibet

Abstract The nature of the lost lithosphere that subducted between India and Tibet since the Paleocene remains controversial, with existing propositions including it being either entirely continental, oceanic, or a mixture of the two. As the subduction history of this lost lithosphere strongly controlled Tibetan intraplate tectonism, we attempt to further constrain its nature (density structure) by reproducing the histories of magmatism and crustal thickening and present-day plateau properties with numerical models. By matching time-evolving geological patterns, we find that the Tibetan tectonism away from the Himalayan syntaxis is most consistent with the initial subduction of a cratonic terrane at 55±5 Ma followed by a buoyant tectonic plate with a thin crust (e.g., a broad Indian continental margin), with limited or no oceanic crust. We propose that the subduction of this “Himalandia” was analogous to what would happen if modern Zealandia+ Australia were to undergo subcontinental collision and subduction.