Tibetan Plateau growth linked to crustal thermal transitions since the Miocene

The topographic transition of central-northern Tibet since the early Miocene has created a consistently high and flat plateau similar to that of today. However, to date, the associated deep crust and/or /mantle events are poorly understood, mainly due to an early Miocene metamorphic-magmatic lull within the Qiangtang Block. To address this issue, we undertook a study of crustal xenoliths and zircon xenocrysts in 6.0-2.3 Ma lavas in the Qiangtang Block. The occurrence of 22.6-12.9 Ma high-temperature-low-pressure granulite xenoliths implies that the middle crust of the block has been very hot since that time. Zircon xenocrysts and granitic xenoliths from 6.0-2.3 Ma lavas were studied and shown to have high delta O-18 values, which supports Miocene crustal melting and the formation of unexposed, coeval felsic plutons. Combined with paleoelevation data from the Tibetan Plateau, our results suggest that the early Miocene cold-hot thermal transition of the middle-lower crust was near-synchronous with topographic evolution from high-relief mountains to a flat plateau, which supports crustal flow as the main topographic smoothing mechanism for central-northern Tibet.

Automated summary

This study investigates crustal xenoliths and zircon xenocrysts in lavas from the Qiangtang Block to better understand the deep crust and mantle events associated with the topographic transition of central-northern Tibet. The findings suggest that the middle crust of the block has been hot since the early Miocene, supporting the formation of unexposed felsic plutons during crustal melting. The results also indicate that the early Miocene cold-hot thermal transition of the middle-lower crust was synchronous with the topographic evolution from high-relief mountains to a flat plateau, highlighting the role of crustal flow in the topographic smoothing mechanism for central-northern Tibet.