How and How Much Did Western Central Tibet Raise by India–Asia Collision?

Abstract

This study uses geochemical mohometers to investigate the paleo-crustal thickness and elevation of western Tibet through the Cretaceous to Eocene. The northern Lhasa Block and southern Qiangtang Block (QB) had a similar paleo-crustal thickness of ∼55 km during the Late Cretaceous, but the latter had reached its present-day thickness (∼70 km) and elevation (∼5.5 km) by the mid-Eocene, which was not caused by underthrusting of Indian crust according to isotopic evidence. Our study demonstrates the western and central QB shared a similar early Paleogene tectonomagmatic evolution with the formation of a continues proto-plateau in central Tibet, resulting from crustal shortening and subsequent lithospheric foundering. This in turn implies underthrusting of the Indian lithosphere beneath the western QB after Eocene, given the present-day lithospheric difference between the western and central QB. Our reconstruction of paleo-crustal thickness and elevation, however, suggests the Indian underthrusting caused minimal further crustal thickening and uplift.