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

Abstract

AbstractThis 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.