Palaeomagnetic and geochronologic results from lower cretaceous volcanics of the western Qiangtang terrane and implications for the Lhasa-Qiangtang collision.

The Lhasa-Qiangtang collision is key to understanding the formation and evolution of the Tibetan Plateau; however, the precise timing of this event remains hotly debated. To address this uncertainty, we present a combined palaeomagnetic and geochronologic study of Lower Cretaceous Meiriqieco Formation rhyolites from the western Qiangtang terrane. Our geochronologic data reveal an Early Cretaceous (ca. 113-109) age for the Meiriqieco Formation, contradicting previous Late Jurassic assignments. The tilt-corrected site-mean direction yields a palaeopole at 74.3°N, 250.5°E with A95 = 4.7° (N = 23). Integrating our new and existing palaeomagnetic data, we place the western Qiangtang terrane at ~ 23.1°N during the Early Cretaceous. Comparison with Early Cretaceous palaeomagnetic data from the western Lhasa terrane indicates that convergence of the two terranes occurred no later than the Early Cretaceous (ca. 132-100 Ma).