Magma migration and surface uplift in Pamir–western Tibet driven by deep lithospheric dynamics

Abstract

Abstract There are two parallel >1200-km-long semi-continuous (ultra)potassic magmatic belts in the southern (Karakorum-Lhasa) and the northern (Central Pamir–western Kunlun) parts of Pamir–western Tibet. The southern belt is widely attributed to northward subduction of the Indian plate, while it has been suggested that the northern belt relates to the southward subduction of the Asian plate. We report new zircon U-Pb ages and isotopic data for the northern belt that show eastward magma migration between ca. 20 Ma and the present, which are contemporaneous with continental-scale thermochronometric cooling ages. Whereas magma migration in the south was caused by progressive west-to-east Indian lithosphere break-off, magma generation in the north is shown to be related to asthenospheric mantle upflow through a small mantle window (~100 km width) forced by Indian lithosphere underthrusting, Pamir–western Tibet lithosphere mantle dripping, and resistance of the Tarim lithosphere. Northern belt magma migration relates to progressively eastward underthrusting of the Indian lithosphere that took ~15 m.y. to move northward across ~350 km to meet Asian lithosphere. Accordingly, both belts of (ultra)potassic magmatism relate to the northward subduction of the Indian plate that was responsible for plateau uplift in Pamir–western Tibet.