Mantle upwelling induced by a bilateral convergent double subduction during Late Paleozoic in Eastern Tianshan, NW China: Evidence from high-resolution magnetotelluric profile

Abstract

Late Paleozoic oceanic subduction has been proposed for the formation of Eastern Tianshan, NW China, situated in the southern Central Asian Orogenic Belt. However, the patterns and consequences of the subduction remain undetermined. To identify the mode of the Late Paleozoic subduction, a high-resolution magnetotelluric (MT) long-profile across Eastern Tianshan was deployed. A three-dimensional (3D) inversion was conducted to obtain the resistivity model beneath the profile. The most obvious feature in the resistivity model is a well-developed conductor (∼30 Ωm) beneath Turpan-Hami Basin from ∼15 km depth extending to the uppermost mantle. This conductor is preferably ascribed to the metamorphic fluids from an ancient mantle upwelling. In addition, the MT observation suggests a double subduction in the south Kangguer suture, together with a southward dipping subduction in the north Kalamaili Fault during the Late Paleozoic. The bilateral convergent double subduction induced the mantle upwelling and controlled the initial extensional environment during Late Paleozoic in the Turpan-Hami Basin.