Crustal deformation of the eastern Tibetan plateau revealed by magnetotelluric imaging

Abstract

The ongoing collision of the Indian and Asian continents has created the Himalaya and Tibetan plateau through a range of deformation processes. These include crustal thickening, detachment of the lower lithosphere from the plate (delamination) and flow in a weakened lower crust 1‐6 . Debate continues as to which of these processes are most significant 7 . In eastern Tibet, large-scale motion of the surface occurs, but the nature of deformation at depth remains unresolved. A large-scale crustal flow channel has been proposed as an explanation for regional uplift in eastern Tibet 6,8,9 , but existing geophysical data 10,11 do not constrain the pattern of flow. Magnetotellurics uses naturally occurring electromagnetic waves to image the Earth’s subsurface. Here we present magnetotelluric data that image two major zones or channels of high electrical conductivity at a depth of 20-40 km. The channels extend horizontally more than 800 km from the Tibetan plateau into southwest China. The electrical properties of the channels imply an elevated fluid content consistent with a weak crust 12,13 that permits flow on a geological timescale. These findings support the hypothesis that crustal flow can occur in orogenic belts and contribute to uplift of plateaux. Our results reveal the previously unknown complexities of these patterns of crustal flow. Many previous studies of the IndiaAsia