Some thermotectonic aspects of the Tibetan plateau

Abstract

Advective heat transfer plays a prominent role in the thermal evolution of tectonically active regions, such as the Tibetan plateau. Different tectonic histories lead to different thermal evolutions, so that a study of the present and ancient thermal signatures can improve our understanding of thermotectonic histories. We use an “upwind” finite-element method to calculate the thermal consequences of two tectonic models suggested by previous studies, and compare the calculated results with observations. Many factors that may affect the thermal structure are investigated, including advection, frictional/shear heating, latent heat of melting, and heat refraction. An imbricated thrust model yields a thermal structure that agrees best with observations of heat flow, crustal low-velocity zones, leucogranites and inverted metamorphism. We suggest that a heterogeneous thermal structure exists beneath Tibet. Southern Tibet has a relatively hot mid-crust and cold mantle resulting from frictional/ shear heating and advective cooling that are due to active thrusting, whereas northern Tibet has a relatively cool crust and hot mantle resulting from thermal relaxation in a region of thickened crust after the cessation of thrusting.