Mesozoic-Cenozoic tectonothermal evolution of the eastern part of the Tibetan Plateau (Songpan-Garzê, Longmen Shan area): insights from thermochronological data and simple thermal modelling

Abstract We present a synthesis of the tectonic and thermochronological evolution of the Eastern Tibet since the Triassic. The long-term cooling histories obtained on magmatic and metamorphic rocks of the South Songpan-Garzê, Kunlun and Yidun blocks are similar showing a very slow and regular cooling during Late Jurassic and Cretaceous, confirming the suspected lack of major tectonic events between c . 150 and 30 Ma. The exhumation linked to the Tertiary growth of the Tibetan Plateau initiated around 30 Ma and concentrates at the vicinity of the major tectonic structures. Exhumation rates increased again from about 7 Ma in the Longmen Shan. To interpret this very slow cooling rate between Late Jurassic and Early Cenozoic from granites of this area, we use a simple 1D thermal model that takes into account the thermal properties of both sediments and crust. The results suggest that: (1) high temperature (500 °C) can be kept over a long period of time; (2) during Cretaceous, cooling is mostly controlled by the thermal properties of sediments of continental origin; and (3) the initial Late Triassic rapid cooling rate was caused by the large thermal contrast between the granite body and the sedimentary rocks rather than by a high exhumation rate.