TWO STAGES OF THERMAL EVOLUTION OF THE CONTINENTAL LITHOSPHERE

A.P. Trubitsyn

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

atrub@ifz.ru

Abstract. The evolution of the continental lithosphere, unlike the oceanic one, lasts more than 3.5 billion years. This evolution was largely determined by thermal factors, such as the removal of heat from the outer surface, the interaction of the conductive layer of the lithosphere with mantle thermal convection and the strong dependence of the viscosity of the upper layers of the Earth on temperature. The aim of the work is to simulate long-term interaction of these factors over a period of several billion years on the basis of the whole-mantle thermal convection equations. In our evolutionary model the nucleus of continental lithosphere with the thickness of 50 km was inserted in the mantle, which then began to grow in depth due to the reorganization of convection under the continental lid with a conductive heat transfer mechanism. For the self-consistent modeling of the lithosphere thickness changes in time we set the condition of viscosity jump by three orders of magnitude with a decrease in local temperature below 1200 °C. The results of successive calculations demonstrated that the initial period of growth of the continental lithosphere due to its cooling, which takes about one billion years, is subsequently replaced by its slow thinning due to accumulation of heat under a thick heat-insulating lithospheric cover. The calculated maximum of the average thickness of the growing lithosphere, estimated by temperature and viscosity, is 162 km, while estimated by the conventional point of intersection of the lithospheric geotherms with mantle adiabat it is 100 km more. The increase in the average mantle temperature from the heat-insulating effect is about 100 K/Gy and continues both at the stage of the lithosphere thickening and at the subsequent stage of its slow thinning. The mantle warming up due to the presence of continents is one of the competing factors in the global process of the Earth's secular cooling. The conclusion about the presence of two stages in the evolution of the continental lithosphere clarifies the existing ideas about the formation of the current state of the outer layers of the Earth.

Keywords: continental lithosphere, mantle convection.

About the author

TRUBITSYN Alexander P. – Cand. Sci. (Phys. and Math.), leading researcher, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Moscow, Russia. Tel.: +7 (499) 254-91-95. E-mail: atrub@ifz.ru

Cite this article as: Trubitsyn A.P. Two stages of thermal evolution of the continental lithosphere, Geofizicheskie Protsessy i Biosfera (Geophysical Processes and Biosphere), 2019, vol. 18, no. 1, pp. 5–12 (in Russian). https://doi.org/10.21455/gpb2019.1-1

English version: Izvestiya, Atmospheric and Oceanic Physics, 2019, vol. 55, iss. 7. ISSN: 0001-4338 (Print), 1555-628X (Online). URL: https://link.springer.com/journal/volumesAndIssues/11485