Influence of the viscosity of the early Earth's mantle on its cooling dynamics
Abstract
In its early evolution, the Earth's mantle likely experienced several episodes of complete melting. After a first stage of rapid and significant crystallisation (i.e., Magma Ocean stage), the mantle cooling is slowed down because of the rheological transition that occurs at a critical melt fraction of 30-40%. From this transition, the early mantle continued to crystallise from the bottom up to the surface, while thick thermal boundary layers grew above and below this reservoir (i.e., Mushy stage). Once the mantle becomes fully solidified, large-scale geodynamical flows may eventually arise resulting in global convection and modern tectonics. We have developed numerical models to monitor the thermal evolution of a cooling and crystallising mushy mantle from an initially partially molten mantle. These models integrate recent and strong experimental constraints from mineral physics such as adiabatic temperature profiles and liquidus/solidus up 140 GPa for different mantle compositions. Our preliminary results show that the mushy mantle cooling is strongly dependent on the parameters used to calculate the viscosity of the solid fraction of the cooling mantle. In this presentation, we will illustrate these early processes and discuss the global deep consequences of this early cooling event.
- Publication:
-
EPSC-DPS Joint Meeting 2019
- Pub Date:
- September 2019
- Bibcode:
- 2019EPSC...13..432M