Mantle convection during magma ocean crystallization
Abstract
Partial or even complete melting of the mantle may have occurred early in the planet's history, leading to the emergence of magma oceans. Depending on how the crystallization has proceed in the magma ocean, solid mantle formed upwards and/or downwards. The solid-liquid phase change, where solid is in contact with liquid of similar composition may allow the matter to flow through. Whether the flow through the phase change takes place or not, may depends by the latent heat transferred through the molted region during topography variations due to solid viscous flow. The boundary is permeable when the topography formed by viscous deformation is erased by the heat transfer in the magma ocean at greater rate than it is generated. Linear and weakly non linear analysis have shown that Rayleigh-Bernard flow subjects to two penetrative boundaries is characterised by a non-deforming translation or long wavelength weakling deforming mode at relatively low Rayleigh number. Both modes lead to an efficient heat transfer, such as convection affected by only one boundary affected by solid-liquid phase change. In this study, using 2D Cartesian numerical simulations, we explore how the solid convection may be affected by these boundary conditions, and we systematically analyse the solid dynamics at relatively high Rayleigh number (Ra > 10 Racritic) to better speculate on the dynamics which may have affected the primordial formation of the Earth or Rocky planets. Our results suggest that in presence of two permeable phase change boundaries, the solid thermal structure of the down- and up- welling regions are similar to the non-deforming translation mode, and that the wavelength of the weakly-deforming mode increases with Rayleigh number, leading to a whole non-deforming translation mode for vigorous mantle convection. The presence either of one or of two phase change enhances the efficiency of heat transfer compared to the equivalent without phase change at the boundary.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI11B0009M
- Keywords:
-
- 1060 Planetary geochemistry;
- GEOCHEMISTRYDE: 3630 Experimental mineralogy and petrology;
- MINERALOGY AND PETROLOGYDE: 5455 Origin and evolution;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8147 Planetary interiors;
- TECTONOPHYSICS