The Role of Magmatic Styles in Planetary Thermal Evolution Models

Abstract

Previous studies that investigated the effects of magmatism on the interior dynamics, in particular for Earth-sized planets, suggest that magmatism leads to more efficient mantle cooling. However, the extent to which different magmatic styles influence the thermal evolution of planets, and in particular smaller rocky bodies, has not yet been systematically investigated. Using geodynamic models, we compare the evolution of Mercury-, Mars-, the Moon-, and Venus-like bodies under “fully intrusive” and “fully extrusive” magmatism. For all planets, fully intrusive cases result in hotter and thinner lithospheres and, at the same time, colder deep mantles and core-mantle boundaries compared to fully extrusive cases. During planetary evolution, intrusive models generate more melt and at shallower depths than extrusive models, thereby potentially leading to different melt compositions. While the global average temperature of the entire silicate interior is lower on Venus in the intrusive scenario compared to the extrusive scenario, the opposite is true for smaller bodies. This can be explained not only by their smaller size and lower temperatures, which allow for less melt production than on Venus, but also by their lithospheric regimes with lower mobility due to colder lithospheric temperatures. For large planets such as Venus, when an intrusive magmatism dominates, which promotes lithospheric recycling, cold recycled material leads to higher cooling efficiency than in the extrusive case. The release of latent heat due to the crystallization of intruded melt can further amplify lithospheric recycling for large bodies, while for smaller planets this generally leads to slower cooling.