Density and fate of silicate melts in the early Earth s mantle

• Applicant: Dr. Sylvain Petitgirard
• Subject Area: Mineralogy, Petrology and Geochemistry ; Geophysics
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276731265

The formation and early history of the Earth was marked by large-scale melting events that facilitated the segregation of the iron-rich core. Recently, it has been proposed that a deep basal magma ocean (BMO) could have formed concomitantly with the very last stage of Earth s accretion. The formation of a thick layer of magma at the interface between the mantle and the core has great implications for the Earth s formation. Firstly, this layer of magma would influence the thermal state of the mantle and the core, with a possible delay of the Earth s dynamo, and secondly might also lead to the formation of a hidden reservoir, which could store incompatible elements over time. Although the formation of a BMO is a very attractive solution for explaining many aspects of the early Earth, it is still unclear how such a thick layer of magma would be sustained at the core-mantle interface. This is mainly due to a lack of experimental data on the densities as well as composition of melts produced at such depths. Here I propose to address the existence of a basal magma ocean by investigating the densities of various melt compositions, as well as the partitioning of iron between solid and liquid phases at the relevant conditions of the BMO. The data provided in the framework of this proposal will additionally be of great value for models of mantle crystallisation, chemical evolution and the redox state of the early earth proposed in the projects of Dr. Steinle-Neumann, Prof. Rubie and Prof. Frost, respectively.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1833: Building a Habitable Earth
• International Connection: France, Switzerland
• Cooperation Partners: Dr. Louis Hennet; Wim Malfait, Ph.D.; Dr. Georg Spiekermann