In situ study of the redox interaction between iron and cerium in silicate melts

Redox reactions play a crucial role in magma geochemistry influencing several phenomena. Mineral-melt partitionning is such a phenomenom and serves as an oxybarometeter for magmatic systems. Cerium displays mineral-melt partitionning into zircon even though the access of reduced Iron in magmetic systems should forbid the Cerium oxydation, at the core of its mineral-melt partitionning. One hypothesis developed in the litterature is the presence of a charge-transfer reaction between Cerium and Iron occuring during quench. Even though similar charge transfers have been observed between different elements, the charge transfer between Cerium and Iron is only suspected. We will investigate in situ the redox state of both Cerium and Iron at high temperature in silicate melts using Cerium L3-edge XANES spectroscopy and Iron K-edge XANES spectroscopy. This will allow us to assess if the redox interaction is of charge transfer nature or a diffusive process.