The effect of network-formers (Si, Ti, Al and P) on ferric/ferrous ratio in silicate melts: experimental study and improvement of existing models.

• Applicant: Professor Dr. Francois Holtz, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 233220105

Geochemical processes occurring in magmatic systems depend strongly on oxygen fugacity and on the Fe3+/Fe2+ ratio in silicate melts. This ratio can be theoretically predicted using available thermodynamic models. The available thermodynamic models take compositional parameters into account, but mainly for network modifying cations (Ca, Mg, Na, K). There are few systematic studies allowing us to take the effects of network forming cations into account (Si, Al, Ti, P). In this project, the effect of Al on the Fe3+/Fe2+ ratio in silicate melts will be investigated experimentally at 1 bar. The results will be combined with recent previous datasets on the effects of Si, P und Ti on the Fe3+/Fe2+ ratio in silicate melts to provide a consistent thermodynamic model predicting accurately the effect of melt composition, in particular SiO2, Al2O3, TiO2 and P2O5, on the Fe3+/Fe2+ ratio of mafic melts. The results are of importance for mafic melts generated in the Earth and for their differentiation products (silicic melts) but also for the interpretation of the formation and evolution of basalts from the Moon or other planetary systems, which differ from Earth basalts by their Al/Si ratio.

• DFG Programme: Research Grants
• International Connection: Russia
• Cooperation Partner: Dr. Alexander Borisov, Ph.D.