Distribution of ferric and ferrous iron in mafic and ultramafic rocks of the deep continental crust

We aim to investigate the distribution of Fe3+ and Fe2+ in deep crustal rocks from one of the few exposed continental sections on the Earth by means of a Synchrotron Mössbauer Source (SMS). The focus is the mafic-ultramafic sequence from Valsesia, Italy, which might represent the only available continental crust-mantle transition zone. The goal is to investigate whether the different lithologies in the sequence record the same pressure (P), temperature (T) and redox conditions and how these are modified in magmas during cooling, solidification and subsequent metamorphic recrystallization in the lower crust. We propose to analyse garnet, spinel and pyroxenes, that show a variety of textures, compositions and compositional zoning.The dataset will improve the knowledge on Fe3+ and Fe2+ distribution in mafic systems at the crust-mantle transition zone, allowing for a first investigation of oxidation state of magmas during their earliest phases of differentiation in such a setting.