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ISTeP - UMR 7193
Institut des Sciences de la Terre de Paris

Séminaire ISTeP - Muriel Laubier

(LMV)

Linking the redox state of magmas to that of their mantle source

Arc magmas are more oxidized than mid-ocean ridge magmas, likely because the mantle source region of arc magmas has been modified by a release of oxidized and volatile-rich fluids from the subducting slab. In particular, the migration of Fe-bearing fluids released during serpentine devolatilization to the mantle wedge is likely to result in the oxidation of mantle Fe2+ to Fe3+. However, it is still up to debate whether the variations in Fe3+/ΣFe of magmas from various environments arise due to differences in mantle fO2 or to differentiation processes in the arc crust such as partial crystallization and degassing. Here our aim is to combine different fO2 proxies in order to carefully reconstruct mantle source fO2 from the compositions of melt inclusions and erupted glasses from mid-ocean ridge, hot spot and arc settings. These fO2 proxies include Fe3+/ΣFe measured by micro-X-ray absorption near edge structure (µ-XANES) spectroscopy and trace element proxies that were calibrated experimentally such as V/Sc and V/Yb ratios, Cu, Zn/Fe*.

16/06/2017, Salle Fourcade à 12h30

06/06/17

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