Header
Accueil du site > Publications > No FeS layer in Mercury ? Evidence from Ti/Al measured by MESSENGER

No FeS layer in Mercury ? Evidence from Ti/Al measured by MESSENGER

Cartier, C. ; Namur, O. ; Nittler, L.R. ; Weider, S.Z. ; Crapster-Pregont, E. ; Vorburger, A. ; Franck, E.A. ; Charlier, B., EPSL

No FeS layer in Mercury ? Evidence from Ti/Al measured by MESSENGER

Cartier, C. ; Namur, O. ; Nittler, L.R. ; Weider, S.Z. ; Crapster-Pregont, E. ; Vorburger, A. ; Franck, E.A. ; Charlier, B.

Earth and Planetary Science Letters, 2020, 534, 116108

Abstract :

In this study we investigate the likeliness of the existence of an iron sulfide layer (FeS matte) at the core-mantle boundary (CMB) of Mercury by comparing new chemical surface data obtained by the X-ray Spectrometer onboard the MESSENGER spacecraft with geochemical models supported by high-pressure experiments under reducing conditions. We present a new data set consisting of 233 Ti/Si measurements, which combined with Al/Si data show that Mercury’s surface has a slightly subchondritic Ti/Al ratio of 0.035 ±0.008. Multiphase equilibria experiments show that at the conditions of Mercury’s core formation, Ti is chalcophile but not siderophile, making Ti a useful tracer of sulfide melt formation. We parameterize and use our partitioning data in a model to calculate the relative depletion of Ti in the bulk silicate fraction of Mercury as a function of a putative FeS layer thickness. By comparing the model results and surface elemental data we show that Mercury most likely does not have a FeS layer, and in case it would have one, it would only be a few kilometers thick (<13 km). We also show that Mercury’s metallic Fe(Si) core cannot contain more than ∼1.5 wt.% sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic Ti/Al ratio of Mercury’s surface.

Voir en ligne : https://doi.org/10.1016/j.epsl.2020...




publié vendredi 7 février 2020