A primordial sulfides layering in the Mercury's magma ocean
Authors: Ch.-Ed. Boukaré, Steve Parman and Marc Parmentier
To explain the high sulfur content and low FeO content of the Mercury’s surface lavas, it has been proposed that Mercury is deprived of oxygen compared to the Earth, Moon and Mars. Such reducing conditions would lead to significant differences between the evolution of the Mercury magma ocean (MMO) and the canonical Lunar magma ocean. Here, we investigate the formation of sulfide layering produced by the solidification of a global magma ocean in Mercury. We use experimentally determined sulfur solubility in silicate melts to predict the depth at which sulfides precipitate in the case of ideal fractional solidification. The model produces primordial sulfide layers whose thickness and locations depend upon the oxygen fugacity and initial sulfur content of the Mercurian magma ocean. A geodynamic model is then used to test under which conditions the initial mineralogical layering can be preserved during the very early evolution of the Mercury’s mantle. An intriguing question is the role these sulfides rich layer on mantle dynamics as they are expected to incorporate substantial amount of radioactive elements.
Caption:
(Left) Putative primordial layering in S and U due to ideal fractional
solidification of the mercurian magma ocean. The bulk initial suflur
content of the silicate mantle is 5 % wt. (right) Temporal evolution of
the maximum advective heat flux for the layering shown on the left. The
maximum advectived heat flux can be interpreted as a proxy for the
intensity and timing of major magmatic event associated to decompression
melting in mantle up-wellings. It is interesting to see that the oxygen fugacity can play an important role in the thermal history of Mercury. The animations that correspond to the
numerical simulations of cases 1, 2, 3 and 4 can be found by clicking on
the links below.
Related paper:
C.-É. Boukaré, S.W. Parman, E.M. Parmentier, 2019, Production and preservation of
sulfide layering in Mercury’s mantle, JGR:Planets, doi:
10.1029/2019JE005942.