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Also present are the ‘monosulfide solid solution’ (mss) and ‘intermediate solid solution’ (iss) phases. The exchange of a chalcophile element, such as Pb, between sulfide and silicate melt can be described by the following reaction: corresponds to the valence of Pb in silicate and sulfide melts.
The observed mineralogy of mantle sulfides, however, likely represents low temperature (, Fe S and Ni S) showing the major element composition of the mantle sulfides (in weight %). Assuming Pb is present in dilute concentrations, we can express Equation (1) in terms of the equilibrium constant (Brenan et al.
It is notable that the model using the relationship shown in Equation 5 (panel B) provides the slope (−1) predicted by the reaction stoichiometry.
In contrast, the model using the relationship in Equation 2 (panel A), yields a substantially non-stoichiometric dependency (−0.63 slope).
These authors controlled plotted as a function of log[Fe O].
The log[Fe O] values have been corrected for the activity of Fe S (see Kiseeva and Wood 2013).
In this article, we explore the occurrence of sulfides in the Earth’s mantle, the role of sulfides in the partitioning of chalcophile elements in magmatic systems, and the abundance of chalcophile elements in mantle-derived silicate melts. Eclogitic sulfides are generally similar with respect to their Cu content compared to peridotite-hosted sulfides, but are consistently lower in Ni, with average concentrations ~3 wt% Ni.
They are observed in upper-mantle peridotites and oceanic basalts, in mantle xenoliths, and are also the most common mineral inclusion in diamonds.
Despite sulfur being a minor component in the mantle – present at concentrations of ~150–300 parts per million (ppm) S in the bulk silicate Earth (e.g.
This could potentially be due to the uncertainties in the f S2 measurements or due to the deviation from ideality in the Fe–Ni–Cu–S system.
Additional discussion can be found in Gaetani and Grove (1997).