The S content of silicate melts at sulfide saturation: New experiments and a model incorporating the effects of sulfide composition

Abstract

The extent to which sulfur dissolves in silicate melts saturated in an immiscible sulfide phase is a fundamental question in igneous petrology and plays a primary role in the generation of magmatic ore deposits, volcanic degassing, and planetary differentiation. In igneous systems, sulfide melts can be described as FeS-NiS-CuS 0.5 solutions with Fe/(Fe+Ni+Cu) significantly less than 1. Despite the presence of Ni and Cu in the sulfide, however, most experimental studies to date have concentrated on the effects of silicate melt composition on sulfur solubility and have used essentially pure FeS as the sulfide liquid. We have carried out 49 new experiments at pressures of 1.5-24 GPa and temperatures of 1400 to 2160 °C to investigate the effects of sulfide composition on sulfur solubility as well as extending the pressure and temperature ranges of the available data on sulfide saturation. We find that in the compositional range of most igneous sulfide melts [Fe/(Fe+Ni+Cu) > 0.6] sulfur solubility decreases linearly with Fe content such that at Fe/(Fe+Ni+Cu) of 0.6 the sulfur content at saturation is 0.6 times the value at pure FeS saturation. At lower values of Fe/(Fe+Ni+Cu), however, deviations from this ideal solution relationship need to be taken into consideration. We have treated these non-idealities by assuming that FeS-NiS-CuS 0.5 liquids approximate ternary regular solutions. We have fitted our data, together with data from the literature (392 in total), to equations incorporating the effects of silicate melt composition, sulfide liquid composition, and pressure on the solubility of sulfur at sulfide saturation ([S] SCSS). The temperature dependence of [S] SCSS was assumed either to be an unknown or was taken from 1 bar thermodynamic data. The most important best-fit silicate melt compositional term reflects the strongly positive dependence of [S] SCSS on the FeO content of the silicate melt. The best-fit value of this parameter is essentially independent of our assumptions about temperature dependence of [S] SCSS or the solution properties of the sulfide. All natural compositions considered here exhibit positive dependences of [S] SCSS on temperature and negative dependences on pressure, in accord with previous studies using smaller data sets.

Behavior of Ga, In, Sn, and Te in Copper Matte Smelting

“…the system. This conclusion is in good agreement with the recent survey of Smythe et al [34] on matte-slag systems and the assessment by Shishin et al [35] The experimental EPMA data of the iron silicate slag and the copper matte were normalized to 100 pct, and the average values were plotted as a function of the variables used in the study. The distribution coefficients of the trace elements Me between copper matte and slag L m/s (Me) were calculated from the LA-ICP-MS data obtained by the following Eq.…”

Impact of MgO and K2O on Slag-Nickel Matte Equilibria

“…This was based on the assumption of sulfur solubility by FeS species at the experimental oxygen partial pressures of this study. [25,26] The concentrations of sulfur in pure iron silicate slag and in the MgO-containing slag obtained in this study were in a good agreement with the previous measurements by Strengell et al [16] and Piskunen et al, [17] though the earlier studies equilibrated the slags with nickel-copper-iron mattes with the Ni/Cu ratios of 2 and 4 (w/w), respectively. This indicates an insignificant effect of the Ni/Cu ratio on the activity of iron in the matte which is in good agreement with the findings by Font et al [11,12] It complies with the almost ideal behavior of Cu 2 S-FeS-Ni 3 S 2 mattes.…”

“…This indicates an insignificant effect of the Ni/Cu ratio on the activity of iron in the matte which is in good agreement with the findings by Font et al [11,12] It complies with the almost ideal behavior of Cu 2 S-FeS-Ni 3 S 2 mattes. [26,27] On the other hand, the solubility of copper in slags measured by Strengell et al [16] was slightly higher compared to the present observations, obviously due to the much higher copper concentration of matte in their study. Meanwhile, the solubility of nickel in their study was just slightly lower due to the same reason, related to differences in the matte compositions.…”

The timeline of the lunar bombardment: Revisited

“…This assumption is not unreasonable given the isotopic and compositional similarities between the compositions of the terrestrial mantle and the Moon, which suggest their mutual equilibration (Pahlevan and Stevenson, 2007;Lock et al, 2016;Lock and Stewart, 2017). Similarities in S concentration between the Earth and lunar mantle are also evident from the parti- The red curve shows SCSS calculated for the residual melt layer as crystallization proceeds, based on the evolving pressure at the base of the melt layer, according to the parameterization of Smythe et al (2017). The strong decrease of SCSS after ∼85% of the LMO has crystallized is caused by the evolving composition of the residual silicate liquid during the late stages of LMO crystallization (Elkins-Tanton et al, 2011).…”