Sulfides are, thus, unique in their ability to fractionate Re from Os in magmatic systems and to control the Os isotope systematics during melting of the Earth's mantle. This difficulty can be partly circumvented by carrying out studies at the mineral scale to identify different generations of mantle sulfide, each with their own 187Os/ 188Os (cf. Joseite-B appears at this temperature as a limited solid solution from Bi 3.95 Te 0.90 S 2.15 to Bi 4.15 Te 1.75 S 2.10 at 400☌. The isothermal diagram at 400☌ is shown in Fig. Because of this, these metasomatic sulfides will develop more radiogenic 187Os/ 188Os over time, which will mix into the whole-rock signature and obscure the actual age of melt depletion of that peridotite. Isothermal section of Bi-Te-S ternary system at 500☌ (modified after Yusa 1979)7). For example, metasomatic sulfides, which can be introduced to a mantle peridotite through basaltic melt percolation and/or fluid infiltration, will typically introduce Re into a virtually Re-free peridotite. However, the same thing that makes the Re/Os system so useful in dating ancient melt events is also responsible for its biggest caveat. sulfide) scale to date ancient melting events in the Earth's mantle (e.g. This approach can be applied at both the whole-rock and mineral (i.e. If melt-depleted peridotites can be presumed to have lost all their Re during partial melting, then their 187Os/ 188Os can potentially be used to derive model ages that ostensibly track melt extraction events (reviewed in Lorand and Luguet 2016). THEORETICAL CONSIDERATIONS ON PARTITIONING OF CHALCOPHILE ELEMENTS INTO SULFIDES Of course, how the concentrations of these elements in sulfides may be used as petrogenetic indicators hinges on our understanding of their partitioning behaviour between sulfide and silicate melt during mantle melting. The structural model used in this work has been extended to predict other properties, such as molar volume, phase diagrams, sulphide capacity and all the thermodynamic properties of binary and ternary silicate systems. ( 1998) also noted that Ni concentrations of diamond-hosted sulfide inclusions correlate broadly with Os, and that Re/Os may be a more robust petrogenetic indicator for differentiating between peridotitic and eclogitic sulfides. To conclude, the model proposed in this study links melt composition, structure and thermodynamic properties. Additionally, extension of published data on the Cu-S system (Barton, 1973) to the univariant phase equilibria involving fahlore and ‘high-chalcocite’ in the Cu-Sb-As-S system (Luce et al. The marked difference in Ni concentrations between peridotite- and eclogite-hosted sulfides has been used as a paragenetic discriminator ( Bulanova et al. Log aS 2-T diagrams for several sulphosalts (and sulphides) are constructed from published thermochemical data. The Ni and Cu concentrations in sulfide inclusions in both peridotite- and eclogite-type diamonds are broadly similar compared to intergranular sulfides in peridotite and eclogite xenoliths, respectively. Even though sulfides are accessory phases in mantle xenoliths (<0.1%) they are the most common mineral inclusions found in diamonds, accounting for 35%–46% of all diamond inclusions in the Finsch, Koffiefontein and Premier kimberlite pipes of South Africa ( Harris and Gurney 1979).
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