Internally consistent database for sulfides and sulfosalts in the system Ag2S-Cu2S-ZnS-FeS-Sb2S3-As2S3: Update

The thermodynamic database for Ag2S-Cu2S-ZnS-FeS-Sb2S3-As2S3 sulfides and sulfosalts applicable to temperatures above 119°C has been updated based on the results of recent petrologic, experimental, and theoretical studies. Solution and end-member properties of fahlore [∼(Ag,Cu)10(Fe,Zn)2(Sb,As)4S13] have been adjusted to allow for (1) revisions of the description of Fe-Zn partitioning with sphalerite that incorporate sphalerite activity-composition relations derived from the cluster variation method (CVM) model of a previous study, (2) the assumption that the miscibility gaps observed in high-Ag fahlores from the Husky Mine (Yukon, Canada) approximate a temperature of 170°C, and (3) an increase in the Ag-Cu partitioning between fahlore and polybasite (Ag,Cu)16(Sb,As)2S11 required to reproduce compositions of fahlore in the polybasite + Sb-fahlore + ZnS sphalerite assemblage reported in previous experimental studies. The resulting minor parameter adjustments produce a database that demonstrably reproduces the composition data reported for a wide-range of sulfide ore deposits. They result in revised estimates for the Gibbs energies of formation of end-member fahlore components from the simple sulfides that, except for Cu10Zn2Sb4S13, are less temperature dependent than those previously inferred (at 200 and 400°C: −23.27 and −24.84 kJ/gfw for Ag10Zn2Sb4S13, −115.18 and −116.57 kJ/gfw for Cu10Zn2Sb4S13, −85.14 and −75.20 kJ/gfw for Cu10Fe2Sb4S13, and −3.81 and 9.10 kJ/gfw for Ag10Fe2Sb4S13). The database is extended to PbS-bearing supersystems containing the galena + fahlore + sphalerite assemblage. Predicted initial Ag-contents of galena calculated from this database agree with those inferred from petrological studies of Ag-Pb-Zn ores from the Coeur d'Alene district, Idaho, USA and Julcani, Peru.