gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/002646199548600 The Phase System Fe-Ir-S at 1100, 1000 and 800°C Makovicky E. 1 Karup-Møller S. 2 Department of Mineralogy, The Geological Central Institute, University of Copenhagen, Østervoldgade 10, DK 1350 Copenhagen K, Denmark Department of Geology and Geotechnical Engineering, The Technical University of Denmark, DK 2800 Lyngby, Denmark 6 1999 63 3 379 385 18 2 1998 3 8 1998 Copyright © 1999, The Mineralogical Society 1999 Abstract

Phase relations in the dry condensed Fe-Ir-S system were determined at 1100, 1000 and 800°C. Orientational runs were performed at 500°C. Between 1100 and 800°C, the system comprises five sulphides and an uninterrupted field of γ(Fe,Ir). Fe2−xS dissolves 5.8 at.% Ir at 1100°C, 3.4 at.% Ir at 1000°C and 1.0 at.% Ir at 800°C. The solubility of Fe in Ir2S3, IrS2 and IrS−3 increases with decreasing temperature, reaching 2.5 at.% in the latter two sulphides at 800°C. Thiospinel ‘FeIr2S4’ is non-stoichiometric, from Fe22.3Ir19.8S58.0 to Fe18.9Ir23.1S58.0, depending on as and aFe i.e. on a phase association. Thiospinel is absent at 800 and 500°C.

 Keywords platinum group elements iridium phase system iron-iridium-sulphur