9627479 Sack This project is composed experimental studies, theoretical studies and petrologic applications of sulfosalts/sulfides in the system Ag2S-Cu2S-ZnS-FeS-As2S3-Sb2S3-S and Bi-, Mn-, Cd-, and Hg- substituted supersystems. The experimental studies will characterize the net transport equilibria of low variance assemblages critical for developing an internally consistent thermodynamic database, and exchange and net transport equilibria critical for extending the database for Ag2S-Cu2S-ZnS-FeS-As2S3-Sb2S3-S sulfosalts/sulfides to Mn-, Hg-, Cd-, and Bi-bearing supersystems. Theoretical studies will: (1) obtain an accurate model for the Gibbs energy of (Zn,Fe)S sphalerites with explicit provisions for strong short-range order on its metallic sublattice utilizing a variation of Kikuchi's cluster variation techniques, (2) an internally consistent thermodynamic database for Ag2S-Cu2S-ZnS-FeS-As2S3-Sb2S3-S sulfosalts/sulfides from analysis of published calorimetric, crystallographic, and phase equilibrium studies, thermochemical models previously developed by the PI, results of activity and of net transport experiments, (3) thermodynamic mixing properties of Mn-, Cd-, and Hg-bearing tetrahedrite-tennantites and sphalerites, and (4) non-idealities, activity-composition relations, and standard state properties associated with the Bi-Sb substitutions in stibnite-bismuthinite (Sb,Bi)2S3 solutions and coexisting sulfosalts Ag(Sb,Bi)S2 myargyrite-matildites, Cu(Sb,Bi)S2 chalcostibite-emplectites, and Pb(Sb,Bi)2S4 zinkenite-bonchevites. The petrologic applications include the recalibration of sphalerite cosmobarometer to obtain formation pressures, masses and dimensions of asteroids parental to IAB, IIIAB and IIICD iron meteorites and for application to terrestrial sulfide deposits, and application of composite thermochemical database to develop ore deposition models for zoned polymetallic base metal deposits involving multicomponent sulfosalts in southern India and Peru.
