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Ag-Cu exchange equilibria between alpha -miargyrite, chalcostibite, pyrargyrite, and high-skinnerite; constraints on Ag-Cu mixing in alpha -miargyrite and chalcostibite

Daniel E. Harlov
Ag-Cu exchange equilibria between alpha -miargyrite, chalcostibite, pyrargyrite, and high-skinnerite; constraints on Ag-Cu mixing in alpha -miargyrite and chalcostibite
Mineralogical Magazine (June 1999) 63 (3): 399-411

Abstract

Ag-Cu exchange equilibria between alpha -miargyrite AgSbS (sub 2) and pyrargyrite Ag (sub 3) SbS (sub 3) and between chalcostibite CuSbS (sub 2) and both pyrargyrite and high-skinnerite Cu (sub 3) SbS (sub 3) are reported for the temperature range 150-350 degrees C. All of these features are constrained by Ag-Cu exchange experiments (evacuated silica tubes; variable mass ratio) over the temperature range 120-400 degrees C. Chalcostibite is found to take very little Ag into its structure. Utilizing Ag-Cu data from this study as well as the Ag-Cu solution models for pyrargyrite and high-skinnerite, a two-site Ag-Cu non-convergent ordered solution model for alpha -miargyrite (W (super AMrg) (sub Agcu) = 15.0; W (super BMrg) (sub AgCu) = 10.0; Delta G (super *) (sub s) = 10.0; and Delta G (super *) (sub XCuS) = 14.0+ or -5 kJ/gfw) and a one-site Ag-Cu mixing model for chalcostibite (W (super Chst) (sub AgCu) = 25.0 kJ/gfw) are formulated. These results are constrained by a miscibility gap between alpha -miargyrite and chalcostibite from 225 to 325 degrees C. The mixing model for alpha -miargyrite is expanded to include As for which alpha -miargyrite has a limited solubility along the Sb-As join with smithite AgAsS (sub 2) .


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 63
Serial Issue: 3
Title: Ag-Cu exchange equilibria between alpha -miargyrite, chalcostibite, pyrargyrite, and high-skinnerite; constraints on Ag-Cu mixing in alpha -miargyrite and chalcostibite
Author(s): Harlov, Daniel E.
Affiliation: GeoForschungsZentrum, Potsdam, Federal Republic of Germany
Pages: 399-411
Published: 199906
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 30
Accession Number: 1999-066044
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199922
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