2 D29. Investigations in Economic Geology

Sunday, 22 October 2017
8:00 AM - 12:00 PM
Skagit 5

FAHLORE THERMOCHEMISTRY: GAPS INSIDE THE (CU,AG)10(FE,ZN)2(SB,AS)4S13 CUBE

Paper number: 2-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

Possible topologies of miscibility gaps in arsenian (Cu,Ag)10(Fe,Zn)2(Sb,As)4S13 fahlores are examined. These topologies are based on a thermodynamic model for fahlores whose calibration has been verified for (Cu,Ag)10(Fe,Zn)2Sb4S13 fahlores, and conform with experimental constraints on the incompatibility between As and Ag in (Cu,Ag)10(Fe,Zn)2(Sb,As)4S13 fahlores, and with experimental and natural constraints on the incompatibility between As and Zn and the nonideality of the As for Sb substitution in Cu10(Fe,Zn)2(Sb,As)4S13 fahlores. It is inferred that miscibility gaps in (Cu,Ag)10(Fe,Zn)2As4S13 fahlores have critical temperatures several oC below those established for their Sb counterparts (170 to 185C). Depending on the structural role of Ag in arsenian fahlores, critical temperatures for (Cu,Ag)10(Fe,Zn)2(Sb,As)4S13 fahlores may vary from comparable to those inferred for (Cu,Ag)10(Fe,Zn)2As4S13 fahlores, if the As for Sb substi- tution stabilizes Ag in tetrahedral metal sites, to temperatures approaching 370C, if the As for Sb substitution results in an increase in the site preference of Ag for trigonal-planar metal sites. The latter topology is more likely based on comparison of calculated miscibility gaps with composi- tions of fahlores from nature exhibiting the greatest departure from the Cu10(Fe,Zn)2(Sb,As)4S13 and (Cu,Ag)10(Fe,Zn)2Sb4S13 planes of the (Cu,Ag)10(Fe,Zn)2(Sb,As)4S13 fahlore cube. 

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-293454

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.