|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Department of Earth & Space Sciences, Box 351310, University of Washington, Seattle, WA, 98195-1310, USA
2 Shell Canada Limited, P.O. Box 100, Station M, Calgary, Alberta T2P 2H5, Canada
3 Department of Geology, Box 642812, Washington State University, Pullman, WA, 99164-2812, USA
* E-mail: sack{at}geology.washington.edu
Fahlores [~(Cu,Ag)10(Zn,Fe)2Sb4S13] from the Keno Hill mining district, central Yukon, Canada record virtually the entire petrogenetic history of a Cretaceous hydrothermal system extending over 40 km outward from the Mayo Lake granitic pluton. These fahlores are an essential constituent of polymetallic sulphide veins developed in a graphitic Mississippian quartzite, where they occur in association with sphalerite, pyrargyrite, galena and siderite. Fahlores exhibit pronounced east-west zoning in average Ag/(Ag+Cu) and Zn/(Zn+Fe) values, with these simultaneously increasing and decreasing from east to west over 20 km of hydrothermal activity. These zonations are coupled with average Ag/(Ag+Cu) and Zn/(Zn+Fe) values in fahlore roughly paralleling the 300°C isotherm for fahlores in equilibrium with pyrargyrite, miargyrite and sphalerite in the simple system Ag2S-Cu2S-ZnS-FeS-Sb2S3. Early high-Ag, high-Zn fahlores from the eastern and western mines have Ag/(Ag+Cu) and Zn/(Zn+Fe) values requiring temperatures 
400°C, in agreement with temperatures established from the As-content of arsenopyrite coexisting with pyrite, pyrrhotite and sphalerite. Ag/(Ag+Cu) and Zn/(Zn + Fe) values in later, main-stage fahlores are consistent with the 250–310°C range of temperatures established for boiling of Keno Hill fluids. Finally, Ag- and Fe-rich fahlores were produced by retrograde Fe-Zn exchange with sphalerite or crystallized from late-stage epithermal fluids which produced polybasite, stephanite, acanthite and wire silver. One such fahlore exhibits unmixing into high-Ag and low-Ag varieties. This is the first reported miscibility gap for freibergite fahlores and confirms the earlier prediction of such gaps.
KEYWORDS: fahlore, petrogenetic indicator, Keno Hill, Yukon, Canada
This article has been cited by other articles:
|
|
 |
|
  S. Staude, T. Wagner, and G. Markl MINERALOGY, MINERAL COMPOSITIONS AND FLUID EVOLUTION AT THE WENZEL HYDROTHERMAL DEPOSIT, SOUTHERN GERMANY: IMPLICATIONS FOR THE FORMATION OF KONGSBERG-TYPE SILVER DEPOSITS Can Mineral, October 1, 2007; 45(5): 1147 - 1176. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Kharbish, E. Libowitzky, and A. Beran The effect of As-Sb substitution in the Raman spectra of tetrahedrite-tennantite and pyrargyrite-proustite solid solutions European Journal of Mineralogy, July 1, 2007; 19(4): 567 - 574. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. O. Sack and D. S. Ebel Thermochemistry of Sulfide Mineral Solutions Reviews in Mineralogy and Geochemistry, January 1, 2006; 61(1): 265 - 364. [Full Text] [PDF]
|
|
|
|
 |
|
 R. O. Sack, R. Fredericks, L. S. Hardy, and D. S. Ebel Origin of high-Ag fahlores from the Galena Mine, Wallace, Idaho, U.S.A. American Mineralogist, May 1, 2005; 90(5-6): 1000 - 1007. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. I. Chutas and R. O. Sack Ore genesis at La Colorada Ag-Zn-Pb deposit in Zacatecas, Mexico Mineralogical Magazine, December 1, 2004; 68(6): 923 - 937. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
