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Fahlore as a petrogenetic indicator: Keno Hill Ag-Pb-Zn District, Yukon, Canada

Published online by Cambridge University Press:  05 July 2018

R. O. Sack ,
J. V. G. Lynch  and
F. Foit Jr.
R. O. Sack*
Affiliation:
Department of Earth & Space Sciences, Box 351310, University of Washington, Seattle, WA, 98195-1310, USA
J. V. G. Lynch
Affiliation:
Shell Canada Limited, P.O. Box 100, Station M, Calgary, Alberta T2P 2H5, Canada
F. Foit Jr.
Affiliation:
Department of Geology, Box 642812, Washington State University, Pullman, WA, 99164-2812, USA
*
* E-mail: [email protected]
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Abstract

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

fahlorepetrogenetic indicatorKeno HillYukon, Canada.
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 5 , October 2003 , pp. 1023 - 1038
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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References

Amcoff, O. (1976 The solubility of silver and antimony in galena. Neues Jahrbuch fiir Mineralogie Monatshefte, 247—261.Google Scholar
Aragon, R., McCaUister, R.H. and Harrison, H.R. (1984 Cation diffusion in titanomagnetites. Contributions to Mineralogy and Petrology, 85, 174— 185.CrossRefGoogle Scholar
Balabin, A.I. and Sack, R.O. (2000 Thermodynamics of (Zn,Fe)S sphalerite: a CVM approach with large basis clusters. Mineralogical Magazine, 64, 923—943.CrossRefGoogle Scholar
Boyle, R.W. (1965 Keno Hill-Galena Hill lead-zinc-silver deposits, Yukon Territory. Geological Survey of Canada, Bulletin, 111.Google Scholar
Brown, K.L. (1989 Kinetics of gold precipitation from experimental hydrothermal sulfide solutions. Pp. 320—327 in: The Geology of Gold Deposits: The Perspective in 1988 (Keays, R.R., Ramsay, W.R.H. and Groves, D.I., editors). Economic Geology Monograph 6. Economic Geology Publishing Co., El Paso, Texas.Google Scholar
Deen, J.A., Rye, R.O., Munoz, J.L. and Drexler, J.W. (1994 The magmatic hydrothermal system at Julcani, Peru: evidence from fluid inclusions and hydrogen and oxygen isotopes. Economic Geology. 89, 1924—1938.CrossRefGoogle Scholar
Ebel, D.S. (1993 Thermochemistry of fahlore (tetra-hedrite) and biotite mineral solutions. PhD thesis. Purdue University, Indiana, USA.Google Scholar
Ebel, D.S. and Sack, R.O. (1989 Ag-Cu and As-Sb exchange energies in tetrahedrite -tennantite fah-lores. Geochimica et Cosmochimica Ada, 53, 2301—2309.CrossRefGoogle Scholar
Ebel, D.S. and Sack, R.O. (1991 Arsenic-silver incompatibility in fahlore. Mineralogical Magazine. 55, 521—528.CrossRefGoogle Scholar
Ebel, D.S. and Sack, R.O. (1994 Experimental determination of the free energy of formation of freibergite fahlore. Geochimica et Cosmochimica Ada, 58, 1237—1242.CrossRefGoogle Scholar
Fryklund, V.C., Jr. (1964 Ore deposits of the Coeur d'Alene district, Shoshone County, Idaho. US Geological Survey Professional Paper, 445, 103 pp.Google Scholar
Ghosal, S. and Sack, R.O. (1999 Bi-Sb energetics in sulfosalts and sulfides. Mineralogical Magazine, 63, 723—733.CrossRefGoogle Scholar
Goodell, P.C. and Petersen, U. (1974 Julcani mining district, Peru: a study of metal ratios. Economic Geology, 69, 347—361.CrossRefGoogle Scholar
Hall, W.E. and Czamanske, GK. (1972 Mineralogy and trace-element content of the Wood River lead-silver deposit, Blaine County, Idaho. Economic Geology. 67, 350—361.CrossRefGoogle Scholar
Hoda, S.N. and Chang, L.L.Y. (1975 Phase relations in the system PbS-Ag2S-Sb2S3 and PbS-Ag2S-Bi2S3 . American Mineralogist, 60, 621—633.Google Scholar
Hutchison, M.N. and Scott, S.D. (1981 Sphalerite geobarometer in the Cu-Fe-Zn-S system. Economic Geology, 76, 143—153.CrossRefGoogle Scholar
Indolev, L.N., Nevoysa, LA. and Bryzgalov, LA. (1971 New data on the composition of stibnite and the isomorphism of copper and silver. Doklady Akademii NaukSSSR, 199, 115—118.Google Scholar
Jeanloz, R. and Johnson, M.L. (1984 A note on the bonding, optical spectrum and composition of tetrahedrite. Physics and Chemistry of Minerals, 11, 52—54.CrossRefGoogle Scholar
Keighin, C.W. and Honea, R.M. (1969 The system Ag-Sb-S from 600°C to 200°C. Mineralium Deposita, 4, 153—171.CrossRefGoogle Scholar
Kennedy, G.C. (1950 A portion of the system silica-water. Economic Geology, 45, 629—653.CrossRefGoogle Scholar
Large, R.R., Huton, D.L., McGoldrick, P.J., Ruxton, P.A. and McArthur, G. (1989 Gold distribution and genesis in Australian volcanogenic massive sulfide deposits and their significance for gold transport models. Pp. 520—536 in: The Geology of Gold Deposits: The Perspective in 1988 (Keays, R.R., Ramsay, W.R.H. and Groves, D.I., editors). Economic Geology Monograph 6. Society of Economic Geologists, Tulsa, Oklahoma.Google Scholar
Lueth, V.W., Goodell, P.C. and Pingitore, N.E. (1990 Encoding the evolution of an ore system in bismuthinite-stibnite compositions. Economic Geology, 85, 1462—1472.CrossRefGoogle Scholar
Lusk, J., Scott, S.D. and Ford, C.E. (1993 Phase relations in the Fe-Zn-S system to 5 kbar and temperatures between 325 and 100°C. Economic Geology, 88, 1880—1903.CrossRefGoogle Scholar
Lynch, J.V.G. (1989a) Large-scale hydrothermal zoning reflected in the tetrahedrite-freibergite solid solution, Keno Hill Ag-Pb-Zn district, Yukon. The Canadian Mineralogist, 27, 383—400.Google Scholar
Lynch, J.V.G. (1989b) Hydrothermal zoning in the Keno Hill Ag-Pb-Zn vein system: a study in structural geology, mineralogy, fluid inclusions and stable isotope geochemistry. PhD thesis, University of Alberta, Alberta, Canada.Google Scholar
Lynch, J.V.G. and Mengel, F. (1995 Metamorphism of arsenopyrite-pyrite-sphalerite-pyrrhotite lenses, western Cape Breton Island, Canada. The Canadian Mineralogist, 33, 105—114.Google Scholar
Lynch, J.V.G., Longstaffe, F.J. and Nesbitt, B.E. (1990 Stable isotopic and fluid inclusion indications of hydrothermal paleofiow, boiling and fluid mixing in the Keno Hill Ag-Pb-Zn district, Yukon territory, Canada. Geochimica et Cosmochimica Ada, 54, 1045—1059.CrossRefGoogle Scholar
O'Leary, M.J. and Sack, R.O. (1987 Fe-Zn exchange reaction between tetrahedrite and sphalerite in natural environments. Contributions to Mineralogy and Petrology, 96, 415—425.CrossRefGoogle Scholar
Petersen, U., Noble, D.C., Arenas, M.J. and Goodell, P.C. (1977 Geology of the Julcani mining district, Peru. Economic Geology, 72, 931—949.CrossRefGoogle Scholar
Sack, R.O. (1992 Thermochemistry of tetrahedrite-tennantite fahlores. Pp. 243—266 in: The Stability of Minerals (Ross, N.L. and Price, G.D., editors). Mineralogical Society Series, Chapman & Hall, London.Google Scholar
Sack, R.O. (2000 Internally consistent database for sulfides and sulfosalts in the system Ag2S-Cu2S-ZnS-Sb2S3-As2S3. Geochimica et Cosmochimica Ada, 64, 3803—3812.CrossRefGoogle Scholar
Sack, R.O. (2002 Note on “Large-scale hydrothermal zoning reflected in the tetrahedrite-freibergite solid solution, Keno Hill Ag-Pb-Zn district, Yukon” by Gregory J.V. Lynch. The Canadian Mineralogist, 40, 1717—1719.CrossRefGoogle Scholar
Sack, R.O. and Ebel, D.S. (1993 As-Sb exchange energies in tetrahedrite-tennant ite fahlores and bournonite-seligmannite solid solutions. Mineralogical Magazine, 57, 633—640.CrossRefGoogle Scholar
Sack, R.O. and Goodell, P.C. (2002 Retrograde reactions involving galena and Ag-sulphosalts in a zoned ore deposit, Julcani, Peru. Mineralogical Magazine, 66, 1043—1062.CrossRefGoogle Scholar
Sack, R.O. and Loucks, R.R. (1985 Thermodynamic properties of tetrahedrite-tennantites: Constraints on the interdependence of the Ag^Cu, Fe^Zn, Cu^Fe, and As^Sb exchange reactions. American Mineralogist, 70, 1270—1289.Google Scholar
Sack, R.O., Kuehner, S.M. and Hardy, L.S. (2002 Retrograde Ag-enrichment in fahlores from the Coeur d'Alene mining district, Idaho, USA. Mineralogical Magazine, 66, 215—229.CrossRefGoogle Scholar
Seward, T.M. (1989 The hydrothermal chemistry of gold and its implications for ore formation: boiling and conductive cooling as examples. Pp. 398—404 in: The Geology of Gold Deposits: The Perspective in 1988 (Keays, R.R., Ramsay, W.R.H. and Groves, D.I., editor). Economic Geology Monograph 6. Society of Economic Geologists, Tulsa, Oklahoma.Google Scholar
Sewell, D.A., Love, G. and Scott, V.D. (1985 Universal correction procedure for electron-probe microanaly-sis: II. The absorption correction. Journal of Physics D: Applied Physics, 18, 1245—1268.CrossRefGoogle Scholar
Sharp, T.G. and Buseck, P.R. (1993 The distribution of Ag and Sb in galena: Inclusions versus solid solution. American Mineralogist, 78, 85—95.Google Scholar
Sharp, Z.D., Essene, E.J. and KeUy, W.C. (1985 A re-examination of the arsenopyrite geothermometer; pressure considerations and applications to natural assemblages. The Canadian Mineralogist, 23, 517—537.Google Scholar
Sorokin, V.I., Novikov, V.K., Egorov, V.K., Popov, V.I. and Sipavina, L.V. (1975 An investigation of Fe-sphalerites by means of Mossbauer spectroscopy. Geochimiya, 9, 1329—1335.Google Scholar
Toulmin, P., III, Barton, P.B., Jr. and Wiggins, L.B. Geology 1 83 — 88. (1991 Commentary on the sphalerite geobarometer. American Mineralogist, 76, 1038—1051.Google Scholar
Watson, K.W. (1986 Silver-lead-zinc deposits of the Keno Hill-Galena Hill area, Yukon Territory. Yukon Geology, 1, 83–88.Google Scholar