Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Papike, J.J. Articles by Shearer, C.K. Search for Related Content GeoRef GeoRef Citation

Terrestrial analogs of martian sulfates: Major and minor element systematics of alunite–jarosite from Goldfield, Nevada

Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131, U.S.A.

Correspondence: ^* E-mail: jkarner{at}unm.edu

Alunite and jarosite from Goldfield, Nevada, show spectacular relationships between early alunite and later jarosite. In some cases, jarosite overgrows alunite with the same crystallographic orientation and sharp contacts. Electron microprobe analyses of these phases show that they fall in the alunite-jarosite quadrilateral defined by alunite, KAl₃(SO₄)₂(OH)₆; natroalunite, NaAl₃(SO₄)₂(OH)₆; jarosite, KFe₃³⁺(SO₄)₂(OH)₆; and natrojarosite, NaFe₃³⁺(SO₄)₂(OH)₆. A large compositional gap occurs between alunite-natroalunite and jarosite-natrojarosite. This gap has no crystal chemical basis because Al and Fe³⁺ can readily substitute for each other in octahedral site coordination. We believe the "on-off switch" behavior between early alunite and later jarosite is caused by an oxidant entering the system, oxidizing Fe²⁺ in solution to Fe³⁺, raising the Eh and possibly oxidizing H₂S to lower the pH, and thus stabilizing jarosite relative to alunite. The activity of Fe (as Fe²⁺) increased in the solution because of prolonged alunite crystallization but could not readily enter the crystal structure until it was oxidized to Fe³⁺. The jarosite overgrowths show striking oscillatory zoning of Na- and K-rich bands. This reflects up to an order of magnitude change in the fluid K/Na ratio. These textures are interpreted to represent rapid growth and kinetic control of delivery of free Na and K to the crystal-fluid interface. This could be due to some combination of Na and K diffusion rates in the solution and complex ion breakdown involving Na and K.

Key Words: Jarosite • Mars • electron microprobe • terrestrial analogs

This article has been cited by other articles:

				S. J. Mills, I. C. Madsen, I. E. Grey, and W. D. Birch IN SITU XRD STUDY OF THE THERMAL DECOMPOSITION OF NATURAL ARSENIAN PLUMBOJAROSITE Can Mineral, June 1, 2009; 47(3): 683 - 696. [Abstract] [Full Text] [PDF]

				L. C. Basciano and R. C. Peterson Crystal chemistry of the natrojarosite-jarosite and natrojarosite-hydronium jarosite solid-solution series: A synthetic study with full Fe site occupancy American Mineralogist, May 1, 2008; 93(5-6): 853 - 862. [Abstract] [Full Text] [PDF]

				L. C. Basciano and R. C. Peterson Jarosite hydronium jarosite solid-solution series with full iron site occupancy: Mineralogy and crystal chemistry American Mineralogist, August 1, 2007; 92(8-9): 1464 - 1473. [Abstract] [Full Text] [PDF]

				J.J. Papike, P.V. Burger, J.M. Karner, C.K. Shearer, and V.W. Lueth Terrestrial analogs of martian jarosites: Major, minor element systematics and Na-K zoning in selected samples American Mineralogist, February 1, 2007; 92(2-3): 444 - 447. [Abstract] [Full Text] [PDF]