Conditions of Formation of the Iron-Containing Minerals, Hällefors Silver Mines, Bergslagen, Sweden

A. W. Jasiński*
Institute of Earth Sciences, Free University, De Boelelaan 1085, 1007 MC Amsterdam, The Netherlands
*Present address: Technical University of Wrocław, Institute of Inorganic Chemistry and Metallurgy of Rare Elements, 50-370 Wrocław, Wybrzeże Wyspiańskiego 27, Poland.

Abstract: The Hällefors silver deposit is regarded as a volcanogenic-exhalative iron ore deposit with dispersed amounts of Ag-Pb-Zn (±Cu) which has undergone secondary remobilization leading to the concentration of sulphides and sulphosalts. Based on data from the iron oxides and sulphides, the sulphide-sulphosalt mineralization is believed to have been formed in two stages. The first is characterized by the ranges 573-473 K and 2.25–1.5 kbar, higher gradient of changes of log aS2 with temperature and mostly sulphide precipitation; the second by the ranges 473–443 K, lower gradient of changes of log aS2 and mainly sulphosalt deposition. Assuming the precipitation was from fluids and aqueous solutions, possible conditions of formation of some of the iron minerals have been determined.

Keywords: iron oxides • iron sulphides • Hällefors mine • Bergslagen • Sweden

Mineralogical Magazine; March 1986 v. 50; no. 355; p. 101-110; DOI: 10.1180/minmag.1986.050.355.13
© 1986, The Mineralogical Society
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