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Mineralium Deposita

, Volume 35, Issue 4, pp 285–301 | Cite as

Invisible gold in ore and mineral concentrates from the Hillgrove gold-antimony deposits, NSW, Australia

  • P. M. Ashley
  • C. J. Creagh
  • C. G. Ryan
ARTICLE

Abstract

Vein-hosted mesothermal stibnite-gold mineralisation at the Hillgrove Au-Sb mine in northeastern New South Wales has a halo of veinlet and disseminated auriferous arsenopyrite and arsenian pyrite in metasedimentary and granitic host rocks. About 50–55% of the gold produced at Hillgrove occurs invisibly in arsenopyrite and pyrite. Gold losses of ∼20% into tailings are due to this mineral chemical factor. From PIXE probe analyses, it has been found that arsenopyrite contains 255–1500 ppm Au and pyrite 24–223 ppm Au, with Au contents of each mineral correlating moderately with As content. Arsenopyrite and pyrite also contain anomalous values of Cu, Ag and Sb, whereas paragenetically later stibnite contains little invisible gold, but minor Fe, As, Ag, Cu and Pb. The precipitation of invisible gold in arsenopyrite and pyrite by a possible (Fe, Au)3+= (As-S)3− substitution mechanism may have been facilitated by rapid, non-equilibrium conditions involving pressure decreases and wall rock reaction (sulphidation, carbonatisation), as a prelude to the main stage of stibnite and gold deposition.

Keywords

Pyrite Host Rock Gold Deposition Wall Rock Chemical Factor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • P. M. Ashley
    • 1
  • C. J. Creagh
    • 1
  • C. G. Ryan
    • 2
  1. 1.Division of Earth Sciences, University of New England, Armidale, New South Wales 2351, Australia e-mail: pashley@metz.une.edu.auAU
  2. 2.CSIRO Division of Mineral Exploration and Mining, P.O. Box 136, North Ryde, New South Wales 2113, AustraliaAU

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