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Mineralium Deposita

, Volume 35, Issue 7, pp 656–671 | Cite as

Petrography, mineralogy and geochemistry of the Zarshuran Carlin-like gold deposit, northwest Iran

  • H. H. Asadi
  • J. H. L. Voncken
  • R. A. Kühnel
  • M. Hale
ARTICLE

Abstract

Gold mineralisation at Zarshuran, northwestern Iran, is hosted by Precambrian carbonate and black shale formations which have been intruded by a weakly mineralised granitoid. Granitoid intrusion fractured the sedimentary rocks, thereby improving conditions for hydrothermal alteration and mineralisation. Silicification is the principal hydrothermal alteration along with decalcification and argillisation. Three hydrothermal sulphide mineral assemblages have been identified: an early assemblage of pyrrhotite, pyrite and chalcopyrite; then widespread base metal sulphides, lead-sulphosalts and zoned euhedral arsenical pyrite; and finally late network arsenical pyrite, massive and colloform arsenical pyrite, colloform sphalerite, coloradoite, and arsenic–antimony–mercury–thallium-bearing sulphides including orpiment, realgar, stibnite, getchellite, cinnabar, lorandite and a Tl-mineral, probably christite. Most of the gold at Zarshuran is detectable only by quantitative electron microprobe and bulk chemical analyses. Gold occurs mainly in arsenical pyrite and colloform sphalerite as solid solution or as nanometre-sized native gold. Metallic gold is found rarely in hydrothermal quartz and orpiment. Pure microcrystalline orpiment, carbon-rich shale, silicified shale with visible pyrite grains and arsenic minerals contain the highest concentrations of gold. In many ways Zarshuran appears to be similar to the classic Carlin-type sediment-hosted disseminated gold deposits. However, relatively high concentrations of tellurium at Zarshuran, evidenced by the occurrence of coloradoite (HgTe), imply a greater magmatic contribution in the mineralising hydrothermal solutions than is typical of Carlin-type gold deposits.

Keywords

Shale Pyrite Gold Deposit Black Shale Hydrothermal Alteration 
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

  • H. H. Asadi
    • 1
  • J. H. L. Voncken
    • 3
  • R. A. Kühnel
    • 2
  • M. Hale
    • 2
  1. 1.Ministry of Culture and Higher Education, Dr. Beheshti Avenue, Shahid Sabounchi Cross, Tehran, IranIR
  2. 2.International Institute for Aerospace Survey and Earth Sciences, Kanaalweg 3, 2628 EB Delft, NetherlandsNL
  3. 3.Faculty of Civil Engineering and Geosciences, Department of Applied Earth Sciences, Delft University of Technology, Mijnbouwstraat 120, 2628 RX Delft, The Netherlands e-mail: j.h.l.voncken@ta.tudelft.nlNL

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