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Chinese Journal of Geochemistry

, Volume 13, Issue 1, pp 13–23 | Cite as

Gold solubility in SiO2-HCl-H2O system at 200 °C: a preliminary assessment of the implications of silicification with regard to gold mineralization

  • Wang Shengyuan 
  • Fan Wenling 
Article

Abstract

The complexation between gold and silica was experimentally, confirmed and calibrated at 200 °C:
$$\begin{gathered} Au^ + + H_3 SiO_4^ - \rightleftharpoons AuH_3 SiO_4^0 \hfill \\ \log K_{(200^\circ C)} = 19.26 \pm 0.4 \hfill \\ \end{gathered} $$

Thermodynamic calculations show that AuH3SiO 4 0 would be far more abundant than AuCl 2 under physicochemical conditions of geological interest, suggesting that silica is much more important than chloride as ligands for gold transport. In systems containing both sulfur and silica, AuH3SiO 4 0 would be increasingly more important than Au (HS) 2 as the proportion of SiO2 in the system increases.

The dissolution of gold in aqueous SiO2 solutions can be described by the reaction:
$$\begin{gathered} Au + 1/4O_2 + H_4 SiO_4^0 \rightleftharpoons AuH_3 SiO_4^0 + 1/2H_2 O \hfill \\ log K_{(200^\circ C)} = 6.23 \hfill \\ \end{gathered} $$
which indicates that SiO2 precipitation is an effective mechanism governing gold deposition, and thus explains the close association of silicification and gold mineralization.

Key words

gold solubility SiO2-HCl-H2O system silicification gold mineralization complexation 

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Copyright information

© Institute of Geochemistry, Chinese Academy of Sciences 1994

Authors and Affiliations

  • Wang Shengyuan 
    • 1
  • Fan Wenling 
    • 1
  1. 1.Open Laboratory of Ore Deposit Geochemistry, Institute of GeochemistryChinese Academy of Sciences Guiyang

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