Evidence for electrochemical deposition of gold onto arsenopyrite
Möller, Peter; Sastri, Chaturvedula S.; Kluckner, Manfred; Rhede, Dieter; Ortner, Hugo M.
European Journal of Mineralogy Volume 9 Number 6 (1997), p. 1217 - 1226
published: Dec 2, 1997
manuscript accepted: Jun 2, 1997
manuscript received: Mar 17, 1997
ArtNo. ESP147050906013, Price: 29.00 €
Abstract A detailed study of the distribution of As and S around gold grains in arsenopyrite reveals that, in most cases, gold is bordered by areas of both high and low As/S ratios. Interpreting these ratios in terms of pand n-type conductivity, it is suggested that gold is precipitated in minute galvanic couples fed by fluids that are not necessarily supersaturated with respect to gold in terms of the macro-environment. The important factor in controlling gold accumulation is the micro-environment at sites acting as galvanic couples. An electrochemical process is suggested by (i) the specific distribution of different As/S ratio regions and (ii) the corrosion phenomena often observed alongside well-preserved crystal faces of arsenopyrite at sites of visible old accumulation. The absence or presence of corroded surfaces on arsenopyrite correlates with high and low As/S ratios, respectively.