Experimental study of gold-hydrosulphide complexing in aqueous solutions at 350–500°C, 500 and 1000 bars using mineral buffers

Experimental determination of the stabilities of Au2S(cr) at 25°C and at 25–250°C

“…The method used in LMTG to prepare samples for gold and silver analysis is described in Tagirov et al (2005). Sampled experimental solutions were evaporated in an oven at 60°C.…”

“…Until now, measurements of gold solubility have been performed at temperatures 100-500°C (analysis of the literature data is given in Benning and Seward, 1996;Stefáns-son andSeward, 2004 andTagirov et al, 2005). It is well established that in sulfide-rich solutions gold dissolves with the formation of AuHS 0 ðaqÞ and AuðHSÞ 2 À , which are the dominant Au complexes in hydrothermal sulphide-bearing solutions Au ðcrÞ þ H 2 S 0 ðaqÞ þ HS À ¼ AuðHSÞ À 2 þ 0:5H 2ðgÞ ð1Þ…”

A spectrophotometric study of aqueous Au(III) halide–hydroxide complexes at 25–80°C

“…Au(I) has a 5d 10 electronic configuration and in aqueous solution prefers linear complexes with two unidentate ligands; chloride and bisulfide Au(I) complexes account for Au transport in most hydrothermal fluids (e.g., Huheey et al, 1993;Seward, 2003a, 2004;Tagirov et al, 2005Tagirov et al, , 2006. [AuCl 2 ] À disproportionates at low chloride concentrations, especially at low temperatures (e.g., 10 À4 m at 25°C and increasing with increasing temperature; Gammons et al, 1997).…”

The solubility of gold in hydrogen sulfide gas: An experimental study

“…Inasmuch as complexes with HS À and H 2 S are the principal forms of dissolved gold in aqueous liquids (e.g., Hayashi and Ohmoto, 1991;Benning and Seward, 1996;Loucks and Mavrogenes, 1999;Stefansson and Seward, 2004;Tagirov et al, 2005) and H 2 S partitions strongly into the vapor phase of hydrothermal systems, it is also likely that gaseous H 2 S is an essential component in promoting the volatile transport of gold. In this paper, we report the results of an experimental study of the solubility of gold in hydrogen sulfide gas, and show that gold forms stable complexes with H 2 S that serve to greatly increase its solubility over that predicted by the vapor pressure of metallic gold or even more volatile species like AuS.…”