The partitioning behavior of silver in a vapor–brine–rhyolite melt assemblage

Experimental constraints on Pt, Pd and Au partitioning and fractionation in silicate melt–sulfide–oxide–aqueous fluid systems at 800°C, 150MPa and variable sulfur fugacity

“…The concentration of Fe exhibits slight variability; however, the range of Fe concentrations in silicate glass is consistent with that reported in previous experimental studies at similar conditions (e.g., Simon et al, 2008). The concentration of S in some recovered glasses exhibits slight heterogeneity; these values are attributed to uncertainty associated with analyzing low sulfur concentrations that are near the detection limit.…”

“…Stable PtO species within the melt structure are reduced to elemental Pt in colloidal suspension within the melt (Ertel et al, 1999) as a function of the reduction of the experiment oxidation state during run up. Simon et al (2008) suggest that initial noble metal solubilities in the melt are relatively high, approaching the 10 lg/g range, over the first 12-24 h of a run before the experimental charge comes to equilibrium with the intrinsic redox state of the pressure vessel; hence, an excess of Pt is initially dissolved in the melt. As the charge approaches osmotic redox equilibrium, the fO 2 of the metal-oversaturated melt decreases.…”

“…Several previous studies have discussed the inherent difficulty in quantifying the solubility of noble metals in quenched silicate melts with oxidation states lower than the mt-hematite buffer. The LA-ICP-MS spectra from ablation of silicate glasses are routinely complicated by the presence of spatially heterogeneous distributions of some metals (e.g., Ag; Simon et al, 2008). This so called ''nano-nugget effect" (cf., Borisov and Palme, 1997;Ertel et al, 1999;Simon et al, 2007), as observed in LA-ICP-MS spectra has been interpreted previously as either a quench-exsolution phenomenon (e.g., Cottrell and Walker, 2006) or as a product of redox reactions within the charge (e.g., Ertel et al, 1999).…”

Gold and copper in volatile saturated mafic to intermediate magmas: Solubilities, partitioning, and implications for ore deposit formation

“…The elevated solubility of Au in the silicate melt itself at initially high fO 2 may also contribute to nugget formation. Elevated solubility of Ag in the melt at the beginning of the experiments due to initially high fO 2 was also suggested by Simon et al (2008) to explain the formation of Ag nuggets in rhyolite melts.…”

The partitioning of molybdenum(VI) between aqueous liquid and vapour at temperatures up to 370°C

“…The potential for a combination of liquid-and vapourphase transport in such systems has led to considerable interest in the vapour-liquid fractionation of ore metals, which is critical to ore deposit modeling. To this end, a body of metal fractionation data has been collected by way of experiments conducted in hydrothermal autoclaves, as well as analyses of natural and synthetic fluid inclusions, geysers and hot springs (e.g., Smith et al, 1987;Heinrich et al, 1999;Ulrich et al, 1999;Audetat et al, 2000;Palmer et al, 1999Palmer et al, , 2000Shmulovich et al, 2002;Audetat and Pettke, 2003;Rusk et al, 2004;Pokrovski et al, 2002Pokrovski et al, , 2005Pokrovski et al, , 2008Simon et al, 2005Simon et al, , 2006Simon et al, , 2008Cauzid et al, 2007;Klemm et al, 2008;Nagaseki and Hayashi, 2008). These studies have led to an increased understanding of the fractionation of many elements, and suggest that metals such as Cu, Au and As may partition preferentially into the vapour over the liquid.…”