Un nouveau contrôleur de débit d'eau

Description of a controller for the water flow, without any moving metallic piece.Description d'un contrôleur de débit d'eau ne comportant aucune pièce métallique en mouvement.Gout Robert, Harrichoury Jean-Claude, Lurde Claude. Un nouveau contrôleur de débit d'eau. In: Bulletin de Minéralogie, volume 105, 6, 1982. pp. 697-698

Un nouveau contrôleur de débit d'eau

Description of a controller for the water flow, without any moving metallic piece.Description d'un contrôleur de débit d'eau ne comportant aucune pièce métallique en mouvement.Gout Robert, Harrichoury Jean-Claude, Lurde Claude. Un nouveau contrôleur de débit d'eau. In: Bulletin de Minéralogie, volume 105, 6, 1982. pp. 697-698

The effect of sulfur on vapor liquid fractionation of metals in hydrothermal systems

International audienceDespite the growing evidence that the vapor phase, formed through magma degassing and ore fluid boiling, can selectively concentrate and transport metals, the effects of major volatile components like sulfur, chlorine or carbon dioxide on the metal vapor liquid fractionation and vapor-phase transport under magmatic-hydrothermal conditions remain poorly known. We performed systematic experiments to investigate the effect of sulfur ligands on metal vapor liquid partitioning in model H2O S NaCl KCl NaOH systems at temperatures from 350 to 500 °C. Results show that at acidic-to-neutral conditions, vapor liquid equilibrium distribution coefficients, Km = mvapor / mliquid, where m is the mass concentration of the metal in corresponding phase, of metalloids (As, Sb) and base metals (Zn, Fe, Pb, Ag) are in the range 0.1 1.0 and 0.001 0.1, respectively, and are not significantly affected by the presence of geologically common sulfur concentrations, up to 1 3 wt.% S. In contrast, the partitioning of Cu, Au, and Pt into the vapor increases by a factor of 100 in comparison to the S-free water salt system, yielding Km values of 0.5 1.0, 1 10, and 10 20, respectively, due to formation of volatile neutral complexes with H2S and, possibly, SO2. In neutral-to-basic systems, Zn, Pb, Fe and Ag show 10 100-fold increase of their partition coefficients, whereas Cu, Au and Pt exhibit Km values of up to several orders of magnitude lower, compared to acidic conditions at similar temperature, pressure and sulfur contents. These vapor liquid distribution patterns result from combined effects of i) formation of volatile species with reduced sulfur ligands in the vapor phase, ii) changes in the metal speciation in the coexisting liquid phase as a function of pH, and iii) solute solvent interactions in both phases. Our data explain the vapor liquid fractionation trends for many metals as inferred in coexisting brine and vapor inclusions from magmatic-hydrothermal deposits, and provide a first experimental evidence for the dramatic increase of the mobility of Cu, Au and Pt in sulfur-enriched acidic magmatic-hydrothermal vapors, consistent with geological models of Au ± Cu ores formation and distribution in porphyry-epithermal settings

Fluid density control on vapor-liquid partitioning of metals in hydrothermal systems

International audienceHot aqueous fluids, both vapor and saline liquid, are primary transporting media for metals in hydrothermal-magmatic systems. Despite the growing geological evidence that the vapor phase, formed through boiling of magmatic ore-bearing fluids, can selectively concentrate and transport metals, the physical-chemical mechanisms that control the metal vapor-liquid fractionation remain poorly understood. We performed systematic experiments to investigate the metal vapor-liquid partitioning in model water-salt-gas systems H2O-NaCl-KCl-HCl at hydrothermal conditions. Measurements show that equilibrium vapor-liquid fractionation patterns of many metals are directly related to the densities of the coexisting vapor and liquid phases. Despite differences in the vapor-phase chemistry of various metals that form hydroxide, chloride, or sulfide gaseous molecules of contrasting volatile properties, water-solute interaction is a key factor that controls the metal transfer by vapor-like fluids in Earth's crust. These findings allow quantitative prediction of the vapor-liquid distribution patterns and vapor-phase metal transport in a wide range of conditions. Our density model accounts well for the vapor-brine distribution patterns of Na, Si, Fe, Zn, As, Sb, and Ag observed in fluid inclusions from magmatic-hydrothermal deposits. For Au and Cu, the partitioning in favor of the liquid phase, predicted in a sulfur-free system, contrasts with the copper and gold enrichment observed in natural vapor-like inclusions. The formation of stable complexes of Cu and Au with reduced sulfur may allow for their enhanced transport by sulfur-enriched magmatic-hydrothermal vapors