Fluid inclusion evidence for barbotage and its role in gold deposition at the Darasun goldfield (Eastern Transbaykalia,Russia)

“Barbotage” is a process of gas penetration through a layer of liquid as a flow of dispersed small gas bubbles. Barbotage is widely used in technology particularly due to its high coefficients of interphase energy and material transfer. It promotes the heat- and mass-exchange processes as well as the chemical interactions in gas-liquid systems. Upon investigation of the fluid regime at the magmatic-hydrothermal system of Darasun goldfield (Eastern Transbaikalia, Russia) we have found evidences of barbotage as an effective mechanism resulting in the formation of vein gold deposits. In spite of the fact that early associations of gold ores in the Darasun goldfield deposits were formed from a heterogeneous fluid, their histograms of fluid salinity distributions are quite different. These differences can be explained by including into the ore-forming process the stage at which the vapour phase generated by boiling rose up as a stream of small bubbles. The corresponding scheme of the formation of the Darasun goldfield hydrothermal ore-bearing system is proposed and discussed. The possibility to use gallium fractionation and the fluid salinity distribution in hydrothermal systems as the indicators of barbotage participation in hydrothermal ore-forming processes is evaluated.