THE ROLE OF MERCURY-ORGANIC INTERACTIONS IN THE HYDROTHERMAL TRANSPORT OF MERCURY

Despite the common association between mercury deposits and liquid hyd rocarbons, the effects of mercury organic interactions on mercury tran sport have received little attention. In this study, vee estimate the extent of aqueous mercury complexation, and the partitioning of mercur y among aqueous liquid, aqueous vapor, and an organic phase, quantifyi ng the relative importance of each phase in mercury transport. The cal culations suggest that significant mercury transport in the aqueous li quid, predominantly as Hg-(aq)(O), is only possible under relatively o xidizing and alkaline conditions. re frequent occurrence of liquid hyd rocarbons in mercury-depositing hydrothermal systems, however, implies that conditions are reducing and that aqueous liquid transport of mer cury is relatively unimportant. High concentrations of mercury also ca n be dissolved in aqueous vapor. However, boiling rarely occurs at the depths at which the ore solutions originate, and thus, the presence o f a vapor phase is unlikely during mercury transport. Extrapolation of low-temperature experimental measurements of mercury solubilities in organic phases enables quantitative estimates of mercury concentration s in liquid hydrocarbons under hydrothermal conditions. Our calculatio ns suggest that extremely high concentrations of mercury can dissolve in the organic phase and that organic phase transport may control merc ury mobilities in many mercury ore-forming hydrothermal systems.