Mercury in Zinc Deposits: Economic Geology of a Polluting Element

Zinc concentrates with a mercury content of >600 tons are processed by zinc smelters each year, with primary zinc producers contributing significantly to anthropogenic mercury emissions. The chief host of mercury in zinc concentrates is sphalerite, the mercury content of which varies depending on the type and age of the deposit. Sphalerites from Proterozoic exhalative deposits have high mercury concentrations; they were formed during periods when the mercury input via emanations from the mantle was high. Sphalerites from Phanerozoic exhalative and vein-type deposits have intermediate mercury concentrations; they probably received most of their mercury from fluid-rock interaction, with direct input of gaseous mercury from a mantle source being less important. Mississippi Valley-type deposits have low mercury concentrations; they probably formed from mineralizing solutions, the mercury content of which has been scavenged by organic phases.