Mid Ocean Ridge Ore Deposits Patrick Loury and Olivia Miller

Processes of Ore Formation Exhalative deposition Related to submarine hot-springs or fumaroles Mineralizing fluids pour onto the seafloor or raise to some height before deposition Deposit characteristics are a function of: Water depth, temperature, and salinity Distance from vent Proximal ore deposits Intermediate volcanic processes and products Distal ore deposits Lateral transmission of ore forming fluids through seawater Host rocks: volcanic tuffs and seafloor sediments

Volcanogenic Massive Sulfide (VMS) Deposits Lenses of polymetallic massive sulfides that form in submarine volcanic environments Distribution: 800 known deposits worldwide Age: Archean to present day Classification based on chemical composition and host rock lithology: Cu-Zn, Zn-Cu and Zn-Pb-Cu groups Mafic dominated, bimodal mafic, siliciclastic mafic, bimodal felsic, high sulfidation bimodal felsic, siliciclastic felsic groups

Sp, sphalerite; Gn, galena; Py, pyrite; Ba, barite; Cpy, chalcopyrite; Po, pyrrhotite; and Hem, hematite (Taylor et al., 1995)

$862 million cleanup VMS deposits provide: at least 22% of the world's Zn 6% of the world's Cu 9.7% of the world's Pb 8.7% of it's Ag 2.2% of it's Au World’s Most Acidic Water $862 million cleanup (Galley et al., 2007, Nordstron et al., 2000)