Mid Ocean Ridge Ore DepositsPatrick 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

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

VMS deposits provide: at least 22% of the world's Zn6% of the world's Cu9.7% of the world's Pb 8.7% of it's Ag 2.2% of it's Au

$862 million cleanup

(Galley et al., 2007, Nordstron et al., 2000)

World’s Most Acidic Water