Seafloor massive sulfide deposits or SMS deposits, are modern equivalents of ancient volcanogenic massive sulfide ore deposits or VMS deposits. The term has been coined by mineral explorers to differentiate the modern deposit from the ancient.
SMS deposits were first recognized during the exploration of the deep oceans and the mid ocean ridge spreading centers in the early 1960s. Deep ocean research submersibles, bathyspheres and remote operated vehicles have visited and taken samples of black smoker chimneys, and it has been long recognised that such chimneys contain appreciable grades of Cu, Pb, Zn, Ag, Au and other trace metals.
SMS deposits form in the deep ocean around submarine volcanic arcs, where hydrothermal vents exhale sulfide-rich mineralising fluids into the ocean.
SMS deposits are laterally extensive and consist of a central vent mound around the area where the hydrothermal circulation exits, with a wide apron of unconsolidated sulfide silt or ooze which precipitates upon the seafloor.
Beginning about 2008, technologies were being developed for deepsea mining of these deposits.