Several French expeditions have found 24 active hydrothermal vents in the axial zone of the East Pacific Rise, in a 20-kilometer belt several hundred kilometers wide and centered on 13° N. The vents have produced, on the sea bottom, accumulations of ore consisting of the sulfides of Zn (the predominant component), Fe and Cu. The high-temperature (up to 320°C) vents, the so-called 'black smokers,' eject a suspension of the heavy-metal sulfides, which are gradually oxidized and dissipated in the bottom water. The authors analyzed the concentrations of Fe, Mn, Zn and Cu in 42 samples of suspended matter from water collected in large inert sampling bottles at distances of up to 100 m from the bottom (depths 2450 to 2800 m) in an area measuring 50 km × 20 km, located in the axial zone of the East Pacific Rise. Also analyzed were a few samples collected at the same depths outside the survey area. The results of this first area mapping of the dispersion haloes of high-temperature vents confirm that metal concentrations in the suspended matter of bottom water are very indicative of the presence of hydrothermal vents. Haloes of suspended Zn stand out most prominently in areas of present-day ocean vents that emit mainly zinc sulfides.