Hot (> 300 °C) hydrothermal fluids from mid ocean ridges are isotopically light, with δFe between -0.2 and -0.8‰. Particles in hydrothermal plumes are isotopically heavy relative to the hydrothermal fluids, with δFe between 0.1 and 1.1‰. Hydrothermal deposits have average δFe between -1.6 and 0.3‰. The sulfide minerals within these deposits have δFe between -2.0 and 1.1‰.