High-temperature hydrothermal activity occurs in all ocean basins and along ridge crests of all spreading rates. While it has long been recognized that the fluxes associated with such venting are large, precise quantification of their impact on ocean biogeochemistry has proved elusive Here, we report a comprehensive study of heat, fluid and chemical fluxes from a single submarine hydrothermal field. To achieve this, we have exploited the integrating nature of the non-buoyant plume dispersing above the Rainbow hydrothermal field, a long-lived and tectonically hosted high-temperature vent site on the Mid-Atlantic Ridge. Our calculations yield heat and volume fluxes for high-temperature fluids exiting the seafloor of similar to 0.5 GW and 450 Ls(-1), together with accompanying chemical fluxes, for Fe. Mn and CH4 of similar to 10, similar to 1 and similar to 1 mol s(-1), respectively. Accompanying fluxes for 25 additional chemical species that are associated with Fe-rich plume particles have also been calculated as they are transported away from the Rainbow vent site before settling to the seabed High-temperature venting has been found to recur at least once every similar to 100 km along all slow-spreading ridges investigated to-date, with half of all known sites on the Mid-Atlantic Ridge occurring as long-lived and tectonically hosted systems If these patterns persist along all slow- and ultraslow-spreading ridges, high-temperature venting of the kind reported here could account for similar to 50% of the on-axis hydrothermal heat flux along similar to 30,000 km of the similar to 55,000 km global ridge crest (C) 2010 Elsevier Ltd All rights reserved