A previously unrecognized type of hydrothermal vent system, in which geothermally heated water emanates from the deep seafloor, has been reported this week in Nature Communications. The hot, mineral-rich fluids are chemically different to those emanating from other vent sites, and may affect the way in which global heat budgets are calculated.

Hydrothermal vents typically form in areas where the Earth’s tectonic plates are spreading apart. At these sites, circulating seawater is heated by magma below the seafloor and becomes more acidic, leaching metals from the surrounding rocks. The metals are redeposited once hot water spewing out of vents, or chimneys, at the seabed hits cold seawater.

Matthew Hodgkinson and colleagues analyse samples from the Von Damm Vent Field in the Caribbean Sea, which was discovered in 2010 by scientists and crew on board the RRS James Cook. They note that the vent site hosts a of community of fauna similar to that at the Mid-Atlantic Ridge, but that the minerals and chemistry at the Von Damm site are very different to any other known vents, with chimneys and mounds formed largely of talc, rather than the more usual sulphide minerals. In addition, the system has a very energetic heat flux of around 500 megawatts, much more than would be expected here, since the Von Damm Vent Field is located on the flanks of a spreading area and not in between two plates spreading apart.

The unusual positioning of the new vent field suggests that other, similar vent fields may have been overlooked. These new vent sites could be important drivers of the exchange of chemicals and heat between the Earth’s interior and the oceans, and may affect current global assessments of the impact of hydrothermal vents on the oceans.