What Drives Hydrothermal Activity at Lost City?
The chemistry of the vent fluids and fluid circulation at Lost City are not driven by interaction of seawater with hot lava or by cooling of magma at depth. Instead hydrothermal activity at Lost City is driven by chemical reactions between seawater and mantle rocks that make up the underlying basement. This is unlike almost all other known hot spring systems on the seafloor. The mantle, or peridotite, rocks that comprise the Atlantis massif generally occur at much greater depths in the Earth – typically at depths greater than about 6 kilometers. Because of faulting these mantle rocks are now exposed at or near the seafloor and they are out of equilibrium with their surroundings. These rocks contain large amounts of the mineral olivine (a Mg-Fe silicate) which reacts with seawater at temperatures below 400°C and forms serpentine minerals (hydrous Mg-silicates) and magnetite, an iron oxide that is highly magnetic. This process, referred to as serpentinization, has major geophysical, geoc
