Hydrothermal Processes

Hydrothermal circulation of seawater through newly formed ocean crust along the global mid-ocean ridge system was only discovered in the late twentieth century, yet it has already been recognized as a major mechanism for delivering chemicals to, and removing them from, the ocean that is comparable to global riverine fluxes in its importance. Hydrothermal activity can occur in a range of geologic settings along an oceanic spreading axis, emitting fluids with a wide range of temperature and composition. Hydrothermal circulation occurs in every ocean basin on Earth, along the full spectrum of mid-ocean ridges that encircle the globe, from the fastest spreading and most magmatically robust to the slowest. The authors review the size and scale of fluxes associated with hydrothermal flow, the processes that control the composition of the fluids venting from the seafloor, and the range of mineral deposits they produce. The authors further review the broader impact of hydrothermal venting on ocean biogeochemical budgets and its contribution to deep-ocean sediments. This article closes with some recommendations for future research.