Serpentinization

Serpentinization is the hydration and alteration of ultramafic rocks, especially peridotite, through reaction with water. It forms serpentine minerals and can produce hydrogen and heat.

Peridotite: A coarse-grained ultramafic rock composed mainly of olivine and pyroxene. Its olivine and pyroxene are the principal minerals altered during serpentinization.
Hydrothermal vent: A seafloor opening that emits heated, chemically altered water. Seawater circulating through serpentinized rocks feeds some vent systems.
Mid-ocean ridge: A submarine mountain chain formed where tectonic plates move apart and new oceanic crust develops. Faulting at ridges lets seawater reach hot ultramafic rocks.
Volume expansion: An increase in a material's volume during a physical or chemical transformation. Hydration commonly expands the solid mineral assemblage and can fracture surrounding rock.
Olivine: A magnesium-iron silicate mineral common in the upper mantle and ultramafic rocks. Water reacts with olivine to form serpentine and iron-bearing products.
Lost City Hydrothermal Field: A hydrothermal field on the Mid-Atlantic Ridge known for alkaline, methane-rich fluids. Its fluids emerge from active serpentinization of mantle rocks.
Ophiolite: A fragment of oceanic lithosphere tectonically emplaced onto a continent. Ophiolites preserve accessible exposures of serpentinized mantle rocks.
Earthquake: Ground shaking caused by sudden slip on a fault or other rapid release of stored energy. Serpentinization-related weakening and fluid pressure can influence fault behavior.
Serpentine group: A group of hydrous magnesium-iron silicate minerals with layered or fibrous structures. These hydrous minerals are the defining products of the alteration.
Methanogenesis: The biological production of methane by certain microorganisms under anaerobic conditions. Hydrogen from serpentinization can provide energy for microbial methane production.

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