Magmatic water or
juvenile water is water that exists within, and in equilibrium with, a
magma or water-rich volatile fluids that are derived from a magma. This magmatic water is released to the atmosphere during a
volcanic eruption. Magmatic water may also be released as
hydrothermal fluids during the late stages of magmatic crystallization or solidification within the Earth's
crust. The crystallization of
hydroxyl bearing
amphibole and
mica minerals acts to contain part of the magmatic water within a solidified
igneous rock. Ultimate sources of this magmatic water includes water and hydrous minerals in rocks melted during
subduction as well as
primordial water brought up from the deep
mantle.