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.