Abstract: Eclogite, an important high-pressure metamorphic rock in subduction zone, mainly consists of garnet and omphacite which are known as nominally anhydrous minerals (NAMs). With the increasing temperature and pressure during slab subduction, the water-rich fluid is released, but garnet and omphacite in eclogite can still carry a certain amount of water and therefore become important carriers of water transporting to the interior of earth. During the exhumation of ultra-high pressure rocks, garnet and omphacite can release water as hydroxyl exsolution due to the decreasing pressure, which can consequently cause a series of important geodynamic processes such as retrograde metamorphism and even syn-exhumation magmatism. This paper summarized the analytical methods of water in minerals, the mechanism of water dissolved in garnet and omphacite, the controlling factors of water solubility (e.g., chemical composition, pressure, temperature, water fugacity, and oxygen fugacity) and the behavior of water in eclogite during slab subduction / exhumation. The future direction and key scientific problems are also prospected. 

Key words: subduction zone, eclogite, nominally anhydrous minerals, water content