Water Solubility in Fe‐Bearing Wadsleyite at Mantle Transition Zone Temperatures
Hongzhan Fei, Tomoo Katsura
Abstract
Abstract Wadsleyite can store significant amounts of H 2 O in its crystal structure as hydroxyl. However, H 2 O solubility in Fe‐bearing wadsleyite remains poorly constrained at mantle transition zone temperatures. Previous studies (e.g., Demouchy et al., 2005 [ https://doi.org/10.2138/am.2005.1751 ]; Litasov et al., 2011 [ https://doi.org/10.1007/s00269-010-0382-3 ]) focused primarily on Fe‐free systems, which do not represent the Earth's interior because Fe may affect the H 2 O solubility. Here, we investigated the temperature dependence of H 2 O solubility in Fe‐bearing and Fe‐free wadsleyite at 1500–2100 K. The results indicate that H 2 O solubility in Fe‐bearing wadsleyite is higher than in Fe‐free samples at 1800–1900 K, corresponding to transition zone geotherm, but there is no clear Fe content dependence in the Fe‐bearing samples. Wadsleyite can contain approximately 1.0 wt.% H 2 O at transition zone temperatures. The H 2 O solubility in wadsleyite is lower than ringwoodite along a plume geotherm, which may result in dehydration melting at the 520‐km discontinuity by upwelling flow in plumes.