Water Solubility in Fe‐Bearing Wadsleyite at Mantle Transition Zone Temperatures
Water Solubility in Fe‐Bearing Wadsleyite at Mantle Transition Zone Temperatures
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DOI：
10.1029/2021gl092836
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发表时间：
2021-04
影响因子：
5.2
通讯作者：
H. Fei;T. Katsura
中科院分区：
文献类型：
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作者：
H. Fei;T. Katsura
Wadsleyite可以在其晶体结构中以羟基的形式储存大量的水。然而，在地幔过渡带温度下，水在含铁瓦德利岩中的溶解度仍然受到很差的限制。先前的研究（例如，Demouchy等人，2005 [https://doi.org/10.2138/am.2005.1751]]； Litasov等人，2011 [https://doi.org/10.1007/s00269-010-0382-3]]）主要集中在无铁系统上，这些系统不能代表地球内部，因为铁可能会影响水的溶解度。在这里，我们研究了水在1500-2100 K时在含铁和不含铁瓦德利石中的溶解度与温度的关系。结果表明，在1800 ~ 1900 K时，含铁瓦德利石中H2O的溶解度高于不含铁的样品，对应于过渡带地热，但含铁样品中没有明显的铁含量依赖性。在过渡区温度下，Wadsleyite可以含有大约1.0 wt.%的H2O。沿羽流地热，wadsleyite的H2O溶解度低于环状woodite，这可能导致羽流上涌流在520 km不连续处脱水熔融。
Wadsleyite can store significant amounts of H2O in its crystal structure as hydroxyl. However, H2O 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 H2O solubility. Here, we investigated the temperature dependence of H2O solubility in Fe‐bearing and Fe‐free wadsleyite at 1500–2100 K. The results indicate that H2O 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.% H2O at transition zone temperatures. The H2O 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.