Partial dehydration of brucite and its implications for water distribution in the subducting oceanic slab
Partial dehydration of brucite and its implications for water distribution in the subducting oceanic slab
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水镁石的部分脱水及其对俯冲洋板中水分布的影响
DOI：
10.1016/j.gsf.2021.101342
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发表时间：
2022
影响因子：
8.9
通讯作者：
Junfeng Zhang
中科院分区：
文献类型：
--
作者：
Xinzhuan Guo;Takashi Yoshino;Sibo Chen;Xiang Wu;Junfeng Zhang
俯冲海洋板片内的含水矿物是水的重要宿主。澄清含水矿物的稳定场有助于了解水从地表到地球内部的运输和分布。我们通过在 3 GPa 和高达 1300 K 的温度下在开放和封闭系统中进行电导率测量，研究了水镁石（一种含水矿物的原型）的稳定性。与特征阻抗谱相关的电导率急剧增加表明，具有低水逸度的开放系统中的单晶水镁石在 950 K 时发生部分脱水，这比之前在封闭系统中通过相平衡实验定义的温度低约 300 K。相比之下，水镁石在封闭系统中在 1300 K 时完全脱水，这与之前的研究一致。部分脱水可能会产生高度缺陷的结构，但不会导致水镁石立即分解为方镁石和水。水活度对含水矿物的稳定性起着关键作用。过渡带深度俯冲大洋板片的高润湿行为引起的低水分活度（aH2O）可能会导致致密水合硅酸镁（DHMS）部分脱水，从而显着降低DHMS的温度稳定性（这一机制已被先前对超水合B相的研究证实）。因此，过渡区可能成为 DHMS 的“死区”，大部分水将储存在过渡区的瓦兹利石和尖伍德石中。
Hydrous minerals within the subducting oceanic slab are important hosts for water. Clarification of the stability field of hydrous minerals helps to understand transport and distribution of water from the surface to the Earth’s interior. We investigated the stability of brucite, a prototype of hydrous minerals, by means of electrical conductivity measurements in both open and closed systems at 3 GPa and temperatures up to 1300 K. Dramatic increase of conductivity in association with characteristic impedance spectra suggests that partial dehydration of single-crystal brucite in the open system with a low water fugacity occurs at 950 K, which is about 300 K lower than those previously defined by phase equilibrium experiments in the closed system. By contrast, brucite completely dehydrates at 1300 K in the closed system, consistent with previous studies. Partial dehydration may generate a highly defective structure but does not lead to the breakdown of brucite to periclase and water immediately. Water activity plays a key role in the stability of hydrous minerals. Low water activity (aH2O) caused by the high wetting behavior of the subducted oceanic slab at the transition zone depth may cause the partial dehydration of the dense hydrous magnesium silicates (DHMSs), which significantly reduces the temperature stability of DHMS (this mechanism has been confirmed by previous study on super hydrous phase B). As a result, the transition zone may serve as a ‘dead zone’ for DHMSs, and most water will be stored in wadsleyite and ringwoodite in the transition zone.
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影响因子：
3.5
作者：
Palot, M.;Jacobsen, S. D.;Pearson, D. G.
通讯作者：
Pearson, D. G.
1）3万个微卫星位置、PCR引物、多态性频率等信息数据库。
DOI：
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发表时间：
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期刊：
影响因子：
--
作者：
通讯作者：
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影响因子：
5.3
作者：
T. Yoshino;Yu Nishihara;S. Karato
通讯作者：
T. Yoshino;Yu Nishihara;S. Karato
H2O 在 0.21–4.18 GPa 和 20–350°C 下的电导率
影响因子：
--
作者：
Hai;Hongsen Xie;Yousheng Xu;Maoshuang Song;Jie Guo;Yueming Zhang
通讯作者：
Yueming Zhang
作为水镁石脱水产物的纳米晶多孔方镁石聚集体
影响因子：
2.1
作者：
P. Aken;F. Langenhorst
通讯作者：
F. Langenhorst