Interaction between Cerium and H2O in Hydrous Rhyolitic Melts
Interaction between Cerium and H2O in Hydrous Rhyolitic Melts
复制标题
含水流纹岩熔体中铈和水的相互作用
DOI：
10.1021/acsearthspacechem.0c00206
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发表时间：
2020
影响因子：
3.4
通讯作者：
Saito Satoshi
中科院分区：
文献类型：
--
作者：
Kondo Nozomi M.;Kono Yoshio;Ohara Koji;Nakada Ryoichi;Ina Toshiaki;Skrzypek Etienne;Yamada Akihiro;Saito Satoshi
硅酸盐熔体中的铈（Ce）被认为提供了关于地球和行星内部硅酸盐岩浆性质的重要信息，特别是关于其氧化态的信息。然而，Ce在硅酸盐熔体中的行为可能并不简单，特别是在含水硅酸盐熔体中，其中发生Ce4 +/Ce3+比率的强烈抑制。在这里，我们研究了铈和水之间的相互作用在含水流纹质熔体的结构。在1GPa和1300 ° C下从熔体中淬火的含水流纹质玻璃显示出通过掺入Ce显著降低H2O溶解度。对分布函数分析表明，Ce的掺入对含水流纹质玻璃的局域结构没有明显的影响，但对T-OH（T为Si或Al）的拉曼峰强度有明显的影响。Ce的掺入降低了T-OH物种的比例，增加了Q4和Q3物种的比例。这些结果表明，在熔体中的OH −和掺入的Ce之间发生了直接的电荷转移反应，即Cemelt4 ++2（OH）熔体-→ Cemelt3 ++ H2O + Omelt。这一反应导致了流纹质熔体中Ce 4+向Ce 3+的电荷转移，从而不可避免地产生Ce 3+。X射线吸收近边结构（XANES）测量显示，在掺Ce的含水流纹岩玻璃中几乎完全是三价Ce（Ce3+），这支持了Ce3+通过Ce和OH −之间的电荷转移反应产生。结果表明，Ce~（4+）/Ce~（3+）比值的降低可能是由于Ce与H发生了电荷转移反应，表明Ce~（4+）/Ce~（3+）比值可能与岩浆的氧化态有着复杂的关系。
Cerium (Ce) in silicate melt is considered to provide important information about the nature of silicate magmas in the Earth’s and planetary interiors, especially about their oxidation state. However, the behavior of Ce in a silicate melt may not be simple, particularly in hydrous silicate melt, where a strong depression of the Ce4+/Ce3+ratio occurs. Here we investigate the interaction between cerium and H2O in the structure of hydrous rhyolitic melts. Hydrous rhyolitic glasses quenched from melts at 1 GPa and 1300 °C show a significant decrease of H2O solubility by the incorporation of Ce. Pair distribution function analyses show no distinct change in the local structures of hydrous rhyolitic glasses with the incorporation of Ce, while we found a distinct change in the intensity of the T–OH (where T is Si or Al) Raman peak. The incorporation of Ce decreases the proportion of T–OH species and increases those ofQ4andQ3species. These results suggest the occurrence of a direct charge transfer reaction between OH−in the melt and incorporated Ce as Cemelt4++ 2(OH)melt–→ Cemelt3++ H2O + Omelt. This reaction causes a charge transfer from Ce4+to Ce3+in the hydrous rhyolitic melt, and it inevitably produces Ce3+. X-ray absorption near-edge structure (XANES) measurements show almost completely trivalent Ce (Ce3+) in the Ce-incorporated hydrous rhyolitic glasses, which supports the production of Ce3+through the charge transfer reaction between Ce and OH−. The decrease of Ce4+/Ce3+ratio reported in hydrous silicate melts would be due to the charge transfer reaction between Ce and H, which implies that the Ce4+/Ce3+ratio in hydrous silicate melts may bear a complex relationship to the oxidation state of magmas.