Protonation in germanium equivalents of ringwoodite, anhydrous phase B, and superhydrous phase B
Protonation in germanium equivalents of ringwoodite, anhydrous phase B, and superhydrous phase B
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菱伍德石、无水 B 相和超水 B 相的锗当量的质子化
DOI：
10.2138/am.2008.2739
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发表时间：
2008
影响因子：
3.1
通讯作者：
B. Wunder
中科院分区：
文献类型：
--
作者：
S. Thomas;M. Koch‐Müller;V. Kahlenberg;R. Thomas;D. Rhede;R. Wirth;B. Wunder
摘要 为了深入了解地幔硅酸盐的羟基溶解度和可能的水化机制，并测试锗类似物模型在水相关缺陷研究中的实用性，我们目前的工作重点是硅酸盐的锗类似物的质子化。为此，在活塞缸装置中在 2 GPa 和 950-1000 °C 的水过量条件下合成了尖角伍德石的 Ge 类似物、无水 B 相 (anhB) 和首次超水 B 相 (shyB)。使用电子探针微量分析 (EPMA)、透射电子显微镜 (TEM)、X 射线衍射以及拉曼和红外 (IR) 光谱来表征实验产品。 Ge-ringwoodite 含有 900 至 2200 ppm H2O（按重量计），远低于 Smyth 等人的研究。 (2003) 观察到在 22 GPa 和 1500 °C 下合成的 Si 当量，但比 Hertweck 和 Ingrin (2005) 发表的 γ-Mg2GeO4 高 200 倍。除了这种差异之外，Ge-ringwoodite 中 H 的结合机制也与 Si-ringwoodite 不同。 Ge-anhB目前被认为在Si系统中是无水的，按重量计含有2400至5300ppm的水。基于单晶X射线衍射分析和红外光谱构建了锗酸盐anhB的水合模型，其中OH通过水石榴石取代[VGe·4(OH)O]x和空位Mg位点[VMg·2(OH)O]x掺入。对于 Ge-shyB，本研究中获得的水浓度和结合机制与在 22 GPa 和 1200 °C 下合成的硅酸盐相的报告结果相同（Koch-Müller 等，2005）。因此，锗酸盐是水合地幔硅酸盐的良好低压类似物，其中质子化由化学计量控制。然而，对于名义上的无水矿物，我们不建议在与水相关的研究中使用锗酸盐作为高压模型。在这些Ge类似物中，通常是在低得多的压力下合成的，即较低的水逸度，OH的掺入似乎在定性和定量上与高压硅酸盐当量不同，因为羟基溶解度受其他因素（例如水逸度和固有缺陷）的控制。
Abstract To gain insight into hydroxyl solubilities and possible hydration mechanisms of mantle silicates, as well as to test the utility of germanium analog models in studies of water-related defects, our present work is focused on the protonation of germanium analogs of silicates. For this purpose Ge-analogs of ringwoodite, anhydrous phase B (anhB), and for the first time, superhydrous phase B (shyB), were synthesized in a piston cylinder device at 2 GPa and 950-1000 °C under water-excess conditions. Electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and X-ray diffraction as well as Raman and infrared (IR) spectroscopy were used to characterize the experimental products. Ge-ringwoodite incorporates from 900 to 2200 ppm H2O by weight, which is much less than Smyth et al. (2003) observed for the Si-equivalent synthesized at 22 GPa and 1500 °C, but 200× more than published for γ-Mg2GeO4 by Hertweck and Ingrin (2005). In addition to this discrepancy, the incorporation mechanism of H in Ge-ringwoodite also differs from that of Si-ringwoodite. Ge-anhB, which is currently believed to be anhydrous in the Si-system, contains from 2400 to 5300 ppm water by weight. A hydration model for germanate anhB was constructed based on single-crystal X-ray diffraction analysis and IR spectroscopy, in which OH is incorporated via the hydrogarnet substitution [VGe·4(OH)O]x and via vacant Mg sites [VMg·2(OH)O]x. For Ge-shyB the water concentration and incorporation mechanism obtained in this study are identical to results reported for the silicate phase synthesized at 22 GPa and 1200 °C (Koch-Müller et al. 2005). Thus, germanates are good low-pressure analogs for hydrous mantle silicates in which protonation is controlled by stoichiometry. However, for nominally anhydrous minerals we cannot recommend the use of germanates as high-pressure models in water-related studies. In these Ge-analogs, which are usually synthesized at much lower pressures, i.e., lower water fugacities, OH incorporation seems to differ from the high-pressure silicate equivalents qualitatively and quantitatively, as hydroxyl solubility is governed by other factors such as water fugacity and intrinsic defects.
影响因子：
5.3
作者：
Inoue, T;Weidner, DJ;Parise, JB
通讯作者：
Parise, JB
DOI：
10.1029/jb091ib05p04673
发表时间：
1986-04-10
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS
影响因子：
--
作者：
MAO, HK;XU, J;BELL, PM
通讯作者：
BELL, PM
高达 30 GPa 的水合尖晶石 (γ-Mg_2SiO_4) 的同步加速器红外研究
DOI：
--
发表时间：
2006
期刊：
Phys. Chem. Minerals 33
影响因子：
--
作者：
Chamarro Perez;E.M.;I.Daniel;J.-C.Chervin;P.Dumas;J.D.Bass;T.Inoue
通讯作者：
T.Inoue