Temperature dependence and mechanism of hydrogen incorporation in olivine at 12.5–14.0 GPa
Temperature dependence and mechanism of hydrogen incorporation in olivine at 12.5–14.0 GPa
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DOI：
10.1029/2007gl030737
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发表时间：
2007-08
影响因子：
5.2
通讯作者：
K. Litasov;E. Ohtani;H. Kagi;S. Jacobsen;S. Ghosh
中科院分区：
文献类型：
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作者：
K. Litasov;E. Ohtani;H. Kagi;S. Jacobsen;S. Ghosh
在12.5-14.0 GPa和1100-2000°C的水饱和条件下，研究了氢在（Mg，Fe）_2SiO_4橄榄石中的浓度和掺入机理。与顽火辉石和含水熔体共存的橄榄石（Fo 90-Fo 95）的氢含量从1100°C时的约4600 ppmw增加到1200°C时的最大值6250 ppmw。在1400°C以上，橄榄石的氢含量非线性地降低，在1800-2000°C范围内达到160-240 ppmw，其中存在高熔体分数并且没有顽火辉石。回收的橄榄石的偏振红外光谱在3450-3650 cm−1范围（I组）和3160-3450 cm−1范围（II组）都显示出OH吸收带。结果表明，橄榄石的水化与Mg和Si位空位有关。样品的微探针分析表明，橄榄石中的硅明显不足。在1400°C和过渡带压力下，橄榄石的储水能力可能不超过硅镁石的1.5-2.0倍。
The concentration and incorporation mechanisms of hydrogen into (Mg, Fe)2SiO4 olivine have been studied under water saturated conditions at 12.5–14.0 GPa and 1100–2000°C. The hydrogen content of olivine (Fo90–Fo95) coexisting with enstatite and hydrous melt increases from about 4600 ppmw at 1100°C to a maximum of 6250 ppmw at 1200°C. Above 1400°C, the hydrogen content of olivine decreases non‐linearly, reaching 160–240 ppmw in the 1800–2000°C range where there is a high melt fraction and no enstatite. Polarized infrared spectra of the recovered olivines exhibit OH absorption bands in both the 3450–3650 cm−1 range (group I) and 3160–3450 cm−1 range (group II). Results indicate that hydration of olivine is associated with both Mg and Si site vacancies. Microprobe analyses of the samples show a clear deficit of Si in olivine. The water storage capacity of olivine is probably no more than 1.5–2.0 times less than wadsleyite at 1400°C and transition zone pressures.