Petrogenetic grid in the system MgO-SiO2-H2O up to 30 GPa, 1600°C:: Applications to hydrous peridotite subducting into the Earth's deep interior -: art. no. B03206
Petrogenetic grid in the system MgO-SiO2-H2O up to 30 GPa, 1600°C:: Applications to hydrous peridotite subducting into the Earth's deep interior -: art. no. B03206
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DOI：
10.1029/2003jb002651
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发表时间：
2004-03-25
影响因子：
3.9
通讯作者：
Maruyama, S
中科院分区：
文献类型：
--
作者：
Komabayashi, T;Omori, S;Maruyama, S
利用Schreinemakers分析方法，建立了MgO-SiO_2-H_2 O系统在30 GPa和1600 ℃下的半定量成岩网格。该网格包括含水wadsleyite、含水ringwoodite和致密含水硅酸镁（DHMS）的稳定性关系：相A、相D、相E和超水相B。阐明了这些含水相之间的一系列化学反应。在地幔过渡带（410-660公里深度），含水的wadsleyite和含水的ringwoodite是稳定的，即使在1600 ℃的标准地幔温度，而在其他深度，名义含水相，包括DHMS是稳定的低于1400 ℃。新发现的含水wadsleyite和含水ringwoodite相变是多相和多反应的，因为它们的组成既不是MgO-SiO 2也不是Mg 2SiO 4-H2O系，不同于单一的转变在干燥Mg 2SiO 4系统。网格表明，俯冲板状橄榄岩中的水将通过几个DHMS和橄榄石的含水多晶型物，通过叶蛇纹石分解后的固-固反应被输送到上地幔底部。最后，DHMS将释放上地幔-下地幔边界层或更深层次的自由水。我们还研究了预测的脱水反应在板状橄榄岩沿着几个可能的压力-温度路径的深度分布之间的关系，在每个俯冲带的地震频率的模式。结果表明，俯冲板片中含水相的脱水可能是中深源地震活动的起源。
A semiquantitative petrogenetic grid in the system MgO-SiO2-H2O up to 30 GPa and 1600degreesC was constructed using Schreinemakers analysis on previous experimental data. The grid includes stability relations of hydrous wadsleyite, hydrous ringwoodite, and dense hydrous magnesium silicates (DHMSs): phase A, phase D, phase E, and superhydrous phase B. A sequence of chemical reactions among these hydrous phases was clarified. In the mantle transition zone (410-660-km depth), hydrous wadsleyite and hydrous ringwoodite are stable even at a standard mantle temperature of 1600degreesC, whereas in the other depths, nominal hydrous phases including DHMSs are stable below 1400degreesC. Newly found phase transitions in hydrous wadsleyite and hydrous ringwoodite are multiphase and multireaction because their compositions are on neither MgO-SiO2 nor Mg2SiO4-H2O tie lines, different from single transition in the dry Mg2SiO4 system. The grid indicates that water in the subducting slab peridotite would be transported to the bottom of the upper mantle by several DHMSs and hydrous polymorphs of olivine, via solid-solid reactions after antigorite decomposition. Finally, DHMSs would dehydrate to liberate free water at the upper mantle-lower mantle boundary layer or deeper level. We also examined a relation between the predicted depth distributions of dehydration reactions in slab peridotite along several possible pressure-temperature paths and the mode of seismic frequency in each subduction zone. The result suggests a possible origin of intermediate to deep seismicity by the dehydration of hydrous phases in the subducting slab.