The phase boundary between wadsleyite and ringwoodite in Mg2SiO4 determined by in situ X-ray diffraction
The phase boundary between wadsleyite and ringwoodite in Mg2SiO4 determined by in situ X-ray diffraction
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DOI：
10.1007/s00269-005-0053-y
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发表时间：
2006-03
影响因子：
1.4
通讯作者：
T. Inoue;T. Irifune;Y. Higo;T. Sanehira;Yuichiro Sueda;A. Yamada;T. Shinmei;D. Yamazaki;J. Ando;K. Funakoshi;W. Utsumi
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作者：
T. Inoue;T. Irifune;Y. Higo;T. Sanehira;Yuichiro Sueda;A. Yamada;T. Shinmei;D. Yamazaki;J. Ando;K. Funakoshi;W. Utsumi
利用同步辐射X射线对Mg_2SiO_4中的硅镁石和林伍德石的相界进行了测定。尽管这些高压相具有密切相关的结构的类似的X射线衍射轮廓，我们能够确定的基础上的差异配置文件的变化，通过利用新引入的压力振荡系统的相互相变的发生。当我们使用Shim的黄金压力标度时，边界位于约18.9 GPa和1，400 °C（Shim等人，在Earth Planet Sci Lett 203：729-739，2002年），这略低于（约0.8 GPa）从Katarina和Ito的淬火实验（J Geophys Res 94：15663-15670，1989年）确定的压力。虽然由于动力学问题，仅根据现有数据很难限制克拉珀龙斜率，但通过结合受本实验很好限制的aP-T位置和Akaogi等人的量热数据（J Geophys Res 94：15671-15685，1989）计算的相边界[P（GPa）=13.1+4.11×10−3×T（K）]合理地解释了实验误差内的所有现有数据。当我们使用安德森的金压力标度（安德森等人，J Appl Phys 65：1535-1543，1989）时，我们的相边界位于~18.1 GPa和1，400 ℃，并且外推边界与黑田等人（Phys Chem Miner 27：523-532，2000）的相边界一致，后者是使用基于相同压力标度的校准在高温（1，800 - 2，000 ℃）下确定的。我们的新相边界与Suzuki等人（Geophys Res Lett 27：803-806，2000）基于在较低温度（<1，000 °C）下使用Brown和德克尔的NaCl压力标度的原位X射线实验的相边界略微一致。
The phase boundary between wadsleyite and ringwoodite in Mg2SiO4has been determined in situ using a multi-anvil apparatus and synchrotron X-rays radiation at SPring-8. In spite of the similar X-ray diffraction profiles of these high-pressure phases with closely related structures, we were able to identify the occurrence of the mutual phase transformations based on the change in the difference profile by utilizing a newly introduced press-oscillation system. The boundary was located at ~18.9 GPa and 1,400°C when we used Shim’s gold pressure scale (Shim et al. in Earth Planet Sci Lett 203:729–739, 2002), which was slightly (~0.8 GPa) lower than the pressure as determined from the quench experiments of Katsura and Ito (J Geophys Res 94:15663–15670, 1989). Although it was difficult to constrain the Clapeyron slope based solely on the present data due to the kinetic problem, the phase boundary [P(GPa)=13.1+4.11×10−3×T(K)] calculated by a combination of aP–Tposition well constrained by the present experiment and the calorimetric data of Akaogi et al. (J Geophys Res 94:15671–15685, 1989) reasonably explains all the present data within the experimental error. When we used Anderson’s gold pressure scale (Anderson et al. in J Appl Phys 65:1535–1543, 1989), our phase boundary was located in ~18.1 GPa and 1,400°C, and the extrapolation boundary was consistent with that of Kuroda et al. (Phys Chem Miner 27:523–532, 2000), which was determined at high temperature (1,800–2,000°C) using a calibration based on the same pressure scale. Our new phase boundary is marginally consistent with that of Suzuki et al. (Geophys Res Lett 27:803–806, 2000) based on in situ X-ray experiments at lower temperatures (<1,000°C) using Brown’s and Decker’s NaCl pressure scales.