Compressibility of hydrous wadsleyite (β‐phase) in Mg2SiO4 by high pressure X‐ray diffraction
Compressibility of hydrous wadsleyite (β‐phase) in Mg2SiO4 by high pressure X‐ray diffraction
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DOI：
10.1029/97gl51794
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发表时间：
1997-07
影响因子：
5.2
通讯作者：
H. Yusa;T. Inoue
中科院分区：
文献类型：
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作者：
H. Yusa;T. Inoue
在含水条件下15.5 GPa1300°C合成的样品，首次在金刚石顶压机上用原位X射线衍射仪测量了含水硅滑石的等温压缩系数。二次离子质谱仪测定水合水滑石样品的H2O含量为2.5±0.3wt%。目前的含水水滑石的晶胞参数在误差范围内符合正交对称。现代含水水滑石的a、c轴线压缩率与无水滑石非常相似，但b轴方向的线压缩系数比无水黄铁矿高∼15%。因此，在压力导数(K‘0)固定为4.3的情况下，计算出的体积弹性模量(K0)为155±2 GPa.这个值比无水水滑石小5∼11%。在此基础上，讨论了400公里附近的地震不连续问题。
Isothermal compressibility of hydrous wadsleyite has been measured for the first time by using in‐situ X‐ray diffraction in a diamond anvil apparatus at pressures up to 8.5 GPa of a sample which was synthesized at 15.5 GPa and 1300°C under hydrous conditions. The hydrous wadsleyite sample included 2.5 ± 0.3 wt% of H2O as determined by secondary ion mass spectroscopy. The cell parameters of the present hydrous wadsleyite are fit to the orthorhombic symmetry within error. The linear compressibilities along a‐ and c‐axes of the present hydrous wadsleyite are very similar to those of the anhydrous wadsleyite, but the liner compressibility along the b‐axis of the present hydrous wadsleyite is ∼15% larger than that of the anhydrous wadsleyite. Consequently, the calculated bulk modulus (K0) is 155 ± 2 GPa with the pressure derivative (K′0) fixed to 4.3. This value is 5∼11% smaller than that of anhydrous wadsleyite. On the basis of the above result, the seismic discontinuity around 400 km is discussed.