中文摘要：

采用金刚石对顶砧高压装置和同步辐射X射线衍射技术,在常温下对两种天然橄榄石单晶（含铁的铁镁橄榄石（Mg1.83Fe0.17）SiO4和不含铁的纯镁橄榄石Mg2SiO4）进行了高压结构行为研究。实验结果表明,两种天然橄榄石单晶在最高压力为9.9GPa的条件下没有发生相变。采用二阶Birch-Murnaghan状态方程描述压力-晶胞体积（p-V）关系,获得了铁镁橄榄石和纯镁橄榄石在零压下的晶胞体积（0.2929（3）、0.2899（1）nm3）和体积模量（140（3）、151（2）GPa）。两种镁橄榄石呈高度各向异性,轴压缩性表现为：b轴的压缩率最大,c轴次之,a轴的压缩率最小。随着铁组分的加入,橄榄石的体波速减小,两种橄榄石的体波速相差5.2%,该结果对于研究上地幔的物质构成和弹性波速具有一定的意义。

英文摘要：

In situ X-ray diffraction measurements for natural Fe-bearing and Fe-free Mg2 SiO4 forsterite single-crystals （（Mgl. aa Fe0.17 ）SiO4 and Mg2SiO4 ） were performed with diamond anvil cell high- pressure device and synchrotron radiation X-ray diffraction at room temperature. The experimental results showed that no phase transition of two natural olivine single-crystals was observed within the upper highest pressure of 9. 9 GPa. The isothermal relationship of pressure and volume in the two kinds of crystals is well described by the second-order Birch-Murnaghan equation of state with the zero-pressure unit cell volume and zero-pressure bulk modulus of 0. 292 9（3） nma and 140（3） GPa for Fe-bearing forsterite and 0. 289 9 （1） nma and 151 （2） GPa for Fe-free forsterite, respectively. The linear compressibilities along a,b and c axes （ka ,ke and kc） are elastically anisotropic in the two kinds of for- sterite and the anisotropy can be described as kb〉kc〉ka. With the addition of iron into the crystals, the bulk velocity of olivine decreases and the difference between the two kinds of forsterite single crystals is 5.2%. This result will be significant for the study of the composition of the earth＇s upper mantle and its elastic wave velocities.