Elasticity of natural majorite and ringwoodite from the catherwood meteorite
Elasticity of natural majorite and ringwoodite from the catherwood meteorite
复制标题
卡瑟伍德陨石中天然多数石和尖晶石的弹性
DOI：
10.1029/97gl03217
复制
发表时间：
1997
影响因子：
5.2
通讯作者：
R. Jeanloz
中科院分区：
文献类型：
--
作者：
S. Sinogeikin;J. Bass;A. Kavner;R. Jeanloz
用布里渊光谱法测定了Catherwood陨石中天然多晶majorite (Mg0.78Fe0.21Ca0.01)SiO3和ringwoodite (Mg0.75Fe0.25)2SiO4的声速和弹性模量。这是第一次对铁含量与地幔相当的天然高压相进行声学测量。镁铁石的绝热体积模量Ks=164(4) GPa，剪切模量μ=87(2) GPa，这是石榴石结构硅酸盐的典型数值。天然立方镁铁石的弹性模量和声速均略低于铁含量相当的铝硅酸盐石榴石。此外，天然镁镁石的体积模量和剪切模量与纯镁镁石的体积模量没有明显区别，且这些模量对铁含量的依赖性较小。而环伍德石(Ks=193（3), μ=113(2)）的聚集体弹性模量和声速随Fe含量的增加变化明显。在γ相中加入10%的Fe，其速度变化与Mg2SiO4中β→γ转变的速度变化相当。因此，在建立过渡带的矿物学模型时，有必要考虑铁的影响。
Sound velocities and elastic moduli of natural polycrystalline majorite (Mg0.78Fe0.21Ca0.01)SiO3, and ringwoodite (Mg0.75Fe0.25)2SiO4 from the Catherwood meteorite were measured by Brillouin spectroscopy. These are the first acoustic measurements for such natural high‐pressure phases with Fe contents comparable to that of the Earth's mantle. The adiabatic bulk modulus of majorite is Ks=164(4) GPa, and the shear modulus is μ=87(2) GPa, which are typical values for garnet‐structured silicates. Both the elastic moduli and the sound velocities of natural cubic majorite are slightly lower than values for aluminosilicate garnets with comparable Fe contents. Moreover, the bulk and shear moduli of natural majorite are indistinguishable from those of pure Mg majorite, and the dependence of these moduli on Fe content is small. In contrast, ringwoodite (Ks=193(3), μ=113(2)) exhibits a pronounced change in the aggregate elastic moduli and sound velocities with increasing Fe content. The addition of 10% Fe to γ‐phase changes the velocity by an amount comparable to the velocity change across the β→γ transition in Mg2SiO4. It is therefore necessary to account for the effect of Fe in constructing mineralogical models of the transition zone.