SiO_{2} Glass Density to Lower-Mantle Pressures.
SiO_{2} Glass Density to Lower-Mantle Pressures.
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DOI：
10.1103/physrevlett.119.215701
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发表时间：
2017-11
影响因子：
8.6
通讯作者：
S. Petitgirard;W. Malfait;B. Journaux;I. Collings;E. Jennings;I. Blanchard;I. Kantor;A. Kurnosov;M. Cotte;T. Dane;M. Burghammer;D. Rubie
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文献类型：
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作者：
S. Petitgirard;W. Malfait;B. Journaux;I. Collings;E. Jennings;I. Blanchard;I. Kantor;A. Kurnosov;M. Cotte;T. Dane;M. Burghammer;D. Rubie
地球深处物质的对流或沉降主要受不同储集层之间密度差异的制约。因此，了解固体和熔融硅酸盐之间的密度差异对于理解和模拟过去和现在地球的动态行为是至关重要的。SiO_2是地幔的主要成分，是高压下硅酸盐熔体行为的参考模型系统。在这里，我们将我们最近开发的X射线吸收技术应用于密度高达110 Gpa的SiO_2玻璃，使这种测量的压力范围翻了一番。我们的密度数据验证了最近的分子动力学模拟，并与以前在较低压力下进行的实验研究很好地吻合。SiO_2玻璃的密度迅速增加到40 Gpa，但密度趋势趋于平缓，接近于SiO_2矿物密度在60 Gpa以上。密度数据在∼17和∼60 Gpa处呈现两个不连续，这可以分别与硅配位从4增加到混合5/6配位和从5/6增加到6倍有关。当∼为40 GPa时，SiO_2玻璃的密度比镁SiO_3玻璃的密度高，而在80 GPa以上，SiO_2玻璃的密度与镁SiO_3玻璃的密度相同。我们对SiO_2玻璃的研究结果表明，玄武岩或热解岩熔体中SiO_2含量随压力的变化对最终熔体密度的影响最小，而铁在熔体和残余固体之间的分配是控制地幔下部熔体浮力的主要因素。
The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO_{2} is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO_{2} glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO_{2} minerals above 60 GPa. The density data present two discontinuities at ∼17 and ∼60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO_{2} glass becomes denser than MgSiO_{3} glass at ∼40 GPa, and its density becomes identical to that of MgSiO_{3} glass above 80 GPa. Our results on SiO_{2} glass may suggest that a variation of SiO_{2} content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.