Shock and Detonation Physics, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM, 87545, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, CA, 94025, USA.
Nat Commun. 2017 Nov 14;8(1):1481. doi: 10.1038/s41467-017-01791-y.
Understanding how rock-forming minerals transform under shock loading is critical for modeling collisions between planetary bodies, interpreting the significance of shock features in minerals and for using them as diagnostic indicators of impact conditions, such as shock pressure. To date, our understanding of the formation processes experienced by shocked materials is based exclusively on ex situ analyses of recovered samples. Formation mechanisms and origins of commonly observed mesoscale material features, such as diaplectic (i.e., shocked) glass, remain therefore controversial and unresolvable. Here we show in situ pump-probe X-ray diffraction measurements on fused silica crystallizing to stishovite on shock compression and then converting to an amorphous phase on shock release in only 2.4 ns from 33.6 GPa. Recovered glass fragments suggest permanent densification. These observations of real-time diaplectic glass formation attest that it is a back-transformation product of stishovite with implications for revising traditional shock metamorphism stages.
了解造岩矿物在冲击加载下的转变方式对于模拟行星体之间的碰撞、解释矿物中冲击特征的意义以及将其用作冲击条件（如冲击压力）的诊断指标至关重要。迄今为止，我们对受冲击材料经历的形成过程的理解仅基于对回收样品的原位分析。因此，常见的中尺度材料特征（如散斑玻璃，即受冲击的玻璃）的形成机制和起源仍然存在争议且无法解决。在这里，我们展示了在 33.6 GPa 下，熔融二氧化硅在冲击压缩下结晶为蓝丝辉石，然后在 2.4 ns 内通过冲击释放转变为非晶相的原位泵浦探针 X 射线衍射测量。回收的玻璃碎片表明其发生了永久致密化。这些实时散斑玻璃形成的观测结果证明了它是蓝丝辉石的反向转变产物，这对修正传统的冲击变质阶段具有重要意义。
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