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Unconventional high-pressure Raman spectroscopy study of kinetic and peak pressure effects in plagioclase feldspars
Physics and Chemistry of Minerals ( IF 1.4 ) Pub Date : 2020-01-31 , DOI: 10.1007/s00269-020-01080-z
Melissa Sims , Steven J. Jaret , Jeffrey R. Johnson , Matthew L. Whitaker , Timothy D. Glotch

We present the results of a high-pressure semi-hydrostatic study of two plagioclase minerals, andesine and albite, using diamond anvil cells (DACs) to characterize in situ variations in Raman spectra under different static pressures. In this work, we also examined the kinetic effects on deformation at both long and short timescales through non-traditional experiments in which the DAC was either dropped or struck with a mallet. We examined the effects of strain rate, quench rate, and pressure duration on the Raman spectra of plagioclase. We observed that amorphization occurred in all the plagioclase samples we analyzed, and that amorphization onset and permanence differ depending on the composition, kinetics, energy input, and peak pressure. In andesine, samples pressurized above a peak pressure of 18 GPa, amorphization is permanent. Below this critical pressure, the phase has ‘memory’, and crystalline andesine reforms on decompression. Our findings suggest the presence of a thermodynamic energy well in andesine around 18 GPa, and we show that any additional energy input while close to 18 GPa results in amorphization becoming permanent. The effect of the energy well may be relevant for longer duration impacts. For such impacts, equilibrium state studies of deformation and phase formation were previously considered to be applicable. These experiments illuminating the presence of memory effects in plagioclase have implications for comparing static compression, in which samples are measured while under compression, with shock compression, for which samples are measured after decompression.

中文翻译:

斜长石中动力学和峰值压力效应的非常规高压拉曼光谱研究

我们展示了两种斜长石矿物中长石和钠长石的高压半流体静力学研究结果,使用金刚石砧单元 (DAC) 来表征不同静压下拉曼光谱的原位变化。在这项工作中,我们还通过非传统实验(其中 DAC 被掉落或用木槌敲击)来检查在长和短时间尺度上对变形的动力学影响。我们检查了应变速率、淬火速率和压力持续时间对斜长石拉曼光谱的影响。我们观察到在我们分析的所有斜长石样品中都发生了非晶化,并且非晶化的开始和持久性因成分、动力学、能量输入和峰值压力而异。在中长石中,样品加压超过 18 GPa 的峰值压力,非晶化是永久性的。在这个临界压力之下,该相具有“记忆”,并且在减压时结晶中长石重新形成。我们的研究结果表明,在 18 GPa 左右的中长石中存在热力学能量井,并且我们表明,在接近 18 GPa 时任何额外的能量输入都会导致非晶化成为永久性的。能量井的影响可能与持续时间较长的影响有关。对于这种影响,变形和相形成的平衡状态研究以前被认为是适用的。这些阐明斜长石中存在记忆效应的实验对于比较静态压缩(在压缩下测量样品)与冲击压缩(在减压后测量样品)具有重要意义。我们的研究结果表明,在 18 GPa 左右的中长石中存在热力学能量井,并且我们表明,在接近 18 GPa 时任何额外的能量输入都会导致非晶化成为永久性的。能量井的影响可能与持续时间较长的影响有关。对于这种影响,变形和相形成的平衡状态研究以前被认为是适用的。这些阐明斜长石中存在记忆效应的实验对于比较静态压缩(在压缩下测量样品)与冲击压缩(在减压后测量样品)具有重要意义。我们的研究结果表明,在 18 GPa 左右的中长石中存在热力学能量井,并且我们表明,在接近 18 GPa 时任何额外的能量输入都会导致非晶化成为永久性的。能量井的影响可能与持续时间较长的影响有关。对于这种影响,变形和相形成的平衡状态研究以前被认为是适用的。这些阐明斜长石中存在记忆效应的实验对于比较静态压缩(在压缩下测量样品)与冲击压缩(在减压后测量样品)具有重要意义。我们表明,接近 18 GPa 的任何额外能量输入都会导致非晶化成为永久性的。能量井的影响可能与持续时间较长的影响有关。对于这种影响,变形和相形成的平衡状态研究以前被认为是适用的。这些阐明斜长石中存在记忆效应的实验对于比较静态压缩(在压缩下测量样品)与冲击压缩(在减压后测量样品)具有重要意义。我们表明,接近 18 GPa 的任何额外能量输入都会导致非晶化成为永久性的。能量井的影响可能与持续时间较长的影响有关。对于这种影响,变形和相形成的平衡状态研究以前被认为是适用的。这些阐明斜长石中存在记忆效应的实验对于比较静态压缩(在压缩下测量样品)与冲击压缩(在减压后测量样品)具有重要意义。
更新日期:2020-01-31
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