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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The nature of maskelynite in shocked meteorites: not diaplectic glass but a glass quenched from shock-induced dense melt at high pressures
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The nature of maskelynite in shocked meteorites: not diaplectic glass but a glass quenched from shock-induced dense melt at high pressures

机译：受冲击的陨石中金丝晶的性质：不是双折玻璃，而是在高压下由冲击引起的致密熔体淬灭的玻璃

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摘要

Maskelynite, an important constituent of shocked meteorites, once thought to be diaplectic plagioclase glass formed by shock-induced solid-state transformation. Our systematic investigation of shocked L-chondrites and SNC meteorites indicates that maskelynite does not contain inherited fractures or cleavage, and shock-induced fractures. We found no evidence for models calling for melting that initiated in PDFs and affected the whole crystals. Maskelynite grains are smooth and display radiating cracks emerging from their surfaces into neighboring pyroxene. This is indicative of shock-induced melting and quenching of the dense melt at high pressure, thus erasing the inherited and shock-induced fractures. This was followed by relaxation of the dense plagioclase glass, which induced the expansion cracks in pyroxene and olivine. Enrichment in potassium, deviation from stoichiometry, degradation of igneous zoning, the presence of offshoots of maskelynite in pyroxene, the lack of vesiculation in the melt pockets, melt veins and molten mesostasis are clear evidence for melting and quenching under high pressure. Our investigations present unequivocal evidence that maskelynite in meteorites is not diaplectic plagioclase glass formed by solid-state transformation, but a dense quenched glass. The duration of the shock pulse in natural events can be several orders of magnitude longer than in shock experiments. Since kinetic effects are crucial factors in promoting phase transitions, vitrification and melting, experimentally induced solid-state vitrification of plagioclase produced in dynamic experiments is inadequate for calibration of peak shock pressures in maskelynite-bearing natural samples.
机译：Maskelynite是冲击陨石的重要组成部分，曾经被认为是由冲击诱导的固态转变形成的双折斜长石玻璃。我们对震惊的L球粒陨石和SNC陨石的系统研究表明，马斯克林岩不包含遗传性裂缝或劈裂，也不包含激波诱发的裂缝。我们发现没有证据表明需要融化的模型始于PDF并影响了整个晶体。 Maskelynite晶粒光滑，并显示出从其表面向邻近的辉石中出现的辐射裂纹。这表明在高压力下激振引起的熔化和致密熔体的淬火，从而消除了遗传性和激振引起的裂缝。接下来是致密的斜长石玻璃的松弛，这引起了辉石和橄榄石的膨胀裂纹。钾的富集，化学计量的偏离，火成岩带的降解，辉石中存在辉绿岩的分支，熔体袋中没有气泡，熔体脉和熔体介晶是在高压下熔融和淬火的明显证据。我们的研究提供了明确的证据，陨石中的辉绿岩不是固态转变形成的双折斜长石玻璃，而是致密的淬火玻璃。自然事件中冲击脉冲的持续时间可能比冲击实验长几个数量级。由于动力学效应是促进相变，玻璃化和融化的关键因素，因此在动态实验中实验性产生的斜长石固态玻璃化不足以校准含蒙砂石的天然样品中的峰值冲击压力。

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