Abstract The α ↔ β phase transition in quartz is accompanied by relatively large, anisotropic changes in cell volume and elastic stiffness properties. Because quartz is among the most abundant minerals in Earth's continental crust, these changes have the potential to profoundly influence the state of stress, mechanical properties, metamorphism, and rheology of crustal rocks. Laboratory experiments confirm strongly enhanced microcracking as rocks cross the transition. In addition, limited seismological studies suggest that the α ↔ β transition may cause extensive microcracking in the crust. However, the micromechanical basis for potential transition-induced damage has not been quantitatively explored. Here we use numerical methods to show that elastic stresses arising from the transition can greatly exceed the brittle tensile and shear strengths of common crustal rocks and minerals at various confining pressures. In particular, we show that contraction during the down-temperature β → α transition is far more effective than expansion during the up-temperature α → β transition at promoting possible brittle failure and/or recrystallization (damage). Our results suggest that the α ↔ β transition may play an important role in damaging the continental crust, particularly in rock volumes that experience geologically rapid changes in temperature or pressure. In these environments, the transition may weaken rocks, establish transient permeability, facilitate advective mass transport and metamorphic reactions, and potentially nucleate earthquakes.

中文翻译：

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石英α↔β相变：它会驱动大陆地壳的损伤和反应吗？

摘要 石英中的 α ↔ β 相变伴随着晶胞体积和弹性刚度特性的相对较大的各向异性变化。由于石英是地球大陆地壳中含量最丰富的矿物之一，因此这些变化有可能对地壳岩石的应力状态、力学性质、变质作用和流变学产生深远的影响。实验室实验证实，当岩石穿过过渡时，微裂纹会显着增强。此外，有限的地震学研究表明，α ↔ β 转变可能会在地壳中引起广泛的微裂纹。然而，尚未定量探索潜在转变引起的损伤的微机械基础。在这里，我们使用数值方法表明，在各种围压下，转变产生的弹性应力可以大大超过普通地壳岩石和矿物的脆性拉伸和剪切强度。特别是，我们表明，在促进可能的脆性破坏和/或再结晶（损坏）方面，低温 β → α 转变期间的收缩远比升温 α → β 转变期间的膨胀更有效。我们的研究结果表明，α ↔ β 转变可能在破坏大陆地壳方面发挥重要作用，特别是在经历温度或压力地质快速变化的岩石体积中。在这些环境中，转变可能会削弱岩石，建立瞬态渗透率，促进对流质量传输和变质反应，并可能导致地震成核。