The single-slip hypothesis revisited: Crystal-preferred orientations of sheared quartz aggregates with increasing strain in nature and numerical simulation
The single-slip hypothesis revisited: Crystal-preferred orientations of sheared quartz aggregates with increasing strain in nature and numerical simulation
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DOI：
10.1016/j.jsg.2011.07.008
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发表时间：
2011-10
影响因子：
3.1
通讯作者：
L. Keller;M. Stipp
中科院分区：
文献类型：
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作者：
L. Keller;M. Stipp
本研究讨论了自然剪切石英聚集体中的织物发展，并将其与根据多晶塑性理论的纹理建模结果进行比较，特别强调单个 c 轴最大值的形成。所研究的自然剪切带样品在约 650 ± 50 °C 下变形，应变增加至 γ ≈ 14，并显示出晶界迁移再结晶的动态再结晶微观结构。中子衍射织构分析产生 c 轴极图，在极图外围具有单个最大值。该最大值并不与垂直于较高应变的剪切面对齐，而是根据剪切感向倾斜方向旋转。这种旋转与单滑移假说不一致，表明这种 c 轴图案的形成是由多个滑移系统上的多滑移控制的。根据多晶塑性理论，如果组合{101´1}<12´10> {r}、{1´011}<12´10> {z}和{101´1}<12´10>棱镜滑移占主导地位，并且一定与通常提出的(0001)<12´10>基底滑移无关，则这种石英织物可以发展。多滑移纹理的发展与明确的石英织物和叶状结构之间的不对称性的剪切感解释一致。对于石英中占主导地位的 (0001)<12´10> 基底滑移和 γ > 2，数值模拟预测垂直于剪切面的单个外围最大值和平行于剪切面的 ∼30° 向内位置的两个 a 最大值。该模拟对应于自然观察到的在不同变形条件下形成的石英的 CPO 图案，并且与单滑移假设一致。因此，我们结合的自然数据和数值数据表明，单滑假说是对单个 c(0001) 最大值的可能解释，但并不普遍正确。
This study discusses the fabric development in naturally sheared quartz aggregates in comparison to results from texture modeling according to the polycrystalline plasticity theory with particular emphasis on the formation of a single c-axis maximum. The investigated natural shear zone samples were deformed at about 650 ± 50 °C with increasing strain up to γ ≈ 14 and show dynamic recrystallization microstructures of grain boundary migration recrystallization. Neutron diffraction texture analysis results in c-axis pole figures with a single maximum at the periphery of the pole figure. This maximum does not align with the shear plane normal towards higher strain, but rotates towards an inclined orientation in accordance with the sense of shear. Such a rotation is inconsistent with the single-slip hypothesis and suggests that the formation of this c-axis pattern is controlled by multi-slip on several slip systems. Based on the polycrystalline plasticity theory, this quartz fabric can develop if combined {101¯1}〈12¯10〉 {r}, {1¯011}〈12¯10〉 {z} and {101¯1}〈12¯10〉 prism slip dominates and must not be related to the commonly proposed (0001)〈12¯10〉 basal slip. The multi-slip texture development is in agreement with the shear sense interpretation from the asymmetry between well-defined quartz fabrics and the foliation. For dominant (0001)〈12¯10〉 basal slip in quartz and γ > 2, numerical simulations predict a single peripheral maximum perpendicular to the shear plane and two a-maxima with a ∼30°-inward position parallel to the shear plane. This simulation corresponds to naturally observed CPO patterns of quartz formed at different deformation conditions and it is in agreement with the single-slip hypothesis. Hence, our combined natural and numerical data suggest that the single-slip hypothesis is a possible explanation for a single c(0001)-maximum but not universally true.