University of Liverpool, Liverpool, L69 3BX, UK.
Drexel University, Philadelphia, PA, 19104, USA.
Nat Commun. 2019 Feb 15;10(1):686. doi: 10.1038/s41467-019-08587-2.
Deformation in Earth's lithosphere is localised in narrow, high-strain zones. Phyllosilicates, strongly anisotropic layered minerals, are abundant in these rocks, where they accommodate much of the strain and play a significant role in inhibiting or triggering earthquakes. Until now it was understood that phyllosilicates could deform only by dislocation glide along layers and could not accommodate large strains without cracking and dilation. Here we show that a new class of atomic-scale defects, known as ripplocations, explain the development of layer-normal strain without brittle damage. We use high-resolution transmission electron microscopy (TEM) to resolve nano-scale bending characteristic of ripplocations in the phyllosilicate mineral biotite. We demonstrate that conjugate delamination arrays are the result of elastic strain energy release due to the accumulation of layer-normal strain in ripplocations. This work provides the missing mechanism necessary to understand phyllosilicate deformation, with important rheological implications for phyllosilicate bearing seismogenic faults and subduction zones.
地球岩石圈的变形集中在狭窄的高应变带中。叶状硅酸盐是一种各向异性很强的层状矿物，在这些岩石中含量丰富，它们容纳了大部分应变，并在抑制或引发地震方面发挥了重要作用。到目前为止，人们认为叶状硅酸盐只能通过层间的位错滑移来变形，如果不发生开裂和膨胀，就无法容纳大的应变。在这里，我们表明，一类新的原子尺度缺陷，称为 ripplocations，解释了在没有脆性损伤的情况下层法线应变的发展。我们使用高分辨率透射电子显微镜 (TEM) 来解析叶状硅酸盐矿物黑云母中 ripplocations 的纳米尺度弯曲特征。我们证明，共轭分层阵列是由于层法线应变在 ripplocations 中积累而导致弹性应变能释放的结果。这项工作为理解叶状硅酸盐的变形提供了必要的缺失机制，对含有叶状硅酸盐的地震活动断层和俯冲带具有重要的流变学意义。
