A closer look into slickensides: Deformation on and under fault surfaces
A closer look into slickensides: Deformation on and under fault surfaces
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DOI：
10.1016/j.jsg.2023.104860
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发表时间：
2023-04
影响因子：
3.1
通讯作者：
D. Ortega-Arroyo;M. Peč
中科院分区：
文献类型：
--
作者：
D. Ortega-Arroyo;M. Peč
准确描述自然断层面和伴生断层岩对于理解断裂带的过程和性质是非常重要的。滑面——记录断层位移和磨损的沟槽抛光表面——在断层滑动过程中形成可测量的粗糙度和特征微结构。通过计算三种不同断层表面的功率谱和高度分布，量化了天然滑面粗糙度，并分析了滑面下形成的微观结构。滑面表面表现出各向异性的自仿射粗糙度，在平行方向（0.53±0.07）和垂直方向（0.6±0.1）上对应的平均赫斯特指数与其他断层表面的报告一致。此外，表面高度呈非高斯分布，其偏度和峰度粗糙度参数对观测尺度有明显的依赖性。在表面下，微观结构分析表明，S-C-C '织物在c -平面平行主滑移带附近发育，其特征是碎屑尺寸急剧减小，主滑移面（PSS）薄（≤100 μm），富含纳米颗粒。这些微观结构存在于大多数分析样品中，表明它们通常形成于滑岩开发过程中，无论岩性或构造背景如何。我们的研究结果表明，1)PSS可能是由沿弱取向结构的渐进局部化引起的；2)沿PSS的变形足以将岩石粉碎成纳米颗粒；3)通过研究断层表面的高度分布可以进一步表征断层的几何形状，这可能会影响断层的应力分布和摩擦响应。
Accurate descriptions of natural fault surfaces and associated fault rocks are important for understanding fault zone processes and properties. Slickensides--grooved polished surfaces that record displacement and wear along faults-- develop measurable roughness and characteristic microstructures during fault slip. We quantify the roughness of natural slickensides from three different fault surfaces by calculating the surfaces power spectra and height distributions and analyze the microstructures formed below the slickensides. Slickenside surfaces exhibit anisotropic self-affine roughness with corresponding mean Hurst exponents in directions parallel-- 0.53 ± 0.07-- and perpendicular --0.6 ± 0.1-- to slip, consistent with reports from other fault surfaces. Additionally, surfaces exhibit non-Gaussian height distributions, with their skewness and kurtosis roughness parameters having noticeable dependence on the scale of observation. Below the surface, microstructural analyses reveal that S–C–C′ fabrics develop adjacent to a C-plane-parallel principal slip zone characterized by a sharp decrease in clast size and a thin (≤100 μm) nanoparticulate-rich principal slip surface (PSS). These microstructures are present in most analyzed samples suggesting they commonly form during slickenside development regardless of lithology or tectonic setting. Our results suggests that 1) PSS likely arise by progressive localization along weaker oriented fabrics 2) deformation along PSS's is energetic enough to comminute the rocks into nanometric grains, and 3) fault geometry can be further characterized by studying the height distributions of fault surfaces, which are likely to impact stress distributions and frictional responses along faults.