Abstract Major decollements located within buried overpressured shale commonly develop in thrust fronts, accretionary prisms and sedimentary deltas controlled by gravity tectonics. In seismic data, it is possible to observe only large scale deformation of what is commonly designed as mobile shale but the precise geometry and the dynamic evolution of these bodies remains poorly understood. It is often difficult to define if we are dealing with ductile or brittle deformation and to understand the role of the fluids in time and space during deformation. For this reason, large scale outcrops were studied in the Parras Basin (Mexico), which makes possible a direct observation of the shale tectonic processes. This work suggests changes in space and time of the deformation processes which occurred within the shale formation hosting the decollement. Distributed deformation was observed within the shale formation hosting the decollement compared to more localized deformation above. Also a change of the rheology of the shale over time occurred progressively toward brittle processes in the whole sedimentary pile. XRD and microscopic studies have shown that diagenetic processes are favored in the shear zones of penetrative deformation leading notably to reverse gradient of illitization. The isotopic analysis of cements in veins and the study of associated fluid inclusions have shown that fluid dynamics also evolved during time showing notably evidence for widespread fluid migration issued from rocks located below the decollement during the beginning of the deformation. Progressively, the tectonic system located above the decollement tends to be preserved from fluid migration coming from below the decollement and to be influenced only by local fluid migration (closed system).

中文翻译：

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页岩构造过程：来自帕拉斯盆地（墨西哥东北部）的现场证据

摘要 埋藏超压页岩内的主要滑脱通常发育在重力构造控制的逆冲锋、增生棱柱和沉积三角洲中。在地震数据中，可以仅观察到通常设计为移动页岩的大尺度变形，但对这些物体的精确几何形状和动态演化仍知之甚少。通常很难定义我们是在处理韧性变形还是脆性变形，并了解流体在变形过程中的时间和空间作用。出于这个原因，在帕拉斯盆地（墨西哥）研究了大规模的露头，这使得直接观察页岩构造过程成为可能。这项工作表明了发生在承载脱滑作用的页岩地层内的变形过程的空间和时间变化。与以上更局部的变形相比，在承载脱滑的页岩地层中观察到分布变形。此外，随着时间的推移，整个沉积堆中的页岩流变性逐渐向脆性过程发生变化。XRD 和显微研究表明，在穿透变形的剪切带中，成岩过程有利于显着导致伊利石化的反向梯度。对矿脉中胶结物的同位素分析和对相关流体包裹体的研究表明，流体动力学也在一段时间内演变，显示出在变形开始期间从位于脱胶层下方的岩石发出的广泛流体迁移的明显证据。逐步，