Abstract

The Urf Al-Mahib area, located to the southern part of the Eastern Desert (SED) of Egypt, is covered mainly by juvenile Neoproterozoic crust and Nubian sandstones. Field investigation and structural analyses give evidence that the area of Urf Al-Mahib developed through four successive phases of deformation (D₁, D₂, D₃ and D₄). D₁ was an attenuated phase represented by tight to isoclinal folds (F₁), tightly appressed fold closures and sheared-out hinges, and axial plane foliation (S₁), as well as mineral and stretching lineations (L₁). Structural fabrics formed during the D₂ phase embrace minor- and map-scale prominent F₂ overturned folds with NW (to NNW)-dipping long upper limbs and short lower overturned limbs and axial planes striking NE (to ENE)‒SW (to WSW) and dipping to the NW at moderate angles. F₂ folds are geometrically- and kinematically-related to thrust propagation, and often have SE (to SSE) vergence. Thrust faults, that striking NE (to ENE)‒SW (to WSW) and dipping NW to NNW, are also common in this stage. D₃ structures contain pervasive vertical to inclined mesoscopic open to very open folds (F₃), whose axes plunge NW (to NNW) and SE (to SSE) at moderate to steep angles. The latest D₄ deformation phase is represented by abundant small- and large-scales WNW‒ESE trending dextral semi-ductile-semi-brittle-shear zones.

中文翻译：

---

埃及东南沙漠多变形Urf Al-Mahib带的构造演化

摘要

位于埃及东部沙漠（SED）南部的Urf Al-Mahib地区主要覆盖着新元古代地壳和努比亚砂岩。现场调查和结构分析表明，Urf Al-Mahib的区域通过四个连续的变形阶段（D ₁，D ₂，D ₃和D ₄）发展。D ₁是一个衰减相，表现为紧密到等时线褶皱（F ₁），紧密贴合的褶皱闭合和剪切的铰链，轴向平面叶状构造（S ₁）以及矿物和伸展构造（L ₁）。D ₂期间形成的结构织物阶段包括次要和地图尺度的显着F ₂翻转褶皱，向北（向NNW）浸入较长的上肢和短的向下翻转的四肢，并且轴向平面撞击NE（向ENE）‒SW（向WSW）并向NW倾斜角度适中。F ₂倍数在几何和运动学上与推力传播有关，并且通常具有SE（至SSE）聚散度。在这个阶段，冲刺断层也很普遍，例如冲刺NE（到ENE）‒SW（到WSW）和NW到NNW。D ₃结构包含从垂直到倾斜的介观孔，这些孔向非常开放的褶皱（F ₃）敞开，其折叠轴以NW（与NNW）和SE（与SSE）的角度从中等角度倾斜到陡峭角度。最新的D ₄ 形变阶段以大量的WNW‒ESE趋势性右旋半韧性半脆性剪切带为代表。