The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone (HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N-trending pegmatite dikes. Whole-rock geochemistry of the pegmatites reveals a peraluminous (S-type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N-trending tectonic fabrics, such as axial planar foliation and dextral-shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space-localized decompression-induced partial melting of peraluminous garnet-bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage (D3) in the evolution of the south Eastern Desert terrane, due to end-orogeny system pressure-release.

中文翻译：

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埃及东南沙漠 Wadi Ibib 的新元古代含 U-Th-REE 伟晶岩：同构造深海形成模型的结构和地球化学测量

Wadi Ibib地区位于新元古代哈米萨纳剪切带（HSZ）的北部，是泛非造山运动后期演化的高应变带，可能是构造逃逸构造。角闪岩相泥质变沉积窗口出现在高速带的轴向部分，与大量N向伟晶岩岩脉明显相关。伟晶岩的全岩地球化学显示出过铝（S型）亲和力，K/Rb比率低，U、Th、REE、Rb、Li、Cs、Y、Nb和Ta的浓度升高。构造上，伟晶岩组沿高带带剪切面侵入，对应于变沉积母岩中的轴向平面理理和右旋剪切等区域性N向构造组构。字段关系，包括结构上下文，再加上 Wadi Ibib 伟晶岩的地球化学特征，不支持它们作为演化花岗质岩浆的补充部分形成。空间局部减压诱导的含过铝石榴石变泥岩的部分熔融是形成这些伟晶岩的潜在过程。这种减压与东南沙漠地体演化后期变形阶段（D3）的区域逃逸构造和应力轴排列有关，这是由于终末造山系统压力释放所致。