Ibrahim WS, Mostafa MS, Ibrahim ME, Watanabe K and Soliman FA
The Nugrus –Sikait belt comprises metamorphic exposures which are mainly represented by two nappes; upper nappe (dismembered ophiolitic rocks) and lower nappe (pelitic, para-amphibolite and cataclastics assemblages) separated by ophiolitic mélange. Intra-cratonic association (granitic and gabbroic rocks) intrudes these rock associations. Styles, overprinting relationships between the different structural fabrics, where each rock assemblages show its own tectonic print revealed that Nugrus-Sikait belt underwent five distinct episodes of deformation (from D1to D5). Compression event (D1) with NW-SE to NNW-SSE s1 trend. E-W thrust faulting and forming E-W isoclinal folds (Df1). Compression event (D2) with NE-SW to ENE-WSW s1 trend. NW-SE thrust faulting and forming NW-SE folding (Df2). Transpressonal sinistral shearing (D3) with NW-SE to NNW-SSEs1 trend including top-to- NW oblique-slip shearing and NNE-SSW dextral strike-slip shearing led to development of the Nugrus- Sikait ductile shear zone and formed NNW-SSE folding (Df3). This event associated with emplacement of granitic intrusions, which cause folding around horizontal N-S direction (Df4). Extensional event (D4) with NE-SW to ENE-WSW s3 trend deformation probably related to exhumation of the complex with NNW-SSE normal and strike-slip faulting. Extensional event (D5) with NNW-SSE to N-S s3 trend restricted to the alkali feldspar granite. ENE-WSW to E-W normal faulting, this event associated with emplacement of post granitic dikes and veins. The tectonic evolution of the NSB can place important insights into a proposed tectonic model suggesting a back-arc basin tectonic environment. The basin was formed as faulted bounded basin controlled mainly by E-W and N-S trending.
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