Abstract
The Neoproterozoic basement complex of the western segment of the Allaqi Shear Zone (ASZ) in the extreme southern part of the Egyptian Nubian Shield comprises four main lithologic units: gneisses, amphibolites, island arc metasediments, and intrusives. In the present study, these units investigated at the outcrop scale, as well as petrographically and geochemically. Gneisses are subdivided into three types: hornblende, muscovite, and biotite gneisses. The hornblende and muscovite gneisses have para-gneissic origin, while the biotite gneiss has igneous protolith. Amphibolites have intermediate andesitic to basaltic andesite composition, with igneous origin, and were formed in island-arc environments. The metagabbros are subalkaline and have within-plate geochemical characteristics. The metasediments involve graphite-muscovite, albite, chlorite, biotite-muscovite, carbonate, and tremolite-actinolite schists, in addition to metagreywackes. The bulk chemistry of metasedimentary succession revealed their formation within active continental margin setting with pelitic to semi-pelitic and psammitic precursor. The previously mentioned lithologic units are poly deformed and intensively affected by shearing and thrusting. These structures strike in various direction: WNW-ESE, NNE-SSW, NW-SE, NW-SE, and E-W, which are consistent with the automatic and manual principal component analyses (PCA) lineament extraction.