The Atalla Shear Zone (ASZ) is a NW-oriented
mega-shear that belongs to the Najd-Shear Corridor in
the Central Eastern Desert of Egypt. The present study
focused on the structural and tectonic evolution of the
ASZ throughout integrated space-born optical-based
mapping and structural-field work. The ASZ area comprises
a Neoproterozoic rock succession including serpentinites,
island-arc assemblage of metasediments and
metavolcanics, Dokhan Volcanics, Hammamat Sediments,
and granitoids. A lithological mapping was carried
out using Landsat-8 (ETM+) and ASTER, and the image
processing techniques included false color composites
(FCC), principal component analysis (PCA), and RGB
band ratios (BR). The predominant trends were
ENE-WSW and NE-SW. The transcurrent shearing
related to ENE-WSW shortening in the ASZ resulted in
prominent transpressive shear structures among which we
find shear-related folds, imbricated fans and antiformal
stacks, and passive-roofed- and domino-style-thrust
duplexes. A reasonable structural history involving four
successive deformation phases (D1–D4) was established.
D1 was recorded within the amphibolitic enclaves found
at Um Baanib area. D2 was a syn-accretion shortening
stage, concurrent with the E–W assembly of Gondwanalands,
and responsible for the W- and WSW-propagated
thrusts and thrust-related folds. D3 and D4 were
post-accretion phases that resulted in formation of the
Najd-related ASZ with sinistral sense of shearing. The
emplacement and exhumation of the Meatiq Gneiss
Dome, and also the deposition of the Hammamat
Volcanosedimentary Sequence in fault-controlled sags
and pull-apart, are believed to be post-accretion and
associated with the D3 phase. |
