Assiut university researches
Repeated magmatic pulses in the East African
Orogen in the Eastern Desert, Egypt: An old
idea supported by new evidence
Anders Mattias Lundmark , Arild Andresen , Mohamed A. Hassan b,
Lars Eivind Augland , Gamal Yehia Boghdady
Abstract:
This paper presents U–Pb ID-TIMS geochronological data
from granitoids in the Hafafit area in the Central and South
Eastern Desert, Egypt. It dates several Neoproterozoic
magmatic pulses and metamorphic events, and constrains
one episode of U, Nb and Ta mineralisation along the Nugrus
Shear Zone, part of the Eastern Desert Shear Zone, to 608±1
Ma. The data testify to the localized nature of deformation in
the Eastern Desert, illustrating that previous subdivisions of
granitoids into “Older” and “Younger” based on field criteria
are inadequate. With robust ages fromgranitoids in theMeatiq,
El Sibai and El Shalul areas the newages indicate 6 pulses of
magmatism and/or metamorphism at (1) 705–680, (2) c. 660,
(3) 635–630, (4) 610–604, (5) 600–590 and (6) c. 540 Ma.
Most pulses are defined by ages from granitoids in both
gneiss windows/domes and in the overlying eugeoclinal
allochthon; the two tiers represent different crustal levels of
related rocks. We propose that pulses 1–3 are syn-orogenic,
pulses 4 and 5 reflect exhumation of mid-crustal gneisses
along the Eastern Desert Shear Zone, whereas the final pulse
post-dates the East African orogeny. Based on available data
we propose that the tectono-magmatic evolution above
applies to the entire Eastern Desert.
Key words:
East African orogeny U–Pb geochronology Neoproterozoic
Eastern Desert, Egypt Magmatic pulses
Published in:
Gondwana Research,Vol.22,PP.227–237