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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Henry, B, Liégeois, J.P., Nouar, O, Derder, MEM, Bayou, B, Bruguier, O, Ouabadi, A, Belhai, D, Amenna, M, Hemmi, A & Ayache, M. 2009. ‘Repeated granitoid intrusions during the Neoproterozoic along the western boundary of the Saharan metacraton, Eastern Hoggar, Tuareg shield, Algeria: An AMS and U-Pb zircon age study’. Tectonophysics 474: 417-434. Amsterdam : Elsevier. DOI: 10.1016/j.tecto.2009.04.022. I.F. 1.677.
Article in a scientific Journal / Article in a Journal
The N-S oriented Raghane shear zone (8°30') delineates the western boundary of the Saharan metacraton
and is, with the 4°50'; shear zone, the most important shear zone in the Tuareg shield. It can be followed on
1000 km in the basement from southern Aïr, Niger to NE Hoggar, Algeria. Large subhorizontal movements
have occurred during the Pan-African orogeny and several groups of granitoids intruded during the
Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of
granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and
detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to
the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all
the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The
AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed
zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby
mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved
locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the
Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the
case of the contemporaneous plutons in the Assodé-Issalane terrane whose structures are only related to the
subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S
oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE
oriented when further. These NW-SE oriented structures appear to be characteristic of the late
Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the
Murzuq craton. This evolution reflects the rheological contrast existing along the Raghane shear zone
marking the western boundary of the Saharan metacraton.