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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Brahimi, S., Liégeois, J.P., Ghienne, J.F., Munschy, M. & Bourmatte, A. 2018. ‘The Tuareg shield terranes revisited and extended towards the northern Gondwana margin: Magnetic and gravimetric constraints’. Earth-Science Reviews 185: 572-599. Amsterdam : Elsevier. DOI: https://doi.org/10.1016/j.earscirev.2018.07.002. I.F. 7.49.
Article in a scientific Journal / Article in a Journal
The Trans-Saharan Belt is one of the most important orogenic systems constitutive of the Pan-African cycle,
which, at the end of the Neoproterozoic, led to the formation of the Gondwana Supercontinent. It is marked by
the opening and closing of oceanic domains, collision of continental blocks and the deformation of thick synorogenic
sedimentary basins. It extends from north to south over a distance of 3000 km in Africa, including the
Nigerian Shield and the Tuareg Shield as well as their counterparts beneath the Phanerozoic oil-rich North- and
South-Saharan sedimentary basins. In this study, we take advantage of potential field methods (magnetism and
gravity) to analyze the crustal-scale structures of the Tuareg Shield terranes and to track these Pan-African
structures below the sedimentary basins, offering a new,>1000 km extent. The map interpretations are based
on the classical potential field transforms and two-dimensional forward modeling. We have identified geophysical
units and first-order bounding lineaments essentially defined owing to magnetic and gravimetric anomaly
signatures. In particular, we are able to highlight curved terminations, which in the Trans-Saharan context have
been still poorly documented. We provide for the first time a rheological map showing a categorization of
contrasted basement units from the south of the Tuareg Shield up to the Atlas Belt. These units highlight the
contrasted rheological behavior of the Tuareg tectonostratigraphic terranes during (i) the northerly Pan-African
tectonic escape characteristic of the Trans-Saharan Belt and (ii) the North Sahara basin development, especially
during intraplate reworking tied to the Variscan event. The discovery of a relatively rigid E-W oriented unit to
the south of the Atlas system, and on which the escaping Pan-African terranes were blocked, offers a new
perspective on the structural framework of the north-Gondwana margin. It will help to understand how occurred
the rendezvous of the N-S oriented Pan-African terranes and the E-W oriented Cadomian peri-Gondwanan terranes