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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Abdelsalam, M.G., Gao, S.S. & Liégeois, J.P. 2011. ‘Upper mantle structure of the Saharan Metacraton’. Journal of African Earth Sciences 60: 328-336. DOI: 10.1016/j.jafrearsci.2011.03.009. I.F. 1.219.
Article in a scientific Journal / Article in a Journal
The 500,000 km2 Saharan Metacraton in northern Africa (metacraton refers to a craton that has been
mobilized during an orogenic event but that is still recognisable through its rheological, geochronological
and isotopic characteristics) is an Archean–Paleoproterozoic cratonic lithosphere that has been destabilized
during the Neoproterozoic. It extends from the Arabian–Nubian Shield in the east to the Trans-
Saharan Belt in the west, and from the Oubanguides Orogenic Belt in the south to the Phanerozoic cover
of North Africa. Here, we show that there are high S-wave velocity anomalies in the upper 100 km of the
mantle beneath the metacraton typical of cratonic lithosphere, but that the S-wave velocity anomalies in
the 175–250 km depth are much lower than those typical of other cratons. Cratons have possitive S-wave
velocity anomalies throughout the uppermost 250 km reflecting the presence of well-developed cratonic
root. The anomalous upper mantle structure of the Saharan Metacraton might be due to partial loss of its
cratonic root. Possible causes of such modification include mantle delamination or convective removal of
the cratonic root during the Neoproterozoic due to collision-related deformation. Partial loss of the
cratonic root resulted in regional destabilization, most notably in the form of emplacement of high-K
calc-alkaline granitoids. We hope that this work will stimulate future multi-national research to better
understand this part of the African Precambrian. Specifically, we call for efforts to conduct systematic
geochronological, geochemical, and isotopic sampling, deploy a reasonably-dense seismic broadband
seismic network, and conduct systematic mantle xenoliths studies.