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7490016 
Journal Article 
Palaeoproterozoic granitoids from the Bas Draa and Tagragra d'Akka Inliers western Anti-Atlas, Morocco : part of the jigsaw puzzle concerning the West African Craton 
Mortaji, A; Ikenne, M; Gasquet, D; Barbey, P; Stussi, JM 
2000 
Yes 
Journal of African Earth Sciences
ISSN: 1464-343X 
31 
3-4 
523-538 
French 
CCC:000167482800004 
Two Palaeoproterozoic plutonic units are recognised in the Bas Draa and Tagragra d'Akka Inliers (western Anti-Atlas, Morocco) using mineralogical and chemical data. The first one consists of a calc-alkaline suite of diorites, monzogabbrodiorites, granodiorites and granites (50.9 < SiO(2) < 70.9%). Its mineralogy (oligoclase-andesine, amphibole, biotite, titanite +/- magnetite +/- epidote) and their chemical features are those of calc-alkaline I-type granites. Available isotopic data and rare earth element patterns suggest a tower crustal, or mantle, origin with variable contamination by crustal material. The second one corresponds to peraluminous granodiorites, granites and leucogranites (61.7 < SiO(2) < 74.8%). Its mineralogy (oligoclase, biotite, muscovite +/- garnet +/- tourmaline) and peraluminous composition reflects a crustal source. The nature and chemical signature of these two coeval plutonic units imply interaction between mantellic magmas and a continental crust. The siliciclastic nature of their sedimentary host rocks (Palaeoproterozoic in age) corroborates the existence of an older continental domain of probable Archaean age. The lack of a volcaniclastic series in the two inliers precludes any volcanic-are at that time. A back-arc geodynamic context, similar to that described in the Palaeozoic of Argentina, is proposed. A comparison with the Reguibat and the Leo Rises shows the existence of two large Palaeoproterozoic domains in the West African Craton: (i) an older, recycled Archaean crust to the west and north (Man, Tiris and Anti-Atlas); and (ii) a Palaeoproterozoic juvenile domain located to the southeast and northeast (Baoule-Mossi Block and eastern Reguibat Rise). (C) 2001 Elsevier Science Limited. All rights reserved. 
Physical Sciences - Other Topics; 2.1 ga, cote-divoire, u-pb, geochronology, geochemistry, magmatism,; terrains, orogen, zircon, massif