Le magmatisme basique filonien néoprotérozoïque de la boutonnière de Zenaga, Anti-Atlas central, Maroc: pétrologie, géochimie et signification géodynamique |
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Authors: | A Hafid JP Sagon M Julivert ML Arboleya A Saquaque A El-Boukhari A Saidi JMF Soler |
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Institution: | a Département de Géologie, Faculté des Sciences et Techniques Guéliz BP 618, Université Cadi Ayyad, Marrakech, Maroc;b Département de Pétrologie, 3ème Étage T26, 4, place Jussieu 75252 Paris Cedex 05, France;c Département de Geologia. Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain;d REMINEX (Groupe ONA), 26 Avenue Allal El-Fassi, Daoudiate, Marrakech, Maroc;e Département de Géologie, Faculté des Sciences Semalalia BP S15, Université Cadi Ayyad, Marrakech, Maroc;f Département de Mineralogia y Pétrologia, Facultad de Ciencias, Fuentanueva s/n, 18002 Granada, Spain |
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Abstract: | Before the Pan-African Orogeny, the Palæoproterozoic basement and its Neoproterozoic cover (limestones and quartzites) of the Zenaga Inlier were cross-cut by a swarm of doleritic dykes. They are more or less altered. The primary mineral assemblage consists of plagioclase, clinopyroxene, very rare orthopyroxene, ilmenite, apatite, micropegmatite and sometimes hornblende and biotite. Mineralogical and geochemical studies indicate that the dolerites are continental tholeiites. Two groups of dykes have been distinguished. Accordingly, rare earth elements, P2O5, Zr, Th, Ba and Sr contents are higher in group I than in group II, which is richer in V. Group I comprises the north-south and northwest-southeast swarms, while group II corresponds to northeast-southwest and east-west swarms, which were emplaced later. These geochemical variations may be explained by a higher degree of melting of the mantle source for the later group II. Doleritic dykes of Zenaga had been emplaced during an extensional episode, prior to Pan-African folding. |
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